control device

Abstract

To suppress electrical disconnection of wiring between a BGA-type element and a printed circuit board, while securing a degree of freedom of layout of wiring at a corner part of the BGA-type element.SOLUTION: A control device comprises: a printed circuit board 1; and a BGA microcomputer 2 that is a BGA-type element mounted on the printed circuit board 1. The BGA microcomputer 2 is electrically and mechanically connected to the printed circuit board 1 via solder 4 provided on a surface opposing to the printed circuit board 1. The printed circuit board 1 has first and second through-openings 5 and 6 formed separately from each other to be symmetric with respect to a diagonal line X of the BGA microcomputer 2. Solder 4a, 4b and 4g positioned at corner parts 2b of the BGA microcomputer 2 is connected to electronic components through wiring La, Lb and Lg extending through an area between the first and second through-openings 5 and 6.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a control device. [Background technology]

[0002] Patent Document 1 discloses a printed circuit board on which a BGA element is mounted. This printed circuit board has a circular through-hole formed on a diagonal line passing through a corner of the BGA element.

[0003] Similarly, Patent Document 2 discloses a printed circuit board on which a BGA element is mounted, which has an L-shaped through-hole extending continuously along the corner of the BGA element so as to cross a diagonal line passing through the corner. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-119107 [Patent Document 2] Japanese Patent Application Laid-Open No. 2007-165469 Summary of the Invention [Problem to be solved by the invention]

[0005] The printed circuit boards of Patent Documents 1 and 2 were designed to address the problem that, when the printed circuit board is bent due to, for example, an external input, excessive stress acts on the multiple connection terminals at the corners of the BGA-type element, causing electrical disconnections between the connection terminals and the printed circuit board.

[0006] More specifically, in Patent Document 1, circular through-holes are provided on diagonal lines passing through the corners of the BGA element to prevent stress caused by deformation of the printed circuit board from being transmitted to the corners of the BGA element. However, there is a risk that the circular through-holes may not be effective in suppressing stress transmission relative to the area of ​​the through-hole.

[0007] On the other hand, the L-shaped through-hole in Patent Document 2 has a larger area than the circular through-hole in Patent Document 1, and has a greater effect in suppressing stress transmission relative to the area of ​​the through-hole, but there is a risk that it will not be possible to ensure freedom in wiring layout at the corners of the BGA-type element.

[0008] The present invention was devised in consideration of the current situation, and one of its objectives is to provide a control device that can suppress electrical disconnections between a BGA type element and a printed circuit board while ensuring freedom in the layout of wiring at the corners of the BGA type element. [Means for solving the problem]

[0009] In one aspect of the present invention, the through portion extends in a tangential direction of the corner except at a point where it intersects with a diagonal line of the BGA element passing through the corner. [Effects of the Invention]

[0010] According to the present invention, it is possible to prevent electrical disconnections between the BGA element and the printed circuit board while ensuring the degree of freedom in the layout of wiring at the corners of the BGA element. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 2 is a plan view showing the internal configuration of the control device of the first embodiment. [Figure 2] 2 is a plan view of the printed circuit board showing the arrangement of a plurality of solders on the printed circuit board of the first embodiment. FIG. [Figure 3] FIG. 1 is a plan view of a printed circuit board showing a wiring pattern in a conventional printed circuit board. [Figure 4] FIG. 10 is a plan view of a printed circuit board showing the arrangement of a plurality of solders on the printed circuit board of the second embodiment. [Figure 5] 10 is a graph showing the analysis results of stress in solder versus the angle between the first and second through-hole portions. [Figure 6]10 is a graph showing the analysis results of stress in solder versus the width of the first and second through-hole portions. [Figure 7] 10 is a graph showing the analysis results of stress in solder versus the distance between the first and second through-hole portions. [Figure 8] 10 is a graph showing the analysis results of stress in solder versus the length of the first and second through-hole portions. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, an embodiment of a control device of the present invention will be described with reference to the drawings. (First embodiment) FIG. 1 is a plan view showing the internal configuration of a control device of the first embodiment, and more specifically, a plan view of a printed circuit board 1 on which a BGA microcomputer 2 is mounted. FIG. 2 is a plan view of the printed circuit board 1 of the first embodiment, showing the arrangement of multiple solders 4 on the printed circuit board 1. In FIG. 2, the square outline of the BGA microcomputer 2 is shown by a dashed line. In addition, in FIG. 2, for simplicity, the wiring pattern around only one first through-hole portion 5 is shown.

[0013] The control device is an electronic control device for controlling the shifting of an automatic transmission used in a vehicle. This electronic control device includes a printed circuit board 1, a BGA (Ball Grid Array) microcomputer 2 that is a BGA type element mounted on the printed circuit board 1, and a housing (not shown) that accommodates the printed circuit board 1 and the BGA microcomputer 2.

[0014] The printed circuit board 1 is made of synthetic resin and has a rectangular, or in this embodiment, square, plate shape, and is attached and fixed to a housing (not shown) via fixing members (not shown), such as screws. The printed circuit board 1 has through holes 3 provided near each of its four corners 1b.

[0015] As shown in FIG. 1, the BGA microcomputer 2 is formed in a generally square plate shape smaller than the printed circuit board 1. The BGA microcomputer 2 is disposed in the center of the printed circuit board 1 so that each side 2a of the BGA microcomputer 2 faces each side 1a of the printed circuit board 1. The BGA microcomputer 2 has solder 4, which are multiple connection terminals, provided on the surface facing the printed circuit board 1. By melting the solder 4, the BGA microcomputer 2 is electrically and mechanically connected to the surface 1c of the printed circuit board 1. As shown in FIG. 2, in the center of the BGA microcomputer 2, the solder 4 is equally spaced to form a 4×4 matrix M1. On the other hand, as shown in FIG. 2, in the peripheral portion of the BGA microcomputer 2, the solder 4 is equally spaced in four rows in the longitudinal center of each side 2a of the BGA microcomputer 2, and is equally spaced in three rows in the corners 2b, which are the remaining portions located on both sides of the longitudinal center. More specifically, in the longitudinal center of each side 2a, the solder 4 is equally spaced to form a 4×8 matrix M2. Meanwhile, at each corner 2b of the BGA microcomputer 2, 27 solder pieces 4 are arranged at equal intervals in three rows in an L-shape that is symmetrical with respect to a diagonal line X of the BGA microcomputer 2 (including an extension of the diagonal line, which corresponds to the diagonal line of the printed circuit board 1). As shown in Figure 2, at each corner 2b, three solder pieces 4 are arranged on the diagonal line X of the BGA microcomputer 2.

[0016] In the printed circuit board 1, elongated through-portions 3 extending linearly across the diagonal line X of the BGA microcomputer 2 are formed at positions between each corner 1b of the printed circuit board 1 and a corner 2b of the BGA microcomputer 2, near the corner 2b. In other words, the printed circuit board 1 is formed with elongated through-portions 3 extending in a direction perpendicular to the diagonal line X, except for the positions at which the printed circuit board 1 intersects with the diagonal line X of the BGA microcomputer 2 that passes through the corner 2b. Here, the direction perpendicular to the diagonal line X of the BGA microcomputer 2 is the direction along the tangent line Y that passes through the vertex P of each corner 2b.

[0017] The through portion 3 has a first through hole portion 5 and a second through hole portion 6 that are elongated and formed in the same shape. The first through hole portion 5 and the second through hole portion 6 are spaced apart from each other so as to be symmetrical with respect to the diagonal line X of the BGA microcomputer 2. In other words, the first through hole portion 5 and the second through hole portion 6 extend linearly on either side of a point where they intersect with the diagonal line X of the BGA microcomputer 2.

[0018] As shown in FIGS. 1 and 2 , the first through-hole portion 5 is disposed on one side of the diagonal line X when viewed from a direction perpendicular to the printed circuit board 1. The first through-hole portion 5 extends in a direction (tangential direction) along a tangent line Y passing through the vertex P of the BGA microcomputer 2. That is, as shown in FIG. 1 , the first through-hole portion 5 extends such that the angle α formed by the first through-hole portion 5 and a line Z parallel to the side 2a is 45 degrees. The first through-hole portion 5 has a generally rectangular shape and has an inner arc-shaped portion 5a formed in an arc shape at one end in the direction of the tangent line Y and an outer arc-shaped portion 5b formed in an arc shape at the other end in the direction of the tangent line Y. The inner arc-shaped portion 5a of the first through-hole portion 5 faces the inner arc-shaped portion 6a of the second through-hole portion 6. 2, the outer arc-shaped portion 5b is positioned closer to the vertex P of the corner 2b of the BGA microcomputer 2 than the third piece of solder 4 along the direction of the side 2a from the vertex P. Also, as shown in FIG. 1, the length A of the first through-hole portion 5 along the direction of the tangent Y is longer than the width B of the first through-hole portion 5 along the diagonal X of the BGA microcomputer 2. Also, the distance C (shortest distance) from the vertex P of the corner 2b of the BGA microcomputer 2 to the inner arc-shaped portion 5a of the first through-hole portion 5 is shorter than the distance D between the inner arc-shaped portion 5a of the first through-hole portion 5 and the inner arc-shaped portion 6a of the second through-hole portion 6.

[0019] Similarly, as shown in FIGS. 1 and 2 , the second through-hole portion 6 is disposed on the other side of the diagonal line X when viewed from a direction perpendicular to the printed circuit board 1. The second through-hole portion 6 extends in the direction of a tangent line Y passing through the vertex P of the corner portion 2 b of the BGA microcomputer 2. That is, the second through-hole portion 6 extends such that the angle α formed by the second through-hole portion 6 and a line Z parallel to the side 2 a of the BGA microcomputer 2 is 45 degrees. The second through-hole portion 6 has a generally rectangular shape and includes an inner arc-shaped portion 6 a formed in an arc shape at one end in the direction of the tangent line Y and an outer arc-shaped portion 6 b formed in an arc shape at the other end in the direction of the tangent line Y. The inner arc-shaped portion 6 a of the second through-hole portion 6 faces the inner arc-shaped portion 5 a of the first through-hole portion 5. The outer arc-shaped portion 6b is positioned closer to the vertex P than the solder 4 that is third from the vertex P of the corner 2b of the BGA microcomputer 2 along the direction of the side 2a. The length A of the second through-hole portion 6 along the direction of the tangent Y is longer than the width B of the second through-hole portion 6 along the diagonal X of the BGA microcomputer 2. The distance C (shortest distance) from the vertex P of the corner 2b of the BGA microcomputer 2 to the inner arc-shaped portion 6a of the second through-hole portion 6 is shorter than the distance D between the inner arc-shaped portion 5a of the first through-hole portion 5 and the inner arc-shaped portion 6a of the second through-hole portion 6.

[0020] The first region R1 of the printed circuit board 1, which is located between the first through-hole portion 5 and the side 2a of the BGA microcomputer 2, is a portion that is relatively more rigid than the corner 1b of the printed circuit board 1. The reason why the rigidity of the first region R1 is relatively high is that, while the corner 1b of the printed circuit board 1 is a free end, the first region R1 is supported by multiple solders 4 at the outermost part of the corner 2b and is therefore less likely to deform.

[0021] For the same reason, the second region R2 of the printed circuit board 1 located between the second through-hole portion 6 and the side 2a of the BGA microcomputer 2 is a portion that is relatively more rigid than the corner portion 1b of the printed circuit board 1.

[0022] Next, the wiring pattern of the wiring L drawn from the solder 4 provided at the corner 2b of the BGA microcomputer 2 to the surface 1c of the printed circuit board 1 will be described.

[0023] First, for convenience of explanation, the solders 4 from the solder 4 closest to the vertex P of the corner 2b to the sixth solder 4 along the length direction of the side 2a facing the first through-hole portion 5 are defined as "solder 4a," "solder 4b," "solder 4c," "solder 4d," "solder 4e," and "solder 4f," in order from the vertex P side. Furthermore, the five solders 4 in the row adjacent to solders 4a to 4f are defined as "solder 4g," "solder 4h," "solder 4i," "solder 4j," and "solder 4k," in order from the vertex P side.

[0024] 2, the wiring La, Lb, and Lg drawn from the solders 4a, 4b, and 4g extend between the first and second through-holes 5 and 6 along the diagonal line X of the BGA microcomputer 2 and are electrically connected to related electronic components. The wiring Lc, Ld, Le, and Lf drawn from the solders 4c, 4d, 4e, and 4f extend to the outside of the BGA microcomputer 2 perpendicular to the side 2a and are electrically connected to other related electronic components. The wiring Lh, Li, Lj, and Lk drawn from the solders 4h, 4i, 4j, and 4k bypass the solders 4b, 4c, 4d, and 4e and then extend to the outside of the BGA microcomputer 2 perpendicular to the side 2a and are electrically connected to other related electronic components. (Effects of the first embodiment) 3 is a plan view of a printed circuit board 1 showing a wiring pattern in the printed circuit board 1 of the prior art (Patent Document 2). Note that Patent Document 2 does not actually show a wiring pattern, but shows an example of a wiring pattern that a person skilled in the art could design in a BGA microcomputer 2.

[0025] 3, in the conventional technology, the wires La and Lb drawn from the solders 4a and 4b extend in a direction perpendicular to the side 2a, then tilt away from the vertex P to avoid interference with the L-shaped through-hole 7, and then extend perpendicular to the side 2a. Similarly, the wires Lc and Ld drawn from the solders 4c and 4d are influenced by the paths of the wires La and Lb, and then tilt away from the vertex P, like the wires La and Lb, and then extend perpendicular to the side 2a. Similarly, the wires Lg, Lh, Li, and Lj drawn from the solders 4g, 4h, 4i, and 4j bypass the solders 4a, 4b, 4c, and 4d, then extend perpendicular to the side 2a, and then extend between the wires La and Lb, between the wires Lb and Lc, between the wires Lc and Ld, and between the wires Ld and Le, respectively, in the same manner as the wires La, Lb, Lc, and Ld. As shown in Fig. 3, the distance between adjacent wires La, Lb, Lc, Ld, Lg, Lh, Li, and Lj is narrower in the inclined region W due to the avoidance of the L-shaped through-hole portion 7. This distance becomes narrower toward the center in the longitudinal direction of the side 2a. In the conventional technology shown in Fig. 3, the distance between wires Ld and Lj is narrowest in the inclined region W, and there is a risk that wires Ld and Lj will be connected in the inclined region W during the wiring plating process.

[0026] However, in this embodiment, the through portion 3 extends in a direction along the tangent Y to the corner 2b of the BGA microcomputer 2 except for the portion where it intersects with the diagonal X of the BGA microcomputer 2. More specifically, the through portion 3 has an elongated first through-hole portion 5 and a second through-hole portion 6 that extend in a direction along the tangent Y to the corner 2b of the BGA microcomputer 2, and the first and second through-hole portions 5, 6 are spaced apart from each other.

[0027] Therefore, the wirings La, Lb, and Lg drawn from the solders 4a, 4b, and 4g near the vertex P of the corner 2b of the BGA microcomputer 2 extend parallel to each other through the region between the first and second through-holes 5 and 6, spaced a predetermined distance from each other, before being connected to associated electronic components. The remaining wirings Lc, Ld, Le, Lf, Lh, Li, Lj, and Lk drawn from the solders 4c, 4d, 4e, 4f, 4h, 4i, 4j, and 4k extend perpendicular to the side 2a, spaced a predetermined distance from each other, before being electrically connected to other associated electronic components. This ensures layout flexibility for the wirings La to Lk, especially the wirings La, Lb, and Lg, while suppressing the problems associated with the wiring plating process of the prior art.

[0028] Furthermore, when transmission vibrations are transmitted to the printed circuit board 1 through the housing and the printed circuit board 1 bends in its thickness direction, the bending of the printed circuit board 1 reaches the first and second regions R1 and R2 through the first and second through-holes 5 and 6. The first region R1 is supported by the solder 4a and 4b at the outermost corner 2b, while the second region R2 is supported by the solder 4a and 4g, making it a region with higher rigidity than the corner 1b of the printed circuit board 1. Therefore, a portion of the bending of the printed circuit board 1 is absorbed by the first and second regions R1 and R2, preventing excessive stress caused by the bending of the printed circuit board 1 from acting on the solder 4 at the corner 2b, particularly the solder 4a, 4b, and 4g. This reduces damage to the solder 4 and prevents electrical disconnections between the BGA microcomputer 2 and the printed circuit board 1.

[0029] As described above, this embodiment can prevent electrical disconnections between the BGA microcomputer 2 and the printed circuit board 1 while ensuring flexibility in the layout of the wires La to Lk, especially the wires La, Lb, and Lg. (Second embodiment) FIG. 4 is a plan view of the printed circuit board 1 according to the second embodiment, showing the arrangement of a plurality of solders 4 on the printed circuit board 1. In FIG.

[0030] In the second embodiment, the first and second through-hole portions 5, 6 do not extend linearly so as to be perpendicular to the diagonal line X of the BGA microcomputer 2. That is, in this embodiment, the first and second through-hole portions 5, 6 extend so that the angle α formed by each of the first and second through-hole portions 5, 6 and a line Z parallel to the side 2a is 30 degrees. (Effects of the second embodiment) Therefore, in the second embodiment, as in the first embodiment, the wirings La, Lb, and Lg are electrically connected to the electronic components through the region between the first through-hole portion 5 and the second through-hole portion 6, and further, part of the bending of the printed circuit board 1 is absorbed by the first and second regions R1 and R2, which have relatively high rigidity. This makes it possible to prevent electrical disconnections between the BGA microcomputer 2 and the printed circuit board 1 while ensuring freedom in the layout of the wirings La to Lk, especially the wirings La, Lb, and Lg. (Other embodiments) 5 is a graph showing the analysis results of the stress on the solder 4a versus the angle α of the first and second through-hole portions 5, 6. Note that Fig. 5 shows the stress acting on the solder 4a, which is closest to the vertex of the corner 2b and is most susceptible to the stress caused by the bending of the printed circuit board 1, as a representative of the solder 4 located at the corner 2b. The angle α of the first and second through-hole portions 5, 6 is the angle α formed by the line Z parallel to the side 2a of the BGA microcomputer 2 and each of the first and second through-hole portions 5, 6, as shown in Figs. 1 and 4.

[0031] As shown in Figure 5, the stress (maximum stress) acting on the solder 4a is highest when the angle α is 0 degrees and decreases until the angle α reaches 10 degrees. This stress fluctuates slightly within the range of 10 to 40 degrees, but reaches its minimum when the angle α is 45 degrees. This stress also increases linearly within the range of α between 45 degrees and 90 degrees.

[0032] The stress acting on the solder 4a when the first and second through-hole portions 5, 6 are not provided in the printed circuit board 1 is shown by a thick line Q parallel to the horizontal axis of the graph. As shown in Fig. 5, the line Q has a value that is significantly larger than the stress acting on the solder 4a when the angle α is 0 degrees.

[0033] Fig. 6 is a graph showing the analysis results of the stress in the solder 4a versus the width B of the first and second through-hole portions 5, 6. Note that Fig. 6 shows the stress in the solder 4a versus the width B of the first and second through-hole portions 5, 6 that extend linearly as shown in Fig. 1.

[0034] As shown in Figure 6, the stress (maximum stress) acting on the solder 4a decreases at a predetermined rate when the width B is between 1 and 2 mm, and decreases at a smaller rate when the width B is between 2 and 3 mm than when the width B is between 1 and 2 mm.

[0035] Fig. 7 is a graph showing the analysis results of the stress in the solder 4a versus the distance C between the first and second through-hole portions 5, 6. Note that Fig. 7 shows the stress in the solder 4a versus the distance C between the first and second through-hole portions 5, 6 that extend linearly as shown in Fig. 1.

[0036] As shown in FIG. 7, the stress (maximum stress) acting on the solder 4a increases at a predetermined rate when the distance C is 1 to 2 mm, and increases at a rate greater than when the distance C is 2 to 3 mm.

[0037] Fig. 8 is a graph showing the analysis results of the stress in the solder 4a versus the length A of the first and second through-hole portions 5, 6. Note that Fig. 8 shows the stress in the solder 4a versus the length A of the first and second through-hole portions 5, 6 that extend linearly as shown in Fig. 1.

[0038] As shown in FIG. 8, the stress (maximum stress) acting on the solder 4a gradually decreases when the length A of the first and second through-holes 5, 6 is between 3.5 and 4.75 mm, but decreases sharply when the length A is between 4.75 and 6 mm. When the length A of the first and second through-holes 5, 6 is relatively long, between 4.75 and 6 mm, the area of ​​the first and second regions R1, R2 (see FIG. 1) with relatively high rigidity adjacent to the corner 2b of the BGA microcomputer 2 increases. Therefore, when the printed circuit board 1 flexes due to transmission vibration, this flexure is more easily absorbed by the wider first and second regions R1, R2. This makes it difficult for the stress associated with the flexure of the printed circuit board 1 to act on the solder 4 at the corner 2b, particularly the solder 4a. Therefore, the longer the length A of the first and second through-holes 5, 6, the smaller the stress acting on the solder 4a.

[0039] In each of the above embodiments, an example is disclosed in which the printed circuit board 1 has the first and second through hole portions 5, 6, but an example in which the printed circuit board 1 has only the first through hole portion 5 or the second through hole portion 6 may also be applied to the present invention. [Explanation of symbols]

[0040] 1 Printed circuit board, 1b Corner portion, 2 BGA microcomputer, 2b Corner portion, 3 Through portion, 4 Solder, X Diagonal line, 5 First through hole portion, 6 Second through hole portion, Y Tangent line, La to Lk Wiring

Claims

1. A control device incorporating a printed circuit board on which a BGA type element is mounted, characterized in that the printed circuit board has a through-hole provided at a position outside the corner of the BGA type element, and the through-hole extends approximately perpendicular to the diagonal of the BGA type element except for the point where it intersects with the diagonal of the BGA type element passing through the corner.

2. 2. The control device according to claim 1, The control device is characterized in that the through portion has a first through-hole portion and a second through-hole portion extending linearly on either side of a point where the through-hole portion intersects with a diagonal line of the BGA type element.

3. 3. The control device according to claim 2, an angle formed between the first through-hole portion and a line parallel to a side of the BGA element facing the first through-hole portion is 10 to 90 degrees; A control device characterized in that the angle formed between the second through-hole portion and a line parallel to the side of the BGA type element facing the second through-hole portion is 10 to 90 degrees.

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