Electronic component package and electronic circuit board using the same

Abstract

To provide an electronic component package capable of suppressing breakage of solder bumps and achieving a longer life without increasing the package size.SOLUTION: An electronic component package 1 includes a rectangular wiring substrate 10 and a plurality of pad electrodes 30 arranged in a grid pattern on the bottom surface 10b of the wiring substrate 10. The plurality of pad electrodes 30 include circular standard pad electrodes 31 provided at the corners of the wiring substrate 10 other than the four corners, and almond- or teardrop-shaped deformed pad electrodes 32 provided at the four corners of the wiring substrate 10. The longitudinal direction of the deformed pad electrodes 32 is oriented in a diagonal direction from the corner portion to which the deformed pad electrodes 32 belong toward the center of the wiring substrate 10.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an electronic component package and an electronic circuit board on which the electronic component package is mounted. [Background technology]

[0002] Electronic component packages that use pads arranged in a grid pattern, such as LGA (Land Grid Array), can experience stress at the corners when continuously subjected to temperature shrinkage and other factors, leading to breakage of the solder bumps connecting the electronic component package to the circuit board.

[0003] As a measure to prevent solder bump breakage, for example, Patent Document 1 describes a method of increasing the size of the bumps at the four corners of an electronic component package, while Patent Document 2 describes a method of employing square lands at the four corners of the package and tilting the orientation of the square lands in the diagonal direction of the electronic component package. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 11-097569 [Patent Document 2] Japanese Patent Application Laid-Open No. 2001-127202 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the method described in Patent Document 1, which enlarges the bump size at the four corners of the package, makes it difficult to layout large bumps within a limited area, and the planar size of the package also increases.In addition, there is a risk of package mounting defects occurring due to the difference in solder volume compared to normal-sized bumps other than those at the four corners.

[0006] Furthermore, in the method described in Patent Document 2, in which the square lands are tilted in the diagonal direction of the package, the clearance between adjacent lands becomes insufficient, increasing the probability of package mounting defects.

[0007] Therefore, an object of the present invention is to provide an electronic component package that can suppress breakage of solder bumps and achieve a longer life without increasing the package size, and to provide a highly reliable electronic circuit board on which such an electronic component package is mounted. [Means for solving the problem]

[0008] In order to solve the above problem, the electronic component package according to the present invention comprises a rectangular wiring board and a plurality of pad electrodes arranged in a grid pattern on the bottom surface of the wiring board, the plurality of pad electrodes including circular standard pad electrodes provided at locations other than the four corners of the wiring board and almond-shaped or teardrop-shaped deformed pad electrodes provided at the four corners of the wiring board, and the longitudinal direction of the deformed pad electrodes is oriented diagonally from the corner portion to which the deformed pad electrodes belong toward the center of the wiring board.

[0009] According to the present invention, even when the electronic component package is subjected to thermal stress while surface-mounted on a motherboard, breakage of the solder bumps can be suppressed, thereby extending the life of the electronic component package and providing a highly reliable electronic component package.

[0010] The deformed pad electrode preferably 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 deformed pad electrode to be elongated in the diagonal direction of the wiring substrate. This prevents the solder bump from breaking and extends its lifespan.

[0011] In this case, the deformed pad electrode preferably has a circular portion, a first sharp portion protruding from the center of the circular portion toward the center of the wiring substrate, and a second sharp portion protruding in the opposite direction from the first sharp portion. Furthermore, it is preferable that the length of the first sharp portion is equal to the length of the second sharp portion. This allows the solder bump connected to the deformed pad electrode to be elongated in the diagonal direction of the wiring substrate, thereby preventing breakage of the solder bump and extending its lifespan.

[0012] The electronic component package according to the present invention further includes a plurality of solder bumps connected to the plurality of pad electrodes, and the planar shape of the solder bumps is preferably the same as the planar shape of the pad electrodes to which the solder bumps are connected, thereby preventing breakage of the solder bumps at the four corners of the wiring substrate and achieving a longer lifespan.

[0013] Furthermore, an electronic circuit board according to the present invention comprises a motherboard having a plurality of land electrodes and the above-described electronic component package according to the present invention mounted on the motherboard, wherein the pad electrodes are connected to the land electrodes via solder bumps, and the planar shape of the land electrodes is the same as the planar shape of the pad electrodes to which the land electrodes are connected.

[0014] According to the present invention, the solder bumps can be elongated in the diagonal direction of the package, and the fracture distance of the solder bumps can be increased, thereby providing an electronic circuit board with high connection reliability between the electronic component package and the motherboard. [Effects of the Invention]

[0015] According to the present invention, it is possible to provide an electronic component package that can suppress breakage of solder bumps and achieve a longer life without increasing the package size, and a highly reliable electronic circuit board on which the electronic component package is mounted. [Brief explanation of the drawings]

[0016] [Figure 1]1(a) and (b) are schematic perspective views showing the configuration of an electronic component package according to an embodiment of the present invention, where (a) is a view from the top side and (b) is a view from the bottom side. [Figure 2] FIG. 2 is a schematic plan view showing the electrode layout on the bottom surface of the electronic component package. [Figure 3] FIG. 3 is an enlarged view of a corner portion of the bottom surface of the electronic component package, and particularly shows the shape of the deformed pad electrode. [Figure 4] 4(a) and 4(b) are schematic plan views showing the shape of the modified pad electrode. [Figure 5] FIG. 5 is a diagram showing the shape of a solder bump, where (a) shows the state where it is mounted on the deformed pad electrode 32, and (b) shows the state where it is separated from the deformed pad electrode. [Figure 6] FIG. 6 is a schematic cross-sectional view showing the configuration of an electronic circuit board including an electronic component package, and shows the state in which the electronic component package is mounted on a motherboard. [Figure 7] FIG. 7 is an explanatory diagram of a crack occurring in a solder bump. DETAILED DESCRIPTION OF THE INVENTION

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

[0018] Fig. 1 is a schematic perspective view showing the configuration of an electronic component package according to an embodiment of the present invention, where (a) is a view from the top side and (b) is a view from the bottom side, and Fig. 2 is a schematic plan view showing the electrode layout on the bottom surface of the electronic component package.

[0019] As shown in Figures 1(a) and (b), this electronic component package 1 includes a wiring board 10, various electronic components 20 mounted on the top surface 10a of the wiring board 10, a plurality of pad electrodes 30 formed on the bottom surface 10b of the wiring board 10, and a plurality of solder bumps 40 provided on each of the plurality of pad electrodes 30.

[0020] The wiring board 10 is preferably a multilayer wiring board (semiconductor-embedded board) with a semiconductor IC chip built in. The wiring board 10 is preferably rectangular, with each side preferably having a length of 4.5 to 5.0 mm.

[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] A plurality of pad electrodes 30 are arranged in a grid pattern on the bottom surface 10b of the wiring board 10. In this embodiment, the pad electrodes 30 are provided at all pad electrode formation positions defined in the grid pattern, but this is not necessarily required and they may be provided at any necessary positions. The pad electrodes 30 come in two shapes: circular standard pad electrodes 31 provided at pad electrode formation positions other than the four corners of the wiring board 10, and almond-shaped (or teardrop-shaped) modified pad electrodes 32 provided at pad electrode formation positions at the four corners of the wiring board 10. The diameter of the standard pad electrodes 31 is preferably 200 to 400 μm.

[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] 3(a) to 3(c) are enlarged views of the vicinity of the corner portion of the bottom surface of the electronic component package (area M in FIG. 2), and in particular show the shape of the deformed pad electrode.

[0025] 3(a) to 3(c), the deformed pad electrode 32 is almond-shaped and has a circular portion 32a of the same size as the standard pad electrode 31 integrated with two sharp portions 32s1 and 32s2 protruding in opposite directions from the circular portion 32a. Specifically, the deformed pad electrode 32 has the circular portion 32a, a first sharp portion 32s1 protruding from the circular portion 32a toward the center of the wiring substrate 10, and a second sharp portion 32s2 protruding in the opposite direction from the first sharp portion 32s1. The center of the deformed pad electrode 32 is located on a diagonal line DL1 connecting the corner portion 10c1 to which the deformed pad electrode 32 belongs and the corner opposite the corner portion 10c1, and the first and second sharp portions 32s1 and 32s2 are located on both sides of the diagonal line DL1 in the extending direction.

[0026] At least one deformed pad electrode 32 is always provided at the pad formation positions at the four corners of the wiring substrate 10, and is not provided anywhere other than the four corners. The first sharp portion 32s1 of the deformed pad electrode 32 faces toward the center of the wiring substrate 10, and the second sharp portion 32s2 faces toward the corner portion 10c. Therefore, the longitudinal direction of the deformed pad electrode 32 faces the extension direction of the diagonal line DL1 that runs from the corner portion to which the deformed pad electrode belongs, through the center of the wiring substrate 10, toward the opposite corner portion.

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

[0028] As shown in Fig. 3(b), when the clearance 30c is wide, the second sharp portion 32s2 of the deformed pad electrode 32 can be extended diagonally outward, thereby widening the width of the solder bump 40 in the diagonal direction of the wiring substrate 10. Also, as shown in Fig. 3(c), when the clearance 30c is narrow, the first sharp portion 32s1 can be extended diagonally inward, thereby widening the width of the solder bump 40 in the diagonal direction of the wiring substrate 10. In this way, the lengths of the first sharp portion 32s1 and the second sharp portion 32s2 may be different from each other or may be the same.

[0029] It is desirable that the first sharp portion 32s1 and the second sharp portion 32s2 are contained within the clearance range, but they may protrude slightly. The sharp portions may have a pointed tip, and the degree of change in width toward the tip is not particularly limited. In other words, the change in width toward the tip may be constant, may decrease, or may increase toward the tip.

[0030] 4(a) and (b) are schematic plan views showing the shape of the teardrop-shaped modified pad electrode 32. FIG.

[0031] As shown in Figures 4(a) and 4(b), the teardrop-shaped deformed pad electrode 32 has a circular portion 32a and one sharp portion 32s protruding from the circular portion 32a. In Figure 4(a), the sharp portion 32s is formed from the circular portion 32a toward the center of the substrate. In Figure 4(b), the sharp portion 32s is formed from the circular portion 32a toward the corner of the substrate. In this way, the deformed pad electrode 32 may have the sharp portion 32s provided only on one side of the diagonal line DL1.

[0032] As described above, solder bumps 40 are pre-connected to each pad electrode 30. The planar shape of the solder bumps 40 is preferably approximately the same as that of the underlying pad electrode 30 on which they are mounted. That is, if the planar shape of the pad electrode is circular, the solder bumps will also be circular; if it is almond-shaped, the solder bumps will also be almond-shaped; and if it is teardrop-shaped, the solder bumps will also be teardrop-shaped. There is no particular method for forming the solder bumps 40, and they can be formed by well-known methods such as plating or screen printing.

[0033] 5A and 5B are diagrams showing the shape of the solder bump 40, in which (a) shows the state where it is mounted on the deformed pad electrode 32, and (b) shows the state where it is separated from the deformed pad electrode 32. FIG.

[0034] 5(a) and 5(b), the deformed solder bump 42 preferably has the same shape as the deformed pad electrode 32. The deformed pad electrode 32 is connected to a land electrode 50 on the motherboard side via the solder bump 40, and the land electrode 50 also preferably has the same shape as the deformed pad electrode 32. The planar size of the solder bump 40 is preferably slightly smaller than that of the deformed pad electrode 32.

[0035] FIG. 6 is a schematic perspective view showing the configuration of an electronic circuit board 100 including the electronic component package 1. As shown in FIG.

[0036] 6, the electronic circuit board 100 includes a motherboard 2 and an electronic component package 1 mounted on the motherboard 2. A plurality of land electrodes 50 are provided on an upper surface 2a of the motherboard 2, facing a plurality of pad electrodes 30 of the electronic component package 1, and the pad electrodes 30 are connected to the corresponding land electrodes 50 via solder bumps 40.

[0037] The shape of the land electrode 52 connected to the deformed pad electrode 32 is preferably the same as that of the deformed pad electrode 32. That is, in the land matrix within the mounting area of ​​the electronic component package 1, the land electrodes 51 other than those at the four corners are preferably circular, and the land electrodes 52 at the four corners are preferably teardrop-shaped (or almond-shaped). This allows the solder bump 40 to be elongated in the diagonal direction, thereby increasing the fracture distance of the solder bump 40.

[0038] FIG. 7 is an explanatory diagram of a crack occurring in the solder bump 40. As shown in FIG.

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

[0040] 7(a), in the case of a circular solder bump 40, its length is the same in all directions, and the length in the direction in which cracks 45 occur is short, making the solder bump 40 prone to fracture. However, as shown in FIG. 7(b), the solder bump 40 according to this embodiment is long in the direction in which cracks 45 occur, so the occurrence of cracks 45 can be suppressed, and even if cracks 45 do occur, it is possible to buy time before the cracks 45 propagate and the solder bump 40 completely fractures.

[0041] As described above, the electronic component package 1 according to this embodiment includes a wiring board 10 on which an electronic component 20 is mounted, a plurality of pad electrodes 30 formed on the bottom surface 10b of the wiring board 10, and a plurality of solder bumps 40 provided on each pad electrode 30. The plurality of pad electrodes 30 include circular standard pad electrodes 31 provided at locations other than the four corners of the wiring board 10, and deformed pad electrodes 32 provided at the four corners of the wiring board 10. The deformed pad electrodes 32 have an almond or teardrop shape in plan view, and the longitudinal direction of the deformed pad electrodes 32 is oriented in the diagonal direction of the wiring board 10. This prevents breakage of the solder bumps 40 connected to the deformed pad electrodes 32, thereby extending the life of the solder bumps 40. This improves the reliability of the connection with the motherboard 2.

[0042] The above describes a preferred embodiment of the present invention, but the present invention is not limited to the above embodiment, and various modifications are possible within the scope of the present invention, and it goes without saying that these modifications are also included within the scope of the present invention.

[0043] For example, the initial shape of the solder bumps 40 before the reflow process for surface-mounting the electronic component package 1 on the motherboard 2 does not necessarily have to be the same as the pad electrodes 30, and the planar shape may be circular (the three-dimensional shape may be cylindrical or spherical). Whatever the shape, the solder bumps 40 fit the shape of the pad electrodes 30 after the reflow process, so they can be made to have approximately the same shape as the pad electrodes 30. However, if the initial shape of the solder bumps 40 is the same as the pad electrodes 30, there will be less deformation after the reflow process, and the probability of connection failure can be reduced. [Example]

[0044] A thermal fatigue simulation was performed on electronic component modules according to an example and a comparative example. The electronic component module according to the example employed almond-shaped pad electrodes and solder bumps in the corners, and also employed almond-shaped land electrodes on the motherboard side. The planar shapes of the pad electrodes and solder bumps other than those in the corners were circular. On the other hand, the electronic component module according to the comparative example employed circular pad electrodes and solder bumps throughout, with all bumps having the same shape.

[0045] In the thermal fatigue simulation, thermal stress was applied to the electronic component module by repeatedly changing the temperature from low to high. The temperature conditions for applying thermal stress were to increase the temperature from 25°C to 85°C, hold at 85°C for 5 minutes, decrease the temperature from 85°C to -40°C, hold at -40°C for 5 minutes, and return from -40°C to 25°C, which was one cycle. The temperature increase and decrease rates were 18°C / min.

[0046] As a result of the above simulation, in the electronic component module of the comparative example, cracks in the solder bumps at the corners progressed as the thermal cycle increased, leading to early breakage of the solder bumps. In contrast, in the electronic component module of the example, the center portion of the solder bumps remained connected even after the thermal cycle that led to breakage in the comparative example, and no breakage occurred. The durability of the electronic component module of the example was improved by 5% or more compared to the electronic component module of the comparative example. [Explanation of symbols]

[0047] 1. Electronic component package 2 Motherboard 2a Top of the motherboard 10. Wiring board 10a Top surface of wiring board 10b Bottom of wiring board 10c, 10c1 corner 20 Electronic Components 30 Pad Electrode 30c Clearance 31 Standard pad electrodes 32 Deformed pad electrode 32a Circular section 32s sharp part 32s1 First Sharp Section 32s2 2nd sharp part 40 solder bumps 41 Standard Solder Bumps 42 Deformed solder bumps 45 Crack 50, 51, 52 Land electrodes 100 Electronic Circuit Board DL1 diagonal

Claims

1. a rectangular wiring substrate; and a plurality of pad electrodes arranged in a grid pattern on a bottom surface of the wiring substrate; The plurality of pad electrodes are a standard circular pad electrode provided at a corner other than the four corners of the wiring board, and a modified almond-shaped or teardrop-shaped pad electrode provided at the four corners of the wiring board; The electronic component package according to claim 1, wherein the longitudinal direction of the deformed pad electrode is oriented in a diagonal direction from the corner portion to which the deformed pad electrode belongs toward the center of the wiring substrate.

2. 2. The electronic component package according to claim 1, wherein the deformed pad electrode has a circular portion and a sharp portion that protrudes from the center of the circular portion toward the center or the corner portion of the wiring substrate.

3. 2. The electronic component package of claim 1, wherein the deformed pad electrode has a circular portion, a first sharp portion protruding from the center of the circular portion toward the center of the wiring substrate, and a second sharp portion protruding in a direction opposite to the first sharp portion.

4. 4. The electronic component package according to claim 3, wherein the length of said first sharp portion is equal to the length of said second sharp portion.

5. Further comprising a plurality of solder bumps connected to each of the plurality of pad electrodes, 3. The electronic component package according to claim 2, wherein the planar shape of the solder bump is the same as the planar shape of the pad electrode to which the solder bump is connected.

6. a motherboard having a plurality of land electrodes; The electronic component package according to claim 1 is mounted on the motherboard, the pad electrodes are connected to the land electrodes via solder bumps, The electronic circuit board according to claim 1, wherein the planar shape of the land electrode is the same as the planar shape of the pad electrode to which the land electrode is connected.

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