JP2010073779A - Electronic circuit device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the reliability of an electronic circuit device by arranging an element of weaker stress among a plurality of electron elements mounted on a circuit board at the outside of an area surrounded by fixed points of the circuit board. <P>SOLUTION: The element (microcomputer 36) having lower resistance to stress than that of the other element among the electron elements mounted on a control board 30 is arranged avoiding an area surrounded by a plurality of points including a point fixed with a bolt 28a and a point fixed to a pedestal 44a with an adhesive. Thus, since free thermal expansion and free thermal contraction are not restrained at a part where the element of low resistance to the stress is arranged in the control board 30, even if thermal expansion and contraction occur on the control board 30, the generation of a warp is suppressed, and the excessive stress is prevented from acting on the element. As a result, the reliability of the device to thermal stress is improved. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an electronic circuit device, and more particularly to an electronic circuit device in which a plurality of electronic elements are mounted on a circuit board.

Conventionally, an electronic circuit device of this type has been proposed in which a control board on which circuit chips (elements) are arranged is fixed to a casing (for example, see Patent Document 1). In this apparatus, the back surface of the above-mentioned control board can be fixed to the casing with an adhesive, or can be physically fixed to the casing with a bolt.
WO2003-81087

  By the way, considering that the control board is fixed to the case at a plurality of points, when the board is thermally expanded and contracted, there is no escape space near the point where the board is fixed, so that the deformation is promoted and warpage occurs. There is a case. Since the warp generated in the substrate may cause an excessive stress to act on the element arranged there, it is desirable to reduce the influence as much as possible.

  The main purpose of the electronic circuit device of the present invention is to further improve the reliability against thermal stress.

  The electronic circuit device of the present invention employs the following means in order to achieve the main object described above.

The electronic circuit device of the present invention is
An electronic circuit device in which a plurality of electronic elements are mounted on a circuit board,
The circuit board is fixed to the case at at least three fixing points;
Of the plurality of electronic elements, an element that is weak against stress is arranged outside a region surrounded by the at least three fixing points.

  In the electronic circuit device of the present invention, the circuit board is fixed to the case at at least three fixing points, and the element that is weak against stress among the plurality of electronic elements mounted on the circuit board is at least three fixing points. It is arranged outside the enclosed area. Since the outside of the area surrounded by the fixing point between the circuit board and the case is less likely to be warped due to thermal expansion and contraction than in the area, the element having the weaker stress among the plurality of electronic elements is fixed by the fixing point of the circuit board. By disposing outside the enclosed region, it is possible to suppress an excessive stress from acting on the element having a weaker stress even if thermal expansion / shrinkage occurs in the circuit board. As a result, the reliability of the apparatus against thermal stress can be further improved. Here, examples of the “element having a lower stress” include CSP (Chip Size Package).

  In such an electronic circuit device of the present invention, the circuit board is fixed to the case by combining a physical fixing point that is physically fixed and a chemical fixing point that is chemically fixed. You can also. If it carries out like this, it can suppress that a circuit board deform | transforms large with respect to thermal expansion and contraction, fixing a circuit board with a case reliably. In this aspect of the electronic circuit device of the present invention, the circuit board is fixed to the case with the element that is more susceptible to stress among the plurality of electronic elements being further away from the physical fixing point than the chemical fixing point. It can also be. In this way, it is possible to more reliably suppress an excessive stress from acting on the element having a lower stress. In the electronic circuit device of the present invention of these aspects, the physical fixing point may be a fixing point fixed by a bolt, and the chemical fixing point may be a fixing point fixed by adhesion. it can. In this case, if an adhesive having thermal conductivity is used, the heat generated by the substrate can be radiated to the case through the fixing point.

  In the electronic circuit device of the present invention, the circuit board may be a resin board. Since the resin substrate tends to have a larger linear expansion coefficient than a ceramic substrate or the like, the significance of applying the present invention becomes greater.

  Furthermore, the electronic circuit device of the present invention may be configured as an electronic control unit for shift control attached to the automatic transmission. In this case, the automatic transmission may be a vehicle-mounted transmission.

  Next, the best mode for carrying out the present invention will be described using examples.

  FIG. 1 is an external view showing the external appearance of an automatic transmission 10, FIG. 2 is a block diagram showing an outline of the configuration of an electronic circuit device 20 as an embodiment of the present invention, and FIG. 2 is an external view showing an external appearance of a case 40 of the electronic circuit device 20. FIG. The electronic circuit device 20 according to the embodiment is configured as an AT electronic control unit (ATECU) in an automobile in which an automatic transmission (AT) 10 is mounted in an engine room together with an engine (not shown), as shown in FIG. The automatic transmission 10 is attached to a transmission case 12. This electronic circuit device 20 sets a gear position based on the vehicle speed, throttle opening, and shift position, and is an actuator (built in a hydraulic circuit) that turns on and off a clutch and a brake mounted on the automatic transmission 10 based on the set gear position. As shown in FIG. 2, a control board 30 on which a plurality of electronic elements are mounted, a shift position sensor 22 for detecting the operation position of the shift lever, A connector 24 and the like for communicably connecting to an engine electronic control unit for controlling the engine are provided, and these are fixed to the case 40. Although not shown, the shift position sensor 22 includes a permanent magnet attached to the rotor and a magnetic sensor (for example, a hall element) attached to the stator and detecting a magnetic field of the permanent magnet.

  The control board 30 is configured as a resin board such as a glass epoxy board, for example, and is fixed to the case 40 with bolts 28a to 28c at three locations as shown in FIG. As shown in FIG. 3, bolt holes 42 a to 42 c into which the bolts 28 a to 28 c are inserted are formed in the case 40, and three convex pedestals 44 a to 44 c integrated with the case 40 are formed. In addition, the back side of the control board 30 is bonded and fixed to the pedestals 44a to 44c using an adhesive separately from the fixing by the bolts 28a to 28c. In the examples, a silicone-based adhesive having excellent thermal conductivity was used as the adhesive. Therefore, the heat generated by the electronic elements mounted on the control board 30 is radiated from the control board 30 to the case 40 via the bases 44a to 44c.

  The electronic elements mounted on the control board 30 include a power supply IC 32 for supplying power to each part, a solenoid drive circuit 34 for driving a linear solenoid valve in the hydraulic circuit, and a microcomputer (microcomputer) for controlling the entire apparatus. 36). Of these, the microcomputer 36 is an ultra-small package called CSP (Chip Size Package) in the embodiment, and is less resistant to stress than other mounting elements. The microcomputer 36 reduces the stress acting on the joint portion with the control board 30 due to the difference in coefficient of linear expansion with the control board 30, so that the gap between the chip and the board is an underfill agent (for example, a liquid epoxy resin). Etc.).

  FIG. 4 is a cross-sectional view schematically showing a cross section of the electronic circuit device. 4A shows a cross section of the electronic circuit device 20 of the embodiment, and FIG. 4B shows a cross section of the electronic circuit device of the comparative example. In the embodiment, the microcomputer 36 which is an element having low resistance to stress as compared with other elements (power supply IC 32, solenoid drive circuit 34, etc.) among the electronic elements mounted on the control board 30 is shown in FIG. As shown to a), the area | region enclosed by the point fixed by the bolts 28a-28c and the point fixed to the bases 44a-44c with the adhesive agent is removed and arrange | positioned. This is because, as shown in FIG. 4B, a bolt 128 is added to the right end in the vicinity of the area where the microcomputer 36, which is an element having low resistance to stress, is mounted instead of bonding to the bases 44a to 44c. When the control board 30 is fixed to the case 140, the region surrounded by the points fixed by the bolts 28a to 28c and 128 restrains the free thermal expansion and free thermal contraction of the control board 30, so that warpage is likely to occur. This is based on the fact that excessive stress acts on the element to cause a malfunction (damage to the microcomputer 36, peeling of the underfill agent, etc.). In the embodiment, the chemically fixed portion such as an adhesive is more absorbable with respect to the deformation of the control substrate 30 than the physically fixed portion. The microcomputer 36 is arranged away from a point physically fixed by the bolts 28a to 28c rather than a point fixed to the pedestals 44a to 44c by an adhesive.

  According to the electronic circuit device 20 of the embodiment described above, among the electronic elements mounted on the control board 30, an element having low resistance to stress compared to other elements (such as the power supply IC 32 and the solenoid drive circuit 34). The (microcomputer 36) is an element having low resistance to the stress of the control board 30 because the area surrounded by the points fixed by the bolts 28a to 28c and the points fixed to the bases 44a to 44c by the adhesive is removed. The free thermal expansion and free thermal contraction are not constrained at the portion where is disposed, and even if the thermal expansion and contraction of the control board 30 occurs, the warpage of the control board 30 is suppressed, and an excessive stress is applied to the element. It can suppress acting. As a result, the reliability of the apparatus against thermal stress can be further improved. In addition, since the element having low resistance to stress is arranged farther from the point physically fixed by the bolts 28a to 28c than the point chemically fixed by the adhesive, the stress acting on the element is made smaller. The reliability of the apparatus can be further improved.

  In the electronic circuit device 20 according to the embodiment, the control board 30 is fixed to the case 40 by combining physical fixing with the bolts 28a to 28c and chemical fixing with an adhesive. The control board 30 may be fixed to the case 40 using only the fixing, or the control board 30 may be fixed to the case 40 using only the chemical fixing using an adhesive or the like. Further, the number of points where the control board 30 is fixed to the case 40 may be any number as long as it is three or more.

  In the electronic circuit device 20 according to the embodiment, among the electronic elements mounted on the control board 30, elements having lower resistance to stress than other elements are chemically fixed to the case 40 by the control board 30 with an adhesive. Although it should be arranged away from the point that is physically fixed by the bolts 28a to 28c than the point that is fixed, it is not always necessary to be arranged away from the point that is fixed physically than the point that is fixed chemically. There is no.

  In the electronic circuit device 20 of the embodiment, the microcomputer 36 constituted by the CSP is exemplified as an element having low resistance to stress compared with other elements among the electronic elements mounted on the control board 30. It is not limited to the above, and may be appropriately selected according to the element to be mounted according to the specifications of the apparatus.

  In the electronic circuit device 20 of the embodiment, a resin substrate is used as the control substrate 30, but the material of the base material is not limited to this, and other materials such as ceramics may be used. . However, the effect obtained by applying the present invention becomes larger as the material has a larger linear expansion coefficient.

  In the embodiment, the electronic circuit device of the present invention is applied to the electronic control unit that controls the automatic transmission 10 mounted on the automobile. However, the electronic circuit unit is installed in an automatic transmission mounted on a vehicle other than the automobile. It may be applied, or may be applied to an electronic control unit that controls other devices.

  Here, the correspondence between the main elements of the embodiment and the main elements of the invention described in the column of means for solving the problems will be described. In the embodiment, the power supply IC 32, the solenoid drive circuit 34, the microcomputer 36, and the like correspond to “electronic elements”, and the control board 30 corresponds to “circuit board”. The correspondence between the main elements of the embodiment and the main elements of the invention described in the column of means for solving the problem is the same as that of the embodiment described in the column of means for solving the problem. It is an example for specifically explaining the best mode for doing so, and does not limit the elements of the invention described in the column of means for solving the problem. That is, the interpretation of the invention described in the column of means for solving the problems should be made based on the description of the column, and the examples are those of the invention described in the column of means for solving the problems. It is only a specific example.

  The best mode for carrying out the present invention has been described with reference to the embodiments. However, the present invention is not limited to these embodiments, and various modifications can be made without departing from the gist of the present invention. Of course, it can be implemented in the form.

  The present invention can be used in the manufacturing industry of electronic circuit devices.

1 is an external view showing an external appearance of an automatic transmission 10. FIG. It is a block diagram which shows the outline of a structure of the electronic circuit apparatus 20 as one Example of this invention. It is an external view which shows the external appearance of case 40 of the electronic circuit apparatus 20 of an Example. It is sectional drawing which represented the cross section of the electronic circuit apparatus typically.

Explanation of symbols

  10 automatic transmission, 12 transmission case, 20 electronic circuit device, 22 shift position sensor, 24 connector, 28a-28c, 128 volts, 30 control board, 32 power supply IC, 34 solenoid drive circuit, 36 microcomputer (microcomputer), 40,140 Case, 42a-42c Bolt hole, 44a-44c Pedestal.

Claims (8)

An electronic circuit device in which a plurality of electronic elements are mounted on a circuit board,
The circuit board is fixed to the case at at least three fixing points;
An electronic circuit device, wherein an element that is weak against stress among the plurality of electronic elements is disposed outside a region surrounded by the at least three fixing points.   The electronic circuit device according to claim 1, wherein the circuit board is fixed to the case by combining a physical fixing point that is physically fixed and a chemical fixing point that is chemically fixed.   3. The electronic circuit device according to claim 2, wherein the circuit board is fixed to the case with an element that is weaker to stress among the plurality of electronic elements being moved away from the physical fixing point than the chemical fixing point. The electronic circuit device according to claim 2 or 3,
The physical fixing point is a fixing point fixed by a bolt,
The chemical fixing point is a fixing point that is fixed by adhesion. Electronic circuit device.   5. The electronic circuit device according to claim 1, wherein an element that is weak against stress among the plurality of electronic elements is a CSP (Chip Size Package). 6.   The electronic circuit device according to claim 1, wherein the circuit board is a resin substrate.   The electronic circuit device according to claim 1, wherein the electronic circuit device is configured as an electronic control unit for shift control attached to the automatic transmission.   The electronic circuit device according to claim 7, wherein the automatic transmission is an in-vehicle transmission.

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