DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0130] Preferred embodiments of the present invention will hereinafter be described in detail with reference to the accompanying drawings.

[0131] Whenever circumstances require it for convenience in the following embodiments, they will be described while being divided into a plurality of sections or embodiments. However, unless otherwise specified in particular, they are not irrelevant to one another. One thereof has to do with modifications, details and supplementary explanations of some or all of the other.

[0132] When reference is made to the number of elements or the like (including the number of pieces, numerical values, quantity, range, etc.) in the following embodiments, the number thereof is not limited to a specific number and may be greater than or less than or equal to the specific number unless otherwise specified in particular and definitely limited to the specific number in principle.

[0133] It is also needless to say that components (including element or factor steps, etc.) employed in the following embodiments are not always essential unless otherwise specified in particular and considered to be definitely essential in principle.

[0134] Similarly, when reference is made to the shapes, positional relations and the like of the components or the like in the following embodiments, they will include ones substantially analogous or similar to their shapes or the like unless otherwise specified in particular and considered not to be definitely so in principle, etc. This is similarly applied even to the above-described numerical values and range.

[0135] Members each having the same function in all the drawings for describing the embodiments are respectively identified by the same reference numerals and their repetitive description will therefore be omitted.

[0136] (First Embodiment)

[0137] FIG. 1 is a cross-sectional view showing one example of a structure of a high-frequency package according to a first embodiment of the present invention, FIG. 2 is an external perspective view illustrating one example of a structure of an optical module with the high-frequency package shown in FIG. 1 built therein, FIG. 3 is a cross-sectional view depicting the structure of the optical module shown in FIG. 2 , FIG. 4 is a plan view showing one example of a layout of parts built in the optical module shown in FIG. 2 , FIG. 5 is a cross-sectional view illustrating one example of the layout of the parts built in the optical module shown in FIG. 2 , FIG. 6 is a cross-sectional view showing a structure of a high-frequency package according to a modification of the first embodiment, FIG. 7 is a partly plan view illustrating one example of a structure of a microstrip line of a wiring board employed in the high-frequency package shown in FIG. 1 , FIG. 8 is a partly cross-sectional view showing the structure of the microstrip line shown in FIG. 7 , FIG. 9 is a partly plan view depicting a structure of a microstrip line illustrative of a modification of the microstrip line of the wiring board employed in the high-frequency package shown in FIG. 1 , FIG. 10 is a partly cross-sectional view showing the structure of the microstrip line illustrative of the modification shown in FIG. 9 , FIG. 11 is a perspective view and a cross-sectional view showing a structure of a high-frequency package illustrative of another modification of the first embodiment, FIG. 12 is a cross-sectional view depicting one example of a cap-mounted structure shown in FIG. 1 , FIG. 13 is a plan view of the cap-mounted structure shown in FIG. 12 , FIG. 14 is a cross-sectional view cut along line A-A of FIG. 13 , FIG. 15 is a bottom view of the cap-mounted structure shown in FIG. 13 , FIG. 16 is a plan view showing one example of the relationship of position between surface layer wirings and a cap employed in the cap-mounted structure shown in FIG. 12 , FIG. 17 is a bottom view illustrating a structure of the cap as seen in the direction indicated by an arrow C of FIG. 14 , FIG. 18 is a side view showing the structure of the cap shown in FIG. 17 , FIG. 19 is a cross-sectional view illustrating the structure of the cap shown in FIG. 17 and an enlarged partly cross-sectional view of its corner, FIG. 20 is an enlarged partly cross-sectional view cut along line A-A of FIG. 13 , FIG. 21 is an enlarged partly cross-sectional view cut along line B-B of FIG. 13 , FIG. 22 is an enlarged partly plan view showing one example of the relationship of position between the surface layer wirings employed in the cap-mounted structure shown in FIG. 12 and an opening of the cap employed therein, FIG. 23 is a cross-sectional view illustrating a structure of a high-frequency package illustrative of a further modification of the first embodiment, FIG. 24 is an enlarged partly cross-sectional view showing one example of a structure wherein a radiating member is mounted to the cap shown in FIG. 12 , FIGS. 25, 26 and 27 are respectively cross-sectional views depicting structures of high-frequency packages illustrative of still further modifications of the first embodiment, FIG. 28 is a plan view showing a structure of a high-frequency package illustrative of a still further modification of the first embodiment, FIG. 29 is a cross-sectional view of the high-frequency package shown in FIG. 28 , FIGS. 30, 31 and 32 are respectively plan views showing structures of high-frequency packages illustrative of still further modifications of the first embodiment, FIG. 33 is a plan view depicting a structure of a high-frequency package illustrative of a still further modification of the first embodiment, FIG. 34 is a cross-sectional view of the high-frequency package illustrated in FIG. 33 , FIG. 35 is a plan view depicting a structure of a high-frequency package illustrative of a still further modification of the first embodiment, FIG. 36 is a cross-sectional view of the high-frequency package depicted in FIG. 35 , FIG. 37 is a plan view depicting a structure of a high-frequency package illustrative of a still further modification of the first embodiment, and FIG. 38 is a cross-sectional view of the high-frequency package illustrated in FIG. 37 , respectively.

[0138] The semiconductor device according to the first embodiment shown in FIG. 1 is a semiconductor package equipped with an optical communication IC (Integrated Circuit), e.g., a high-frequency package 1 capable of performing high-speed transmission at 40 Gbps. Incidentally, the high-frequency package 1 is mounted to an optical module (an electronic device such as a semiconductor module device) 14 shown in FIGS. 2 and 3 and has a coaxial cable 7 used as one for signal transmission on the high-frequency side.

[0139] Now, the coaxial cable 7 employed in the first embodiment is one example of a transmission line. Incidentally, the transmission line is a wiring path for transmitting high frequency power, such as a microstrip line, a feeder cable or the like. A general wiring is a line for transmitting power regardless of high and low frequencies. While an input portion thereof and an output portion thereof are electrically connected to each other, characteristics at the transmission of the power are not necessarily taken into consideration. Accordingly, there may be a case in which high frequency power is not transmitted (the output is zero) even though low frequency power is transmitted.

[0140] On the other hand, the transmission line is of a line wherein wiring shapes or configurations and configurations and layouts of peripheral conductors including wirings, the quality of a material for an insulating layer, and the thickness and structure of the insulating layer are designed in such a manner that power is propagated with efficiency without a substantial reduction in output due to attenuation and reflection of the power in the course of its propagation.

[0141] The high-frequency package 1 according to the first embodiment comprises a package substrate (wiring board) 4 used as a chip carrier having a microstrip line 4 g made up of a signal surface layer wiring (surface layer wiring) 4 c and GND layers (ground conductor layers) 4 f formed inside through the signal surface layer wiring 4 c and an insulating layer 4 e , a high-frequency semiconductor chip 2 electrically connected to and mounted onto a main surface 4 a of the package substrate 4 by flip-chip connection with a plurality of solder bump electrodes 5 interposed therebetween, a coaxial cable 7 whose core line 7 a is electrically connected to the signal surface layer wiring 4 c , an underfill resin 6 poured between a main surface 2 a of the semiconductor chip 2 and the main surface 4 a of the package substrate 4 to protect the flip-chip connected portion, and ball electrodes 3 used as a plurality of external connecting terminals disposed within a back surface 4 b located on the side opposite to the main surface 4 a of the package substrate 4 .

[0142] Namely, the high-frequency package 1 is one wherein a signal of a high frequency (e.g., 40 Gbps) inputted from the coaxial cable 7 is directly inputted to the semiconductor chip 2 so as to propagate through the solder bump electrodes 5 via the signal surface layer wiring 4 c of the package substrate 4 . The high-frequency package 1 has a structure wherein the high-frequency signal can be transmitted by only the microstrip line at the whole surface layer of the package substrate 4 .

[0143] Owing to the transmission of the high-frequency signal by only the microstrip line at the surface layer of the package substrate 4 without through via-based wirings or the like, the high-frequency signal can be thus transmitted without a loss in frequency characteristic.

[0144] Namely, vias (also including through holes) are not transmission lines but wirings. In order to realize the efficient propagation of power through the transmission line, wiring widths, the thickness of each interlayer insulating film, spaces between adjacent patterns, material physical values, etc. are designed as parameters so that its characteristic impedance becomes a desired value. However, since it is difficult to make the pattern of each via and each interlayer conductor vertical and constitute them as a coaxial structure, the design for obtaining the desired characteristic impedance is difficult. Accordingly, a loss in power at each via portion is apt to occur.

[0145] From this point of view, the technology described in Unexamined Patent Publication No. Hei 5(1993)-167258, for connecting the neighborhood of a portion where a core line of a coaxial cable and its corresponding each bump pad are connected, as the via configuration will cause a characteristic impedance mismatch at the connecting portion. Further, the technology is considered to need, when an attempt is made to embed the coaxial cable into a substrate in its thickness direction, such a manufacturing process that a hole is defined in the substrate by a drill or the like, the coaxial cable is inserted into the hole and then positioned therein, and each bump pad and its corresponding core line are connected to each other, after which the hole is buried. This structure increases the number of processes as compared with a general process of manufacturing a wiring board. This structure will lead to cost up with a difficult technology of cable connection and embedding.

[0146] On the other hand, since the wiring board can be manufactured by the known technology in the first embodiment, no cost up takes place.

[0147] Incidentally, the surface layer wirings such as the signal surface layer wiring 4 c , the GND surface layer wirings 4 h employed in the first embodiment are of wirings which are formed of, for example, copper or the like and disposed on the uppermost layer on the main surface 4 a side of the package substrate 4 . They may be exposed onto the main surface 4 a or coated with a non-conductive thin film or the like.

[0148] It is desirable that when high-speed transmission such as 40 Gbps or the like is performed, the signal surface layer wiring 4 c of the microstrip line 4 g is of the shortest. Thus, the solder bump electrodes 5 , of the plurality of solder bump electrodes 5 connected to the semiconductor chip 2 of the package substrate 4 , which are disposed toward the coaxial cable 7 (coaxial connector 11 ) from the center of the semiconductor chip 2 , are connected to the signal surface layer wiring 4 c.

[0149] Preferably, any of the solder bump electrodes 5 disposed on the outermost periphery, of the plurality of solder bump electrodes 5 is connected to the signal surface layer wiring 4 c.

[0150] Consequently, high-speed signal transmission in which a loss in the frequency characteristic of a high frequency has been suppressed to the minimum, can be realized. Since it is possible to reduce carrying of noise on the microstrip line 4 g , a reduction in high-frequency characteristic can be also suppressed.

[0151] In the high-frequency package 1 , the plurality of ball electrodes (bump electrodes) 3 provided as the external connecting terminals are disposed on the back surface 4 b of the package substrate 4 in an array form. Accordingly, the high-frequency package 1 is a semiconductor package of a ball grid array type.

[0152] Thus, the package can be downsized as compared with an outer-lead protrusion type high-frequency package wherein outer leads protrude outwards from the package substrate 4 .

[0153] Incidentally, while the microstrip line 4 g transmits a high-frequency signal as an electromagnetic wave in the insulating layer 4 e lying between the signal surface layer wiring 4 c and its corresponding internal GND layer 4 f , both of GND surface layer wirings (ground surface layer wirings) 4 h disposed on both sides of a signal surface layer wiring 4 c with an insulating portion interposed therebetween form a microstrip line 4 g in a surface layer of a package substrate 4 as shown in FIG. 7 .

[0154] A frame member 8 extending along an outer peripheral portion of the package substrate 4 is attached to the package substrate 4 in the high-frequency package 1 . Further, the frame member 8 is provided with a coaxial connector (linkup or junction member) 11 fit onto the coaxial cable 7 together with a glass bead 12 . Thus, the coaxial cable 7 is fit in the coaxial connector 11 , the core line 7 a of the coaxial cable 7 is connected to its corresponding core line 12 a of the glass bead 12 , and the core line 12 a is in solder-connection 31 to the signal surface layer wiring 4 c of the package substrate 4 (it may be connected thereto by a conductive resin or the like).

[0155] Incidentally, the diameter of the coaxial connector 11 is about 10 mm, for example.

[0156] The package substrate 4 is a substrate formed of, for example, glass-contained ceramic or the like. The package substrate 4 has a thickness of about 1 mm, for example and is formed thereinside with an internal signal wiring 4 d used as a signal line for connecting the flip-chip connected solder bump electrode 5 and its corresponding ball electrode 3 used as the external connecting terminal, except for the GND layers 4 f.

[0157] The high-frequency package 1 having such a structure is built in such an optical module (semiconductor module device) 14 or the like as shown in FIG. 2 and mounted on its module substrate (junction member) 13 .

[0158] A structure of the optical module 14 will now be described.

[0159] The optical module 14 shown in FIGS. 2 through 5 is a module for high-speed optical communications, e.g., a module product mounted to a communication system apparatus or the like of a communication network base station.

[0160] The optical module 14 according to the first embodiment has a size of L (ranging from 100 mm to 200 mm)×M (ranging from 60 mm to 150 mm), for example, as shown in FIG. 2 and a height (T) ranging from 10 mm to 25 mm as shown in FIG. 3 . However, the size and height of the optical module 14 are not limited to these numerical values.

[0161] The high-frequency package 1 according to the first embodiment is mounted on the module substrate 13 of the optical module 14 . The module substrate 13 is covered as a whole with a module case 15 . A plurality of fins 16 are formed side by side on the surface of the module case 15 . Placing the fins 16 under wind 18 enables an improvement in the dissipation of the optical module 14 .

[0162] Incidentally, an external terminal of the optical module 14 is a module connector 17 attached to the module substrate 13 . Part of the module connector 17 is exposed to the back side of the module case 15 .

[0163] In the optical module 14 , as shown in FIGS. 4 and 5 , a high-frequency light signal inputted from its input is converted into an electric signal by an optoelectronic transducer 20 . Further, the electric signal passes through the microstrip line 4 g of the package substrate 4 via an amplifier device 19 so as to enter into the high-frequency semiconductor chip 2 on the input side, followed by transformation into a low-frequency signal, which in turn is transmitted to the outside of the optical module 14 via the internal signal wiring 4 d of the package substrate 4 , the corresponding solder bump electrode 5 and the module substrate 13 shown in FIG. 1 and the module connector 17 .

[0164] On the other hand, a signal inputted from the module connector 17 passes through a path opposite to the above path and is transmitted as an output.

[0165] Incidentally, while FIG. 4 shows that the high-frequency semiconductor chip 2 is provided two on the input and output sides, the input and output sides may be built in one semiconductor chip 2 .

[0166] In FIG. 4 , arrows indicated by solid lines, of arrows indicative of the flows of signals for input and output show the transmission of the light signals by optical fibers, whereas arrows indicated by dotted lines thereof show the transmission of the electric signals through the coaxial cables 7 or microstrip lines 4 g.

[0167] Next, FIG. 6 shows a modification of the high-frequency package 1 . A core line 7 a of a coaxial cable 7 is connected directly to a signal surface layer wiring 4 c of a package substrate 4 by solder or the like.

[0168] Namely, the coaxial cable 7 is directly connected to the package substrate 4 without the use of a coaxial connector 11 by solder or the like.

[0169] In this case, a step 4 k for disposing the coaxial cable 7 is provided at an end of the package substrate 4 , and a GND surface layer wiring 4 h is provided on the surface of the step 4 k . Upon placement of the coaxial cable 7 on the step 4 k , a shield (GND) 7 b for covering the core line 7 a of the coaxial cable 7 , and the GND surface layer wiring 4 h on the step 4 k are electrically connected to each other by solder or the like.

[0170] Owing to the direct attachment of the coaxial cable 7 to the package substrate 4 in this way, the high-frequency package 1 can be reduced in thickness and a cost reduction can be achieved because the coaxial connector 11 expensive and relatively large in diameter is not used.

[0171] A preferable shape or configuration of a GND layer 4 f corresponding to an inner layer in a package substrate 4 will next be explained using FIGS. 7 through 10 .

[0172] First, FIGS. 7 and 8 respectively show a case in which the GND layer 4 f placed inside the substrate extends to an end of the package substrate 4 in a microstrip line structure 21 using a microstrip line 4 g , and a case in which a structure wherein a coaxial structure 22 using a coaxial cable 7 and the microstrip line structure 21 are connected to each other, is taken.

[0173] In this case, a high-speed signal inputted from and outputted to the package outside passes through a path of the coaxial cable 7 , a signal surface layer wiring 4 c of the package substrate 4 and a semiconductor chip 2 . At this time, a core line 7 a of the coaxial cable 7 is connected to the signal surface layer wiring 4 c of the package substrate 4 , and a shield 7 b used as GND, of the coaxial cable 7 is connected to its corresponding GND surface layer wirings 4 h of the package substrate 4 .

[0174] Further, a frame member 8 for supporting the coaxial cable 7 might be fixedly secured onto the package substrate 4 . Further, the frame member 8 and the shield 7 b of the coaxial cable 7 or the GND surface layer wirings 4 h of the package substrate 4 might be connected to each other. Incidentally, the corresponding GND surface layer wiring 4 h and the GND layer 4 f used as the inner layer are connected to each other by via wirings 4 i as shown in FIG. 8 .

[0175] Thus, in order to bring the signal surface layer wiring 4 c on the package 4 to the microstrip line structure 21 over it whole area so as to reduce L (inductance) of GND, there is a need to expose the GND layer 4 f at the end of the substrate to thereby connect it to the shield 7 b of the coaxial cable 7 or GND of the frame member 8 , or form at the substrate end, the via wirings 4 i for connecting the corresponding GND surface layer wiring 4 h and the GND layer 4 f used as the inner layer and cut and expose the via wirings 4 i upon substrate cutting-off to thereby connect the same to the coaxial cable 7 or GND of the frame member 8 .

[0176] However, these technologies need high accuracy upon positioning of the surface-layer/inner-layer wirings of the package substrate 4 and has a fear that when a pasty material such as Cu is used for wiring, it leads to wiring sagging, and a difficulty arises upon manufacture thereof.

[0177] On the other hand, a structure shown in FIGS. 9 and 10 is one formed with a coplanar line 23 a wherein a signal surface layer wiring 4 c and GND surface layer wirings 4 h are disposed on the same plane (main surface 4 a ) in an area between the outermost peripheral via wiring 4 i of a plurality of via wirings 4 i and a coaxial cable 7 . The coaxial cable 7 and a microstrip line 4 g of a package substrate 4 are connected to each other through the coplanar line 23 a.

[0178] Namely, an area provided outside from the outermost peripheral via wiring 4 i close to the end of the package substrate 4 is defined as a coplanar structure 23 . A coaxial structure 22 , the coplanar structure 23 and a microstrip line structure 21 are connected to one another.

[0179] Thus, the inductance of GND can be reduced.

[0180] Further, in order to make characteristic impedance matching in an area for the coplanar structure 23 , the distance between the signal surface layer wiring 4 c and each of the GND surface layer wirings 4 h is decreased so that they are brought close to each other as shown in FIG. 9 . Incidentally, the accuracy of position displacement between the via wiring 4 i and its corresponding GND layer 4 f used as an inner layer is equivalent to the prior art (e.g., about 50 μm). Since a novel technology is not required, cost up can be prevented.

[0181] Thus, the interconnection of the coaxial structure 22 , coplanar structure 23 and microstrip line structure 21 makes it possible to reduce a loss in high-frequency signal and bring the characteristic impedance of a high-speed signal path close to a target value.

[0182] Further, the characteristic impedance can be brought closer to a target value by decreasing the distance between the signal surface layer wiring 4 c and each GND surface layer wiring 4 h in the surface layer of the package substrate 4 .

[0183] As a result, degradation of high-speed signal characteristics can be suppressed and an improvement in the electric characteristics of the high-frequency package 1 can be realized without an increase in cost.

[0184] A high-frequency package 1 showing a modification illustrated in FIG. 11 will next be described.

[0185] The high-frequency package 1 shown in FIG. 11 makes use of a thin-type coaxial connector 24 of a plate-shaped member as a junction member between a coaxial cable 7 and a microstrip line 4 g of a package substrate 4 .

[0186] The thin-type coaxial connector 24 has a microstrip line 24 c made up of a signal surface layer wiring (surface layer wiring) 24 a and GND lines (ground wirings) 24 b formed on both sides thereof with insulating portions interposed therebetween. Thus, in the high-frequency package 1 , the signal surface layer wiring 24 a of the microstrip line 4 g of the package substrate 4 , and a core line 7 a of the coaxial cable 7 are electrically connected to each other through the signal surface layer wiring 24 a of the microstrip line 24 c of the thin-type coaxial connector 24 .

[0187] Namely, the signal surface layer wiring 24 a is provided on the surface of an upper stage of a thin ceramic plate or the like with a step 24 d , and the GND lines 24 b are provided on both sides thereof. Further, only the GND lines 24 b are provided at a lower stage of the ceramic plate. The GND lines 24 b provided at the upper and lower stages are connected to each other by means of surface or internal layer vias or the like.

[0188] The coaxial cable 7 is then mounted on the lower stage, the core line 7 a at a leading end thereof is placed on the signal surface layer wiring 24 a at the upper stage, and a shield 7 b of the coaxial cable 7 and the GND lines 24 b at the upper and lower stages of the ceramic plate are connected to one another by solder or the like. Further, the core line 7 a of the coaxial cable 7 and the signal surface layer wiring 24 a at the upper stage are similarly connected to each other by solder or the like.

[0189] Thereafter, the surface layer wirings of the ceramic plate are made opposite to their corresponding surface layer wirings of the package substrate 4 , and their mutual wirings are connected to one another by solder or a conductive resin or the like. Alternatively, they may be connected by gold (Au)-to-gold (Au) crimping, or the ceramic plate and the package substrate 4 may be adhered and fixed to each other.

[0190] Using the thin-type coaxial connector 24 corresponding to the plate-like member as the junction member in this way enables a reduction in the thickness of the high-frequency package 1 .

[0191] Further, the coaxial cable 7 is easy to handle and connector repair is enabled. The thin-type coaxial connector 24 may be attached to both ends of the coaxial cable 7 . One end thereof may be formed as the thin-type coaxial connector 24 , whereas the other end thereof may be formed as such a coaxial connector 11 as shown in FIG. 1 . A connector different in shape from the coaxial cable 7 may be attached. Alternatively, one end may be formed as the thin-type coaxial connector 24 , and the other end may be exposed as a cable end.

[0192] Incidentally, only the coaxial cable 7 may be provided as an alternative to the coaxial cable 7 with the thin-type coaxial connector 24 attached thereto. Alternatively, the high-frequency package 1 may be provided as the high-frequency package 1 with such a thin-type coaxial connector 24 as shown in FIG. 11 mounted thereto.

[0193] A high-frequency package 1 illustrative of a modification shown in FIG. 12 will next be described.

[0194] Of a plurality of ball electrodes 3 used as external connecting terminals, support balls 3 a are first provided at the outermost-peripheral four corners as shown in FIG. 15 in the high-frequency package 1 shown in FIG. 12 .

[0195] This is done to cope with such a problem that when the high-frequency package 1 is mounted on a mounting board such as a module substrate 13 or the like, the ball electrodes 3 are crushed due to the heavy weight of a coaxial connector 11 , so that electrical shorts occur between the adjacent ball electrodes 3 . Since the support balls 3 a are provided at the outermost-peripheral four corners, the support balls 3 a at the corners are capable of supporting a package substrate 4 upon melting of the ball electrodes 3 to thereby prevent the occurrence of such electrical shorts due to the crushing of the ball electrodes 3 .

[0196] Incidentally, the support balls 3 a are respectively formed of, for example, high melting-point solder, a resin or ceramic or the like.

[0197] The high-frequency package 1 shown in FIG. 12 has a cap 9 corresponding to a radiating member mounted to a back surface 2 b opposite to a main surface 2 a of a semiconductor chip 2 with a thermal conductive adhesive 10 interposed therebetween.

[0198] Namely, since the high-frequency semiconductor chip 2 might generate high heat when driven, the radiating cap 9 , or a thermal diffusion plate or radiating fins or the like are attached to the back surface 2 b of the semiconductor chip 2 , whereby the semiconductor chip 2 can be improved in dissipation and the high-frequency package 1 can be also enhanced in dissipation, thus making it possible to prevent degradation of electric characteristics.

[0199] The position of layout of the cap 9 with respect to the package substrate 4 will now be explained. As shown in FIGS. 12 through 14 , the cap 9 is mounted onto the back surface 2 b of the semiconductor chip 2 with the thermal conductive adhesive 10 or the like interposed therebetween so as to cover the semiconductor chip 2 . At this time, the cap 9 may preferably be disposed even on surface layers (microstrip line 4 g ) such as a signal surface layer wiring 4 c and GND surface layer wirings 4 h or the like as shown in FIGS. 16 and 20 .

[0200] Namely, the cap 9 may preferably cover the microstrip line 4 g from thereabove to avoid carrying of noise on the microstrip line 4 g of the surface layer due to an external electromagnetic wave.

[0201] Accordingly, the cap 9 may preferably cover the semiconductor chip 2 and the surface layer wirings to some extent to block entrance of the external electromagnetic waves. However, the cap 9 and the surface layer wirings such as the signal surface layer wiring 4 c and the GND surface layer wirings 4 h or the like must be insulated.

[0202] Thus, the package substrate 4 employed in the first embodiment is formed with openings (wall escape portions) 9 a at leg portions 9 b on a surface layer wiring of a cap 9 as shown in FIG. 17 . Each of the openings takes such a cap shape as not to make contact between the leg portions 9 b of the cap 9 and the surface layer wiring.

[0203] Incidentally, FIGS. 20 and 22 show in detail the relationship of position between the openings 9 a at the leg portions 9 b of the cap 9 and the signal surface layer wiring 4 c and GND surface layer wirings 4 h of the package substrate 4 . Namely, the legs 9 b of the cap 9 are opened as the openings 9 a up to spots lying outside both sides of the GND surface layer wirings 4 h so as not to contact the signal surface layer wiring 4 c and the GND surface layer wirings 4 h.

[0204] Further, spots other than an area for connection of the signal surface layer wiring 4 c corresponding to the surface layer wiring of the package substrate 4 to the coaxial cable 7 are covered with a solder resist 4 j corresponding to an insulative thin film (non-conductive thin film) formed of a resin or the like as shown in FIG. 20 (GND surface layer wirings 4 h are also similar). The solder resist 4 j has an insulating function and even the function of stopping the flow of solder for solder connection 31 of the coaxial cable 7 .

[0205] Thus, since the openings 9 a corresponding to the wall escape portions of the cap 9 , and the solder resist 4 j used as the insulative thin film are formed with respect to the surface layer wirings, the surface layer wirings and the cap 9 can be prevented from contacting.

[0206] Incidentally, the cap 9 is formed, even at the corners and side portions thereof, with cut-away portions 9 c corresponding to such wall escape portions as not to contact the surface layer wiring as shown in FIGS. 17 and 18 .

[0207] Since the cap 9 also needs a shield effect, the whole surface of a base material 9 d made up of a copper alloy or the like is covered with a chrome conductive film 9 e as shown in FIG. 19 . Further, only its outer surface is covered with a non-conductive film 9 f so as to prevent electrical shorts developed in other parts.

[0208] Such a cap 9 is mounted to the same layer as a signal surface layer wiring 4 c and GND surface layer wirings 4 h formed on a main surface 4 a of a package substrate 4 as shown in FIGS. 21 and 22 . Incidentally, the cap 9 corresponds to the same layer as a layer for underlying electrodes of solder bump electrodes 5 .

[0209] At spots unformed with an opening 9 a lying between leg portions 9 b of the cap 9 , the leg portions 9 b are connected to an internal power supply (or GND layer 4 f ) of the package substrate 4 via a conductive material 25 and a via wiring 4 i to enhance the shield effect as shown in FIG. 21 . The cap 9 per se is electrically connected to internal power supply layers (or GND layer 4 f and GND surface layer wirings 4 h ) of the package substrate 4 .

[0210] Thus, the periphery of each solder bump electrode 5 for a high-frequency signal is brought to a state of being surrounded by a GND potential, so that the cap 9 -based shield effect can be enhanced.

[0211] The solder bump electrode 5 for the high-frequency signal, i.e., the solder bump electrode 5 connected to the signal surface layer wiring 4 c may preferably be set as the solder bump electrode 5 disposed approximately in the center of the side of a row of the outermost-peripheral solder bump electrodes 5 as shown in FIG. 22 . A coaxial connector 11 connected to the present solder bump electrode 5 via the signal surface layer wiring 4 c may also be preferably disposed substantially in the center of the side.

[0212] Thus, a microstrip line 4 g can be set to the shortest. High-speed signal transmission can be realized which minimizes a loss in the frequency characteristic of a high frequency. It is also possible to reduce carrying of noise on the microstrip line 4 g.

[0213] Next, a high-frequency package 1 illustrative of a modification shown in FIG. 23 is one having a structure wherein a cap 9 is mounted to the high-frequency package 1 using the thin-type coaxial connector 24 shown in FIG. 11 . According to the high-frequency package 1 shown in FIG. 23 , both thinning and dissipation of the high-frequency package 1 can be enhanced.

[0214] A high-frequency package 1 illustrative of a modification shown in FIG. 24 is one wherein a radiating block (radiating member) 26 is further mounted on the surface of a cap 9 attached to a back surface 2 b of a semiconductor chip 2 with a thermal conductive adhesive 10 interposed therebetween. The high-frequency package 1 can be further enhanced in dissipation.

[0215] A high-frequency package 1 illustrative of a modification shown in FIG. 25 is one showing a structure wherein a second semiconductor chip 27 is further mounted on a package substrate 4 in addition to a semiconductor chip 2 . A cap 9 for covering both chips is mounted thereon.

[0216] In the present example, a signal is inputted via an internal signal wiring 4 d of the package substrate 4 from the semiconductor chip 2 connected to a coaxial cable 7 through a microstrip line 4 g in a surface layer to the second semiconductor chip 27 . Further, the signal is transmitted from a solder bump electrode 5 of the second semiconductor chip 27 to its corresponding ball electrode 3 used as an external connecting terminal via an internal signal wiring 4 d.

[0217] Both high-frequency packages 1 illustrative of modifications shown in FIGS. 26 and 27 are ones wherein balancers 28 are attached to frame members 8 , respectively. The balancer 28 has the function of adjusting the center of gravity of the high-frequency package 1 so that the high-frequency package 1 is not inclined upon mounting of the high-frequency package 1 on a substrate.

[0218] FIG. 26 shows the modification wherein the balancer 28 is fixed to the frame member 8 through a screw member 29 . FIG. 27 shows the modification having a structure wherein a groove is defined in the balancer 28 and fit onto the frame member 8 to mount the balancer 28 on the frame member 8 .

[0219] Thus, in the high-frequency packages 1 shown in FIGS. 26 and 27 , the center of gravity of each high-frequency package is adjusted by the balancer 28 so that the high-frequency package 1 is not inclined upon its mounting onto the substrate.

[0220] The positions of placement of the package substrate 4 and the semiconductor chip 2 will next be described.

[0221] In the high-frequency package 1 , the semiconductor chip 2 may preferably be disposed on the package substrate, preferably, in an area close to the coaxial cable 7 .

[0222] Namely, when the high-frequency signal is transmitted from the coaxial cable 7 to the semiconductor chip 2 through the microstrip line 4 g in the surface layer of the package substrate 4 , noise is carried on the microstrip line 4 g when the microstrip line 4 g is long, so that high-frequency characteristics are degraded. Therefore, the semiconductor chip 2 may preferably be disposed so as to lean toward the coaxial cable 7 as viewed from the central portion of the package substrate 4 in order to prevent it. The semiconductor chip 2 is disposed as close to the coaxial cable 7 as possible.

[0223] Thus, the length of the microstrip line 4 g can be shortened and hence the degradation in the high-frequency characteristics due to the carrying-on of noise can be suppressed.

[0224] The high-frequency package 1 shown in FIG. 13 is one wherein one semiconductor chip 2 is mounted on a package substrate 4 . The semiconductor chip 2 is disposed toward a coaxial connector 11 as viewed from a central portion of the package substrate 4 . By fitting a coaxial cable 7 in the coaxial connector 11 , the semiconductor chip 2 is disposed toward the coaxial cable 7 from the central portion.

[0225] FIGS. 28 and 29 respectively show a case in which a high-frequency semiconductor chip 2 and a low-frequency second semiconductor chip 27 are mounted on a package substrate 4 . The high-frequency semiconductor chip 2 is disposed toward a coaxial connector 11 as viewed from a central portion of the package substrate 4 and placed toward the coaxial connector 11 as viewed from the low-frequency second semiconductor chip 27 . Further, the two coaxial connectors 11 are attached to one semiconductor chip 2 in association with each other.

[0226] FIG. 30 is a modification of the structure of FIG. 28 , wherein a combination of layouts of two coaxial connectors 11 is changed.

[0227] FIGS. 31 and 32 respectively show cases in which one semiconductor chips 2 are mounted on package substrates 4 . FIG.