JP7756017B2 - Control device - Google Patents

Description

The present invention relates to a control device.

Patent Document 1 discloses a printed circuit board mounted with a BGA-type device. This printed circuit board has a circular through-hole formed on a diagonal line passing through the corner of the BGA-type device.

Similarly, Patent Document 2 discloses a printed circuit board mounted with a BGA-type device. This printed circuit board has an L-shaped through-hole that runs continuously along the corner of the BGA-type device, crossing a diagonal line that passes through the corner.

Japanese Patent Application Laid-Open No. 2001-119107 Japanese Patent Application Laid-Open No. 2007-165469

The printed circuit boards in 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 device, causing electrical disconnections between the connection terminals and the printed circuit board.

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.

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 is more effective in suppressing stress transmission relative to the area of the through-hole, but there is a risk that it will be difficult to ensure freedom in wiring layout at the corners of the BGA-type device.

The present invention was devised in light of the current situation, and one of its objectives is to provide a control device that can prevent electrical disconnections between a BGA element and a printed circuit board while ensuring freedom in the layout of wiring in the corners of the BGA element.

In one aspect of the present invention, the through-hole extends in the tangential direction of the corner, except where it intersects with the diagonal of the BGA-type device that passes through the corner.

This invention makes it possible to prevent electrical disconnections between the BGA element and the printed circuit board while ensuring freedom in the layout of wiring at the corners of the BGA element.

FIG. 2 is a plan view showing the internal configuration of the control device according to the first embodiment. 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. FIG. 1 is a plan view of a printed circuit board showing a wiring pattern in a conventional printed circuit board. 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. 10 is a graph showing the analysis results of stress in solder versus the angle between the first and second through-hole portions. 10 is a graph showing the analysis results of stress in solder versus the width of the first and second through-hole portions. 10 is a graph showing the analysis results of stress in solder versus the distance between the first and second through-hole portions. 10 is a graph showing the analysis results of stress in solder versus the length of the first and second through-hole portions.

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 the 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 showing the arrangement of multiple solder joints 4 on the printed circuit board 1 of the first embodiment. Note that in Fig. 2, the square outline of the BGA microcomputer 2 is shown by a dashed line. Also, in Fig. 2, for simplicity of illustration, the wiring pattern around only one first through-hole portion 5 is shown.

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

The printed circuit board 1 is made of synthetic resin and is formed into a rectangular, or in this embodiment, square, plate shape. It 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 the four corners 1b.

As shown in FIG. 1, the BGA microcontroller 2 is formed in a generally square plate shape that is smaller than the printed circuit board 1. The BGA microcontroller 2 is positioned in the center of the printed circuit board 1 so that each side 2a of the BGA microcontroller 2 faces each side 1a of the printed circuit board 1. The BGA microcontroller 2 has multiple solder joints 4, which are connection terminals, provided on the surface facing the printed circuit board 1. By melting these solder joints 4, the BGA microcontroller 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 microcontroller 2, the solder joints 4 are equally spaced to form a 4x4 matrix M1. Meanwhile, as shown in FIG. 2, in the peripheral portion of the BGA microcontroller 2, the solder joints 4 are equally spaced in four rows at the longitudinal center of each side 2a of the BGA microcontroller 2, and are equally spaced in three rows at 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 arranged at equal intervals to form a 4x8 matrix M2. Meanwhile, in each corner 2b of the BGA microcomputer 2, the solder 4 is arranged at equal intervals by arranging 27 solder 4 in three rows in an L-shape that is symmetrical with respect to the diagonal X of the BGA microcomputer 2 (including the extension of that diagonal, which corresponds to the diagonal X of the printed circuit board 1). As shown in Figure 2, in each corner 2b, three solder 4 are arranged on the diagonal X of the BGA microcomputer 2.

Elongated through-holes 3 extending linearly across the diagonal line X of the BGA microcomputer 2 are formed through the printed circuit board 1 at positions between each corner 1b of the printed circuit board 1 and the corner 2b of the BGA microcomputer 2, near the corner 2b. In other words, the printed circuit board 1 is formed with elongated through-holes 3 extending in a direction perpendicular to the diagonal line X, except for the locations where they intersect 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.

The through-hole 3 has a first through-hole 5 and a second through-hole 6 that are elongated and formed in the same shape. The first through-hole 5 and the second through-hole 6 are spaced apart and symmetrical with respect to the diagonal line X of the BGA microcomputer 2. In other words, the first through-hole 5 and the second through-hole 6 extend in straight lines, sandwiching the point where they intersect with the diagonal line X of the BGA microcomputer 2.

As shown in Figures 1 and 2, the first through-hole portion 5 is located 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 the tangent line Y passing through the vertex P of the BGA microcomputer 2. In other words, as shown in Figure 1, the first through-hole portion 5 extends so 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 roughly 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. As shown in FIG. 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 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.

Similarly, the second through-hole portion 6 is located on the other side of the diagonal line X when viewed from a direction perpendicular to the printed circuit board 1, as shown in Figures 1 and 2. The second through-hole portion 6 extends in the direction of a tangent line Y passing through the vertex P of the corner portion 2b of the BGA microcomputer 2. In other words, the second through-hole portion 6 extends so that the angle α formed by the second through-hole portion 6 and a line Z parallel to the side 2a of the BGA microcomputer 2 is 45 degrees. The second through-hole portion 6 is generally rectangular in shape and has an inner arc-shaped portion 6a formed in an arc shape at one end in the direction of the tangent line Y and an outer arc-shaped portion 6b formed in an arc shape at the other end in the direction of the tangent line Y. The inner arc-shaped portion 6a of the second through-hole portion 6 faces the inner arc-shaped portion 5a of the first through-hole portion 5. The outer arc-shaped portion 6b 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. 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.

The first region R1 of the printed circuit board 1, located between the first through-hole portion 5 and the side 2a of the BGA microcomputer 2, is a portion with relatively higher rigidity than the corner 1b of the printed circuit board 1. The relatively higher rigidity of the first region R1 is due to the fact that, while the corner 1b of the printed circuit board 1 is a free end, the first region R1 is supported by multiple solder joints 4 at the outermost edge of the corner 2b, making it less susceptible to deformation.

For the same reason, the second region R2 of the printed circuit board 1, which is 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.

Next, we will explain the wiring pattern of the wiring L that is drawn from the solder 4 provided in the corner 2b of the BGA microcomputer 2 to the surface 1c of the printed circuit board 1.

First, for convenience of explanation, the solder 4 closest to the vertex P of the corner 2b through to the sixth solder 4 along the length of the side 2a facing the first through-hole portion 5 will be 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 through 4f will be defined as "solder 4g," "solder 4h," "solder 4i," "solder 4j," and "solder 4k," in order from the vertex P side.

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 on 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 can design in a BGA microcomputer 2.

As shown in Figure 3, in the prior art, wires La and Lb drawn from solder 4a and 4b extend in a direction perpendicular to side 2a, then tilt away from vertex P to avoid interference with L-shaped through-hole 7, and then extend perpendicular to side 2a. Similarly, wires Lc and Ld drawn from solder 4c and 4d are influenced by the paths of wires La and Lb, and similarly tilt away from vertex P before extending perpendicular to side 2a. Wires Lg, Lh, Li, and Lj drawn from solder 4g, 4h, 4i, and 4j bypass solders 4a, 4b, 4c, and 4d before extending perpendicular to side 2a, and then extend between wires La and Lb, between wires Lb and Lc, between wires Lc and Ld, and between wires Ld and Le, respectively, in the same way as wires La, Lb, Lc, and Ld. As shown in Figure 3, the distance between adjacent wires La, Lb, Lc, Ld, Lg, Lh, Li, and Lj is narrower in the inclined region W that avoids the L-shaped through-hole 7. This distance narrows toward the center of the length of the side 2a. In the conventional technology shown in Figure 3, the distance between wires Ld and Lj is narrowest in the inclined region W, which raises the risk of wires Ld and Lj becoming connected in the inclined region W during the wiring plating process.

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

As a result, the wiring lines La, Lb, and Lg drawn from the solder lines 4a, 4b, and 4g near the apex P of the corner 2b of the BGA microcomputer 2 run 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 the associated electronic components. Furthermore, the wiring lines Lc, Ld, Le, Lf, Lh, Li, Lj, and Lk drawn from the remaining solder lines 4c, 4d, 4e, 4f, 4h, 4i, 4j, and 4k run perpendicular to the edge 2a, spaced a predetermined distance from each other, before being electrically connected to other associated electronic components. This ensures flexibility in the layout of the wiring lines La-Lk, particularly the wiring lines La, Lb, and Lg, while minimizing the problems associated with the wiring plating process of the prior art.

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, R2 through the first and second through-holes 5, 6. The first region R1 is supported by the solder 4a, 4b at the outermost part of the corner 2b, while the second region R2 is supported by the solder 4a, 4g, making it a region with relatively 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, 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.

As described above, this embodiment can prevent electrical disconnections between the BGA microcomputer 2 and the printed circuit board 1 while ensuring freedom in the layout of the wiring La to Lk, especially the wiring 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.

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. In other words, 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 2 a 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 flexure of the printed circuit board 1 is absorbed by the first and second regions R1 and R2, which have relatively high rigidity. Thus, electrical disconnection between the BGA microcomputer 2 and the printed circuit board 1 can be suppressed while ensuring freedom in the layout of the wirings La to Lk, especially the wirings La, Lb, and Lg.
(Other embodiments)
Fig. 5 is a graph showing the analysis results of the stress in 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 apex of the corner 2b and is most susceptible to the influence of the stress associated with 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.

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 is 10 degrees. This stress increases or decreases slightly as the angle α ranges from 10 to 40 degrees, but is at its lowest when the angle α is 45 degrees. This stress also increases linearly when the angle α is greater than 45 degrees and less than or equal to 90 degrees.

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

Figure 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 Figure 6 shows the stress in the solder 4a versus the width B of the first and second through-hole portions 5, 6, which extend linearly as shown in Figure 1.

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.

Figure 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 Figure 7 shows the stress in the solder 4a versus the distance C between the first and second through-hole portions 5, 6, which extend linearly as shown in Figure 1.

As shown in Figure 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 greater rate when the distance C is 2 to 3 mm than when the distance C is 1 to 2 mm.

Figure 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 Figure 8 shows the stress in the solder 4a versus the length A of the first and second through-hole portions 5, 6, which extend linearly as shown in Figure 1.

As shown in Figure 8, the stress (maximum stress) acting on the solder 4a decreases gradually when the length A of the first and second through-hole portions 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-hole portions 5, 6 is relatively long, between 4.75 and 6 mm, the area of the relatively rigid first and second regions R1, R2 (see Figure 1) 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 less likely that the stress associated with the flexure of the printed circuit board 1 will act on the solder 4 at the corner 2b, particularly the solder 4a. Therefore, the greater the length A of the first and second through-hole portions 5, 6, the smaller the stress acting on the solder 4a.

In the above embodiments, examples have been disclosed in which the printed circuit board 1 has first and second through-hole portions 5, 6. However, examples 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.

1: Printed circuit board, 1b: Corner, 2: BGA microcomputer, 2b: Corner, 3: Through-hole, 4: Solder, X: Diagonal, 5: First through-hole, 6: Second through-hole, Y: Tangent, La-Lk: Wiring

Claims (3)

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. 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. 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.