JP2000261110A - Printed wiring board and semiconductor mounting structure using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a larger junction strength without making electrode pads larger by providing a plurality of electrode pads for fusing and joining the projecting electrodes and making leader lines from each electrode pad in radial directions whose origin is a predetermined deformation center. SOLUTION: Lands 602 corresponding to respective electrode pads 601 aligned and arranged at positions opposing to projecting electrodes are formed to connect the electrode pads 601 with wiring. Then, main parts 604a of leader lines 604 for electrically connecting respective electrode pads 601 with the lands 602, which parts 604a being at least near the connecting parts of the respective electrode pads 601, are drawn out inwardly from the respective electrode pads 601 along radiating directions whose origin is a predetermined deformation center O on the board. According to this construction, a part of the projecting electrode is fused towards the main part 604a of leader line when they are joined and the contact angle between the surface of the board and the projecting electrode become larger. Therefore, the junction strength of the projecting electrode against thermal stress is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printed wiring board and a semiconductor mounting device using the same, and more particularly, to a printed wiring board connected to another substrate using a protruding electrode and a semiconductor using the same. It relates to a mounting device.

[0002]

2. Description of the Related Art A variety of semiconductor devices have been proposed along with higher integration of electronic equipment. Among them, a semiconductor device called a BGA (ball grid array) or LGA (land grid array) has been proposed. The device is receiving attention.

In these semiconductor devices, a semiconductor element (semiconductor chip) is mounted on the surface of an interposer (or chip carrier) substrate, and external connection electrode pads are formed on the back surface. Q
As compared with FP (quad flat package), there is an advantage that the size can be greatly reduced.
Furthermore, since the pitch of the external connection electrode pads can be widened to 1.0 to 1.5 mm with respect to the QFP of 0.3 to 0.5 mm, there is an advantage that mounting on a printed wiring board becomes easy.

FIG. 9 is a sectional view showing the structure of a conventional general BGA and its mounting structure. The BGA 1 is configured by mounting the semiconductor element 10 on the surface of an interposer substrate 20. Semiconductor element 10 and interposer substrate 2
0 is electrically connected to the semiconductor element 10 and the bonding wire 30 by a bonding wire 30.
It is sealed and fixed to the interposer substrate 20 by a resin 40 as a sealing resin.

[0005] The printed wiring board 80 on which the BGA 1 is mounted and the interposer substrate 20 are formed by forming the protruding electrodes 5 formed on the back surface of the interposer substrate 20 in advance.
0 and are electrically and mechanically connected. As the projecting electrode 50, a solder alloy having a melting point of 200 ° C. or less is used. In the case of the LGA, only the electrode pads are formed on the back surface of the interposer substrate 20, and the above-mentioned protruding electrodes are not formed.

Semiconductor mounting device 2 including BGA 1 described above
In the case where a high-density, high-definition wiring is formed on the interposer substrate 20, an alumina ceramic substrate is used,
Its coefficient of thermal expansion is about 6-7 ppm / ° C. On the other hand, an organic substrate typified by glass epoxy which is frequently used as the printed wiring board 80 has a thermal expansion coefficient of 1
It is about 2 to 15 ppm / ° C.

As described above, since the thermal expansion coefficients of the interposer substrate 20 and the printed wiring board 80 are significantly different, the heat generated during operation of the semiconductor element 10 causes a large thermal stress due to the difference between the two. Occurs.
This thermal stress is concentrated on the outer peripheral portion of the protruding electrode 50 that joins the substrates 20 and 80, and in the worst case, fatigue failure may occur at the joint.

FIG. 10 is an enlarged sectional view of the projecting electrode 50. The projecting electrode 50 fused and joined has a drum shape as shown in FIG. The concentration is concentrated on the constricted portion of the bonding interface, and the degree of concentration increases as the bonding angle θ with the substrate 80 (electrode pad 801) decreases (is sharper). In order to increase the bonding angle θ, the gap between the substrates may be widened. However, the shape of the protruding electrode 50 at the time of fusion bonding depends on the surface tension of the solder and the mass of the BGA 1. Generally, it is difficult to control.

In order to solve such a problem, Japanese Patent Application Laid-Open No. 7-321247 or Japanese Patent Application Laid-Open No. 9-27047 has been proposed.
Japanese Patent Application Laid-Open No. 7-74139 discloses a technique of increasing the contact angle between an electrode and a substrate in the direction of thermal stress generation by increasing the shape of an electrode pad 801 in the deformation direction to increase the bonding strength.

[0010]

In the above-mentioned prior art, the dimensions of the electrode pads become longer in the direction in which the thermal stress is generated, and the area of the electrode pads becomes larger than before. There is a problem that the mounting density is reduced.

An object of the present invention is to solve the above-mentioned problems of the prior art, and to provide a printed wiring board capable of obtaining a strong bonding strength without increasing the size of an electrode pad, and a semiconductor mounting apparatus using the same. Is to do.

[0012]

In order to achieve the above-mentioned object, the present invention provides a plurality of electrode pads to which a protruding electrode is fused and joined, and a lead-out wiring drawn from each of the electrode pads. It is characterized in that each of the lead-out wirings is drawn out in a radial direction from a predetermined deformation center as a base point.

According to the above feature, the contact angle between the protruding electrode and the surface of the substrate can be increased by using the lead-out wiring without increasing the size of the electrode pad. Therefore, the bonding strength of the protruding electrodes can be improved without increasing the substrate area, that is, without lowering the mounting density of the substrate.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. FIG. 1 is a partial plan view of a printed wiring board 60 according to a first embodiment of the present invention, and a large number of electrode pads are provided on a surface of the substrate, for example, at positions opposed to protruding electrodes formed on a BGA interposer substrate. 601 are arranged and arranged, and corresponding to each electrode pad 601, a land 602 and a via 603 for connecting the electrode pad to a wiring (not shown) formed on the back surface of the substrate or inside the substrate are formed. .

Each of the electrode pads 601 and the lands 60
2 is electrically connected via a lead wiring 604.
In the present embodiment, at least a main portion 604 of each lead-out wiring 604 which is close to a connection portion with each electrode pad 601.
a is drawn inward from each of the electrode pads 601 in the radial direction with a predetermined deformation center O on the substrate 60 as a base point.

FIG. 2A is an enlarged plan view around the electrode pads 601 of the printed wiring board 60, and FIG.
FIG. 9 is a cross-sectional view of the second embodiment of the present invention in which the interposer substrate 20 of A1 is joined to the electrode pads 601 of the printed wiring board 60 via the protruding electrodes 50 along the XX line along the radiation direction. The same reference numerals as those described above represent the same or equivalent parts.

On the surface of the printed wiring board 60, at least the electrode pads 601 and the lead wiring main portion 604
The solder resist layer 605 is formed so as to avoid the vicinity of the connection portion with the electrode pad 601 in FIG. The solder resist layer 605 is formed with a clearance of about 0.05 to 0.1 mm from the electrode pad 601 in consideration of the solder resist pattern formation accuracy and the processing accuracy of the printed wiring board 60.

When the interposer substrate 20 of the BGA 1 is joined to the printed wiring board 60 having such a configuration by the protruding electrodes 50, as shown in FIG. Also dissolves into 604a. For this reason, the contact angle θ between the surface of the substrate 60 and the protruding electrode 50 increases, and the contact angle θ can be made obtuse if necessary. Therefore, even if the printed wiring board 60 receives thermal stress in the right direction in the drawing with respect to the interposer board 20, that is, in the direction of the deformation center O along the radiation direction due to the difference in thermal expansion force between the boards 20, 60. Thus, the bonding strength against this thermal stress can be dramatically improved.

Incidentally, the above-mentioned thermal stress is generated only when the BGA generates heat, and also occurs when cooling from the heat generating state, and the location where the thermal stress is generated differs in each case. For example, when a BGA in which the interposer substrate 20 is ceramic is mounted on the printed wiring board 60 of the present invention, the printed wiring board 60 extends relatively to the interposer substrate 20 when the temperature rises. For this reason, at the outer peripheral portion of the protruding electrode 50, as indicated by the broken line in FIG. 3, the maximum distortion occurs on the interposer substrate 20 side in the radial direction and on the printed wiring board 60 side in the radial direction. Occurs on the outside.

On the other hand, when the temperature decreases, the printed wiring board 60 contracts relatively to the interposer substrate 20, so that the location where the maximum distortion occurs is opposite to that when the temperature rises. That is, as indicated by the broken line in FIG. 4, the light emission occurs outward in the radial direction on the interposer substrate 20 side, and the light emission occurs in the radial direction on the printed wiring board 60 side.

Here, when the temperature is high, the creep phenomenon of the solder is likely to occur and the joint is easily deformed, so that the residual strain tends to decrease at a high temperature. On the other hand, when the state shifts to the low temperature state, the cleave phenomenon hardly occurs, so that a large residual strain is generated as compared with the case where the state shifts to the high temperature state. In other words, cracks are more likely to occur at the joints when the temperature drops. Therefore, the coefficient of thermal expansion K60 of the printed wiring board 60 is compared with the coefficient of thermal expansion K20 of the interposer board 20, and if K60> K20, as described with reference to FIG. If K20> K60, as shown in FIG. 5, the lead wiring may be drawn outward in the radial direction.

The outermost circumference of the substrate and 1 to 1 from the outermost circumference
Regarding the electrode pads 601 up to the second row, wiring is generally drawn outward from the center in the opposite direction to that in FIG. In this case, it is only necessary to determine which side to pull out in consideration of the balance between ease of wiring and reliability. However, the outer electrode pads may be connected to the inner layer from the nearest via, for example, a power supply terminal or a GND terminal, or a wiring may be drawn on the inner layer or the back surface through the via with the inner electrode pad. If it is necessary to turn the via, a via may be formed in the direction of the center of the strain, and the wiring up to that may be drawn out in the direction of the center of the strain and connected to the via.

As described above, according to the present embodiment, the contact angle between the protruding electrode and the substrate surface can be increased by using the existing lead wiring 604 without increasing the size of the electrode pad 601. Therefore, the bonding strength between the protruding electrode and the substrate can be improved without increasing the substrate area, and without reducing the mounting density of the substrate.

Note that even if the solder resist layer 605 formed on the surface of the printed wiring board 60 is formed with a predetermined clearance from the electrode pad 601 as shown in FIG. As shown in FIG. 6, the solder resist layer 605
There is a possibility that the electrode pad 601 is eccentric with respect to the opening 605a, and the extraction wiring 604 is not exposed.

Therefore, the opening formed in the solder resist layer 605 is, as shown in FIG.
It is preferable that a region 605b for exposing the substrate 04 is separately added, or as shown in FIG. 8, an elliptical shape 605c having a longer diameter in the lead-out direction of the lead-out wiring 604. By doing so, the lead wiring 604 can be exposed at least in the vicinity of the connection portion with the electrode pad 601 irrespective of the formation error of the solder resist layer 605 and the like.

[0026]

According to the present invention, the contact angle between the protruding electrode and the surface of the substrate can be increased by utilizing the lead-out wiring without increasing the size of the electrode pad. It is possible to improve the bonding strength of the protruding electrodes without increasing the size, and thus without reducing the mounting density of the substrate.

[Brief description of the drawings]

FIG. 1 is a plan view of a printed wiring board according to a first embodiment of the present invention.

FIG. 2 is a plan view and a cross-sectional view of a main part of a semiconductor mounting device according to a second embodiment of the present invention.

FIG. 3 is a cross-sectional view for explaining the principle of generation of stress strain.

FIG. 4 is a cross-sectional view for explaining the principle of generation of stress strain.

FIG. 5 is a plan view of a printed wiring board according to another embodiment of the present invention.

FIG. 6 is a plan view showing a positional relationship between a solder resist layer and an electrode pad.

FIG. 7 is a plan view showing a positional relationship between a solder resist layer and an electrode pad.

FIG. 8 is a plan view showing a positional relationship between a solder resist layer and an electrode pad.

FIG. 9 is a cross-sectional view showing a conventional BGA and its mounting structure.

FIG. 10 is a cross-sectional view showing a conventional bonding structure of a substrate using protruding electrodes.

[Explanation of symbols]

20 ... interposer substrate, 50 ... protruding electrode, 60 ...
Printed wiring board, 601: electrode pad, 602: land, 603: via, 604: lead-out wiring, 605: solder resist layer

Claims (8)

[Claims] A plurality of electrode pads to which the protruding electrodes are melt-bonded; and lead wires drawn from the respective electrode pads, wherein each of the lead wires has a radial direction with a predetermined deformation center as a base point. A printed wiring board, wherein the printed wiring board has been drawn out along. 2. The printed wiring board according to claim 1, wherein the lead-out wiring is drawn inward along a radial direction with a deformation center as a base point. 3. The printed wiring board according to claim 1, wherein the lead-out wiring is drawn out in a radial direction with the deformation center as a base point. 4. An insulating film is formed on a surface of the printed wiring board except for a window portion exposing at least a part of each electrode pad and a lead-out wiring thereof, and the window portion includes:
4. The printed wiring board according to claim 1, wherein each of the electrode pads has a longer diameter in a lead-out direction of each lead-out wiring. 5. A semiconductor device having a semiconductor element mounted on one main surface of an insulating substrate and a protruding electrode formed on the other main surface is mounted on a printed circuit board having electrode pads formed on the surface. In a semiconductor mounting device in which a protruding electrode and an electrode pad are mounted so as to be joined, the lead-out wiring of each electrode pad formed on the printed wiring board extends along a radial direction with a predetermined deformation center as a base point. A semiconductor mounting device characterized by being drawn out. 6. The printed wiring board has a larger coefficient of thermal expansion than the insulating substrate, and the lead-out wiring is
6. The semiconductor mounting device according to claim 5, wherein the semiconductor mounting device is drawn inward along a radial direction with the deformation center as a base point. 7. The printed wiring board has a smaller coefficient of thermal expansion than the insulating substrate, and the lead-out wiring is
6. The semiconductor mounting device according to claim 5, wherein the semiconductor mounting device is drawn outward along a radial direction with the deformation center as a base point. 8. An insulating film is formed on a surface of the printed wiring board except for a window for exposing at least a part of each electrode pad and a lead-out wiring thereof, and the window includes:
8. The semiconductor mounting device according to claim 5, wherein each of the electrode pads has a longer diameter in a lead-out direction of each lead-out wiring.