JP2007324223A - Attaching structure for heating element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an attaching structure for a heating element suitable for obtaining a high cooling effect and reducing the number of processing man-hour. <P>SOLUTION: The structure includes: a case 1, an electronic circuit substrate 4 arranged along the bottom surface 2 of the case 1, and an electronic component 5 fixed onto the inner wall surface 3 of the case 1. The electronic circuit substrate 4 is obtained by laminating a flexible substrate 10 on a glass epoxy substrate 11, so as to allow part of the flexible substrate 10 to be superimposed on the glass epoxy substrate 11, and so as to allow part of the flexible substrate 10 not to be superimposed on the glass epoxy substrate 11 (a non-superimposition part) to face the inner wall surface 3. The lead 7 of the electronic component 5 is electrically joined with the non-superimposition part of the flexible substrate 10. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a structure for mounting a heating element, and more particularly to a mounting structure for a heating element suitable for realizing a high cooling effect and reducing the number of processing steps.

Conventionally, for example, a technique described in Patent Document 1 is known as a structure for attaching an exothermic electronic component in an environment-resistant electronic control unit mounted on an automobile or the like.
FIG. 5 is a cross-sectional view of the electronic component mounting structure described in Patent Document 1.
FIG. 6 is a perspective view of an electronic component mounting structure described in Patent Document 1. FIG.
5 and 6, an electronic circuit board 4 is disposed inside the housing 1 along the bottom surface 2 of the housing 1.

A heat generating electronic component 5 such as a power transistor is fixed to the inner wall surface 3 of the housing 1 with screws 6. The housing 1 includes heat radiating fins (not shown), absorbs heat generated from the electronic component 5, and cools the electronic component 5 by radiating heat from the heat radiating fin to the outside.
The electronic component 5 includes a lead 7 that inputs and outputs power, a control signal, and the like. One end of the lead 7 is attached to the bottom surface 5 a of the electronic component 5 facing the mounting surface 4 a of the electronic circuit board 4, and the other end of the lead 7 is in a through hole 8 formed in the thickness direction of the electronic circuit board 4. The electronic circuit board 4 is electrically joined by being inserted and soldered.

Since the case 1 and the lead 7 have different coefficients of thermal expansion, a difference in the amount of thermal expansion occurs between the case 1 and the lead 7 due to a temperature change that occurs in the usage environment, and stress due to the thermal expansion is applied to the soldering portion 9 to perform soldering. The part 9 may be broken and disconnected. Therefore, the lead 7 is formed with a bent portion 7a to absorb stress due to thermal expansion. At the time of thermal expansion, since the distance between the electronic component 5 and the electronic circuit board 4 increases, the bent portion 7a rises with respect to the board 4 and absorbs stress due to thermal expansion.
JP 2003-78089 A

However, in the mounting structure described in Patent Document 1, since the bent portion 7a is formed in the lead 7, a forming process for bending a plurality of portions of the lead 7 is required, and there is a problem that the number of processing steps increases.
Accordingly, the present invention has been made paying attention to such an unsolved problem of the conventional technology, and is suitable for mounting a heating element suitable for realizing a high cooling effect and reducing the number of processing steps. The purpose is to provide.

  In order to achieve the above object, the heating element mounting structure according to claim 1 according to the present invention includes a housing having a bottom surface and a wall surface rising from the bottom surface, a substrate disposed along the bottom surface, and the wall surface. A heating element mounting structure in which a lead of the heating element is electrically joined to the substrate, and at least an end of the substrate facing the wall surface is a flexible member The lead of the heating element was electrically joined to the flexible member.

With such a configuration, heat generated from the heat generating element is released to the outside through the housing, thereby cooling the heat generating element.
Further, when the thermal expansion coefficients of the housing and the lead are different, stress is generated due to the difference in thermal expansion between the housing and the lead during thermal expansion, and the stress due to thermal expansion is applied to the joint between the substrate and the lead. At this time, since at least the end portion facing the wall surface of the substrate is made of a flexible member, the flexible member is bent by the stress due to thermal expansion, and the stress due to thermal expansion is absorbed.

Here, the heating element includes, for example, an element that generates heat by power or a signal supplied via a lead, and an element that self-heats regardless of the power or signal supplied via a lead. In the latter case, for example, an element that generates heat due to the influence of disturbance noise or other external environment can be used.
Moreover, the board | substrate should just be comprised with the flexible member at least the edge part which faces a wall surface, and may comprise a part of board | substrate including an edge part with a flexible member, or the whole board | substrate. You may comprise by a flexible member.

Furthermore, the heating element mounting structure according to a second aspect of the present invention is the heating element mounting structure according to the first aspect, wherein the substrate is a flexible substrate.
If it is such a structure, since a flexible substrate has flexibility, a flexible substrate will bend by the stress by thermal expansion, and the stress by thermal expansion will be absorbed.

Further, the heating element mounting structure according to claim 3 according to the present invention is the heating element mounting structure according to claim 2, wherein the substrate is configured such that a part of the flexible substrate overlaps a glass epoxy substrate. The flexible substrate is laminated on a glass epoxy substrate, and the portion of the flexible substrate that does not overlap with the glass epoxy substrate is disposed facing the wall surface, and the lead of the heating element is electrically connected to the portion that does not overlap. Joined.
With such a configuration, when a stress due to thermal expansion is applied to the non-overlapping portion of the flexible substrate, a part of the flexible substrate is fixed to the glass epoxy substrate. The overlapping portion is bent and the stress due to thermal expansion is absorbed.

Furthermore, the heating element mounting structure according to claim 4 according to the present invention is the heating element mounting structure according to any one of claims 1 to 3, wherein the heating element is bonded to the heating element lead of the substrate. A slit was formed around the part.
With such a configuration, since the slit is formed around the joint portion with the lead of the heating element, the flexible member is easily bent. Therefore, a larger stress can be absorbed.
Here, the slit can be formed in a linear shape, a staircase shape, or any other shape.
Further, the extension direction of the slit may be any direction, but is preferably a direction away from the wall surface from the viewpoint of absorbing a larger stress.
Moreover, although the edge part of a slit does not need to open, it is preferable to open from a viewpoint of absorbing a bigger stress. The opening is preferably an end face facing the wall surface of the substrate.

Furthermore, the heating element mounting structure according to claim 5 of the present invention is the heating element mounting structure according to claim 4, wherein the slit is formed along a direction away from the wall surface.
With such a configuration, since the slit is formed along the direction away from the wall surface, the flexible member is more easily bent. Therefore, a larger stress can be absorbed.

  As described above, according to the mounting structure of the heat generating element according to claim 1 of the present invention, the heat generated from the heat generating element is released to the outside through the housing, so that the heat generating element is cooled. The effect that a high cooling effect is realizable is acquired. In addition, since the stress generated by the difference in thermal expansion between the housing and the lead is absorbed by the flexible member, there is no need to form the lead, reducing the number of machining steps compared to the conventional case. The effect that it can do is acquired.

Furthermore, according to the mounting structure for a heat generating element according to claim 4 of the present invention, a greater stress can be absorbed, so that an effect of improving resistance to thermal expansion can be obtained.
Furthermore, according to the mounting structure for a heat generating element according to claim 5 of the present invention, a greater stress can be absorbed, and thus an effect of further improving the resistance to thermal expansion can be obtained.

Embodiments of the present invention will be described below with reference to the drawings. 1 to 3 are views showing an embodiment of a heating element mounting structure according to the present invention.
First, an electronic component mounting structure will be described.
FIG. 1 is a cross-sectional view of an electronic component mounting structure according to the present embodiment.
FIG. 2 is a perspective view of the electronic component mounting structure according to the present embodiment.

1 and 2, the housing 1 has a box shape with an upper opening, and constitutes a housing of an electronic control unit mounted on an automobile or the like. An electronic circuit board 4 is arranged along the bottom surface 2 of the housing 1 inside the housing 1.
The electronic circuit board 4 is configured as a flex-rigid board formed by laminating the flexible board 10 on the glass epoxy board 11 so that a part of the flexible board 10 overlaps the glass epoxy board 11. The flexible substrate 10 has flexibility in the thickness direction. Examples of the flex-rigid board include a flex-rigid board from Fuji Kiko Electronics Co., Ltd. (http://www.fujimme.co.jp/flex.htm: as of January 2006) and a flex-rigid board from Print Electronics Laboratory Co., Ltd. A rigid board (http://www.pdk21.com/rijito1a.html: as of January 2006) can be used.

The electronic circuit board 4 is disposed with a portion of the flexible substrate 10 that does not overlap with the glass epoxy substrate 11 (hereinafter referred to as a non-overlapping portion) facing the inner wall surface 3 of the housing 1.
A heat-generating electronic component 5 such as a power transistor is fixed to the inner wall surface 3 with a screw 6 with its back surface in contact with the inner wall surface 3. The housing 1 includes heat radiating fins (not shown), absorbs heat generated from the electronic component 5, and cools the electronic component 5 by radiating heat from the heat radiating fin to the outside.

  The electronic component 5 includes a lead 7 that inputs and outputs power, a control signal, and the like. One end of the lead 7 is attached to the bottom surface 5 a of the electronic component 5 facing the mounting surface 10 a of the flexible substrate 10, and the other end of the lead 7 is a through hole formed in the thickness direction of the non-overlapping portion of the flexible substrate 10. 8 and soldered to be electrically joined to the non-overlapping portion of the flexible substrate 10.

Next, the operation of the present embodiment will be described.
FIG. 3 is a diagram for explaining an operation when stress is generated due to a difference in thermal expansion between the housing 1 and the lead 7.
Since the case 1 and the lead 7 have different coefficients of thermal expansion, a difference in the amount of thermal expansion occurs between the case 1 and the lead 7 due to temperature changes that occur in the usage environment, and stress due to thermal expansion is applied to the non-overlapping portion of the flexible substrate 10. . At this time, since a part of the flexible substrate 10 is fixed to the glass epoxy substrate 11, as shown in FIG. 3, the non-overlapping portion of the flexible substrate 10 is bent by the stress due to thermal expansion, and the stress due to thermal expansion is absorbed. The Therefore, it is possible to reduce the possibility that the soldering portion 9 is broken and disconnected.

  In this way, in the present embodiment, the flexible circuit board 10 is laminated on the glass epoxy substrate 11 so that a part of the flexible substrate 10 overlaps the glass epoxy substrate 11, and the electronic circuit board 4 is configured. The electronic circuit board 4 was placed with the non-overlapping portion 10 facing the inner wall surface 3, the electronic component 5 was fixed to the inner wall surface 3, and the leads 7 were electrically joined to the non-overlapping portion of the flexible substrate 10.

Thereby, since the electronic component 5 is cooled by releasing the heat generated from the electronic component 5 to the outside through the housing 1, a high cooling effect can be realized. In addition, since the stress generated by the difference in thermal expansion between the housing 1 and the lead 7 is absorbed by the flexible substrate 10, it is not necessary to form the lead 7. Can be reduced.
In the above embodiment, the electronic component 5 corresponds to the heat generating element according to claims 1 to 3.
In the above embodiment, the flexible substrate 10 is not processed. However, the present invention is not limited to this, and the flexible substrate 10 can be configured to absorb a larger stress by forming a slit.

FIG. 4 is a perspective view of an electronic component mounting structure according to another embodiment.
In FIG. 4, two slits 12 are formed on both sides of the soldering portion 9 of the flexible substrate 10 along the direction away from the inner wall surface 3. The slits 12 are formed in parallel and in a straight line. An end portion of the slit 12 is opened at an end surface facing the inner wall surface 3 of the electronic circuit board 4.
With such a configuration, the flexible substrate 10 is more easily bent. Therefore, since a larger stress can be absorbed, resistance to thermal expansion can be improved.
In this case, the electronic component 5 corresponds to the heat generating element according to claim 4 or 5, and the soldering portion 9 corresponds to the joint portion according to claim 4.

It is sectional drawing of the attachment structure of the electronic component which concerns on this Embodiment. It is a perspective view of the attachment structure of the electronic component which concerns on this Embodiment. FIG. 6 is a diagram for explaining an operation when stress is generated due to a difference in thermal expansion between the housing 1 and the lead 7. It is a perspective view of the attachment structure of the electronic component which concerns on other embodiment. It is sectional drawing of the attachment structure of the electronic component of patent document 1. It is a perspective view of the attachment structure of the electronic component of patent document 1.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Case 2, 5a Bottom surface 3 Inner wall surface 4 Electronic circuit board 5 Electronic component 6 Screw 7 Lead 8 Through hole 10 Flexible board 10a Mounting surface 11 Glass epoxy board 12 Slit

Claims (5)

A housing having a bottom surface and a wall surface rising from the bottom surface; a substrate disposed along the bottom surface; and a heating element fixed to the wall surface, wherein a lead of the heating element is electrically bonded to the substrate. A heating element mounting structure,
A mounting structure for a heating element, wherein at least an end of the substrate facing the wall surface is made of a flexible member, and a lead of the heating element is electrically joined to the flexible member. In claim 1,
The heating element mounting structure, wherein the substrate is a flexible substrate. In claim 2,
The substrate is formed by laminating the flexible substrate on the glass epoxy substrate so that a part of the flexible substrate overlaps the glass epoxy substrate, and a portion of the flexible substrate that does not overlap with the glass epoxy substrate is Placed on the wall,
A heating element mounting structure, wherein a lead of the heating element is electrically joined to the non-overlapping portion. In any one of Claims 1 thru | or 3,
A mounting structure for a heating element, wherein a slit is formed around a joint portion of the substrate with a lead of the heating element. In claim 4,
The heating element mounting structure, wherein the slit is formed along a direction away from the wall surface.

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