Electronic component package and electronic circuit board using the same

Abstract

This invention provides an electronic component package that achieves long lifespan by suppressing solder bump breakage without increasing package size. The electronic component package 1 of this invention includes: a rectangular wiring substrate 10; and a plurality of solder pad electrodes 30 arranged in a grid pattern on the bottom surface 10b of the wiring substrate 10. The plurality of solder pad electrodes 30 includes: standard circular solder pad electrodes 31 disposed outside the four corners of the wiring substrate 10; and almond-shaped or teardrop-shaped deformable solder pad electrodes 32 disposed at the four corners of the wiring substrate 10. The long axis of the deformable solder pad electrodes 32 is oriented diagonally from the corner of the deformable solder pad electrode 32 toward the center of the wiring substrate 10.

Description

[Technical Field]

[0001] This invention relates to the packaging of electronic components and an electronic circuit board on which the electronic component package is mounted. [Previous Technology]

[0002] When electronic component packages using LGA (Land Grid Array) and other grid-like solder pads are continuously subjected to temperature shrinkage and other effects, stress will be applied to the corners, causing the solder bumps used to connect the electronic component package to the circuit board to breakage.

[0003] As a countermeasure to prevent solder bump breakage, Patent Document 1 discloses, for example, a method for increasing the size of the bumps at the four corners of an electronic component package. Furthermore, Patent Document 2 discloses a method in which square pads are used at the four corners of the package, and the direction of the square pads is tilted towards the diagonal of the electronic component package. [Prior Art Documents] [Patent Documents]

[0004] Patent Document 1: Japanese Patent Application Publication No. Hei 11-097569; Patent Document 2: Japanese Patent Application Publication No. 2001-127202 [Summary of the Invention]

[0005] (Problem to be solved by the invention) However, in the method described in Patent Document 1, which increases the size of the bumps at the four corners of the package, it is difficult to configure larger bumps within a limited area, and the planar size of the package also becomes larger. In addition, since the amount of solder is different from that of the bumps of normal size outside the four corners, poor package mounting may occur.

[0006] Furthermore, in the method described in Patent Document 2, in which the direction of the square pad is tilted toward the diagonal of the package, the gap between it and the adjacent pad becomes insufficient, which increases the probability of poor package installation.

[0007] Therefore, the object of the present invention is to provide an electronic component package that can suppress solder bump breakage and achieve a long lifespan without increasing the package size. Furthermore, the present invention provides a highly reliable electronic circuit board on which such an electronic component package is mounted. (Technical means to solve the problem)

[0008] In order to solve the above problems, the electronic component package of the present invention is characterized by comprising: a rectangular wiring substrate; and a plurality of pad electrodes arranged in a grid pattern on the bottom surface of the wiring substrate; the plurality of pad electrodes having: a circular standard pad electrode disposed outside the four corners of the wiring substrate; and an almond-shaped or teardrop-shaped deformable pad electrode disposed at the four corners of the wiring substrate; the long axis direction of the deformable pad electrode is oriented towards the diagonal direction, which is from the corner to which the deformable pad electrode is located towards the center of the wiring substrate.

[0009] According to the present invention, even when the electronic component package is subjected to thermal stress while mounted on the surface of a motherboard, it can still suppress the cracking of solder bumps and achieve a long lifespan. Therefore, a highly reliable electronic component package can be provided.

[0010] Preferably, the deformable solder pad electrode has: a circular portion; and a sharp portion that protrudes from the center of the circular portion toward the center or corner of the wiring substrate. This allows the solder bump connected to the deformable solder pad electrode to extend diagonally along the wiring substrate. Therefore, solder bump breakage can be suppressed, resulting in a longer lifespan.

[0011] Preferably, in this case, the deformable solder pad electrode has: a circular portion; a first pointed portion protruding from the center of the circular portion toward the center of the wiring substrate; and a second pointed portion protruding in the opposite direction to the first pointed portion. Furthermore, it is preferable that the length of the first pointed portion is equal to the length of the second pointed portion. This allows the solder bumps connected to the deformable solder pad electrode to extend diagonally along the wiring substrate, thereby suppressing solder bump breakage and achieving a longer lifespan.

[0012] Preferably, the electronic component package of the present invention further includes: a plurality of solder bumps connected to each of the plurality of solder pad electrodes; the planar shape of the solder bumps is the same as the planar shape of the solder pad electrodes to which the solder bumps are connected. This suppresses the cracking of the solder bumps at the four corners of the wiring board and achieves a longer lifespan.

[0013] Furthermore, the electronic circuit board of the present invention is characterized in that it comprises: a motherboard having a plurality of pad electrodes; and the electronic component package of the present invention, which is mounted on the motherboard; the pad electrodes are connected to the pad electrodes via solder bumps, and the planar shape of the pad electrodes is the same as the planar shape of the pad electrodes to which the pad electrodes are connected.

[0014] According to the present invention, the solder bumps can be extended diagonally along the package, thereby extending the breakage distance of the solder bumps. Therefore, it can provide an electronic circuit board with higher reliability in the connection between the electronic component package and the motherboard. (Effects compared to prior art)

[0015] According to the present invention, an electronic component package can be provided, which can achieve long life without increasing the package size and suppressing the cracking of solder bumps, and a highly reliable electronic circuit board on which the electronic component package is mounted.

Implementation Method

[0017] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0018] Figure 1 is a schematic perspective view showing the structure of an electronic component package according to an embodiment of the present invention, (a) being a view viewed from the top surface side, and (b) being a view viewed from the bottom surface side. Figure 2 is a schematic bottom view showing the electrode arrangement on the bottom surface of the electronic component package.

[0019] As shown in Figures 1(a) and (b), the electronic component package 1 includes: a wiring substrate 10; various electronic components 20 mounted on the upper surface 10a of the wiring substrate 10; a plurality of pad electrodes 30 formed on the bottom surface 10b of the wiring substrate 10; and a plurality of solder bumps 40 respectively disposed on the plurality of pad electrodes 30.

[0020] Preferably, the wiring substrate 10 is a multilayer wiring substrate (semiconductor-integrated substrate) with a built-in semiconductor IC chip. Preferably, the wiring substrate 10 is rectangular, with one side having a length of 4.5~5.0mm.

[0021] Various electronic components 20 are mounted on the upper surface 10a of the wiring board 10. The electronic components 20 are, for example, peripheral circuit components such as chip resistors, chip capacitors, chip inductors, and oscillators.

[0022] On the bottom surface 10b of the wiring substrate 10, a plurality of solder pad electrodes 30 are arranged in a grid pattern. In this embodiment, the solder pad electrodes 30 are disposed at all the solder pad electrode forming positions defined by the grid pattern, but this is not mandatory; they can be disposed at the necessary positions. The solder pad electrodes 30 have two shapes: they are composed of standard circular solder pad electrodes 31 disposed at solder pad electrode forming positions other than the four corners of the wiring substrate 10, and almond-shaped (or teardrop-shaped) deformed solder pad electrodes 32 disposed at solder pad electrode forming positions at the four corners of the wiring substrate 10. Preferably, the diameter of the standard solder pad electrode 31 is 200~400μm.

[0023] The shape of the solder bump 40 is the same as the shape of the pad electrode 30 on which the solder bump 40 is mounted. That is, a circular standard solder bump 41 is mounted on the standard pad electrode 31, and an almond-shaped (or teardrop-shaped) deformed solder bump 42 is mounted on the deformed pad electrode 32.

[0024] Figures 3(a) to (c) are enlarged views of the area near the bottom corner of the electronic component package (region M in Figure 2), and are particularly showing the shape of the deformed solder pad electrode.

[0025] As shown in Figures 3(a) to (c), the deformable solder pad electrode 32 is almond-shaped, having an integrally formed circular portion 32a of the same size as the standard solder pad electrode 31 and two sharp portions 32s1 and 32s2 protruding from the circular portion 32a in opposite directions. Specifically, the deformable solder pad electrode 32 has a circular portion 32a, a first sharp portion 32s1 protruding from the circular portion 32a toward the center of the wiring board 10, and a second sharp portion 32s2 protruding in the opposite direction to the first sharp portion 32s1. The center of the deformable solder pad electrode 32 is located on a diagonal DL1 connecting the corner portion 10c1 to which the deformable solder pad electrode 32 belongs to and the corner portion opposite to the corner portion 10c1. The first sharp portion 32s1 and the second sharp portion 32s2 are respectively located on both sides of the extending direction of the diagonal DL1.

[0026] At least one deformable solder pad electrode 32 must be provided at the solder pad formation positions at the four corners of the wiring substrate 10, and none must be provided outside the four corners. The first sharp portion 32s1 of the deformable solder pad electrode 32 faces the center direction of the wiring substrate 10, and the second sharp portion 32s2 faces the corner portion 10c. Therefore, the long axis direction of the deformable solder pad electrode 32 is directed towards the diagonal line DL1 extending from the corner to which the deformable solder pad electrode belongs, through the center of the wiring substrate 10, to the opposite corner.

[0027] The shape of the deformable pad electrode 32 is determined with consideration of the gap 30c between two adjacent pad electrodes. Figure 3(a) shows the case where the lengths of the first pointed portion 32s1 and the second pointed portion 32s2 protruding from the circular portion 32a of the deformable pad electrode 32 are equal.

[0028] As shown in FIG3(b), when the gap 30c is wider, the second sharp portion 32s2 of the deformable solder pad electrode 32 can extend outward diagonally, thereby expanding the width of the solder bump 40 in the diagonal direction of the wiring substrate 10. Furthermore, as shown in FIG3(c), when the gap 30c is narrower, the first sharp portion 32s1 can extend inward diagonally, thereby expanding the width of the solder bump 40 in the diagonal direction of the wiring substrate 10. Thus, the lengths of the first sharp portion 32s1 and the second sharp portion 32s2 can be different or the same.

[0029] While it is desirable for the first pointed portion 32s1 and the second pointed portion 32s2 to converge within the gap, they may also protrude slightly. The pointed portions only need to have a pointed front end; the degree of width variation towards the front end is not particularly limited. That is, the width variation towards the front end can be fixed, or it can be that the width variation decreases towards the front end, or the width variation increases towards the front end.

[0030] Figures 4(a) and (b) are schematic bottom views showing the shape of the teardrop-shaped deformable pad electrode 32.

[0031] As shown in Figures 4(a) and (b), the teardrop-shaped deformable pad electrode 32 has a circular portion 32a and a pointed portion 32s protruding from the circular portion 32a. Figure 4(a) shows the pointed portion 32s formed from the circular portion 32a toward the center of the substrate. Furthermore, Figure 4(b) shows the pointed portion 32s formed from the circular portion 32a toward a corner of the substrate. Thus, the deformable pad electrode 32 may also have a pointed portion 32s provided only on one side in the diagonal DL1 direction.

[0032] As described above, solder bumps 40 are pre-attached to each pad electrode 30. Preferably, the planar shape of the solder bump 40 is substantially the same as that of the pad electrode 30 on which it is mounted. That is, if the planar shape of the pad electrode is circular, the solder bump is also circular; if the planar shape of the pad electrode is almond-shaped, the solder bump is also almond-shaped; if the planar shape of the pad electrode is teardrop-shaped, the solder bump is also teardrop-shaped. The solder bump 40 does not need to be specially formed; it can be formed by known methods such as electroplating or screen printing.

[0033] Figures 5(a) and (b) are diagrams showing the shape of the solder bump 40, (a) showing the state of being mounted on the deformable pad electrode 32, and (b) showing the state of being cut off from the deformable pad electrode 32.

[0034] Preferably, as shown in Figures 5(a) and (b), the deformed solder bump 42 has the same shape as the deformed pad electrode 32. The deformed pad electrode 32 is connected to the pad electrode 50 on the motherboard side via the solder bump 40, but preferably, the pad electrode 50 also has the same shape as the deformed pad electrode 32. Preferably, the planar dimensions of the solder bump 40 are slightly smaller than those of the deformed pad electrode 32.

[0035] Figure 6 is a schematic perspective view of the structure of an electronic circuit board 100 including an electronic component package 1.

[0036] As shown in FIG6, the electronic circuit board 100 includes: a motherboard 2; and an electronic component package 1, which is mounted on the motherboard 2. On the upper surface 2a of the motherboard 2, a plurality of pad electrodes 50 are provided opposite to a plurality of pad electrodes 30 of the electronic component package 1, and the pad electrodes 30 are connected to the corresponding pad electrodes 50 via solder bumps 40.

[0037] Preferably, the shape of the pad electrode 52 connected to the deformable pad electrode 32 is the same as that of the deformable pad electrode 32. That is, preferably, in the pad matrix within the mounting area of ​​the electronic component package 1, the pad electrodes 51 outside the four corners are circular, while the pad electrodes 52 at the four corners are teardrop-shaped (or almond-shaped). This allows the solder bump 40 to extend diagonally and extends the breakage distance of the solder bump 40.

[0038] Figures 7(a) and (b) are explanatory diagrams of cracks generated by solder bump 40.

[0039] As shown in Figures 7(a) and (b), it can be seen that the direction of the stress applied to the electronic component package 1 due to thermal expansion and contraction is larger in the diagonal direction connecting the center and corner of the package, and cracks 45 of solder bumps 40 will be generated in this direction.

[0040] Here, as shown in FIG7(a), when the solder bump 40 is circular, its length is the same in any direction. Since the length in the direction in which the crack 45 is generated is relatively short, the solder bump 40 is prone to breakage. However, as shown in FIG7(b), the solder bump 40 of this embodiment is longer in the direction in which the crack 45 is generated, so it can suppress the generation of the crack 45. In addition, even if the crack 45 is generated, it can still provide time for the crack 45 to progress to the point that the solder bump 40 completely breaks.

[0041] As explained above, the electronic component package 1 of this embodiment includes: a wiring substrate 10 on which an electronic component 20 is mounted; a plurality of solder pad electrodes 30 formed on the bottom surface 10b of the wiring substrate 10; and a plurality of solder bumps 40 disposed on each solder pad electrode 30. The plurality of solder pad electrodes 30 have: a circular standard solder pad electrode 31 disposed outside the four corners of the wiring substrate 10; and deformable solder pad electrodes 32 disposed at the four corners of the wiring substrate 10. The planar shape of the deformable solder pad electrode 32 is almond-shaped or teardrop-shaped, and the long axis of the deformable solder pad electrode 32 is oriented towards the diagonal direction of the wiring substrate 10. Therefore, it can suppress the cracking of the solder bumps 40 connected to the deformable solder pad electrode 32 and extend the life of the solder bumps 40. Therefore, it can improve the reliability of the connection with the motherboard 2.

[0042] The preferred embodiments of the present invention have been described above, but the present invention is not limited to the above embodiments. Various modifications can be made without departing from the spirit of the present invention, and such modifications are of course included within the scope of the present invention.

[0043] For example, before the reflow step of mounting the electronic component package 1 onto the motherboard 2, the initial shape of the solder bump 40 does not necessarily need to be the same as that of the pad electrode 30; its planar shape can also be circular (its three-dimensional shape can be cylindrical or spherical). Regardless of the shape, after the reflow step, the solder bump 40 will conform to the shape of the pad electrode 30, thus it can become approximately the same shape as the pad electrode 30. However, if the initial shape of the solder bump 40 is the same as that of the pad electrode 30, its deformation after the reflow step is less, thus reducing the probability of poor connection. [Example]

[0044] The following describes thermal fatigue simulation of the electronic component module in the embodiments and comparative examples. In the electronic component module of the embodiments, the solder pads and solder bumps at the corners are almond-shaped, and almond-shaped pads are also used on the motherboard side. The planar shape of the solder pads and solder bumps outside the corners is circular. On the other hand, the electronic component module of the comparative example uses circular solder pads and solder bumps throughout, resulting in all bumps having the same shape.

[0045] In the thermal fatigue simulation, temperature changes from low to high temperatures are repeatedly implemented to apply thermal stress to the electronic component module. The temperature conditions used to apply the thermal stress are: heating from 25°C to 85°C, holding at 85°C for 5 minutes, cooling from 85°C to -40°C, holding at -40°C for 5 minutes, and returning from -40°C to 25°C, which constitutes one cycle. The heating and cooling rates are set to 18°C / minute.

[0046] The simulation results show that in the comparative example's electronic component module, along with the increase in thermal cycling, the cracks in the solder bumps at the corners spread, quickly leading to the breakage of the solder bumps. In contrast, in the embodiment's electronic component module, even after the thermal cycle that caused breakage in the comparative example, the central portion of the solder bumps remained connected without breakage. Compared to the comparative example's electronic component module, the embodiment's electronic component module can improve durability by more than 5%. [Simplified Explanation of the Diagram]

[0016] Figures 1(a) and (b) are schematic perspective views showing the structure of an electronic component package according to an embodiment of the present invention, (a) being a view viewed from the top surface side and (b) being a view viewed from the bottom surface side. Figure 2 is a schematic bottom view showing the electrode arrangement on the bottom surface of the electronic component package. Figures 3(a) to (c) are enlarged views of the corners of the bottom surface of the electronic component package, specifically showing the shape of the deformable solder pad electrode. Figures 4(a) and (b) are schematic bottom views showing the shape of the deformable solder pad electrode. Figures 5(a) and (b) are diagrams showing the shape of the solder bump, (a) showing the state mounted on the deformable solder pad electrode 32, and (b) showing the state separated from the deformable solder pad electrode. Figure 6 is a schematic cross-sectional view showing the structure of an electronic circuit board including the electronic component package, showing the state in which the electronic component package is mounted on a motherboard. Figures 7(a) and (b) are explanatory diagrams of cracks generated on the solder bump.

Claims

1. An electronic component package, characterized in that it comprises: a rectangular wiring substrate; and a plurality of pad electrodes arranged in a grid pattern on the bottom surface of the wiring substrate; the plurality of pad electrodes having: circular standard pad electrodes disposed outside the four corners of the wiring substrate; and almond-shaped or teardrop-shaped deformable pad electrodes disposed at the four corners of the wiring substrate; the long axis direction of the deformable pad electrodes is oriented diagonally from the corner of the deformable pad electrode toward the center of the wiring substrate; the deformable pad electrodes have: a circular portion; and a pointed portion protruding from the center of the circular portion toward the center or corner of the wiring substrate.

2. As in request item 1, the electronic component packaging, wherein, The aforementioned deformable solder pad electrode has: a circular portion; a first sharp portion that protrudes from the center of the circular portion toward the center of the wiring substrate; and a second sharp portion that protrudes in the opposite direction to the first sharp portion.

3. As in request item 2, the electronic component packaging, wherein, The length of the first pointed portion is equal to the length of the second pointed portion.

4. The electronic component package of claim 1 further comprises: a plurality of solder bumps connected to each of the plurality of pad electrodes; wherein the planar shape of the solder bumps is the same as the planar shape of the pad electrodes to which the solder bumps are connected.

5. An electronic circuit board, characterized in that it comprises: a motherboard having a plurality of pad electrodes; and an electronic component package of any one of claims 1 to 4, which is mounted on the motherboard; wherein the pad electrodes are connected to the pad electrodes via solder bumps, and the planar shape of the pad electrodes is the same as the planar shape of the pad electrodes to which the pad electrodes are connected.

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