Title:
Copper alloy for electric and electronic instruments
Kind Code:
A1


Abstract:
A copper alloy for electric and electronic instruments, containing Ni of 1 to 3 mass %, Ti of 0.2 to 1.2 mass %, any one or both of Mg and Zr of 0.02 to 0.2 mass %, and Zn of 0.1 to 1 mass %, with the balance being Cu and unavoidable impurities, in which the copper alloy contains at least one of an intermetallic compound comprising Ni, Ti and Mg, an intermetallic compound comprising Ni, Ti and Zr, or an intermetallic compound comprising Ni, Ti, Mg and Zr, and the copper alloy has a stress relaxation rate of 20% or less after holding the alloy at 150° C. for 1,000 hours; and a method of producing the copper alloy for electric and electronic instruments.



Inventors:
Kaneko, Hiroshi (Tokyo, JP)
Mihara, Kuniteru (Tokyo, JP)
Eguchi, Tatsuhiko (Tokyo, JP)
Application Number:
11/607103
Publication Date:
06/14/2007
Filing Date:
12/01/2006
Assignee:
THE FURUKAWA ELECTRIC CO., LTD. (Tokyo, JP)
Primary Class:
Other Classes:
420/473, 420/481, 148/413
International Classes:
C22C9/06
View Patent Images:



Primary Examiner:
TAKEUCHI, YOSHITOSHI
Attorney, Agent or Firm:
WESTERMAN, HATTORI, DANIELS & ADRIAN, LLP (TYSONS, VA, US)
Claims:
1. A copper alloy for electric and electronic instruments, comprising Ni of 1 to 3 mass %, Ti of 0.2 to 1.2 mass %, any one or both of Mg and Zr of 0.02 to 0.2 mass %, and Zn of 0.1 to 1 mass %, with the balance being Cu and unavoidable impurities, wherein the copper alloy contains at least one of an intermetallic compound comprising Ni, Ti and Mg, an intermetallic compound comprising Ni, Ti and Zr, or an intermetallic compound comprising Ni, Ti, Mg and Zr, and wherein the copper alloy has a stress relaxation rate of 20% or less after holding the alloy at 150° C. for 1,000 hours.

2. The copper alloy for electric and electronic instruments according to claim 1, wherein the intermetallic compound comprising Ni, Ti and Mg, the intermetallic compound comprising Ni, Ti and Zr, or the intermetallic compound comprising Ni, Ti, Mg and Zr has an average particle diameter in the range from 5 to 100 nm and a distribution density of from 1×1010 to 1×1013/mm2, and wherein the crystal grain size of a host matrix of the alloy is 10 μm or less.

3. A copper alloy for electric and electronic instruments, comprising Ni of 1 to 3 mass %, Ti of 0.2 to 1.2 mass %, any one or both of Sn and Si of 0.02 to 0.2 mass %, and Zn of 0.1 to 1 mass %, with the balance being Cu and unavoidable impurities, wherein the copper alloy contains at least one of an intermetallic compound comprising Ni, Ti and Sn, an intermetallic compound comprising Ni, Ti and Si, or an intermetallic compound comprising Ni, Ti, Sn and Si, and wherein the copper alloy has a stress relaxation rate of 20% or less after holding the alloy at 150° C. for 1,000 hours.

4. The copper alloy for electric and electronic instruments according to claim 3, wherein the intermetallic compound comprising Ni, Ti and Sn, the intermetallic compound comprising Ni, Ti and Si, or the intermetallic compound comprising Ni, Ti, Sn and Si has an average particle diameter in the range from 5 to 100 nm and a distribution density of from 1×1010 to 1×1013/mm2, and wherein the crystal grain size of a host matrix of the alloy is 10 μm or less.

5. 5-11. (canceled)

12. A method of producing the copper alloy for electric and electronic instruments according to claim 1, comprising the steps of: conducting a solution heat treatment at a temperature of 850° C. or more for 35 seconds or less, cooling from the solution heat treatment temperature to 300° C. at a cooling rate of 50° C./sec or more, cold-rolling at a cold rolling ratio in the range of more than 0% but 50% or less, and aging at a temperature in the range from 450 to 600° C. within 5 hours.

13. A method of producing the copper alloy for electric and electronic instruments according to claim 2, comprising the steps of: conducting a solution heat treatment at a temperature of 850° C. or more for 35 seconds or less, cooling from the solution heat treatment temperature to 300° C. at a cooling rate of 50° C./sec or more, cold-rolling at a cold rolling ratio in the range of more than 0% but 50% or less, and aging at a temperature in the range from 450 to 600° C. within 5 hours.

14. A method of producing the copper alloy for electric and electronic instruments according to claim 3, comprising the steps of: conducting a solution heat treatment at a temperature of 850° C. or more for 35 seconds or less, cooling from the solution heat treatment temperature to 300° C. at a cooling rate of 50° C./sec or more, cold-rolling at a cold rolling ratio in the range of more than 0% but 50% or less, and aging at a temperature in the range from 450 to 600° C. within 5 hours.

15. A method of producing the copper alloy for electric and electronic instruments according to claim 4, comprising the steps of: conducting a solution heat treatment at a temperature of 850° C. or more for 35 seconds or less, cooling from the solution heat treatment temperature to 300° C. at a cooling rate of 50° C./sec or more, cold-rolling at a cold rolling ratio in the range of more than 0% but 50% or less, and aging at a temperature in the range from 450 to 600° C. within 5 hours.

16. A method of producing the copper alloy for electric and electronic instruments according to claim 1, comprising the steps of: conducting a solution heat treatment at a temperature of 850° C. or more for 35 seconds or less, cooling from the solution heat treatment temperature to 300° C. at a cooling rate of 50° C./sec or more, and aging at a temperature in the range from 450 to 600° C. within 5 hours.

17. A method of producing the copper alloy for electric and electronic instruments according to claim 2, comprising the steps of: conducting a solution heat treatment at a temperature of 850° C. or more for 35 seconds or less, cooling from the solution heat treatment temperature to 300° C. at a cooling rate of 50° C./sec or more, and aging at a temperature in the range from 450 to 600° C. within 5 hours.

18. A method of producing the copper alloy for electric and electronic instruments according to claim 3, comprising the steps of: conducting a solution heat treatment at a temperature of 850° C. or more for 35 seconds or less, cooling from the solution heat treatment temperature to 300° C. at a cooling rate of 50° C./sec or more, and aging at a temperature in the range from 450 to 600° C. within 5 hours.

19. A method of producing the copper alloy for electric and electronic instruments according to claim 4, comprising the steps of: conducting a solution heat treatment at a temperature of 850° C. or more for 35 seconds or less, cooling from the solution heat treatment temperature to 300° C. at a cooling rate of 50° C./sec or more, and aging at a temperature in the range from 450 to 600° C. within 5 hours.

20. A copper alloy for electric and electronic instruments, comprising Ni of 1 to 3 mass % and Ti of 0.2 to 1.4 mass % with a ratio (Ni/Ti) of the mass percentage between Ni and Ti in the range from 2.2 to 4.7, any one or both of Mg and Zr in a total amount of 0.02 to 0.3 mass %, and Zn of 0.1 to 5 mass %, with the balance being Cu and unavoidable impurities, wherein the copper alloy contains at least one of an intermetallic compound comprising Ni, Ti and Mg, an intermetallic compound comprising Ni, Ti and Zr or an intermetallic compound comprising Ni, Ti, Mg and Zr, and wherein the copper alloy has a distribution density of the intermetallic compound in the range from 1×109 to 1×1013/mm2, a tensile strength of 650 MPa or more, an electric conductivity of 55% IACS or more, and a stress relaxation rate of 20% or less after holding the alloy at 150° C. for 1,000 hours.

21. A copper alloy for electric and electronic instruments, comprising Ni of 1 to 3 mass % and Ti of 0.2 to 1.4 mass % with a ratio (Ni/Ti) of the mass percentage between Ni and Ti in the range from 2.2 to 4.7, any one or both of Mg and Zr in a total amount of 0.02 to 0.3 mass %, Zn of 0.1 to 5 mass %, and Sn in the range of more than 0 mass % but 0.5 mass % or less, with the balance being Cu and unavoidable impurities, wherein the copper alloy contains at least one of an intermetallic compound comprising Ni, Ti and Mg, an intermetallic compound comprising Ni, Ti and Zr or an intermetallic compound comprising Ni, Ti, Mg and Zr, and wherein the copper alloy has a distribution density of the intermetallic compound in the range from 1×109 to 1×1013/mm2, a tensile strength of 650 MPa or more, an electric conductivity of 55% IACS or more, and a stress relaxation rate of 20% or less after holding the alloy at 150° C. for 1,000 hours.

22. A copper alloy for electric and electronic instruments, comprising Ni of 1 to 3 mass % and Ti of 0.2 to 1.4 mass % with a ratio (Ni/Ti) of the mass percentage between Ni and Ti in the range from 2.2 to 4.7, Mg of 0.02 to 0.3 mass %, Zn of 0.1 to 5 mass %, and any one or at least two of Zr, Hf, In and Ag in a total amount of more than 0 mass % but 1.0 mass % or less, with the balance being Cu and unavoidable impurities, wherein the copper alloy contains at least one of an intermetallic compound comprising Ni, Ti and Mg, an intermetallic compound comprising Ni, Ti and Zr, or an intermetallic compound comprising Ni, Ti, Mg and Zr, and wherein the copper alloy has a distribution density of the intermetallic compound in the range from 1×109 to 1×1013/mm2, a tensile strength of 650 MPa or more, an electric conductivity of 55% IACS or more, and a stress relaxation rate of 20% or less after holding the alloy at 150° C. for 1,000 hours.

23. A copper alloy for electric and electronic instruments, comprising Ni of 1 to 3 mass % and Ti of 0.2 to 1.4 mass % with a ratio (Ni/Ti) of the mass percentage between Ni and Ti in the range from 2.2 to 4.7, Mg of 0.02 to 0.3 mass %, Zn of 0.1 to 5 mass %, Sn in the range of more than 0 mass % but 0.5 mass % or less, and any one or at least two of Zr, Hf, In and Ag in a total amount of more than 0 mass % but 1.0 mass % or less, with the balance being Cu and unavoidable impurities, wherein the copper alloy contains at least one of an intermetallic compound comprising Ni, Ti and Mg, an intermetallic compound comprising Ni, Ti and Zr, or an intermetallic compound comprising Ni, Ti, Mg and Zr, and wherein the copper alloy has a distribution density of the intermetallic compound in the range from 1×109 to 1×1013/mm2, a tensile strength of 650 MPa or more, an electric conductivity of 55% IACS or more, and a stress relaxation rate of 20% or less after holding the alloy at 150° C. for 1,000 hours.

24. A method of producing the copper alloy for electric and electronic instruments according to claim 20, which comprises applying once or at least twice of heat treatment for precipitation by aging at a temperature of from 450 to 650° C. within 5 hours, wherein an electric conductivity before the heat treatment for precipitation by aging is 35% IACS or less.

25. A method of producing the copper alloy for electric and electronic instruments according to claim 21, which comprises applying once or at least twice of heat treatment for precipitation by aging at a temperature of from 450 to 650° C. within 5 hours, wherein an electric conductivity before the heat treatment for precipitation by aging is 35% IACS or less.

26. A method of producing the copper alloy for electric and electronic instruments according to claim 22, which comprises applying once or at least twice of heat treatment for precipitation by aging at a temperature of from 450 to 650° C. within 5 hours, wherein an electric conductivity before the heat treatment for precipitation by aging is 35% IACS or less.

27. A method of producing the copper alloy for electric and electronic instruments according to claim 23, which comprises applying once or at least twice of heat treatment for precipitation by aging at a temperature of from 450 to 650° C. within 5 hours, wherein an electric conductivity before the heat treatment for precipitation by aging is 35% IACS or less.

Description:

TECHNICAL FIELD

The present invention relates to a copper alloy for electric and electronic instruments improved in its properties.

BACKGROUND ART

Heretofore, generally, in addition to a stainless-based steel, copper-based materials such as phosphor bronze, red brass, and brass, which are excellent in electrical conductivity and thermal conductivity, have been used widely as materials for parts of electric and electronic instruments (electrical and electronic machinery and tools).

A demand for small size and light weight of the electric and electronic instruments, accompanied with high density mounting requirement thereof, has been increased in recent years. When the electric and electronic instruments are made further small-sized, a contact area and the thickness of the plate used are reduced. Accordingly materials having higher strength are required for maintaining reliability of the instruments equivalent to those of conventional ones. Connectors fit (contact) to one another by a given magnitude of contact pressure generated by deflection, (that is, deformation) of the materials to allow an electric current or information signals flow or exchange through the joint. Accordingly, it is a fatal defect that the fitting (joining) force is decreased as a result of decrease of the contact pressure during the use, and accordingly the connectors are unable to flow or exchange the electric current or information signals through the joint. This decrease of fitting (joining) forces is referred to as stress relaxation characteristic (creep resistance), and copper alloys free from deterioration of the stress relaxation characteristic, that is, copper alloys having an excellent stress relaxation resistance, are desired for the materials to be used for these electronic parts.

Some of the connectors may be connected to heat-generating instruments, such as CPU (Central Processing Unit) of a personal computer. The connector material is required to be able to promptly dissipate the heat in this case, since the fitting (joining) force is rapidly decreased by acceleration of the stress relaxation due to heating of the connector material. The material is required to have a higher electric conductivity because the heat-dissipating property is ascribed to the electric conductivity of the material. The higher electric conductivity of the material is also required from the view point of exchange of information using high frequency in the future.

The material is also required to have a good bending property for making the electric or electronic instruments small size. Thinning the instruments is one of the strategies for making the instruments compact, and to reduce the height of the connector (to make the connector low in the height) is accompanied by thinning the instruments. Consequently, a connector material having better workability is desired.

The material is desired to have high strength with good electric conductivity while it is excellent in stress relaxation resistance property and bending property by the reasons as described above. Specifically, a material having a strength of 600 MPa or more, an electric conductivity of, preferably, 50% IACS or more, a stress relaxation rate of 20% or less after allowing to stand at 150° C. for 1,000 hours, and the ratio R/t, which is an index of bending property, of 1 or less is desired. Also, a material having a strength of 650 MPa or more and an electric conductivity of 55% IACS or more is demanded.

Examples of a usual method of enhancing the strength of the metallic material include a work reinforcement method, in which a working strain is introduced into the material, a solid solution reinforcement method, in which other elements are allowed to be in the solid solution, and a precipitation reinforcement method, in which a second phase is precipitated to harden the material.

Examples of the alloys prepared by the precipitation reinforcement method include a Cu—Be alloy (C17200), a Cu—Ni—Si alloy (C70250), a Cu—Fe alloy (C19400) and a Cu—Cr alloy (C18040). However, while C17200 alloy has a strength of 1,000 MPa or more and stress relaxation rate of 20% or less with good bending property by applying a reinforcement mechanism for allowing Be to precipitate in the Cu host matrix, the electric conductivity is as low as about 25% IACS. In addition, the use of beryllium (Be) may actually cause an environmental problem.

Although the C70250 alloy prepared by allowing an intermetallic compound comprising Ni—Si to precipitate in the Cu host matrix has a strength of 600 MPa or more and a stress relaxation rate of 20% or less with good bending property, it cannot give an electric conductivity of 50% IACS or more.

Although the C19400 alloy has a strength of 600 MPa or more and an electric conductivity of about 65% IACS by applying a reinforcement mechanism for allowing iron (Fe) to precipitate in the Cu host matrix, the desired properties for the stress relaxation rate and bending property are not satisfied in the C19400 alloy.

The desired properties for the stress relaxation rate and the bending property are not satisfied either in the C18040 alloy as in the C19400 alloy, although the alloy has an electric conductivity of about 80% IACS and a strength of about 600 MPa.

No materials satisfying the desired properties can be obtained using any of the precipitation reinforcement methods as described above, and developments of novel materials are strongly required.

On the other hand, the strength and the electric conductivity have been improved in some copper alloys for the electronic instruments by allowing a Ni—Ti intermetallic compound to uniformly and finely precipitate in the Cu matrix.

In another example, adhesiveness between a lead frame and a resin has been improved by adding aluminum (Al), silicon (Si), manganese (Mn) or magnesium (Mg) to a Cu—Ni—Ti alloy.

However, the desired properties for the copper alloy in accordance with the improvement of performance of recently developed electronic instruments cannot be satisfied even by using these copper alloys, since the desired strength, electric conductivity and bending property as well as stress relaxation resistance, cannot be simultaneously satisfied.

Further, in some examples, various properties of the copper alloy have been improved by allowing a Ni—Ti intermetallic compound to precipitate in copper.

Other and further features and advantages of the invention will appear more fully from the following description, appropriately referring to the accompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic explanatory view for illustrating a test method of stress relaxation property.

FIG. 2 is a schematic explanatory view for illustrating a test method of solder adhesiveness.

DISCLOSURE OF INVENTION

According to the present invention, there is provided the following means:

(1) A copper alloy for electric and electronic instruments, comprising Ni of 1 to 3 mass %, Ti of 0.2 to 1.2 mass %, any one or both of Mg and Zr of 0.02 to 0.2 mass %, and Zn of 0.1 to 1 mass %, with the balance being Cu and unavoidable impurities,

wherein the copper alloy contains at least one of an intermetallic compound comprising Ni, Ti and Mg, an intermetallic compound comprising Ni, Ti and Zr, or an intermetallic compound comprising Ni, Ti, Mg and Zr, and wherein the copper alloy has a stress relaxation rate of 20% or less after holding the alloy at 150° C. for 1,000 hours;

(2) The copper alloy for electric and electronic instruments according to the above item (1),

wherein the intermetallic compound comprising Ni, Ti and Mg, the intermetallic compound comprising Ni, Ti and Zr, or the intermetallic compound comprising Ni, Ti, Mg and Zr has an average particle diameter in the range from 5 to 100 nm and a distribution density of from 1×1010 to 1×1013/mm2, and

wherein the crystal grain size of a host matrix of the alloy is 10 μm or less;

(3) A copper alloy for electric and electronic instruments, comprising Ni of 1 to 3 mass %, Ti of 0.2 to 1.2 mass %, any one or both of Sn and Si of 0.02 to 0.2 mass %, and Zn of 0.1 to 1 mass %, with the balance being Cu and unavoidable impurities,

wherein the copper alloy contains at least one of an intermetallic compound comprising Ni, Ti and Sn, an intermetallic compound comprising Ni, Ti and Si, or an intermetallic compound comprising Ni, Ti, Sn and Si, and

wherein the copper alloy has a stress relaxation rate of 20% or less after holding the alloy at 150° C. for 1,000 hours;

(4) The copper alloy for electric and electronic instruments according to the above item (3),

wherein the intermetallic compound comprising Ni, Ti and Sn, the intermetallic compound comprising Ni, Ti and Si, or the intermetallic compound comprising Ni, Ti, Sn and Si has an average particle diameter in the range from 5 to 100 nm and a distribution density of from 1×1010 to 1×1013/mm2, and

wherein the crystal grain size of a host matrix of the alloy is 10 μm or less;

(5) A method of producing the copper alloy for electric and electronic instruments according to any one of the above items (1) to (4), comprising the steps of:

conducting a solution heat treatment at a temperature of 850° C. or more for 35 seconds or less,

cooling from the solution heat treatment temperature to 300° C. at a cooling rate of 50° C./sec or more,

cold-rolling at a cold rolling ratio in the range of more than 0% but 50% or less, and

aging at a temperature in the range from 450 to 600° C. within 5 hours;

(6) A method of producing the copper alloy for electric and electronic instruments according to any one of the above items (1) to (4), comprising the steps of:

conducting a solution heat treatment at a temperature of 850° C. or more for 35 seconds or less,

cooling from the solution heat treatment temperature to 300° C. at a cooling rate of 50° C./sec or more, and

aging at a temperature in the range from 450 to 600° C. within 5 hours;

(7) A copper alloy for electric and electronic instruments, comprising Ni of 1 to 3 mass % and Ti of 0.2 to 1.4 mass % with a ratio (Ni/Ti) of the mass percentage between Ni and Ti in the range from 2.2 to 4.7, any one or both of Mg and Zr in a total amount of 0.02 to 0.3 mass %, and Zn of 0.1 to 5 mass %, with the balance being Cu and unavoidable impurities,

wherein the copper alloy contains at least one of an intermetallic compound comprising Ni, Ti and Mg, an intermetallic compound comprising Ni, Ti and Zr or an intermetallic compound comprising Ni, Ti, Mg and Zr, and

wherein the copper alloy has a distribution density of the intermetallic compound in the range from 1×109 to 1×1013/mm2, a tensile strength of 650 MPa or more, an electric conductivity of 55% IACS or more, and a stress relaxation rate of 20% or less after holding the alloy at 150° C. for 1,000 hours;

(8) A copper alloy for electric and electronic instruments, comprising Ni of 1 to 3 mass % and Ti of 0.2 to 1.4 mass % with a ratio (Ni/Ti) of the mass percentage between Ni and Ti in the range from 2.2 to 4.7, any one or both of Mg and Zr in a total amount of 0.02 to 0.3 mass %, Zn of 0.1 to 5 mass %, and Sn in the range of more than 0 mass % but 0.5 mass % or less, with the balance being Cu and unavoidable impurities,

wherein the copper alloy contains at least one of an intermetallic compound comprising Ni, Ti and Mg, an intermetallic compound comprising Ni, Ti and Zr or an intermetallic compound comprising Ni, Ti, Mg and Zr, and

wherein the copper alloy has a distribution density of the intermetallic compound in the range from 1×109 to 1×1013/mm2, a tensile strength of 650 MPa or more, an electric conductivity of 55% IACS or more, and a stress relaxation rate of 20% or less after holding the alloy at 150° C. for 1,000 hours;

(9) A copper alloy for electric and electronic instruments, comprising Ni of 1 to 3 mass % and Ti of 0.2 to 1.4 mass % with a ratio (Ni/Ti) of the mass percentage between Ni and Ti in the range from 2.2 to 4.7, Mg of 0.02 to 0.3 mass %, Zn of 0.1 to 5 mass %, and any one or at least two of Zr, Hf, In and Ag in a total amount of more than 0 mass % but 1.0 mass % or less, with the balance being Cu and unavoidable impurities,

wherein the copper alloy contains at least one of an intermetallic compound comprising Ni, Ti and Mg, an intermetallic compound comprising Ni, Ti and Zr, or an intermetallic compound comprising Ni, Ti, Mg and Zr, and

wherein the copper alloy has a distribution density of the intermetallic compound in the range from 1×109 to 1×1013/mm2, a tensile strength of 650 MPa or more, an electric conductivity of 55% IACS or more, and a stress relaxation rate of 20% or less after holding the alloy at 150° C. for 1,000 hours;

(10) A copper alloy for electric and electronic instruments, comprising Ni of 1 to 3 mass % and Ti of 0.2 to 1.4 mass % with a ratio (Ni/Ti) of the mass percentage between Ni and Ti in the range from 2.2 to 4.7, Mg of 0.02 to 0.3 mass %, Zn of 0.1 to 5 mass %, Sn in the range of more than 0 mass % but 0.5 mass % or less, and any one or at least two of Zr, Hf, In and Ag in a total amount of more than 0 mass % but 1.0 mass % or less, with the balance being Cu and unavoidable impurities,

wherein the copper alloy contains at least one of an intermetallic compound comprising Ni, Ti and Mg, an intermetallic compound comprising Ni, Ti and Zr, or an intermetallic compound comprising Ni, Ti, Mg and Zr, and

wherein the copper alloy has a distribution density of the intermetallic compound in the range from 1×109 to 1×1013/mm2, a tensile strength of 650 MPa or more, an electric conductivity of 55% IACS or more, and a stress relaxation rate of 20% or less after holding the alloy at 150° C. for 1,000 hours; and

(11) A method of producing the copper alloy for electric and electronic instruments according to any one of the above items (7) to (10), which comprises applying once or at least twice of heat treatment for precipitation by aging at a temperature of from 450 to 650° C. within 5 hours,

wherein an electric conductivity before the heat treatment for precipitation by aging is 35% IACS or less.

Hereinafter, a first embodiment of the present invention means to include the copper alloys for electric and electronic instruments described in the items (1) to (4) above and the methods of producing the copper alloy for electric and electronic instruments described in the items (5) to (6) above.

A second embodiment of the present invention means to include the copper alloys for electric and electronic instruments described in the items (7) to (10) above and the method of producing the copper alloy for electric and electronic instruments described in the item (11) above.

Herein, the present invention means to include both of the above first and second embodiments, unless otherwise specified.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention is explained in detail below.

In the course of studies for strengthening the copper alloy with an intermetallic compound comprising nickel (Ni) and titanium (Ti) by a precipitation reinforcement method in which a second phase is precipitated, the present inventors have found that a material capable of substantially satisfying the desired properties such as the strength, electric conductivity, bending property, stress relaxation resistance and solder adhesiveness can be produced by modifying the intermetallic compound by adding magnesium (Mg), zirconium (Zr), tin (Sn), silicon (Si) or the like.

The electric and electronic instruments of the present invention, particularly of the first embodiment of the present invention, include instruments mounted for a car.

The first embodiment of the present invention will be described below.

Various properties of an alloy are remarkably improved in the present invention, particularly in the first embodiment of the present invention, by forming an intermetallic compound comprising Ni, Ti and Mg (referred to as “Ni—Ti—Mg” hereinafter), an intermetallic compound comprising Ni, Ti and Zr (referred to as “Ni—Ti—Zr” hereinafter), or an intermetallic compound comprising Ni, Ti, Mg and Zr (referred to as “Ni—Ti—Mg—Zr” hereinafter) precipitated in the Cu host matrix. These intermetallic compounds are utterly different from Ni—Ti precipitates formed in conventional alloys, and provide quite high strength, electric conductivity and stress relaxation resistance property.

As described above, the strength is improved by precipitation strengthening mechanism while the electric conductivity increases, when the Ni—Ti is finely dispersed in the Cu host matrix. However, the magnitude of reinforcement becomes quite large, as compared with precipitation of the Ni—Ti, by allowing the Ni—Ti—Mg, the Ni—Ti—Zr or the Ni—Ti—Mg—Zr to finely disperse individually or compositely in the Cu host matrix. This effect permits materials having excellent strength and electric conductivity to be obtained. This effect is exhibited even when the Ni—Ti is simultaneously dispersed, and the magnitude of reinforcement is larger as the dispersion density of the Ni—Ti—Mg, the Ni—Ti—Zr or the Ni—Ti—Mg—Zr is higher. In this case, the amount of the dispersion density of the Ni—Ti—Mg, the Ni—Ti—Zr or the Ni—Ti—Mg—Zr is desirably equal to or more than that of the Ni—Ti.

The same effect as described above could be also observed when an intermetallic compound comprising Ni, Ti and Sn (referred to as “Ni—Ti—Si” hereinafter), an intermetallic compound comprising Ni, Ti and Si (referred to as “Ni—Ti—Si” hereinafter) or an intermetallic compound comprising Ni, Ti, Sn and Si (referred to as “Ni—Ti—Sn—Si” hereinafter) had been precipitated.

Next, the stress relaxation property will be described below. The stress relaxation resistance property is remarkably improved when the Ni—Ti—Mg, the Ni—Ti—Zr or the Ni—Ti—Mg—Zr is finely, and individually or compositely, dispersed in the Cu host matrix, as compared with the case when the Ni—Ti is finely dispersed in the host matrix. On the contrary, a stress relaxation rate of 20% or less cannot be achieved when only the Ni—Ti is precipitated.

This may be interpreted that, since the Ni—Ti—Mg, the Ni—Ti—Zr or the Ni—Ti—Mg—Zr has a different crystal structure from that of the Ni—Ti compound, the stress relaxation resistance property is remarkably improved by finely dispersing such intermetallic compound having the different crystal structure in the Cu host matrix.

Stress relaxation is a phenomenon by which the strain is released by allowing dislocations in the metal to move. Since the Ni—Ti—Mg, the Ni—Ti—Zr or the Ni—Ti—Mg—Zr has a larger force for fixing the dislocations than the Ni—Ti compound, the stress is hardly relaxed in the alloy containing the former intermetallic compound.

The same phenomenon is confirmed in the alloy containing the Ni—Ti—Sn, the Ni—Ti—Si or the Ni—Ti—Sn—Si. A material being excellent in the stress relaxation resistance property and having the desired properties can be produced by forming these precipitates in the alloy.

The desired properties can be obtained by prescribing the amount of components as described below.

The content of Ni is limited in the range from 1 to 3 mass %, because a sufficient strength cannot be obtained due to a small amount of reinforcement by precipitation when the content of Ni is too small, and the stress relaxation resistance property cannot be improved. On the other hand, a too large amount of Ni causes a decrease of the electric conductivity even after the aging treatment because an excess amount of Ni is solute in the host matrix. In addition, the alloy cannot be produced by an industrially stable process since the temperature for the solution heat treatment (solid solution treatment) comes to near the melting temperature. Further, it is another problem that the bending property becomes poor due to coarsening of crystal grains since a long time of the solution heat treatment at a higher temperature is necessary. The content of Ni is preferably in the range from 1.4 to 2.6 mass %, and more preferably in the range from 1.8 to 2.3 mass %.

The content of Ti is limited in the range from 0.2 to 1.2 mass % because, when the content of Ti is too small, a sufficient strength cannot be obtained due to a small amount of reinforcement by precipitation, and the stress relaxation resistance property cannot be improved. On the other hand, a too large amount of Ti causes a decrease of the electric conductivity even after the aging treatment because an excess amount of Ti is solute in the host matrix. In addition, it is another problem that the bending property becomes poor due to coarsening of crystal grains since a long time of the solution heat treatment at a higher temperature is necessary. The content of Ti is preferably in the range from 0.5 to 1.1 mass %, more preferably in the range from 0.7 to 1.0 mass %.

Mg forms an intermetallic compound (also referred to as a “precipitate” hereinafter) together with Ni, Ti, Zr and the like, and improves the strength, electric conductivity, bending property, stress relaxation resistance property, and the like. The content of Mg is limited in the range from 0.02 to 0.2 mass % because, when the content of Mg is too small, the stress relaxation rate becomes poor due to a small amount of the precipitate comprising Ni, Ti and Mg or the like. On the other hand, the bending property becomes poor due to coarsening of crystal grains when the amount of Mg is too large, since a high temperature and long time of the solution heat treatment is required. In addition, the electric conductivity is poor even by applying an aging treatment since excess Mg remains in the solid solution. The stress relaxation rate also becomes poor probably due to a different proportion of constitution elements in the precipitate. The content of Mg is preferable in the range from 0.05 to 0.15 mass %, and more preferable in the range from 0.08 to 0.12 mass %.

The content of Zr is limited in the range from 0.02 to 0.2 mass % by the same reason as limiting the content of Mg. The content of Zr is preferably in the range from 0.05 to 0.15 mass %, and more preferably in the range from 0.08 to 0.12 mass %.

Sn forms a precipitate together with Ni, Ti and Si, and improves the strength, electric conductivity, bending property, stress relaxation resistance property, and the like. The content of Sn is limited in the range from 0.02 to 0.2 mass % because, when the amount of Sn is too small, the stress relaxation rate becomes poor due to a too small amount of the precipitate comprising Ni, Ti and Sn or the like. The electric conductivity and bending property become poor when the amount of Sn is too large since excess Sn remains in the solid solution. The stress relaxation rate is also poor probably due to the effect of a different proportion of constitution elements in the precipitate. The content of Sn is preferably in the range from 0.05 to 0.15 mass %, and more preferably in the range from 0.08 to 0.12 mass %.

The content of Si is limited in the range from 0.02 to 0.2 mass % because, when the content of Si is too small, the strength and stress relaxation resistance property become poor due to a small amount of the precipitate comprising Ni, Ti and Si or the like, and the electric conductivity becomes poor since excess Ni remains in the solid solution. The electric conductivity decreases when the content of Si is too large, since excess Si is solute in the copper host matrix when a desired precipitate is formed. The content of Si is preferably in the range from 0.05 to 0.15 mass %, and more preferably in the range from 0.08 to 0.12 mass %.

The average particle diameter of the intermetallic compound is usually in the range from 1 to 100 nm, preferably in the range from 5 to 100 nm, as a diameter of corresponding spheres having an equal volume to the volume of the intermetallic compound. A distribution density in the range from 1×1010 to 1×1013/mm2 is preferable since the alloy becomes excellent in the strength and bending property.

The effect for improving the strength is insufficient when the average particle diameter of the intermetallic compound is too small, while the intermetallic compound does not contribute for improving the strength by precipitation when the average particle diameter is too large. The average particle diameter is further preferably in the range from 10 to 60 nm, and more preferably in the range from 20 to 50 nm. The average particle diameter of the intermetallic compound is controlled by the heating temperature and heating time in the aging step. A higher temperature or longer time gives a larger average particle diameter. On the contrary, a lower temperature or shorter time gives a smaller average particle diameter.

When the distribution density of the intermetallic compound is too small, the effect for improving the strength by precipitation becomes insufficient, while coarse precipitates tend to be formed at grain boundaries to deteriorate the bending property when the distribution density is too large. The distribution density is further preferably in the range from 3×1010 to 5×1012/mm2, more preferably in the range from 1×1011 to 3×1012/mm2. The distribution density of the intermetallic compound is controlled by appropriately combining the conditions for the heat treatment for precipitation by aging, cold working that is applied prior to the heat treatment for precipitation by aging, solution heat treatment and hot rolling. The distribution density of the precipitates is calculated as the number of the precipitates per unit area (number/mm2) by measuring the number of the precipitates with a transmission electron microscope observation.

The crystal grain size of the host matrix is preferably 10 μm or less. The bending property is deteriorated when the crystal grain size of the host matrix is too large. The preferable diameter is 5 μm or less. While the lower limit of the crystal grain size of the host matrix is not particularly restricted, it is usually 3 μm. The crystal grain size as used herein refers to the longer diameter of the grains. The crystal grain size of the host matrix is controlled by the heating temperature and heating time in the solution heat treatment step. The higher temperature or longer time gives a larger crystal grain size, while the lower temperature or shorter time gives a smaller crystal grain size.

Zn improves adhesiveness of a solder and prevents plating from being peeled. A preferable use of the present invention is electronic instruments, and most of parts thereof are joined with a solder. Accordingly, improved adhesiveness of the solder causes an improvement of reliability of the parts, which is an essential property for applying to the electronic instruments. The effect of Zn has been discussed in recent years (for example, see Sindo Gijutu Kennkyuukai Shi (Journal of Japan Copper and Brass Association), Vol. 026 (1987), pp. 51-56). This report describes that adding Zn improves heat-peeling resistance. The heat-peeling resistance is considered to be improved by adding Zn, because voids are suppressed from being generated, and they are suppressed from being concentrated at the interface between the host material comprising Ni and Si and diffusion layers. While the example above is for alloys of precipitation type such as Cu—Ni—Si alloys, the same effect has been confirmed in the first embodiment of the present invention.

The content of Zn is limited in the range form 0.1 to 1 mass % because, when the content of Zn is too small, the heat-peeling resistance property is not exhibited, while the electric conductivity is reduced when the content of Zn is too large. The content of Zn is preferably in the range from 0.2 to 0.8 mass %, more preferably in the range from 0.35 to 0.65 mass %.

The stress relaxation rate of the copper alloy for electric and electronic instruments according to the present invention, particularly according to the first embodiment of the present invention, is 20% or less when the alloy is held at 150° C. for 1,000 hours. The rate is preferably 18% or less, and more preferably 16% or less; and although the lower limit is not particularly restricted, it is 10%.

The copper alloy according to the present invention, particularly according to the first embodiment of the present invention, is produced through the steps comprising, for example, hot rolling, cold rolling, solution heat treatment and aging treatment, and if necessary finish cold rolling and stress-relief annealing. The intermetallic compound may be adjusted within the range of the present invention by controlling the conditions, such as the solution heat treatment (temperature) and cooling rate in the subsequent cooling step, in the production process. The hot rolling temperature may be, for example, in the range from 850 to 1,000° C., and the subsequent cold rolling may be conducted at the processing ratio of, for example, 90% or more.

An embodiment of the production method according to the present invention, particularly according to the first embodiment of the present invention, comprises the steps of: conducting a solution heat treatment at 850° C. or more within 35 seconds, cooling from the solution heat treatment temperature to 300° C. at a cooling rate of 50° C./sec or more, cold-rolling at a rolling ratio in the range of more than 0% but 50% or less, and aging at a temperature in the range from 450 to 600° C. within 5 hours. Another embodiment of the production method according to the present invention, particularly according to the first embodiment of the present invention, comprises the steps of: conducting a solution heat treatment at 850° C. or more within 35 seconds, cooling from the solution heat treatment temperature to 300° C. at a cooling rate of 50° C./sec or more, and aging at a temperature from 450 to 600° C. within 5 hours. The finish cold rolling ratio thereafter is preferably 30% or less.

The solution heat treatment is preferably conducted at 850° C. or more within 35 seconds in the present invention, particularly in the first embodiment of the present invention. Recrystallization does not occur when the solution heat treatment temperature is too low, resulting in remarkably deterioration in bending property. Further, solid solutions are not formed even by recrystallization to make it impossible to attain the highest precipitation reinforcement in the subsequent aging step due to the presence of crystallized grains, coarse precipitates or the like. Furthermore, deterioration of the bending property is also apprehended due to the presence of residual crystals, precipitates or the like. The alloy is preferably cooled to 300° C. at a cooling rate of 50° C./sec or more after the solution heat treatment, because when the cooling rate is too small, the elements once incorporated into the solid solution are precipitated. Such precipitates do not contribute to strengthening due to their coarsening.

The upper limit of the solution heat treatment temperature is preferably 1,000° C. or less from the view point of fuel cost. Too long solution heat treatment time causes deterioration of the bending property due to coarsening of crystal grains. The solution heat treatment time is preferably within 25 seconds.

It is preferably that the cold rolling after the solution heat treatment is not conducted, or is conducted at a cold rolling ratio of 50% or less. The higher cold rolling ratio causes deterioration of the bending property. The ratio is more preferably 30% or less.

The aging treatment is preferably conducted at a temperature from 450 to 600° C. within 5 hours. Too low aging treatment temperature results in insufficient strength due to an insufficient amount of precipitates, while too high aging treatment temperature does not contribute to the strength since the precipitates get coarse. The aging treatment temperature is preferably in the range from 480 to 560° C.

The direction of final plastic working as used in the present invention, in particular in the first embodiment of the present invention, refers to the direction of rolling when the rolling is the finally carried out plastic working, or to the direction of drawing when the drawing (linear drawing) is the plastic working finally carried out. The plastic working refers to workings such as rolling and drawing, but working for the purpose of leveling (vertical leveling) using, for example, a tension leveler, is not included in this plastic working.

Next, the second embodiment of the present invention will be described below.

Various properties of the alloy are remarkably improved in the present invention, particularly in the second embodiment of the present invention, by forming an intermetallic compound comprising Ni, Ti and Mg (referred to as “Ni—Ti—Mg” hereinafter), an intermetallic compound comprising Ni, Ti and Zr (referred to as “Ni—Ti—Zr” hereinafter), or an intermetallic compound comprising Ni, Ti, Mg and Zr (referred to as “Ni—Ti—Mg—Zr” hereinafter) precipitated in the Cu host matrix. These intermetallic compounds are utterly different from Ni—Ti precipitates formed in conventional alloys, and provide quite high strength, electric conductivity and stress relaxation resistance property.

As described above, the strength is improved by precipitation strengthening mechanism while the electric conductivity increases, when the Ni—Ti is finely dispersed in the Cu host matrix. However, the magnitude of reinforcement becomes quite large, as compared with precipitation of the Ni—Ti, by allowing the Ni—Ti—Mg, the Ni—Ti—Zr or the Ni—Ti—Mg—Zr to finely disperse individually or compositely in the Cu host matrix. This effect permits materials having excellent strength and electric conductivity to be obtained. This effect is exhibited even when the Ni—Ti is simultaneously dispersed, and the magnitude of reinforcement is larger as the dispersion density of the Ni—Ti—Mg, the Ni—Ti—Zr or the Ni—Ti—Mg—Zr is higher. In this case, the amount of the dispersion density of the Ni—Ti—Mg, the Ni—Ti—Zr or the Ni—Ti—Mg—Zr is desirably equal to or more than that of the Ni—Ti. These Ni—Ti base ternary or multi-component compounds can contribute to the improvement of the stress relaxation resistance property.

Both the strength and stress relaxation resistance property may be improved, without reducing the electric conductivity, by allowing appropriate amounts of Mg or Sn to be in the solid solution.

The desired properties may be obtained by prescribing the amount of components as described below.

The content of Ni is limited in the range from 1 to 3 mass %, because a sufficient strength cannot be obtained due to a small amount of reinforcement by precipitation when the content of Ni is too small, and the stress relaxation resistance property cannot be improved. On the other hand, a too large amount of Ni causes a decrease of the electric conductivity even after the aging treatment because an excess amount of Ni is solute in the host matrix. In addition, the alloy cannot be produced by an industrially stable process since the temperature for the solution heat treatment comes to near the melting temperature. Further, it is another problem that the bending property becomes poor due to coarsening of crystal grains since a long time of the solution heat treatment at a higher temperature is necessary. The content of Ni is preferably in the range from 1.2 to 2.4 mass %, and more preferably in the range from 1.4 to 2.2 mass %.

The content of Ti is limited in the range from 0.2 to 1.4 mass % because, when the content of Ti is too small, a sufficient strength cannot be obtained due to a small amount of reinforcement by precipitation, and the stress relaxation resistance property cannot be improved. On the other hand, a too large amount of Ti causes a decrease of the electric conductivity even after the aging treatment because an excess amount of Ti is solute in the host matrix. In addition, it is another problem that the bending property becomes poor due to coarsening of crystal grains since a long time of the solution heat treatment at a higher temperature is necessary. The content of Ti is preferably in the range from 0.3 to 1.0 mass %, more preferably in the range from 0.35 to 0.9 mass %.

The ratio (Ni/Ti) in the mass percentage between Ni and Ti is limited in the range form 2.2 to 4.7 because both elements should be blended in an appropriate ratio in order to allow the multi-component compounds, such as Ni—Ti base or Ni—Ti—Mg base compounds, to be precipitated as a compound having a stoichiometric composition in Cu. The ratio out of this range is not preferable since the solute elements do not contribute to the formation of the compound and they reduce the electric conductivity by being in the solid solution. The ratio (Ni/Ti) is preferable in the range from 2.6 to 3.8, more preferably in the range form 2.8 to 3.6.

Mg forms an intermetallic compound (also referred to as a “precipitate” hereinafter) together with Ni, Ti and Zr, and improves the strength, electric conductivity, bending property, stress relaxation resistance property, and the like. The content of either or both of Mg and Zr in total is limited in the range from 0.02 to 0.3 mass % because, when the content is too small, the strength becomes poor since the amount of the precipitate comprising Ni, Ti and Mg, the precipitate comprising Ni, Ti and Zr and/or the precipitate comprising Ni, Ti, Mg and Zr is small. When the content is too large, on the other hand, a high temperature and a long time is necessary for the solution heat treatment, and crystal grains get coarse to deteriorate the bending property. In addition, excess Mg and/or Zr remains in the solid solution even by conducting an aging treatment, and the electric conductivity is poor. The content of either or both of Mg and Zr in total is preferably in the range from 0.05 to 0.18 mass %, and more preferably in the range from 0.08 to 0.15 mass %.

The distribution density of the intermetallic compound in the range from 1×109 to 1×1013/mm2 is preferable because the ratio gives excellent strength and bending property.

When the distribution density of the intermetallic compound is too small, the effect for improving the strength by precipitation becomes insufficient, while coarse precipitates tend to be formed at grain boundaries to deteriorate the bending property when the distribution density is too large. The distribution density is further preferably in the range from 3×1010 to 5×1012/mm2, more preferably in the range from 1×1011 to 3×1012/mm2. The distribution density of the intermetallic compound is controlled by appropriately combining the conditions for the heat treatment for precipitation by aging, cold working that is applied prior to the heat treatment for precipitation by aging, solution heat treatment and hot rolling.

The distribution density of the precipitates is calculated as the number of the precipitates per unit area (number/mm2) by measuring the number of the precipitates with a transmission electron microscope observation.

Zn improves adhesiveness of a solder and prevents plating from being peeled. A preferable use of the present invention is electronic instruments, and most of parts thereof are joined with a solder. Accordingly, improved adhesiveness of the solder causes an improvement of reliability of the parts, which is an essential property for applying to the electronic instruments. The effect of Zn has been discussed in recent years (for example, see Sindo Gijutu Kennkyuukai Shi (Journal of Japan Copper and Brass Association), Vol. 026 (1987), pp. 51-56). This report describes that adding Zn improves heat-peeling resistance. The heat-peeling resistance is considered to be improved by adding Zn, because voids are suppressed from being generated, and they are suppressed from being concentrated at the interface between the host material comprising Ni and Si and diffusion layers. While the example above is for alloys of precipitation type such as Cu—Ni—Si alloys, the same effect has been confirmed in the second embodiment of the present invention.

The content of Zn is limited in the range form 0.1 to 5 mass % because, when the content of Zn is too small, the heat-peeling resistance property is not exhibited, while the electric conductivity is reduced when the content of Zn is too large. The content of Zn is preferably in the range from 0.2 to 3.0 mass %, more preferably in the range from 0.3 to 1 mass %.

Sn is solute in the solid solution with Mg and serves for improving the stress relaxation resistance property. The element is effective for suppressing coarse Ni—Ti from precipitating in the cooling step of the solution heat treatment and the hot rolling conducted at a temperature of 900° C. or more, and resulting in improving the strength by enhancing the magnitude of precipitation hardening. Since the alloy system of the present invention permits an ideal solid solution state, in which almost all atoms are in the solid solution, to be formed at a temperature as high as 900° C. or more, it is important for attaining good precipitation reinforcement to prevent coarse compounds from precipitating at a high temperature where atomic diffusion is rapid. This state is favorably realized by adding Sn, and the strength and stress relaxation resistance property are improved by aging precipitation. Further, Sn can prevent coarse compounds from precipitating at grain boundaries, to improve the bending property. While the effect is enhanced as the content of Sn is larger, the electric conductivity becomes poor when the content of Sn is too large since excess Sn remains in the solid solution. The content of Sn is generally in the range of more than 0 mass % but 0.5 mass % or less, preferably in the range from 0.05 to 0.25 mass %.

Zr, Hf, In and Ag improve the strength, electric conductivity, stress relaxation resistance property, and the like by forming precipitates together with Ni and Ti. While the effect is enhanced as the contents of these elements are higher, the bending property is deteriorated due to coarsening of crystal grains when the contents exceed 1.0 mass % since the solution heat treatment at a high temperature for a long time is necessary. In addition, the electric conductivity is also deteriorated since excess atoms remain in the solid solution even by conducting an aging treatment. The total content of Zr, Hf, In and Ag is in the range of more than 0 mass % but 1.0 mass % or less, preferably in the range from 0.05 to 0.5 mass %, and more preferably in the range from 0.07 to 0.3 mass %.

The tensile strength of the copper alloy for the electric and electronic instruments of the present invention, particularly of the second embodiment of the present invention, is 650 MPa or more. The tensile strength is preferably 750 MPa or more. Although the upper limit is not particularly restricted, it is generally 850 MPa.

The electric conductivity of the copper alloy for the electric and electronic instruments of the present invention, particularly of the second embodiment of the present invention, is 55% IACS or more. The electric conductivity is preferably 60% IACS or more. Although the upper limit is not particularly restricted, it is generally 70% IACS.

The stress relaxation rate of the copper alloy for electric and electronic instruments according to the present invention, particularly according to the second embodiment of the present invention, is 20% or less when the alloy is held at 150° C. for 1,000 hours. The rate is preferably 18% or less, and more preferably 16% or less; and although the lower limit is not particularly restricted, it is 10%.

The copper alloy according to the present invention, particularly according to the second embodiment of the present invention, is produced by the steps of: for example, casting, homogenization treatment, hot rolling, cold rolling, solution heat treatment and aging treatment, and, if necessary, finish cold rolling and stress-relief annealing.

While the cooling rate is preferably increased for preventing solute elements from segregating at finally solidified portions at the time of casting, a too rapid cooling rate may form cavities in a resulting ingot to deteriorate the quality or to generate internal defects by enhancing the internal stress of a resulting ingot. Accordingly, the cooling rate is preferably in the range of 1 to 100° C./sec, more preferably in the range from 10 to 80° C./sec.

The alloy is preferably homogenized by annealing at a temperature above the solution heat temperature in accordance with the atomic weight of the solute in the alloy in order to form a solid solution while coarse Ni—Ti base compounds are prevented from precipitating. Homogenizing annealing at a higher temperature than necessary is not preferable since oxidation of elements such as Ti, Mg, Zr and Hf is facilitated to deteriorate such quality as adhesiveness of plating. Accordingly, the temperature for holding an ingot before hot rolling is usually in the range from 800 to 1,050° C., preferably from 900 to 1,000° C., and more preferably from 960 to 1,000° C. The holding time is preferably in the range from 1 hour or more to 10 hours or less in order to make the elements to be solute sufficiently in the solid solution and prevent oxidization. The heating rate is preferably 3° C./min or more, since coarse precipitates are formed when the heating rate to the holding temperature is slow.

The cooling rate is usually increased by showering cold water at a temperature of 20° C. or lower or other methods in order to suppress solute atoms from precipitating in the cooling step during the time from the start to the end of the hot rolling. The cooling rate is preferably in the range from 5 to 300° C./sec, more preferably 50 to 300° C./sec.

Excellent strength, electric conductivity, stress relaxation resistance property and bending property may be obtained by conducting a heat treatment(s) for precipitation by aging once or twice at a temperature in the range from 450 to 650° C. for within 5 hours during the step for reducing the thickness of the alloy by cold rolling.

The strength and electric conductivity become insufficient due to too low heat treatment temperature for precipitation by aging, while the precipitates do not contribute to the strength when the temperature is too high since the precipitates get coarse. The temperature is preferably in the range from 480 to 620° C.

The heat treatment time for precipitation by aging is preferably within 4 hours, and the lower limit thereof is 0.1 hour.

The strength and electric conductivity are further improved by conducting the heat treatment steps for precipitation by aging two or more times with a cold rolling step between the heat treatment steps. The density of dislocations to be introduced in the next cold rolling step may be increased by the fine compounds precipitated in the first aging step, and the dislocations serve as sites for forming a nucleus for precipitation in the second heat treatment step and thereafter for precipitation by aging. Consequently, the strength is further enhanced by increasing the density of the precipitates. Accordingly, the condition for the first aging step is preferably employed so that the highest density of the precipitates is obtained.

The effect of the heat treatment for precipitation by aging is remarkably emphasized by increasing the amount of the solute atoms in the solid solution as large as possible before precipitation of the atoms. In other words, properties such as high strength, high electric conductivity and high stress relaxation resistance may be manifested by forming a good solid solution state before the heat treatment for precipitation by aging in order to permit highly dense and fine precipitation state to be realized by the heat treatment for precipitation by aging. The electric conductivity is usually used as an index of the degree of the solid solution, and the strength and stress relaxation resistance property are improved when the electric conductivity before the heat treatment for precipitation by aging is 35% IACS or less. The strength and stress relaxation resistance become poor when the electric conductivity is more than 35% IACS, since the amount of the solute atoms that are finely precipitated in a high density is small after the heat treatment for precipitation by aging. It is more preferably 30% IACS or less.

The direction of final plastic working as used in the present invention, in particular in the second embodiment of the present invention, refers to the direction of rolling when the rolling is the finally carried out plastic working, or to the direction of drawing when the drawing (linear drawing) is the plastic working finally carried out. The plastic working refers to workings such as rolling and drawing, but working for the purpose of leveling (vertical leveling) using, for example, a tension leveler, is not included in this plastic working.

The copper alloy for the electric and electronic instruments of the present invention may be favorably used, for example, for connectors, terminals, relays and switches, and lead frames, although its application is not restricted thereto.

According to the present invention, it is possible to provide a novel copper alloy for the electric and electronic instruments excellent in the strength, electric conductivity, bending property and stress relaxation resistance property as well as adhesiveness of solder.

The copper alloy of the present invention, in particular of the first embodiment of the present invention, has performance of 600 MPa or more in the strength, 20% or less in the stress relaxation rate after holding at 150° C. for 1,000 hours, 50% IACS or more of the electric conductivity, and 1 or less of the (R/t) ratio, which is an index of the bending property. The metallic material is suitable for terminals, connectors, and relays and switches for the electric and electronic instruments and car-mounting parts.

The copper alloy of the present invention, in particular of the second embodiment of the present invention, has performance of 650 MPa or more in the strength, 20% or less in the stress relaxation rate after holding at 150° C. for 1,000 hours and 55% IACS or more of the electric conductivity. The metallic material is suitable for the terminals, connectors, and relays and switches for the electric and electronic instruments.

The present invention will be described in more detail based on examples given below, but the invention is not meant to be limited by these.

EXAMPLES

Example 1

Alloys comprising Ni, Ti, Mg, Zr, Zn, Sn and Si in the amounts as shown in Tables 1 to 4 with the balance of Cu were melted in a high frequency melting furnace, and each molten alloy was cast with a cooling rate in the range from 10 to 30° C./sec to give an ingot with a thickness of 30 mm, a width of 100 mm and a length of 150 mm. After holding the ingot at 1,000° C. for 1 hour, it was finished to a hot roll plate with a thickness of about 10 mm using a hot rolling machine. Oxide films were removed by shaving both surfaces of the hot roll plate to a depth of about 1.0 mm. The plate was then cold-rolled to a thickness of 0.29 mm followed by subjecting to a solution heat treatment at 950° C. for 15 second in an inert gas, and was cooled to 300° C. over about 3 seconds (a cooling rate of about 300° C./sec) after the solution heat treatment. The plate was further cold-rolled to a thickness of 0.23 mm followed by an aging treatment at 550° C. for 2 hours. The plate was rolled to a thickness of 0.2 mm followed by low temperature annealing at 350° C. for 2 hours to provide plate materials of Examples 1 to 18 and 40 to 57 of the present invention, and Comparative Examples 21 to 34, 60 to 67 and 70 to 73, as test pieces.

Each plate material thus obtained was investigated with respect to [1] tensile strength, [2] electric conductivity, [3] stress relaxation property (SR), [4] bending property (R/t), [5] crystal grain size (GS), [6] size and density of precipitates (PPT) and [7] adhesiveness of solder, by the methods described below. The measuring methods for respective evaluation items are as follows.

[1] Tensile Strength (TS)

Three JIS-13B test pieces cut in the direction parallel to the roll direction were measured according to JIS-Z2241, and an average value (MPa) was obtained.

[2] Electric Conductivity (EC)

Test pieces with a dimension of 10×150 mm was prepared by cutting the plate in the direction parallel to the roll direction, and the electric conductivity of two of the test pieces was measured by the four-probe method in a constant-temperature chamber controlled at 20° C. (±1° C.) to obtain an average value (% IACS). The distance between the probes was 100 mm.

[3] Stress Relaxation Property (SR)

According to the Electronic Materials Manufacturers Association of Japan Standard EMAS-3003, the stress relaxation property was measured at 150° C. for 1,000 hours. FIG. 1 is an explanatory view for illustrating the test method of stress relaxation property. FIG. 1(a) is an explanatory view for illustrating the measuring method of the initial deflection amount δ0. In FIG. 1(a), the reference numeral 1 denotes a test piece, and the reference numeral 4 denotes a sample table. A load of 80% of 0.2% yield strength (proof stress) was applied as an initial stress using a cantilever method. And then, after the test piece was kept at 150° C. for 1,000 hours, it changed its shape so as to return to the position represented by reference numeral 2 in FIG. 1(b). The reference numeral 3 in FIG. 1(b) denotes the position of the test piece without deflection. The permanent deflection δt is represented by Ht−H1.

The stress relaxation rate (%) is represented by δt0×100. This test is used for assessing the stress change under a constant strain for a long time when it is used for a terminal material or the like, and the alloy is considered to be excellent as the stress relaxation rate is smaller.

[4] Bending Property (R/t)

The plate material was cut in a dimension of 10 mm in the width and 25 mm in the length (the direction of the length parallel to the roll direction is defined as GW and the direction of the length perpendicular to the roll direction is defined as BW), the plate was bent with a bending radius R=0 at an angle of W (90°), and the presence of cracks at the bent portion was observed using an optical microscope with 50 times magnification. As an evaluation criterion, a critical bending radius giving no cracks was measured and was expressed by R/t (R: bending radius, t: thickness of the plate).

[5] Crystal Grain Size (GS)

The crystal texture before the final processing step was observed using a scanning electron microscope (magnification of 200 to 1,000 times), and the crystal grain size was measured by the cut method according to JIS-H0501.

[6] Precipitate (PPT)

The test material was punched to give a material with a diameter of 3 mm, and the punched material was polished by a twin-jet polishing method. A photograph of the polished sample was taken using a transmission electron microscope with an acceleration voltage of 300 kV and a magnification of 5,000 to 500,000 times, and the grain size and density of the precipitates were measured based on the photograph. Local deviation of the number of the grains was eliminated by counting the number with n=10 (n denotes the number of observation spots), when the grain size and density were measured. The number obtained was converted into the number per unit area (number/mm2).

[7] Adhesiveness of Solder

Adhesiveness of solder was tested according to the explanatory view as schematically illustrated in FIG. 2. The test piece was cut into a size of 20 mm×20 mm, and the surface of the material was subjected to an electrolytic degreasing, as a pre-treatment, to obtain a material 13 with a thickness of 6 mm. A eutectic solder of Sn—Pb was piled on the surface of the material 13 to provide a solder portion 12. An iron wire 11 with a diameter φ of 2 mm (a length of about 100 mm) prepared by coating a Fe wire with Cu was fixed to the solder portion so that the material 13 was perpendicular to the wire 11 (FIG. 2(a)).

The test piece to which the wire 11 was joined was heated in air, and solder joining strength between the iron wire 11 and the material 13 was measured before and after the heating. The heating condition was at 150° C. for 500 hours in the constant temperature chamber. After taking out of the chamber, the test piece was sufficiently and gradually cooled (annealed) with air, and the tensile strength was tested in the directions of the arrow as shown in FIG. 2(b) to measure the load. The tensile strength was measured at room temperature with a load cell speed of 10 mm/min. The tensile strength was determined when the test material 13 was peeled from the interface of the solder portion 12 and the test material wire 11. The sample in which the test material was not peeled from the interface but the iron wire 11 was pulled from the solder portion 12 was not considered to be the object of evaluation, since adhesiveness between the iron wire 11 and the solder was judged to be poor.

The tensile strength before the heat treatment was also measured as described above, to determine each strength of the test material 13 before and after the heat treatment. The strength was evaluated as “◯” when the proportion of decrease of the strength was 50% or less, and the strength was evaluated as “x” when the proportion of decrease of the strength was 50% or more. Solderability was considered to be excellent with high reliability when the joining strength did not decrease with time (or the material had a high residual strength).

The precipitate was identified by an observation using a transmission electron microscope. Five to ten precipitates were analyzed with an EDX analyzer (energy dispersive apparatus) attached to the transmission electron microscope to confirm the analysis peaks of Ni, Ti, Mg, Zr, Sn and Si. Diffraction patterns were photographed with the transmission electron microscope, and it was confirmed that the precipitates gave a different diffraction pattern from that in which the Ni—Ti precipitate was formed. That is, the different diffraction pattern shows that a precipitate other than Ni—Ti was formed. The diffraction pattern was identified and evaluated by selecting crystal grains containing 10 to 100 precipitates.

The results of evaluations [1] to [7] are also summarized in Tables 1 to 4.

TABLE 1
TiPPTAdhesiveness
ThisNi(massMgZrZnTSECSRR/tR/tGSPPT(×1010/of
invention(mass %)%)(mass %)(mass %)(mass %)(MPa)(% IACS)(%)(GW)(BW)(μm)(nm)mm2)solder
11.550.570.080.5160155.3190.50.54.42021
22.110.780.120.5568552.7180.50.54.82215
32.540.940.140.4270250.8160.50.54.7206
42.901.070.180.4473248.2141.01.04.92116
51.560.580.070.5160555.7170.50.54.820163
62.080.770.110.2567552.0150.50.54.82365
72.510.930.130.5569450.2140.50.54.941156
82.951.090.190.6074549.0121.01.04.1205
92.010.740.050.4468153.8190.50.54.2235
102.100.780.110.5071051.7160.50.54.33315
112.140.790.050.5272350.8180.50.54.32254
122.150.800.050.4672750.6150.50.54.42162
132.020.750.070.080.5268453.5180.50.54.42346
142.050.760.100.100.5169452.9140.50.54.8125
152.010.740.060.080.5068153.8190.50.5413165
162.170.800.090.060.7073350.1150.50.54.2336
172.100.580.100.2371051.7170.50.54.9812
182.110.550.110.6671451.5160.50.54.332165

TABLE 2
NiTiMgAdhesiveness
Comparative(mass(mass(massZrZnTSECSRR/tR/tGSPPTPPTof
example%)%)%)(mass %)(mass %)(MPa)(% IACS)(%)(GW)(BW)(μm)(nm)(×1010/mm2)solder
210.880.330.4550659.3410.50.54.223123
223.301.220.3470138.2332.02.012.42415
233.510.380.4448832481.51.513.32253
242.912.500.5468532.7332.02.013.2126
252.200.810.010.5570250.8350.50.54.84353
262.100.780.550.5573242.3252.02.04.534125
272.080.770.010.3462256.0401.01.012.523265
282.120.790.600.5563343.6222.02.010.94446
292.110.78 0.005 0.0070.2361255.4441.01.011.54515
302.080.770.560.660.3062241.6282.02.012.223156
312.530.940.2072138.1181.01.04.43222X
322.100.780.1372337.3191.01.04.94434X
332.200.810.231.5071239.3190.50.55.53454
342.901.070.302.0273338.3190.50.53.95443

TABLE 3
NiTiAdhesiveness
This(mass(massSnSiZnTSECSRR/tR/tGSPPTPPTof
invention%)%)(mass %)(mass %)(mass %)(MPa)(% IACS)(%)(GW)(BW)(μm)(nm)(×1010/mm2)solder
401.640.650.080.4360454.7200.50.54.42112
412.160.790.130.5268851.8170.50.54.523105
422.631.030.150.3670550.8140.50.54.52798
432.901.150.190.4273547.6121.01.04.62215
441.600.670.080.4760854.9170.50.54.62766
452.080.860.120.1967951.7150.50.54.23124
462.570.960.140.5069749.5110.50.54.34315
472.971.130.190.5874848.7111.01.04.72215
482.080.750.060.4368453.4170.50.54.84523
492.140.820.150.4771450.9150.50.54.23324
502.220.820.060.4372750.4170.50.54.52342
512.250.840.110.4373049.7130.50.54.02145
522.030.760.080.090.5268853.0160.50.54.22516
532.130.810.120.110.4469852.7120.50.54.61331
542.020.780.070.080.4268453.2200.50.54.415156
552.260.890.090.150.6373649.4140.50.54.335264
562.160.650.100.1871451.0150.50.54.7951
572.170.580.120.6371751.0140.50.54.73655

TABLE 4
NiTiSnAdhesiveness
Comparative(mass(mass(massSiZnTSECSRR/tR/tGSPPTPPTof
example%)%)%)(mass %)(mass %)(MPa)(% IACS)(%)(GW)(BW)(μm)(nm)(×1010/mm2)solder
600.950.420.3750958.4390.50.54.927135
613.331.250.2570444.3312.02.011.52515
623.590.440.3949241.0471.51.512.52356
632.912.500.4768838.3322.02.012.2135
642.270.840.010.5070550.2330.50.54.44542
652.180.830.560.5373541.4242.02.04.23412
662.150.820.010.2662655.0391.01.510.52726
672.150.800.620.4763643.2222.02.010.24466
702.310.890.0371150.7330.50.54.13433X
712.220.850.2673342.3340.50.54.24555X
722.320.760.381.4769939.0241.01.04.93734
732.330.560.161.9568336.2302.02.010.85533

As is clear from the Tables 1 and 3, the Examples 1 to 18 and 40 to 57 according to the present invention had good properties with a stress relaxation resistance of 20% or less.

On the contrary, the Comparative Example 21 was poor in the tensile strength, since a sufficient magnitude of precipitation reinforcement could not be obtained due to a small amount Ni. In addition, the stress relaxation rate was poor, since neither Mg nor Zr was added.

Since the Comparative Example 22 required a high temperature and a long time for the solution heat treatment due to large contents of Ni and Ti, the crystal grains got coarse to make the bending property poor. Further, the electric conductivity was also poor, since excess Ni and Ti were solute in the host matrix even after the aging treatment. In addition, the stress relaxation rate was poor since neither Mg nor Zr was added.

The Comparative Example 23 was poor in the bending property due to coarsened crystal grains since a large content of Ni required a solution heat treatment at a high temperature for a long time. In addition, the tensile strength was poor due to a poor density of the Ni—Ti precipitates contributing to the strength since the alloy contained an excess amount of Ni. Further, the electric conductivity was poor due to an excess amount of Ni that was solute in the host matrix even after the aging treatment. Furthermore, the stress relaxation rate was poor since neither Mg nor Zr was added.

Since the Comparative Example 24 required a high temperature and long time of the solution heat treatment due to a large content of Ti, the crystal grains got coarse to make the bending property poor. In addition, the electric conductivity was poor due to an excess amount of Ti that was solute in the host matrix even after the aging treatment. Further, the stress relaxation rate was poor since neither Mg nor Zr was added.

The Comparative Example 25 was poor in the stress relaxation rate due to a small amount of precipitates comprising Ni, Ti and Mg since the content of Mg was low.

Both the electric conductivity and the bending property were poor in the Comparative Example 26 since excess Mg remained in the solid solution, even after the aging treatment, due to a large content of Mg. In addition, the stress relaxation rate was also poor.

Since the Comparative Example 27 contained a small content of Zr, the stress relaxation rate was poor due to a small content of precipitates comprising Ni, Ti and Zr.

A large content of Zr in the Comparative Example 28 required a high temperature and long time of the solution heat treatment, so that the bending property was poor due to coarsening of crystal grains. In addition, the electric conductivity was poor since excess Zr was solute in the host matrix even after the aging treatment. Further, the stress relaxation rate was also poor.

A small content of precipitates comprising Ni, Ti, Mg and Zr resulted in a poor stress relaxation rate in the Comparative Example 29, since it contained a small amount of each of Mg and Zr.

The Comparative Example 30 required a high temperature and long time of the solution heat treatment due to a large content of each of Mg and Zr, and the bending property was poor due to coarsening of crystal grains. In addition, the electric conductivity was poor since excess Mg and Zr were solute in the host matrix even after the aging treatment. Further, the stress relaxation rate was also poor.

The adhesiveness of the solder was deteriorated since no Zn was added in the Comparative Examples 31 and 32.

The electric conductivity was low in the Comparative Examples 33 and 34 since a content of Zn was large.

The above-described Comparative Examples 21 to 34 correspond to comparative examples that are comparable to the present inventions described in the above items (1) and (2).

The tensile strength of the Comparative Example 60 was poor since a sufficient magnitude of precipitation reinforcement could not be attained due to a small content of Ni. In addition, the stress relaxation ratio was poor since the density of the Ni—Ti precipitates was insufficient, and neither Sn nor Si was added.

Since the Comparative Example 61 required a high temperature and a long time for the solution heat treatment due to large contents of Ni and Ti, the crystal grains got coarse to make the bending property poor. Further, the electric conductivity was also poor, since excess Ni and Ti were solute in the host matrix even after the aging treatment. In addition, the stress relaxation rate was poor since neither Sn nor Si was added.

The Comparative Example 62 was poor in the bending property due to coarsened crystal grains since a large content of Ni required a solution heat treatment at a high temperature for a long time. In addition, the tensile strength was poor due to a low density of the Ni—Ti precipitates contributing to the strength since the alloy contained an excess amount of Ni. Further, the electric conductivity was poor due to an excess amount of Ni that was solute in the host matrix even after the aging treatment. Furthermore, the stress relaxation rate was poor since neither Sn nor Si was added.

A large content of Ti in the Comparative Example 63 required a high temperature and long time of the solution heat treatment, so that the bending property was poor due to coarsening of crystal grains. In addition, the electric conductivity was poor since excess Ti was solute in the host matrix even after the aging treatment. Further, the stress relaxation rate was poor since neither Sn nor Si was added.

Since the Comparative Example 64 contained a small content of Sn, the stress relaxation rate was poor due to a small content of precipitates comprising Ni, Ti and Sn.

Both the electric conductivity and the bending property were poor in the Comparative Example 65 since excess Sn remained in the solid solution due to a large content of Sn. In addition, the stress relaxation rate was also poor.

Since the Comparative Example 66 contained a small content of Si, the stress relaxation rate was poor due to a small content of precipitates comprising Ni, Ti and Si.

A large content of Si in the Comparative Example 67 required a high temperature and long time of the solution heat treatment, so that the bending property was poor due to coarsening of crystal grains. In addition, the electric conductivity was poor since excess Si was solute in the host matrix. Further, the stress relaxation rate was also poor.

The adhesiveness of the solder was deteriorated since no Zn was added in the Comparative Examples 70 and 71.

The electric conductivity was low in the Comparative Examples 72 and 73 since a content of Zn was large.

The above-described Comparative Examples 60 to 67 and 70 to 73 correspond to comparative examples that are comparable to the present inventions described in the above items (3) and (4).

Example 2

The condition for the solution heat treatment and the conditions for the subsequent cold rolling and aging were variously changed using the alloy having the same composition as that of the Sample No. 15 in the Example 1 above. Other production conditions were the same as in Example 1. The evaluation items [1] to [7] were conducted in the same manner as in Example 1. The solution heat conditions and results of the evaluations are shown in Table 5.

TABLE 5
Solution heat treatmentAging
Tempe-ColdTempe-ECPPTAdhesive-
ratureTimeCoolingrollingratureTimeTS(%SRR/tR/tGSPPT(×1010/ness
(° C.)(sec)ratio (° C./s)ratio (%)(° C.)(hr)(MPa)IACS)(%)(GW)(BW)(μm)(nm)(mm2)of solder
This
invention
8110001533020550269052.9180.750.75617187
829503011030475168852.0190.50.75518118
83950157010550267754.1180.50.5513231
849001510035500365456.3200.50.5312210
859505200255251.569052.9190.50.5411103
868501515010550368953.0180.50.5512129
8795015300205253.568153.8190.50.5413165
88950152000475460250.31700612229
Compar-
ative
example
91950153520525362257.2240.50.551365
92900152520525361258.0270.50.7551277
938001511020525363956.9260.750.7531052
948003010520525362956.0280.750.7551149
959506013020525369052.9181.51.51112223
96-None--None--None->90525363458.333>2>28169
979501520060525361259.033>2>2412128
989501520020625356159.4340.750.7566674
999501520020400353347.0420.750.7582321
100 9501520020525755359.7320.750.7533333

Table 5 shows that the Examples 81 to 88 had excellent properties.

On the contrary, the stress relaxation rate was poor in the Comparative Examples 91 and 92 since the precipitates got coarse due to the slow cooling rate.

The smaller amount of elements contributing to the precipitation was in the solid solution due to the low solution heat temperature in the Comparative Example 93, and, therefore, the stress relaxation rate was poor since the precipitation density was decreased at the time of aging treatment.

The smaller amount of elements contributing to the precipitation was in the solid solution due to the low solution heat temperature in the Comparative Example 94, and, therefore, the stress relaxation rate was poor since the precipitation density was decreased at the time of solution heat treatment.

The bending property was poor in the Comparative Example 95 due to coarsening of crystal grains since the solution heat time was long.

There caused no recrystallization in the Comparative Example 96 since no solution heat treatment was conducted. Therefore, the measurement of the crystal grain size was impossible since the crystalline texture was fibrous as a result of 90% or more of the cold rolling ratio after the hot rolling. In addition, the bending property and the stress relaxation rate were also poor since the number of precipitations contributing to precipitation was small.

The bending property was poor in the Comparative Example 97 due to high cold rolling ratio after the solution heat treatment.

The strength was poor in the Comparative Example 98 due to coarsening of precipitates since the aging temperature was high.

The strength was poor in the Comparative Example 99 due to fine size of precipitates since the aging temperature was low.

The strength was poor in the Comparative Example 100 due to coarsening of precipitates since the aging time was long.

The above-described Comparative Examples 91 to 100 correspond to comparative examples that are comparable to the present inventions described in the above items (5) and (6).

Example 3

The properties of the product of the present invention, such as high electric conductivity, excellent strength, and excellent stress relaxation resistance property, are exhibited by allowing a Ni—Ti-series, Ni—Ti—Mg-series, Ni—Ti—Zr-series or other multi-component intermetallic compounds based on Ni—Ti to finely precipitate in high density in the Cu host matrix by a heat treatment for annealing for precipitation by aging. For this purpose, the amount in the solid solution of solute atoms should be increased as much as possible in the state before precipitation by aging, and the electric conductivity as an index of the degree of the solid solution is preferably 35% IACS or less, more preferably 30% IACS or less. Therefore, conditions applied in the steps before the heat treatment for precipitation by aging such as [1] casting speed, [2] heating speed, holding temperature and holding time for the subsequent homogenization heat treatment and [3] the subsequent hot rolling, and cooling speed in the hot rolling, were adjusted as follows.

Each alloy comprising Ni, Ti, Mg, Zn, Sn, Zr, Hf, In and Ag in the amounts as shown in Tables 6 to 10 with the balance of Cu was melted in a high frequency melting furnace, and cast to obtain an ingot with a thickness of 30 mm, a width of 100 mm and a length of 150 mm. The ingot was cooled at a cooling rate of 1 to 100° C./sec.

After annealing the ingot at 800 to 1,050° C. for 1 hour for homogenization, it was finished to a hot-rolled plate with a thickness of about 10 mm by hot rolling. The temperature was raised at a ratio of 3° C./minute or more.

The hot rolling was conducted at a cooling rate of 10 to 300° C./sec.

Oxide films were removed by shaving both surfaces of the hot-rolled plate at a depth of about 1.0 mm, and a plate with a thickness of 0.1 to 2 mm was obtained thereafter by cold rolling. This plate was processed and heat-treated according to any one of the steps 1 to 4, 5-1 to 5-4, 6-1 to 6-4 and 7-1 to 7-4 to obtain each test material.

[Step 1]

The plate was subjected to solution heat treatment for 15 to 600 seconds at a temperature of 850 to 1,000° C. in an inert gas followed by cold rolling. Then, the plate was subjected to annealing once for precipitation by aging at a temperature of 450 to 650° C. within 5 hours, and the annealed plate was subjected to final cold rolling at a rolling ratio of more than 0% but 30% or less and stress-relief annealing at 150 to 500° C., to obtain a test material.

[Step 2]

The plate was subjected to solution heat treatment at a temperature of 850 to 1,000° C. for 15 to 600 seconds in an inert gas after cold rolling. Then, the plate was alternately subjected to once or more of cold rolling, and twice or more of annealing for precipitation by aging at a temperature of 450 to 650° C. for within 5 hours. The final aging annealed material was finally cold-rolled at a rolling ratio in the range of more than 0% but 30% or less and subjected to stress-relief annealing at 150 to 500° C., to obtain a test material.

[Step 3]

The plate after cold rolling was subjected to annealing for precipitation by aging once at a temperature of 450 to 650° C. for within 5 hours. Then, the thus-obtained annealed material was subjected to final cold rolling at a rolling ratio in the range of 0% to 30% and stress-relief annealing at 150 to 500° C., to obtain a test material.

[Step 4]

The plate was alternately subjected to twice or more of cold rolling, and twice or more of annealing for precipitation by aging at a temperature of 450 to 650° C. for within 5 hours. Then, the final aging annealed material was subjected to final cold rolling at a rolling ratio in the range of more than 0% but 30% or less and stress-relief annealing at 150 to 500° C., to obtain a test material.

[Steps 5-1 to 5-4]

One, or two or more times of the annealing for precipitation by aging in Step 1, Step 2, Step 3 and Step 4 were performed at a temperature exceeding 650° C. These steps were referred to as Steps 5-1 to 5-4, respectively.

[Steps 6-1 to 6-4]

One, or two or more times of the annealing for precipitation by aging in Step 1, Step 2, Step 3 and Step 4 were performed at a temperature lower than 450° C. These steps were referred to as Steps 6-1 to 6-4, respectively.

[Steps 7-1 to 7-4]

In Step 1, Step 2, Step 3 and Step 4, the plates were annealed for precipitation by aging at a condition of the electric conductivity before annealing for precipitation by aging exceeding 35% IACS. These steps were referred to as Steps 7-1 to 7-4, respectively.

Each plate material thus obtained was investigated with respect to [1] tensile strength (TS), [2] electric conductivity (EC), [3] stress relaxation property (SR), [4] bending property, [5] density of precipitates (PPT) and [6] adhesiveness of solder. The evaluation methods of [1] tensile strength, [2] electric conductivity, [3] stress relaxation property, [5] density of precipitates and [6] adhesiveness of solder were the same as those in Example 1. The evaluation method of the other evaluation item is as follows.

[4] Bending Property (R/t)

The plate material was cut into a size of 0.5 mm in the width and 25 mm in the length, and was bent at an angle W (90°) with the same bending radius (R) as the plate thickness (t). The presence of cracks at the bent portion was observed using an optical microscope with 50 times magnification. With respect to evaluation criteria, samples with no cracks at the surface of the bent portion were evaluated as “◯”, while samples with cracks at the surface of the bent portion were evaluated as “x”.

The precipitates were identified in the same manner as in the Example 1.

The results of the evaluations [1] to [6] are listed together in Tables 6 to 10.

TABLE 6
ZnMgNi/TiStepTSECBendingAdhesiveness
No.Ni mass %Ti mass %mass %mass %ratioNo.MPa% IACSSR %propertyof solderPPT ×1012/mm2
This invention 2012.010.630.510.113.19165555.8161
This invention 2022.100.640.520.093.28270256.0161
This invention 2031.810.560.490.113.23367061.219.51
This invention 2041.920.600.500.113.20468861.8191
This invention 2052.300.720.510.113.19371858.7192
This invention 2062.500.780.510.113.21476556.8183
This invention 2071.500.470.520.093.19266857.2161
This invention 2081.300.400.520.093.25265958.1161
This invention 2091.800.500.500.063.60267557.0171
This invention 2102.010.720.510.092.79367061.3191
This invention 2112.030.611.000.113.33466763.119.51
This invention 2121.810.563.000.123.23268555.8171
This invention 2132.030.600.490.153.38468561.5191
This invention 2141.810.600.500.203.02367061.2181
This invention 2152.030.650.510.113.12267556.8153
This invention 2161.810.550.510.123.29366661.119.50.3
Comparative3.311.030.500.083.21271549.121X4
example 217
Comparative0.710.220.510.093.23262058.1240.1
example 218
Comparative2.010.370.480.095.43365551.3271
example 219
Comparative2.031.350.500.121.50366048.2221
example 220
Comparative1.810.520.000.123.48266558.620X1
example 221
Comparative1.900.600.520.003.17355061.3441
example 222
Comparative1.910.620.550.013.08256556.3381
example 223
Comparative1.910.630.560.503.03267045.419X1
example 224
Comparative1.950.660.510.102.95362143.1270.0001
example 225
Comparative2.010.600.520.133.35467056.822X100
example 226
Comparative1.810.527.020.103.48265145.2221
example 226-1

TABLE 7
Ni
massTiZnMgSnNi/TiStepTSECBendingAdhesiveness
No.%mass %mass %mass %mass %ratioNo.MPa% IACSSR %propertyof solderPPT ×1012/mm2
This invention 2272.010.630.510.110.153.19168555.6161
This invention 2282.100.640.520.090.23.28269356.4161
This invention 2291.810.560.490.110.33.23368860.1181
This invention 2301.920.600.500.110.123.20469059.6191
This invention 2312.010.630.510.110.083.19266655.7161
This invention 2322.100.640.520.090.093.28271055.9161
This invention 2331.810.560.490.110.073.23368060.2191
This invention 2341.920.600.500.110.083.20469561.1191
This invention 2352.300.720.510.110.083.19372558.0192
This invention 2362.500.780.510.110.093.21477056.1183
This invention 2371.500.470.520.090.073.19267556.5161
This invention 2381.300.400.520.090.083.25267058.0161
This invention 2391.800.500.500.060.083.60268656.3171
This invention 2402.010.720.510.090.092.79368260.5191
This invention 2412.030.611.000.110.073.33468062.519.51
This invention 2421.810.563.000.120.083.23269355.6171
This invention 2432.030.600.490.150.083.38469560.7191
This invention 2441.810.600.500.200.093.02368160.6191
This invention 2452.030.650.510.110.073.12268656.5153
This invention 2461.810.550.510.120.083.29367860.319.50.3
Comparative3.311.030.500.080.093.21271549.122X4
example 247
Comparative0.710.220.510.090.073.23262058.9250.1
example 248
Comparative2.010.370.480.090.085.43365550.5281
example 249
Comparative2.031.350.500.120.081.50366048.1221
example 250
Comparative1.810.520.000.120.093.48266559.120X1
example 251
Comparative1.900.600.520.000.073.17355052.2451
example 252
Comparative1.910.620.550.010.083.08256550.9381
example 253
Comparative1.910.630.560.500.093.03267045.120X1
example 254
Comparative1.950.660.510.100.072.95362147.8270.0001
example 255
Comparative2.010.600.520.130.083.35467056.122X100
example 256
Comparative1.810.520.520.1223.48268048.1201
example 257
Comparative1.900.600.520.121.513.17367540.2201
example 258
Comparative1.810.527.020.100.093.48265143.2221
example 258-1

TABLE 8
NiTiZnMgOtherNi/TiStepTSECBendingAdhesivenessPPT ×1012/
No.mass %mass %mass %mass %mass %ratioNo.MPa% IACSSR %propertyof soldermm2
This invention 2591.820.590.520.080.05 Zr3.08269256.8181
This invention 2601.850.510.550.090.04 Hf3.63368560.519.51
This invention 2611.790.530.520.120.05 In3.38468062.2191
This invention 2621.790.530.520.120.1 Ag3.38470260.2191
Comparative1.820.590.520.081.02 Zr3.08267546.220X1
example 263
Comparative1.850.510.550.091.10 Hf3.63367044.322X1
example 264
Comparative1.790.530.520.121.20 In3.38467638.921X1
example 265
Comparative1.790.530.520.121.3 Ag3.38468548.020X1
example 266

TABLE 9
NiTiZn
massmassmassMgSnOtherNi/TiStepTSECBendingAdhesivenessPPT ×1012/
No.%%%mass %mass %mass %ratioNo.MPa% IACSSR %propertyof soldermm2
This invention 2671.820.590.520.080.090.05 Zr3.08270256.1181
This invention 2681.850.510.550.090.070.04 Hf3.63369359.519.51
This invention 2691.790.530.520.120.090.05 In3.38469061.1191
This invention 2701.790.530.520.120.090.1 Ag3.38470559.5191
Comparative1.820.590.520.080.091.02 Zr3.08268045.520X1
example 271
Comparative1.850.510.550.090.071.10 Hf3.63367542.522X1
example 272
Comparative1.790.530.520.120.091.20 In3.38468439.021X1
example 273
Comparative1.790.530.520.120.091.3 Ag3.38469245.320X1
example 274

TABLE 10
NiTiZnMgSnNi/TiStepTSECBendingAdhesiveness
No.mass %mass %mass %mass %mass %ratioNo.MPa% IACSSR %propertyof solderPPT ×1012/mm2
Comparative2.010.630.510.113.195-155665.1280.0004
example 275
Comparative1.810.560.490.113.235-254066.0270.0003
example 276
Comparative1.810.560.490.11 0.083.235-357065.1290.0003
example 277
Comparative2.010.630.510.113.196-153544.2300.0002
example 278
Comparative1.810.560.490.113.236-354242.5320.0001
example 279
Comparative1.810.560.490.11 0.083.236-255141.8300.0001
example 280
Comparative2.010.630.510.113.197-457566.2280.0001
example 281
Comparative1.810.560.490.113.237-354568.1290.0001
example 282
Comparative1.810.560.490.11 0.083.237-256065.1280.0001
example 283
This2.010.630.510.113.19165555.8161
invention 201
This2.100.640.520.090.23.28269356.4161
invention 228
This1.810.560.490.110.33.23368860.1181
invention 229
This1.920.600.500.113.20468861.8191
invention 204

As is clear from Table 6, the Examples 201 to 216 according to the present invention had excellent properties, such as tensile strength of 650 MPa or more, electric conductivity of 55% IACS or more and stress relaxation rate of 20% or less.

On the contrary, high temperature and long time of solution heat treatment was necessary due to a large content of Ni in the Comparative Example 217, and the bending property was poor as a result of coarsening of crystal grains. Further, the electric conductivity was also poor since an amount of Ni in the solid solution was large.

The Comparative Example 218 was poor in the tensile strength, since a sufficient magnitude of precipitation reinforcement could not be obtained due to a small amount Ni.

The electric conductivity was poor in the Comparative Examples 219 and 220 due to an increased amount of elements in the solid solution since the Ni/Ti ratio was out of the range prescribed in the present invention.

The adhesiveness of solder was deteriorated in the Comparative Example 221 since no Zn was added.

The strength of the Comparative Examples 222 and 223 was insufficient due to a small amount of precipitates comprising Ni, Ti and Mg since no Mg or a too small amount of Mg was added. In addition, the stress relaxation rate was also poor due to a small amount of Mg in the solid solution.

Excess Mg remained in the solid solution even by aging treatment in the Comparative Example 224 since the amount of Mg was in excess, so that both the electric conductivity and the bending property were poor.

The strength and the stress relaxation rate were poor in the Comparative Example 225 since the density of precipitates was low.

Coarse precipitates were readily formed at grain boundaries in the Comparative Example 226 due to a high density of precipitates, so that the bending property was poor.

The electric conductivity was decreased in the Comparative Example 226-1 since a large amount of Zn added caused Zn to remain in the solid solution.

The above-described Comparative Examples 217 to 226 and 226-1 correspond to comparative examples that are comparable to the present inventions described in the above item (7).

As is clear from Table 7, the Examples 227 to 246 according to the present invention had excellent properties, such as tensile strength of 650 MPa or more, electric conductivity of 55% IACS or more and stress relaxation rate of 20% or less.

On the contrary, high temperature and long time of solution heat treatment was necessary due to a large content of Ni in the Comparative Example 247, and the bending property was poor as a result of coarsening of crystal grains. Further, the electric conductivity was also poor since an amount of Ni in the solid solution was large.

The Comparative Example 248 was poor in the tensile strength, since a sufficient magnitude of precipitation reinforcement could not be obtained due to a small amount Ni.

The electric conductivity was poor in the Comparative Examples 249 and 250 due to an increased amount of elements in the solid solution since the Ni/Ti ratio was out of the range prescribed in the present invention.

The adhesiveness of solder was deteriorated in the Comparative Example 251 since no Zn was added.

The strength of the Comparative Examples 252 and 253 was insufficient due to a small amount of precipitates comprising Ni, Ti and Mg since no Mg or a too small amount of Mg was added. In addition, the stress relaxation rate was also poor due to a small amount of Mg in the solid solution.

Excess Mg remained in the solid solution even by aging treatment in the Comparative Example 254 since the amount of Mg was in excess, so that both the electric conductivity and the bending property were poor.

The strength and the stress relaxation rate were poor in the Comparative Example 255 since the density of precipitates was low.

Coarse precipitates were readily formed at grain boundaries in the Comparative Example 256 due to a high density of precipitates, so that the bending property was poor.

The electric conductivity was poor in the Comparative Examples 257 and 258, since an amount of Sn was large.

The electric conductivity was decreased in the Comparative Example 258-1 since a large amount of Zn added caused Zn to remain in the solid solution.

The above-described Comparative Examples 247 to 258 and 258-1 correspond to comparative examples that are comparable to the present invention described in the above item (8).

As is clear from Table 8, the Examples 259 to 262 according to the present invention had excellent properties, such as tensile strength of 650 MPa or more, electric conductivity of 55% IACS or more and stress relaxation rate of 20% or less.

On the contrary, an excess amount of Zr in the Comparative Example 263 caused excess Zr to remain in the solid solution to deteriorate both the electric conductivity and the bending property.

An excess amount of Hf in the Comparative Example 264 caused excess Hf to remain in the solid solution to deteriorate both the electric conductivity and the bending property.

An excess amount of In in the Comparative Example 265 caused excess In to remain in the solid solution to deteriorate both the electric conductivity and the bending property.

An excess amount of Ag in the Comparative Example 266 caused excess Ag to remain in the solid solution to deteriorate both the electric conductivity and the bending property.

The above-described Comparative Examples 263 to 266 correspond to comparative examples that are comparable to the present invention described in the above item (9).

As is clear from Table 9, the Examples 267 to 270 according to the present invention had excellent properties, such as tensile strength of 650 MPa or more, electric conductivity of 55% IACS or more and stress relaxation rate of 20% or less.

On the contrary, an excess amount of Zr in the Comparative Example 271 caused excess Zr to remain in the solid solution to deteriorate both the electric conductivity and the bending property.

An excess amount of Hf in the Comparative Example 272 caused excess Hf to remain in the solid solution to deteriorate both the electric conductivity and the bending property.

An excess amount of In in the Comparative Example 273 caused excess In to remain in the solid solution to deteriorate both the electric conductivity and the bending property.

An excess amount of Ag in the Comparative Example 274 caused excess Ag to remain in the solid solution to deteriorate both the electric conductivity and the bending property.

The above-described Comparative Examples 271 to 274 correspond to comparative examples that are comparable to the present invention described in the above item (10).

As is clear from Table 10, the Examples 201, 228, 229 and 204 according to the present invention had excellent properties, such as tensile strength of 650 MPa or more, electric conductivity of 55% IACS or more and stress relaxation rate of 20% or less.

On the contrary, the density of precipitates was low due to a too high aging temperature in the Comparative Examples 275 to 277, and the strength and the stress relaxation rate were poor.

The amount of precipitates was insufficient due to a too low aging temperature in the Comparative Example 278 to 280, so that the density of the precipitates was low to result in poor strength, electric conductivity and stress relaxation rate.

The density of the precipitate after the heat treatment for precipitation by aging was low and the strength and stress relaxation rate was poor in the Comparative Examples 281 to 283, since the samples having an electric conductivity of 35% IACS or more before the heat treatment for precipitation by aging were subjected to the heat treatment for precipitation by aging.

The above-described Comparative Examples 275 to 283 correspond to comparative examples that are comparable to the present invention described in the above item (11).

INDUSTRIAL APPLICABILITY

The copper alloy of the present invention can be favorably applied for connectors of electric and electronic instruments, connectors of terminals, materials of terminals, and the like.

Having described our invention as related to the present embodiments, it is our intention that the invention not be limited by any of the details of the description, unless otherwise specified, but rather be construed broadly within its spirit and scope as set out in the accompanying claims.

This non-provisional application claims priority under 35 U.S.C. § 119 (a) on Patent Application No. 2004-165068 filed in Japan on Jun. 2, 2004, and Patent Application No. 2005-161475 filed in Japan on Jun. 1, 2005, each of which is entirely herein incorporated by reference.