Title:
Probe cleaner and cleaning method
Kind Code:
A1


Abstract:
A probe cleaner for removing foreign objects from the tip part of a probe is formed with a cleaner sheet having a surface part with microfibers and abrading particles affixed to the surface of the microfibers at this surface part. The average fiber diameter of the microfibers is in the range of 0.1 μm or more and 20 μm or less. The average particle diameter of the abrading particles is in the range of 0.05 μm or more and 3.0 μm or less. For cleaning the tip part of a probe, the probe cleaner is set to the surface of a table, the tip part of the probe is caused to penetrate inside the surface part, and the probe is caused to undergo a reciprocal motion in the direction of the thickness of the surface part.



Inventors:
Tamura, Jun (Tokyo, JP)
Kato, Kenji (Tokyo, JP)
Application Number:
11/895469
Publication Date:
03/20/2008
Filing Date:
08/24/2007
Assignee:
NIHON Micro Coating Co., Ltd.
Primary Class:
Other Classes:
51/293, 51/307, 51/308, 51/309
International Classes:
B24B1/00; B24D3/00
View Patent Images:



Primary Examiner:
MORGAN, EILEEN P
Attorney, Agent or Firm:
WEAVER AUSTIN VILLENEUVE & SAMPSON LLP (OAKLAND, CA, US)
Claims:
What is claimed is:

1. A probe cleaner for removing foreign objects attached to the tip part of a probe, said probe cleaner comprising: a cleaner sheet having a surface part with microfibers; and abrading particles affixed to the surface of the microfibers at said surface part.

2. The probe cleaner of claim 1 wherein said microfibers have average fiber diameter in the range of 0.1 μm or more and 20 μm or less.

3. The probe cleaner of claim 1 wherein said microfibers have average fiber diameter in the range of 0.1 μm or more and 10 μm or less.

4. The probe cleaner of claim 1 wherein the average particle diameter of said abrading particles is in the range of 0.05 μm or more and 3.0 μm or less.

5. The probe cleaner of claim 1 wherein said abrading particles include particles of one or more kinds selected from the group consisting of alumina, silicon carbide, silicon oxide, zirconia, aluminum hydroxide and diamond.

6. The probe cleaner of claim 1 wherein said cleaner sheet is a flocked sheet having said microfibers planted on the surface of a base sheet.

7. The probe cleaner of claim 1 wherein said cleaner sheet is a woven or non-woven cloth sheet comprising said microfibers.

8. The probe cleaner of claim 1 wherein said probe has indentations or protrusions at the tip.

9. A method of removing foreign objects from the tip part of a probe, said method comprising the steps of: setting a probe cleaner to the surface of a table, said probe cleaner comprising a cleaner sheet having a surface part with microfibers and abrading particles affixed to the surface of the microfibers at said surface part; causing said tip part of said probe to penetrate inside said surface part; and causing said probe to undergo a reciprocal motion in the direction of the thickness of said surface part.

10. The method of claim 9 further comprising the step of pulling out said probe from said surface part.

11. The method of claim 9 wherein said reciprocal motion is caused while said tip part of said probe remains in the condition of penetrating inside said surface part.

12. The method of claim 9 wherein said probe has indentation or protrusion at said tip.

Description:

This application claims priority on Japanese Patent Application 2006-250342 filed Sep. 15, 2006.

BACKGROUND OF THE INVENTION

This invention relates to a probe cleaner and a cleaning method for cleaning the tip part of a needle-shaped object such as a probe for the inspection of electric properties, a needle for a clinical use and a knitting needle in the finishing step of the production process or before and after a use. This invention relates in particular to such a probe cleaner and cleaning method for removing foreign objects attached to the tip part of a probe used for the inspection of electric properties in the inspection process of a semiconductor device.

In order to improve the production efficiency in the production process of semiconductor devices, a probe is used to contact electrode pads of a plurality of chips formed on a semiconductor wafer for inspecting the electrical characteristics of each chip by applying and detecting test signals through this probe.

In general, such a probe is made of a hard material such as tungsten and beryllium, while the electrode pads are made of a relatively soft material such as aluminum. When the probe is made to contact an electrode pad, foreign objects such as aluminum of the electrode pad become attached to the tip part (the tip and the side surfaces near the tip) of the probe, and this affects the accuracy of the inspection adversely. If a large foreign object is attached to a probe, mutually adjacent probes may become shorted, causing chips to be destroyed. For this reason, the tip part of the probe is cleaned for removing such foreign objects.

As disclosed in Japanese Patent Publications Tokkai 7-244074 and 2004-140013, for example, the tip part of a probe may be cleaned by using a probe cleaner comprising a cleaner sheet made of an elastic material such as silicon rubber and urethane rubber with abrading particles (such as hard particles of aluminum oxide, silicon carbide and diamond) mixed in and by causing the tip part of the probe to penetrate into the interior of this probe cleaner from its surface such that the abrading particles affixed to the elastic material will work on the tip part of the probe.

As disclosed in Japanese Patent Publication Tokuhyo 2005-515645, furthermore, a probe cleaner comprising a cleaner sheet having a sticky gel layer formed on the surface of a plate with minute unevenness prepared thereon has also been used. After the tip part of the probe penetrates into the interior of the gel layer from its surface, the probe is moved while its tip remains in contact with the unevenness of the surface of the plate such that the tip part becomes cleaned.

As the chip size is made smaller in recent years, the electrode pads formed on the chips are becoming smaller and the electrode pads are coming to be formed closer to one another. For this reason, it is becoming necessary to make the probes thin, and relatively soft materials having improved electrical characteristics such as beryllium-copper alloys are coming to be used to form the probes.

If a conventional probe cleaner as described above is used on such a probe, however, the probe is easily worn out by the cleaning process, its useful lifetime being thus adversely affected. The abraded condition of a probe also gives rise to the problem of inspection errors on the electrical characteristics of the chips.

In order to reliably contact the electrode pads on a chip, it has also been known, as shown in FIGS. 5A and 5B, to form indentations 32 and 35 or protrusions 31 and 34 on the tip 30 or 33 of a probe, as disclosed in Japanese Patent Publication Tokkai 8-306749.

If these conventional probe cleaners are used to clean the tip part of such a probe, however, foreign objects attached within the indentations in the tip part cannot be removed sufficiently and the protrusions tend to be worn out by the cleaning process.

SUMMARY OF THE INVENTION

It is therefore an object of this invention to provide a probe cleaner capable of cleaning the tip part of a probe without excessively wearing out the probe by the cleaning process and in particular cleaning the tip part of a probe having indentations or protrusions formed on the tip part.

This invention relates to a probe cleaner and a method of removing foreign objects attached to the tip part of a probe, and in particular to a probe having indentations or protrusions formed at its tip.

A probe cleaner according to this invention is characterized as comprising a cleaner sheet having a surface part with microfibers and abrading particles affixed to the surface of the microfibers at this surface part. During a cleaning process, these abrading particles affixed to the microfibers at the surface part of the cleaner sheet work on the tip part of the probe to remove the foreign objects attached thereto.

The average fiber diameter of the microfibers is in the range of 0.1 μm or more and 20 μm or less, and preferably in the range of 0.1 μm or more and 10 μm or less.

The average particle diameter of the abrading particles is in the range of 0.05 μm or more and 3.0 μm or less. The abrading particles of this invention include particles of one or more kinds selected from the group consisting of alumina, silicon carbide, silicon oxide, zirconia, aluminum hydroxide and diamond.

The cleaner sheet of this invention is a flocked sheet having the microfibers planted on the surface of a base sheet. The abrading particles are affixed to the surface of the microfibers of this flocked sheet. These microfibers with abrading particles affixed thereto are mutually independent, not being attached to one another. In other words, these microfibers can move individually, independent of the other microfibers.

As a variation, the cleaner sheet of this invention may be a woven or non-woven cloth sheet comprising microfibers having abrading particles affixed thereto.

According to a method of this invention, foreign objects attached to the tip part of a probe are removed by the steps of setting a probe cleaner of this invention to the surface of a table, causing the tip part of the probe to penetrate into the surface part of the cleaner sheet and causing the probe to undergo a reciprocal motion in the direction of the thickness of the surface part. The tip part of the probe is thereafter pulled out from the surface part. The probe may be caused to undergo a reciprocating motion in the direction of the thickness of the surface part while the tip part of the probe remains in the condition of penetrating the surface part.

With the invention thus characterized, even a probe having indentations and protrusions formed at the tip can be cleaned easily without wearing it out excessively.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a sectional view of a probe cleaner of this invention and FIG. 1B is a partially sectional enlarged view of a microfiber.

FIGS. 2A and 2B show a probe being cleaned according to this invention, and FIG. 3 is a schematic drawing of a cleaning apparatus.

FIG. 3 is a microgram of a sectional view of a probe cleaner according to this invention.

FIG. 4 is a schematic sectional view of a probe cleaner embodying this invention.

FIGS. 5A and 5B are each an enlarged schematic diagonal view of the tip of a probe.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 1A and 1B show a probe cleaner 20 embodying this invention for removing foreign objects attached to the tip part of a probe (shown at 12 in FIGS. 2A, 2B and 2C), comprising a cleaner sheet 21 having a surface part 24 comprised of microfibers 25 with abrading particles 26 attached to the surface of at least those of the microfibers 25 on the surface part 24 of this cleaner sheet 21. As shown in FIG. 1B, the abrading particles 26 are affixed to the surface of the microfibers 25 by a binder 27.

In the above, the surface part 24 means a portion of the cleaner sheet 21 that will work on the tip of the probe 12. The thickness (or the height) of this surface part 24 is not particularly limited by the invention and it is sufficient if it has the length of the tip part of the probe 12 to be cleaned. It may be in the range of 100 μm or more and less than 1000 μm. As shown in FIGS. 2A and 2B, the cleaning of the tip part of the probe 12 is carried out by sticking the tip part into the surface part 24 of the cleaner sheet 21 by either moving the table 11 in the direction of arrow T1 or moving the probe 12 in the direction of arrow T2. During this cleaning operation, the abrading particles 26 affixed to the microfibers 25 at the surface part 24 of the cleaner sheet 21 work on the tip part of the probe 12 such that foreign objects that may be attached to the tip part of the probe 12 are removed.

The fiber diameter of the microfibers 25 is within the range of 0.1 μm or more and 20 μm or less and preferably 0.1 μm or more and 10 μm or less. Synthetic fibers of nylon, polypropylene, polyethylene, polyethylene terephthalate, polyurethane, acryl, polyvinyl chloride, vinilon or rayon may be used as the microfibers 25.

The size of the abrading particles 26 affixed to the surface of the microfibers 25 is less than the fiber diameter of the microfibers 25 and preferably ½ or less of the fiber diameter. This is because if the size of the abrading particles 26 is too large, the force for stabilizing the abrading particles against the curved surface of the fiber will become weak and the abrading particles working on the tip part of the probe 12 may drop off and become attached to the tip part of the probe 12 to become foreign objects themselves. Abrading particles with average diameter in the range of 0.05 μm or more and 3.0 μm or less are preferred.

No particular limitations are imposed as to the material of the abrading particles, and particles commonly used for polishing may be used for the purpose of this invention. Preferable examples include particles of alumina, silicon carbide, silicon oxide, zirconia, aluminum hydroxide and diamond.

As shown in FIGS. 3 and 4, the cleaner sheet 21 is a flocked sheet comprising microfibers 25 planted to a base sheet 28 such that the aforementioned abrading particles 26 are affixed to the surface of the microfibers 25 of this flocked sheet. These microfibers 25 having the abrading particles 26 affixed thereonto are in the condition of not being affixed to one another among themselves. In other words, each of the microfibers 25 is in the condition of being able to freely move independent of the other microfibers 25.

The lengths of the microfibers 25 of the flocked sheet are in the range of 100 μm or more and 1000 μm (1.0 mm) or less, and preferably 400 μm or more and 600 μm or less. If they are too short, this affects the fiber movements adversely. If they are too long, they cannot easily remain independent and tend to become tangled up such that it becomes difficult to attach the abrading particles 26 to them individually.

As for the base sheet 28, a material with small thermal deformations due to temperature changes is preferred. A sheet with rate of thermal shrinkage 2% or less in the temperature range of 25° C. or more and 150° or less as its mechanical characteristic is used. No particular limitations are imposed as to the size and material of the base sheet 28. A sheet with thickness in the range of 50 μm or more and 188 μm or less, made of PET (polyethylene terephthalate), PEN (polyethylene naphthalate), PPS (polyphenylene sulfide, PEI (polyether imide), PI (polyimide), PC (polycarbonate), PVC (polyvinyl chloride), PP (polypropylene), PVDC (polyvinylidene chloride), nylon, PE (polyethylene) or PES (polyether sulfonate) may be used, but a PET sheet is preferred.

As a practical matter, a layer of adhesive agent (referred to as the adhesive layer, shown at 22 in FIG. 1A) is formed on the back surface of the base sheet 28, and a peelable paper sheet (shown at 23 in FIG. 1A) is removably pasted to the surface of this adhesive layer 22. This peelable paper sheet 23 is peeled off from the surface of the adhesive layer 22, and the probe cleaner 20 of this invention is thereafter pasted on the table 11 of a probe cleaning apparatus 10 through this adhesive layer 22, as shown in FIG. 2C.

As a variation, a woven or non-woven cloth sheet made of microfibers 25 described above may be used as the cleaner sheet 21 of the probe cleaner 20 of this invention. The abrading particles 26 described above are affixed at least to the surface of the microfibers 25 at the position of the surface part 24 of this cleaner sheet 21. This cleaner sheet 21 may also have an adhesive layer 22 formed on its back surface so as to be pasted onto the table 11 of the probe cleaning apparatus 10 through this adhesive layer 22.

As an example of base sheet of this type, too, a sheet with small thermal deformations due to temperature variations is preferred. As explained above with reference to a flocked sheet, there is no particular limitation as to the size or material of the base sheet of this kind. A sheet of synthetic fibers such as polypropylene and polyethylene with thickness in the range of 50 μm or more and 188 μm or less is used as the base sheet.

In this case, too, a layer of adhesive agent (referred to as the adhesive layer, shown at 22 in FIG. 1A) is formed as a practical matter on the back surface of the base sheet 28, and a peelable sheet (shown at 23 in FIG. 1A) is removably pasted to the surface of this adhesive layer 22. This peelable paper sheet 23 is peeled off from the surface of the adhesive layer 22, and the probe cleaner 20 of this invention is thereafter pasted on the table 11 of a probe cleaning apparatus 10 through this adhesive layer 22, as shown in FIG. 2C.

The probe cleaner 20 of the present invention may be produced by dispersing abrading particles in a liquid resin solution, adding a hardening agent thereto to prepare a paint (coating material), applying this paint on the surface of the cleaner sheet 21 by a known coating method such as the reverse roll coating and gravure coating, and drying it. Examples of the resin solution to be used include one or more resin materials selected from polyester resins, polyurethane resins, copolymerized vinyl resins, epoxy resins and phenol resins, dissolved in a solvent. Examples of the solvent include toluene, xylene, MEK (methylethyl ketone), ethyl acetate, cyclohexanone, acetone and alcohols. Examples of hardening agent include isocyanates.

The viscosity of the paint is in the range of 20 cp or more and 300 cp or less, and preferably 50 cp or more and 150 cp or less. If the viscosity of the paint is too low (less than 20 cp), it tends to fall down to the lower layer of the surface part of the cleaner sheet and a sufficient amount of the abrading particles 26 cannot be affixed to the surface of the microfibers 25 at the surface part 24 of the cleaner sheet 21. Thus, the abrading particles cannot work sufficiently on the tip part of the probe during a cleaning operation. If the viscosity is too high (over 300 cp), the paint will remain at the upper layer of the surface part 24 of the cleaner sheet 21, and a layer with the abrading particles 26 fastened by the resin (binder 27) is formed such that mutually adjacent microfibers 25 are attached together. Such a layer tends to cause friction on the tip part of the probe 12.

The mix ratio of the abrading particles 26 in the paint is in the range of 60 weight % or more, and preferably 80 weight % or more and 98 weight % or less. If the ratio of the abrading particles 26 is too low (less than 60 weight %), mutually adjacent microfibers 25 tend to become attached to each other to form a layer of the kind described above.

Composition of the paint is shown in Table 1 below.

TABLE 1
Abrading particles60 weight %-98 weight %
Resin solution 1 weight %-35 weight %
Hardening agent1 weight %-5 weight %

As a preferred example, after abrading particles comprising 60 weight %-98 weight % of silicon carbide were heated and dried, they were mixed with a resin solution obtained by dissolving 1 weight %-35 weight % of saturated polyester resin in a mixed solvent of toluene, xylene, ethylene acetate and MEK to disperse the abrading particles in the resin solution and they were filtered. A paint was prepared immediately before it was applied to a cleaner sheet by adding an isocyanate hardening agent by 1 weight %-5 weight % to adjust the viscosity of the paint to 30 cp-150 cp.

As shown in FIG. 2C, the probe cleaner 20 of this invention thus prepared is pasted on the surface of the table 11 through the adhesive layer (shown at 22 in FIG. 1A). As shown in FIGS. 2A, 2B and 2C, the tip part of a probe 12 is placed on the surface of this cleaner sheet 21 and the table 11 is moved in the direction of arrow T2 such that the tip part of the probe 12 penetrates into the surface part 24 of the cleaner sheet 21. Next, the penetrated tip part of the probe 12 is pulled out of the surface part 24 of the cleaner sheet 21 by moving the table 11 in the direction of arrow T1. By this reciprocating motion of the table 11 in the directions of arrows T1 and T2, foreign objects attached to the tip part of the probe 12 are removed by the surface part 24.

Cleaning tests were carried out by preparing probe cleaners of Test and Comparison Examples and using these prepared probe cleaners to remove foreign objects from the tip parts of probes having indentations and protrusions at the tips. After these probes were cleaned, they were compared regarding the removal rate from these indentations and protrusions, and the presence or absence of wears (abrasions) was examined by visual observation with a microscope.

FIGS. 4A and 4B show the tips of the two kinds of probes Test Probes A and B used for the cleaning test. The tip of Test Probe A is shown in FIG. 5A, having an indentation and a protrusion. The size of its bottom surface is about 90 μm×90 μm, its height is about 70 μm, the diameter of its indentation is about 50 μm, and its depth is about 70 μm. With Test Probe A, the periphery of this indentation forms its protrusion.

The tip of Test Probe B is shown in FIG. 5B, having a plurality of indentations and protrusions. Its bottom surfaces are about 30 μm×30 μm and its height is about 100 μm. Indentations are formed as valleys between the protrusions.

A cleaning apparatus as shown in FIG. 2C was used for the cleaning test under the same conditions for both Test and Comparison Examples. When the contact frequency of the probes to the cleaner sheet of the probe cleaner became 1000 times, 10000 times and 100000 times, the abraded condition of the tip of the probe was observed and the presence and absence of foreign objects attached to the indentation-protrusion at the tip of the probe was observed when the contact frequency reached 100000 times.

TEST EXAMPLE 1

A probe cleaner of Test Example 1 was prepared as follows.

A paint was prepared by heating and drying 1 kg of abrading particles of silicon carbide with average diameter of 0.05 μm, thereafter mixing them with a resin solution obtained by dissolving 310 g of saturated polyester resin in a mixed solvent of toluene, xylene, ethyl acetate and MEK, stirring it to disperse the abrading particles in the resin solution and thereafter filtering them, and adding 60 g of an isocyanate hardening agent and adjusting it immediately before it is applied onto the cleaner sheet. Its viscosity was 50 cp.

The paint was applied to the surface of each of the microfibers on the surface part of the flocked sheet and dried to produce a probe cleaner.

Application of the paint was carried out by using a gravure roller (#50 having grooves in straight lines at regular intervals making angles of 45°).

The flocked sheet was of a PET sheet of thickness 50 μm having microfibers with average fiber diameter of 10 μm and average length 500 μm (500 μm±100 μm) planted.

TEST EXAMPLE 2

The probe cleaner of Test Example 2 was prepared by using the same material and by the same method as for Test Example 1 except that the average diameter of the abrading particles was changed to 0.3 μm.

TEST EXAMPLE 3

The probe cleaner of Test Example 3 was prepared by using the same material and by the same method as for Test Example 1 except that the average diameter of the abrading particles was changed to 3 μm.

TEST EXAMPLE 4

The probe cleaner of Test Example 4 was prepared by using the same material and by the same method as for Test Example 1 except that microfibers with average fiber diameter of 0.1 μm were used for the flocked sheet.

TEST EXAMPLE 5

The probe cleaner of Test Example 5 was prepared by using the same material and by the same method as for Test Example 1 except that microfibers with average fiber diameter of 3 μm were used for the flocked sheet.

TEST EXAMPLE 6

The probe cleaner of Test Example 6 was prepared by using the same material and by the same method as for Test Example 1 except that microfibers with average fiber diameter of 20 μm were used for the flocked sheet.

TEST EXAMPLE 7

The probe cleaner of Test Example 7 was prepared by using the same material and by the same method as for Test Example 1 except that alumina was used as abrading particles.

TEST EXAMPLE 8

The probe cleaner of Test Example 8 was prepared by using the same material and by the same method as for Test Example 1 except that diamond was used as abrading particles.

COMPARISON EXAMPLE 1

The probe cleaner of Comparison Example 1 was prepared by using the same material and by the same method as for Test Example 1 except that the average diameter of the abrading particles was changed to 5 μm.

COMPARISON EXAMPLE 2

A probe cleaner of Comparison Example 2 was prepared as follows.

A paint for aforementioned Test Example 3 (prepared by heating and drying 1 kg of abrading particles of silicon carbide with average diameter of 3 μm, thereafter mixing them with a resin solution obtained by dissolving 310 g of saturated polyester resin in a mixed solvent of toluene, xylene, ethyl acetate and MEK, stirring it to disperse the abrading particles in the resin solution and thereafter filtering them, and adding 60 g of an isocyanate hardening agent and adjusting it immediately before it is applied onto the cleaner sheet, and having a viscosity of 50 cp) was applied to the surface of a PET film by using a gravure roller (#50 having grooves in straight lines at regular intervals making angles of 45°) and dried.

COMPARISON EXAMPLE 3

A probe cleaner of Comparison Example 3 was prepared by applying a paint for aforementioned Test Example 3 to the surface of a foamed film by using a gravure roller (#50 having grooves in straight lines at regular intervals making angles of 45°) and drying.

The compositions of the probe cleaners of Test Examples 1-8 and Comparison Examples 1-3 are summarized in Table 2 below. Results of the test are shown in Table 3 below.

TABLE 2
SheetAbrading particles
Fiber diameterAverage diameter
Type(μm)Material(μm)
Test Example 1Flocked sheet10Silicon carbide0.05
Test Example 2Flocked sheet10Silicon carbide0.3
Test Example 3Flocked sheet10Silicon carbide3
Test Example 4Flocked sheet0.1Silicon carbide0.05
Test Example 5Flocked sheet3Silicon carbide0.05
Test Example 6Flocked sheet20Silicon carbide0.05
Test Example 7Flocked sheet10Alumina0.3
Test Example 8Flocked sheet10Diamond0.3
Comparison Example 1Flocked sheet10Silicon carbide5
Comparison Example 2PET filmSilicon carbide3
Comparison Example 3Foamed filmSilicon carbide3

TABLE 3
Test Probe ATest Probe B
Removal rateRemoval rate
fromWears onfromWears on
indentationsindentationsindentationsprotrusions
Test Example 1CACA
Test Example 2BBBB
Test Example 3ACAC
Test Example 4BABA
Test Example 5AAAA
Test Example 6BABA
Test Example 7CACA
Test Example 8ACAC
ComparisonADAD
Example 1
ComparisonDADD
Example 2
ComparisonDBDD
Example 3

In Table 3, the symbols for the removal rate of foreign objects from indentations are as follows:

A: 95% and over

B: 80-95%

C: 60-80%

D: Below 60%

The symbols for the wears (abrasions) are as follows:

A: No wears after 100000 contacts

B: Wears appear after 100000 contacts

C: Wears appear after 10000 contacts

D: Wears appear after 1000 contacts

It can be seen from the results of Test Examples 1-3 and Comparison Example 1 that the removal rate from indentations drops as the diameters of the abrading particles are made smaller, becoming 60-80% with average particle diameter of 0.05 μm (Test Example 1). The wears become smaller as the diameters of abrading particles are made larger, becoming not detectable after 10000 contacts with average particle diameter of 0.05 μm (Test Example 3) and after 1000 contacts with average particle diameter of 5 μm (Comparison Example 1).

The results of Test Examples 2, 7 and 8 show that no significant changes appear in the removal rate of foreign objects in indentations and the degree of wears even if the kind of abrading particles is changed and that results better than by Comparison Examples can be obtained.

The results of Test Examples 1 and 4-6 show that the removal rate of foreign objects in indentations becomes lower if the fiber diameter is reduced, becoming 80-95% if the fiber diameter is 0.1 μm (Test Example 1) and that the wears begin to appear when the contact number reaches 10000 if the fiber diameter exceeds 110 μm and becomes 20 μm. On the other hand, the amount of wears does not depend very much on the fiber diameter, no wears being detectable after 100000 contacts if the fiber diameter is in the range of 0.1 μm-20 μm.

From the above, it may be concluded that it is preferable to use microfibers with fiber diameters of 0.1 μm-20 μm for the flocked sheet and abrading particles with average particle diameter of 0.05 μm-3 μm to be affixed to these microfibers.

The results of Table 3 generally show that the probe cleaners of Test Examples 1-8 have better removal rates of foreign objects in indentations than those of Comparison Examples, causing less wears on the indentations and protrusions on the probe.

Although probe cleaners and cleaning methods were described above for the tip part of a probe, it goes without saying that the present invention can be used for the removal of foreign objects attached to the tip part of other kinds of needle such as needles for clinical use and for sewing.