JP2007324224A - Attaching structure for heating element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heating element attaching structure, suitable for obtaining a high cooling effect and reducing the number of processing man-hours. <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 lead 7 of the electronic component 5 is electrically joined with the electronic circuit substrate 4. Two slits 12 are formed, in a direction of separating from the inner wall surface 3 on both the sides of a soldering part 9 of the electronic circuit substrate 4, and are formed linear mutually in parallel. <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 use environment. 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 on 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.
Therefore, 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 bonded to the substrate, and a slit is formed around a joint portion of the substrate with the lead of the heating element. Formed.
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 the slit is formed around the joint portion with the lead of the heating element, the substrate is easily bent, and as a result, the substrate 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 electric power or a signal supplied through a lead, and an element that self-heats regardless of electric power or a signal supplied through the 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.

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 a second aspect of the present invention is the heating element mounting structure according to the first aspect, 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 substrate is more easily bent. Therefore, a larger stress can be absorbed.

Furthermore, the heating element mounting structure according to claim 3 according to the present invention is the heating element mounting structure according to any one of claims 1 and 2, wherein the joining portion extends along a direction away from the wall surface. The two slits are formed around the joint, and the two slits are formed such that the distance between them becomes shorter as the distance from the wall surface increases.
With such a configuration, the distance between the slits decreases as the distance from the wall surface increases, so that the substrate is more easily bent. Therefore, a larger stress can be absorbed.
Here, the slit may be formed in a straight line shape, or may be formed in a step shape so as to be closer to the joint portion side as the distance from the wall surface increases.

Furthermore, the mounting structure of the heating element according to claim 4 according to the present invention is the mounting structure of the heating element according to claim 3, wherein the two slits are formed in a straight line and are formed on the wall surface of the substrate. Of the angle formed by the facing end surface and the extending direction of the slit, the angle on the side opposite to the joint is larger than 90 degrees.
With such a configuration, the angle on the side opposite to the joint portion among the angles formed by the end surface facing the wall surface of the substrate and the extending direction of the slit is larger than 90 degrees, so that the substrate is easily bent.

  As described above, according to the mounting structure of the heat generating element according to claim 1 of the present invention, the heat generating element is cooled by releasing heat generated from the heat generating element to the outside through the housing. The effect that a high cooling effect is realizable is acquired. In addition, since the stress caused by the difference in thermal expansion between the housing and the lead is absorbed by the flexure of the substrate, there is no need to form the lead and the machining process can be reduced compared to the conventional case. The effect of being able to be obtained.

Furthermore, according to the mounting structure for a heating element according to claim 2 of the present invention, a larger 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 3 of the present invention, it is possible to absorb a larger stress, so that 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 printed board using a glass epoxy material or the like. However, the present invention is not limited to this, and a metal substrate such as iron, an aluminum alloy, or a copper alloy can be used.
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 components 5, and cools the electronic components 5 by radiating heat from the heat radiating fins 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.
Two slits 12 are formed on both sides of the soldering portion 9 of the electronic circuit board 4 along a 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 4 b facing the inner wall surface 3 of the electronic circuit board 4. Therefore, the electronic circuit board 4 has flexibility in the thickness direction.

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 casing 1 and the lead 7 have different thermal expansion coefficients, a difference in thermal expansion occurs between the casing 1 and the lead 7 due to a temperature change that occurs in the use environment, and stress due to thermal expansion is applied to the electronic circuit board 4. At this time, since the slits 12 are formed on both sides of the soldering portion 9, the electronic circuit board 4 is easily bent. As a result, as shown in FIG. 3, the electronic circuit board 4 (soldering) is caused by stress due to thermal expansion. The region including the portion 9 is bent, and the stress due to thermal expansion is absorbed. Therefore, it is possible to reduce the possibility that the soldering portion 9 is broken and disconnected.

Thus, in this embodiment, the electronic circuit board 4 arranged along the bottom surface 2 and the electronic component 5 fixed to the inner wall surface 3 are provided, and the leads 7 are electrically connected to the electronic circuit board 4. The two slits 12 were formed on both sides of the soldering portion 9 of the electronic circuit board 4.
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. Further, since the stress generated by the difference in thermal expansion between the housing 1 and the lead 7 is absorbed by the bending of the electronic circuit board 4, it is not necessary to perform the forming process on the lead 7, and compared with the conventional case, Processing steps can be reduced.

Further, in the present embodiment, the slit 12 is formed along a direction away from the inner wall surface 3.
Thereby, since a bigger stress can be absorbed, the tolerance with respect to thermal expansion can be improved.
In the above embodiment, the electronic component 5 corresponds to the heat generating element according to claim 1 or 2, and the soldering portion 9 corresponds to the joint portion according to claim 1.
In the above embodiment, the two slits 12 are formed in parallel. However, the present invention is not limited to this, and it can be configured to absorb a larger stress by forming it at a predetermined angle.

FIG. 4 is a perspective view of an electronic component mounting structure according to another embodiment.
In FIG. 4, the two slits 12 are formed such that the angle θ on the side opposite to the soldering portion 9 out of the angle formed by the extending direction of the slit 12 and the end face 4 b is larger than 90 degrees.
With such a configuration, the distance between the slits 12 decreases as the distance from the inner wall surface 3 increases, so that the electronic circuit board 4 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 the third or fourth aspect, and the soldering portion 9 corresponds to the joint part according to the third or fourth aspect.

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 4a Mounting surface 4b End surface 5 Electronic component 6 Screw 7 Lead 8 Through hole 12 Slit

Claims (4)

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 a slit is formed around a joint portion of the substrate with a lead of the heating element. In claim 1,
The heating element mounting structure, wherein the slit is formed along a direction away from the wall surface. In any one of Claim 1 and 2,
Forming the two slits around the joint along the direction away from the wall surface, sandwiching the joint;
The mounting structure for a heating element, wherein the two slits are formed such that the distance between the two slits becomes shorter from the wall surface. In claim 3,
The two slits are formed in a straight line, and an angle between an end surface of the substrate facing the wall surface and an extension direction of the slit is larger than 90 degrees on the side opposite to the joint portion. A heating element mounting structure, wherein the heating element is formed as described above.

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