CN221842738U - Printed Circuit Board - Google Patents

Abstract

The utility model provides a printed circuit board, which comprises an integrated circuit bonding area and a plurality of connecting pads. The integrated circuit bonding region has a center point, and the integrated circuit bonding region includes an inner region corresponding to the center point and a peripheral region connecting the inner region. The bonding pad is disposed in the integrated circuit bonding region. The bonding pad comprises a plurality of first bonding pads, wherein the first bonding pads are arranged in the peripheral area and encircle the central point. In the upper view, each first pad has a geometric center, and each first pad has a long axis passing through the geometric center to form the longest line segment and a short axis passing through the geometric center to form the shortest line segment, wherein the length of the long axis is greater than the length of the short axis, and the long axis is perpendicular to the short axis. Wherein the extension direction of the short axis of at least a part of the first connection pad faces the inner area.

Description

Printed Circuit Board

Technical Field

The utility model relates to a printed circuit board, and in particular to a printed circuit board including a pad.

Background Art

Recently, the packaging of integrated circuits (ICs) has been developed towards miniaturization, resulting in the chip size package (CSP) packaging type. Multi-pin chip size package integrated circuits (such as image sensors) will form a matrix of ball solder joints at the bottom of the package to facilitate soldering with printed circuit boards (PCBs). However, when the integrated circuit and the printed circuit board are soldered together, the thermal expansion coefficient of the chip in the integrated circuit is different from the thermal expansion coefficient (CTE) of the printed circuit board, and the elongation and contraction of the integrated circuit and the printed circuit board are different. Therefore, the integrated circuit and the printed circuit board are easily bent in different directions under the influence of high and low temperature environments, resulting in deformation of the solder joints. If the high and low temperature environments are repeatedly cycled, the solder joints are prone to thermal fatigue and cracking.

Therefore, there is still an urgent need to study a printed circuit board that can improve solder joint deformation.

Summary of the invention

The utility model provides a printed circuit board, which can improve the deformation of solder joints through the design of the shape and arrangement of the pads of the printed circuit board.

According to one embodiment of the utility model, a printed circuit board is provided. The printed circuit board includes an integrated circuit bonding area and a plurality of pads. The integrated circuit bonding area has a center point, and the integrated circuit bonding area includes an inner area corresponding to the center point and a peripheral area connecting the inner area. The pad is arranged in the integrated circuit bonding area. The pad includes a plurality of first pads, and the first pads are arranged in the peripheral area and surround the center point. In the top view, each first pad has a geometric center, and each first pad has a long axis passing through the geometric center to form the longest line segment and a short axis passing through the geometric center to form the shortest line segment, the length of the long axis is greater than the length of the short axis, and the long axis is perpendicular to the short axis. In the top view, the extension direction of the short axis of at least a portion of the first pads is toward the inner area.

In order to better understand the above and other aspects of the present invention, embodiments are given below and described in detail with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic diagram of a printed circuit board that can be bonded to an integrated circuit according to an embodiment of the present invention;

FIG. 1B is a partial enlarged view of a printed circuit board after being bonded to an integrated circuit according to an embodiment of the present invention;

FIG2 is a top view of an integrated circuit bonding area in a printed circuit board according to an embodiment of the present invention;

FIG3 is a top view of an integrated circuit bonding area in a printed circuit board according to another embodiment of the present invention;

FIG. 4A illustrates a simulation result of a temperature difference test after a printed circuit board and an integrated circuit are bonded together according to an embodiment of the present invention;

FIG. 4B illustrates a simulation result of a temperature difference test after a printed circuit board and an integrated circuit are bonded together according to an embodiment of the present invention;

FIG. 4C illustrates a simulation result of a temperature difference test after a printed circuit board and an integrated circuit are bonded together according to a comparative example;

FIG5A is a top view of a first pad of a printed circuit board according to an embodiment of the present invention;

FIG5B is a top view of a first pad of a printed circuit board according to another embodiment of the present invention;

FIG5C is a top view of a first pad of a printed circuit board according to another embodiment of the present invention;

Wherein, the reference numerals are:

10: Printed Circuit Board

100.ICP:Connection pad

100A: IC bonding area

100C: Center point

110C, 210C, 510C, 610C, 710C: Geometric center

101: Internal Area

103: Outer area

110, 1101, 1102, 210, 310A, 310B, 310C: first pad

120: Second pad

110A, 210A, 510A, 610A, 710A: short shaft

110B, 210B, 510B, 610B, 710B: long axis

212:Solder Ball

IC: Integrated Circuit

D1: First direction

D2: Second direction

D3: Third direction

E1～E4: Edge

Y: dotted circle.

DETAILED DESCRIPTION

FIG1A is a schematic diagram of a printed circuit board 10 that can be bonded to an integrated circuit IC according to an embodiment of the present invention. FIG1B is a partial enlarged view (corresponding to the portion of the solder joint) of the printed circuit board 10 after being bonded to the integrated circuit IC according to an embodiment of the present invention. FIG2 is a top view of an integrated circuit bonding area 100A in the printed circuit board 10 according to an embodiment of the present invention.

As shown in FIG. 1A , the printed circuit board 10 includes an integrated circuit bonding area 100A and a plurality of pads 100. The integrated circuit bonding area 100A is a region of the printed circuit board 10 for bonding to the integrated circuit IC. For example, the integrated circuit bonding area 100A overlaps the integrated circuit IC in a first direction D1 (e.g., a vertical direction). The pads 100 are disposed in the integrated circuit bonding area 100A, for example, on a surface of the printed circuit board 10 adjacent to the integrated circuit IC (e.g., an upper surface). The surface of the printed circuit board 10 adjacent to the integrated circuit IC is, for example, a plane formed by a second direction D2 and a third direction D3 (e.g., a plane shown in FIG. 2 ), wherein the first direction D1, the second direction D2, and the third direction D3 may be perpendicular to each other. That is, the first direction D1 may be parallel to the normal direction of the surface of the printed circuit board 10 adjacent to the integrated circuit IC. The pads 100 of the printed circuit board 10 may be electrically connected to corresponding pads ICP in the integrated circuit IC through corresponding solder balls 212 (as shown in FIG. 1B ). That is, the pads 100 of the printed circuit board 10 may overlap the corresponding solder balls 212 and the corresponding pads ICP in the integrated circuit IC in the first direction D1 (eg, the vertical direction) (as shown in FIG. 1B ).

Please refer to FIG. 1A to FIG. 2 simultaneously. The integrated circuit bonding area 100A has a center point 100C, and the integrated circuit bonding area 100A includes an inner region 101 corresponding to the center point 100C and a peripheral region 103 connected to the inner region 101. The peripheral region 103 surrounds the entire inner region 101 and is also the region farthest from the center point 100C. The pad 100 may include a plurality of first pads 110 and a plurality of second pads 120. The first pads 110 are disposed in the peripheral region 103 and surround the center point 100C. The second pads 120 are disposed in the inner region 101 and surround the center point 100C. The shape of the second pads 120 may be different from that of the first pads 110.

In the top view shown in FIG. 2 , the first pad 110 is, for example, non-circular. For example, each first pad 110 has a geometric center 110C, and each first pad 110 has a long axis 110B passing through the geometric center 110C to form the longest line segment and a short axis 110A passing through the geometric center 110C to form the shortest line segment. The length of the long axis 110B is greater than the length of the short axis 110A, and the long axis 110B is perpendicular to the short axis 110A. It can be seen that the first pad 110 is a non-circular structure, for example, an elongated structure. According to one embodiment, the extension direction of the short axis 110A of the first pad 110 is not exactly the same, and the extension direction of the short axis 110A of at least a portion of the first pad 110 is toward the inner area 101 (other portions of the first pad 110 are not shown). According to one embodiment, the length of the major axis 110B is 1.5-2.5 times the length of the minor axis 110A, and the pad area needs to be large enough to provide high current transmission, but the present invention is not limited thereto.

In the embodiment shown in FIG. 2 , the first pads 110 form a circle of first pads 110 in the peripheral region 103. The circle of first pads 110 surrounds the center point 100C of the integrated circuit bonding region 100A, and the extension directions of the short axes 110A of the first pads 110 are all toward the inner region 101, wherein the extension direction of the short axes 110A of a portion of the first pads 110 (e.g., the first pad 1101) is toward the center point 100C of the integrated circuit bonding region 100A, and the extension direction of the short axes 110A of another portion of the first pads 110 (e.g., the first pad 1102) is toward the edges E1-E4 of the integrated circuit bonding region 100A, that is, the extension direction of the short axes 110A is substantially perpendicular to the edges E1-E4.

According to the present embodiment, the extension direction of the short axis 110A of a portion of the first pads 110 (e.g., the first pad 1101) passes through the center point 100C of the integrated circuit bonding area 100A (as indicated by the dotted line passing through the center point 100C and the corresponding geometric center 110C), and the extension direction of the short axis 110A of another portion of the first pads 110 (e.g., the first pad 1102) is offset from the center point 100C of the integrated circuit bonding area 100A (e.g., the extension direction of the short axis 110A of the first pad 1102 is substantially perpendicular to the edges E1-E4). In the present embodiment, the extension direction of the short axis 110A of a portion of the first pads 110 (e.g., the first pad 1101) crosses the center point 100C of the integrated circuit bonding area 100A. FIG2 exemplarily illustrates a circle of first pads 110, and omits illustrating the second pads 120. In other embodiments, the first pads 110 form multiple circles of first pads 110 in the peripheral area 103, such as 2 circles of first pads 110, 3 circles of first pads 110, or more than 3 circles of first pads 110, and the multiple circles of first pads 110 respectively surround the center point 100C (not shown) of the integrated circuit bonding area 100A.

In addition, FIG. 2 also illustrates the outline of the pads ICP in the integrated circuit IC projected onto the integrated circuit bonding region 100A along the first direction D1, such as a circular outline, indicating that a circle of first pads 110 may respectively correspond to the pads ICP in the integrated circuit IC.

Please refer to FIG. 3 , which shows a top view of an integrated circuit bonding area 100A in a printed circuit board 10 according to another embodiment of the utility model. One of the differences between the embodiment of FIG. 3 and FIG. 2 is that the layout of the first pad 210 is different. As shown in FIG. 3 , the shape of the first pad 210 is the same as that of the first pad 110. Similarly, each first pad 210 has a geometric center 210C, and each first pad 210 has a long axis 210B passing through the geometric center 210C to form the longest line segment and a short axis 210A passing through the geometric center 210C to form the shortest line segment, the length of the long axis 210B is greater than the length of the short axis 210A, and the long axis 210B is perpendicular to the short axis 210A. In one embodiment, the extension direction of the short axis 210A of each first pad 210 is not exactly the same, for example, the extension direction of the short axis 210A of at least a portion of the first pads 210 is toward the inner area 101 (the first pads 210 of other portions are not shown).

In the embodiment shown in FIG. 3 , the first pads 210 form a circle of first pads 210 in the peripheral region 103. The circle of first pads 210 surrounds the center point 100C of the integrated circuit bonding region 100A. The extension directions of the short axes 210A of the first pads 210 are all toward the inner region 101, and the extension directions of the short axes 210A of the first pads 210 are all toward the center point 100C of the integrated circuit bonding region 100A. For example, the extension directions of the short axes 210A of the first pads 210 all pass through and intersect the center point 100C of the integrated circuit bonding region 100A (as shown by the dotted line passing through the center point 100C and the corresponding geometric center 210C). FIG3 exemplarily illustrates a circle of first pads 210, and omits illustrating the second pads 120. In other embodiments, the first pads 210 form multiple circles of first pads 210 in the peripheral area 103, such as 2 circles of first pads 210, 3 circles of first pads 210, or more than 3 circles of first pads 210, and the multiple circles of first pads 210 respectively surround the center point 100C (not shown) of the integrated circuit bonding area 100A.

3 also illustrates the outline of the pads ICP in the integrated circuit IC projected onto the integrated circuit bonding region 100A along the first direction D1, such as a circular outline, indicating that a circle of first pads 210 may respectively correspond to the pads ICP in the integrated circuit IC.

It should be understood that the shape and layout of the first pads 110 or 210 of the present invention are not limited to the embodiments shown in FIG. 2 and FIG. 3 .

Generally, when an integrated circuit is soldered to a printed circuit board, the deformation caused by the thermal expansion coefficient is proportional to the distance, and the solder closer to the periphery is more likely to produce thermal fatigue and crack. In order to reduce the probability of solder cracking, underfill can be filled around the solder to reduce the stress value caused by thermal fatigue. However, the use of underfill will increase the difficulty of the process and increase the manufacturing cost. Compared to the comparative example in which all pads in the integrated circuit bonding area are circular, or the comparative example in which the long axis of the pads in the integrated circuit bonding area is oriented toward the inner area of the integrated circuit bonding area, the first pad (110 or 210) according to the embodiment of FIG. 2 or 3 of the present case has a long axis (110B or 210B) and a short axis (110A or 210A), and the extension direction of the short axis (110A or 210A) is oriented toward the inner area 101 of the integrated circuit bonding area 100A. Therefore, based on the physical principle of shear stress, the shear stress generated by the first pad (110 or 210) when the shape and arrangement are changed can be smaller, especially the shear stress at the integrated circuit IC end of the solder joint can be effectively reduced, which can greatly reduce the probability of cracks or ruptures in the solder.

FIG. 4A shows the simulation results of the temperature difference test after the printed circuit board 10 and the integrated circuit are bonded according to an embodiment A of the present invention. Embodiment A may correspond to the embodiment of FIG. 2 and is configured as a single loop-shaped first pad 110, and the other pads 100 are circular second pads 120 (disposed in the inner area 101, not shown). FIG. 4B shows the simulation results of the temperature difference test after the printed circuit board 10 and the integrated circuit are bonded according to an embodiment B of the present invention. Embodiment B may correspond to the embodiment of FIG. 3 and is configured as a single loop-shaped first pad 210, and the other pads 100 are circular second pads 120 (disposed in the inner area 101, not shown). In addition, in FIG. 4A and FIG. 4B, the X-axis corresponds to time (seconds) and the Y-axis corresponds to shear stress (MPa).

FIG4C shows the simulation results of a temperature difference test after the printed circuit board and the integrated circuit are bonded according to a comparative example A, wherein the X-axis corresponds to time (seconds) and the Y-axis corresponds to shear stress (MPa). In comparative example A, the pads of the printed circuit board are all circular, and the area of each pad is 57,000 micrometers square.

In Embodiment A and Embodiment B, the major axis ( 110B or 210B) of the first pad ( 110 or 210 ) of the printed circuit board 10 is 360 micrometers, the minor axis ( 110A or 210A) is 180 micrometers, and the area of the first pad ( 110 or 210 ) is 57,000 micrometers squared.

Finite element method (FEA) is used to simulate the stress of solder joints, and the same temperature difference test simulation is performed on comparative example A, embodiment A and embodiment B. For example, the temperature is lowered from 25°C to -40°C, then raised to 105°C and then lowered again, and the cycle of high temperature (105°C) and low temperature (-40°C) is repeated three times. Since solder cracking often occurs at one end of the solder adjacent to the integrated circuit, after the three high and low temperature cycles are completed, the shear stress of a pad at the same position (e.g., the position corresponding to the dotted circle Y in FIG. 2 ) of the integrated circuits of comparative example A, embodiment A and embodiment B is calculated (the shear stress is calculated by only using the edge of the bonding area 100A and a small cylindrical volume of the pad close to the end of the integrated circuit), and the shear stress difference S0-S2 of the pad of the integrated circuit at high temperature (e.g., 105°C) and low temperature (e.g., -40°C) is calculated. Among them, the shear stress difference S0 of comparative example A is 37.85Mpa, as shown in FIG. 4C .

4A and 4B, the shear stress difference S1 of the pad of the integrated circuit of Example A is 36.81MPa, and the shear stress difference S2 of the pad of the integrated circuit of Example B is 35.47MPa. It can be seen that, compared with Comparative Example A, both Example A and Example B can reduce the shear stress difference of the pad of the integrated circuit, so the situation of solder cracking or breaking can be improved. Moreover, the shear stress difference obtained in Example B is smaller than that in Example A, indicating that the configuration method of the first pad 210 of Example B can generate lower shear stress, which can better prevent the solder from cracking or even breaking.

FIG. 5A illustrates a top view of a first pad 310A of a printed circuit board 10 according to an embodiment of the present invention, wherein the first pad 310A is, for example, shaped like a playground. FIG. 5B illustrates a top view of a first pad 310B of a printed circuit board 10 according to another embodiment of the present invention, wherein the first pad 310B is, for example, elliptical. FIG. 5C illustrates a top view of a first pad 310C of a printed circuit board 10 according to yet another embodiment of the present invention, wherein the first pad 310C is, for example, rectangular. It should be understood that the shape of the first pad of the printed circuit board of the present invention is not limited thereto.

As shown in FIGS. 5A to 5C , the first pads 310A to 310C have geometric centers 510C to 710C, and have short axes 510A to 710A and long axes 510B to 710B, respectively. Similarly, the short axes 510A to 710A and the long axes 510B to 710B pass through the geometric centers 510C to 710C, respectively, and are perpendicular to each other. The length of the short axes 510A to 710A is less than the length of the long axes 510B to 710B. The first pads 110 or 210 in the embodiments of FIGS. 2 and 3 can be replaced with the shapes of the first pads 310A to 310C shown in FIGS. 5A to 5C , respectively.

In summary, one embodiment of the utility model provides a printed circuit board. The printed circuit board includes an integrated circuit bonding area and a plurality of pads. The integrated circuit bonding area has a center point, and the integrated circuit bonding area includes an inner area corresponding to the center point and a peripheral area connected to the inner area. The pad is arranged in the integrated circuit bonding area. The pad includes a plurality of first pads, and the first pads are arranged in the peripheral area and surround the center point. In the top view, each first pad has a geometric center, and each first pad has a long axis passing through the geometric center to form a longest line segment and a short axis passing through the geometric center to form a shortest line segment, the length of the long axis is greater than the length of the short axis, and the long axis is perpendicular to the short axis. In the top view, the extension direction of the short axis of at least a portion of the first pads is toward the inner area. Compared with the comparative example in which the extension direction of the short axis of the first pad is not toward the inner area, since the extension direction of the short axis of the first pad of the present embodiment is toward the inner area, the shear stress generated by the solder joint after the integrated circuit and the printed circuit board are bonded can be smaller, and even if the solder joint is repeatedly subjected to the cycle of high temperature and low temperature environment, it is less likely to produce thermal fatigue and form cracks or even break.

In summary, although the present application has been disclosed as above by way of embodiments, it is not intended to limit the present application. A person skilled in the art of the present application may make various modifications and improvements without departing from the spirit and scope of the present application. Therefore, the scope of protection of the present application shall be subject to the scope defined by the patent application.

Claims (10)

1. A printed circuit board, the printed circuit board comprising:

An integrated circuit bonding region having a center point and including an inner region corresponding to the center point and a peripheral region connected to the inner region; and

A plurality of pads disposed in the IC bonding region,

The plurality of first bonding pads are arranged in the peripheral area and encircle the central point;

Wherein, in the upper view, each first pad has a geometric center, and each first pad has a long axis passing through the geometric center to form the longest line segment and a short axis passing through the geometric center to form the shortest line segment, the length of the long axis is longer than that of the short axis, and the long axis is perpendicular to the short axis,

Wherein, at least a portion of the extending directions of the plurality of short axes of the plurality of first pads face the inner area.

2. The printed circuit board of claim 1, wherein the plurality of directions of extension of the plurality of short axes of the at least a portion of the plurality of first pads are toward the center point.

3. The printed circuit board of claim 2, wherein the plurality of directions of extension of the plurality of stubs of the other portion of the plurality of first pads are toward an edge of the integrated circuit bonding pad.

4. The printed circuit board of claim 1, wherein the plurality of short axes of the plurality of first pads extend in a direction through the center point of the integrated circuit land.

5. The printed circuit board of claim 1, wherein the directions of extension of the plurality of short axes of the plurality of first pads intersect at the center point of the integrated circuit bonding area.

6. The printed circuit board of claim 1, wherein the plurality of first pads form at least one ring of first pads in the peripheral region, the at least one ring of first pads surrounding the center point.

7. The printed circuit board of claim 1, wherein the plurality of first pads form a plurality of circles of first pads in the peripheral region, the plurality of circles of first pads respectively surrounding the center point.

8. The printed circuit board of claim 1, wherein the length of the major axis is 1.5-2.5 times the length of the minor axis.

9. The printed circuit board of claim 1, wherein the plurality of first pads are oval in shape in the top view.

10. The printed circuit board of claim 1, wherein the plurality of pads further comprises a plurality of second pads disposed in the inner region, and wherein the shape of the plurality of second pads is different from the shape of the plurality of first pads.