JP2021174816A - Electronic device - Google Patents

Abstract

To dissipate the heat of a heat generating component 22 inside while a cover 5 is made of synthetic resin to reduce the weight of a housing 2.SOLUTION: A housing 2 is composed of a metal body 4 and a synthetic resin cover 5, and the cover 5 covers a first surface 3A of a circuit board 3 on which a heat generating component 22 is mounted. A window 38 is opened and formed on a second ceiling wall 36b which has a low height as a part of a wall 36 of the cover 5, and a metal heat sink 39 is insert-molded so as to cover the window 38. The package top surface of the heat generating component 22 is in contact with the inner surface of the metal heat sink 39 via a heat transfer member 40. The metal heat sink 39 is subjected to porous surface treatment so as to have a pore having an enlarged diameter at a deeper portion than the surface.SELECTED DRAWING: Figure 1

Description

The present invention relates to an electronic device in which a heat generating component is mounted on a circuit board as an electronic component.

In Patent Document 1, in order to release the heat of heat-generating parts such as FETs to the outside, the main part of the housing lid covering the circuit board is made of an aluminum alloy die-cast product and welded to the housing body made of synthetic resin. An electronic device having a structure in which only the peripheral portion is made of an annular resin member is disclosed. The metal cover member made of an aluminum alloy has a protrusion on the back surface of the region where the heat generating component of the circuit board is mounted, and this protrusion is in contact with the circuit board via thermal paste or the like. The peripheral edge of the metal cover member is roughened by laser processing or the like, and the roughened portion is joined to the annular resin member.

JP-A-2019-75872

In the above-mentioned conventional configuration, the main part of the housing lid is a die-cast product of an aluminum alloy, which is not preferable in terms of weight reduction of the electronic device and also increases the cost of parts. Further, since the rough surface processing by laser processing or the like is performed only on the peripheral edge portion to be joined to the annular resin member, it is necessary to perform the processing for each part, which is troublesome.

According to the present invention, in one aspect of the present invention, the electronic device includes a circuit board on which an electronic component including a heat generating component is mounted on a first surface, and a synthetic resin cover that covers the first surface of the circuit board. A window portion is provided in a region facing the heat generating component in the wall portion facing the first surface of the synthetic resin cover, and the window portion is provided. A metal heat-dissipating plate is arranged so as to close the portion, and the metal heat-dissipating plate is subjected to perforated surface processing in which holes are enlarged deeper than the surface on both sides, and the peripheral portion of the metal heat-dissipating plate is formed. It is insert-molded on the opening edge of the window.

In the above configuration, since only a part of the synthetic resin cover is a window portion provided with a metal heat radiating plate, it is possible to reduce the weight and cost of the heat-generating parts while ensuring the heat radiating property. Since the entire surface of the metal heat-dissipating plate is subjected to a porous surface treatment in which the holes are enlarged in the deep part, a large bonding strength with the insert-molded synthetic resin portion can be obtained, and a substantial heat-dissipating area (surface area) can be obtained. growing.

The exploded perspective view which shows the 1st Example of the electronic device which concerns on this invention. Sectional view in the assembled state. Top view of the circuit board. Top view of the body. An enlarged cross-sectional view of a main part of a metal heat dissipation plate with a multi-layer surface treatment. An exploded perspective view showing a second embodiment of the electronic device. Sectional view in the assembled state.

Hereinafter, the electronic device 1 according to an embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 is an exploded perspective view of the electronic device 1 of the first embodiment, and FIG. 2 is a cross-sectional view of the electronic device 1 in an assembled state. The electronic device 1 is attached to an appropriate position of the vehicle as, for example, a controller of an automatic transmission for a vehicle, and as shown in the figure, a housing, that is, a housing 2, and a circuit board housed inside the housing 2. 3 and.

The housing 2 is composed of a metal body 4 having heat sink portions 6a partially thickened at a plurality of locations on the upper surface of the rectangular bottom wall 6 and a composite having a shape bulging so as to cover the upper surface of the bottom wall 6. It is composed of a resin cover 5.

The circuit board 3 has a rectangular shape with mounting holes 7 at four peripheral locations, and is fixed to the body 4 by screws 8 penetrating the mounting holes 7. A synthetic resin connector 9 for collectively connecting a power supply line and a signal line is attached to one end of the circuit board 3 in the longitudinal direction.

The body 4 and the cover 5 are sealed by a gasket 10 continuously formed in a frame shape and a U-shaped connector gasket 11. The connector gasket 11 is interposed between the connector 9 and the cover 5.

The circuit board 3 is a multilayer board or a double-sided board using a resin base material such as glass epoxy resin or a metal base material, and has a first surface 3A facing the cover 5 side and a second surface 3A facing the body 4 side. Electronic components are surface-mounted on each of the surfaces 3B and both surfaces as component mounting surfaces. Specifically, on the first surface 3A, relatively large electronic components such as a plurality of aluminum electrolytic capacitors 21 (in other words, the height from the mounting surface is high) and heat generating components 22 having a large calorific value such as FETs. Is mounted, and relatively small electronic components (in other words, the height from the mounting surface is low) such as a CPU and an IC chip are mounted on the second surface 3B. Corresponding to such a difference in height of the electronic component, the central portion of the cover 5 bulges upward and does not interfere with the electronic component such as the aluminum electrolytic capacitor 21 between the first surface 3A and the cover 5. Sufficient spacing is secured. On the contrary, the second surface 3B approaches the bottom wall 6 of the body 4 at a relatively small interval.

The heat generating component 22 such as the FET in this embodiment has a flat rectangular package, and is lower in height from the mounting surface than the aluminum electrolytic capacitor 21. In the illustrated example, two heat generating parts 22 are provided. Assuming a center line L (see FIG. 3) extending in the longitudinal direction through the center of the rectangular circuit board 3, these heat generating components 22 are located unevenly on one side of the center line L. The two heat generating parts 22 are arranged side by side in a straight line along the direction of the center line L. Note that FIG. 3 shows the circuit board 3 provided with the connector 9 as a single unit, and electronic components other than the heat generating component 22 are not shown.

The body 4 is made of, for example, a die-cast aluminum alloy product. FIG. 4 is a plan view of the body 4 alone. The body 4 is provided with tongue-shaped bracket portions 25 and 26 for attachment to the vehicle body, and is provided with a gasket groove 27 to which the gasket 10 is fitted on the peripheral edge. Further, four screw holes 28 into which the screws 8 are screwed are formed on the inner peripheral side of the gasket groove 27. Mounting holes 29 for mounting the cover 5 by thermal caulking are formed at the four corners of the rectangular body 4 at positions on the outer peripheral side of the gasket groove 27.

The heat sink portion 6a provided on the bottom wall 6 of the body 4 is formed in a rectangular trapezoidal shape protruding toward the circuit board 3 by partially thickening the bottom wall 6. The heat sink portion 6a is provided in a region of the circuit board 3 on which the heat generating component 22 is projected. Therefore, in the illustrated example, two heat sink portions 6a corresponding to the heat generating component 22 are formed. In the assembled state of the electronic device 1, the top surface of the heat sink portion 6a is close to the second surface 3B of the circuit board 3, and the heat transfer member 30 having flexibility such as heat transfer grease or a heat transfer sheet ( It is in contact with the second surface 3B via (see FIGS. 1 and 2). As a result, a part of the heat generated by the heat generating component 22 is transferred to the heat sink portion 6a and finally dissipated from the outer surface of the body 4. The top surface of the heat sink portion 6a may be brought into direct contact with the second surface 3B of the circuit board 3 without using the heat transfer member 30.

The cover 5 is molded from a synthetic resin, for example, a rigid thermoplastic resin, has a flange portion 31 along one plane on three sides, and has a flange portion 31 on three sides at one end in the longitudinal direction, which is the remaining one side. , The connector accommodating portion 32 corresponding to the outer shape of the connector 9 is formed to be inflated. Caulking pins 33 protruding from the flange portion 31 toward the body 4 side are formed at the four corners of the cover 5 (see FIG. 1). Each of these caulking pins 33 is subjected to so-called thermal caulking that penetrates the mounting hole 29 of the body 4 and heats and pressurizes the tip portion protruding from the mounting hole 29. Therefore, in the assembled state, the tip end portion of the caulking pin 33 is crushed so as to expand in the radial direction from the mounting hole 29, whereby the cover 5 and the body 4 are assembled to each other.

The central portion surrounded by the flange portions 31 on the three sides is formed in a shape bulging from the flange portion 31 as a wall portion 36 covering the first surface 3A of the circuit board 3. In other words, the wall portion 36 faces the first surface 3A of the circuit board 3 with an appropriate interval from the first surface 3A. The wall portion 36 has a flat surface parallel to the circuit board 3.

Here, in the first embodiment, the wall portion 36 has a first ceiling wall portion 36a having a relatively large distance from the circuit board 3 and a second ceiling wall having a relatively small distance from the circuit board 3. It is formed separately from the portion 36b, and both are connected by the inclined wall portion 36c. The boundary between the inclined wall portion 36c, that is, the first ceiling wall portion 36a and the second ceiling wall portion 36b extends parallel to the center line L (see FIG. 3) of the circuit board 3. The second ceiling wall portion 36b occupies a smaller range than the first ceiling wall portion 36a, and is provided in a range covering the two heat generating components 22 on the circuit board 3. The first ceiling wall portion 36a covers an area on which a relatively large electronic component (in other words, a height from the mounting surface) such as an aluminum electrolytic capacitor 21 is mounted.

In other words, in the wall portion 36 set to a height that can cover electronic components having a height from the mounting surface of the aluminum electrolytic capacitor 21 or the like, the width direction corresponding to the arrangement position of the two heat generating components 22. One side portion is formed as a second ceiling wall portion 36b with a low height. The size of the step between the first ceiling wall portion 36a and the second ceiling wall portion 36b (that is, the difference in height between the first ceiling wall portion 36a and the second ceiling wall portion 36b) is determined by the heat generating component in the circuit board 3. It is set in consideration of the height of the top surface of the 22 packages. The first ceiling wall portion 36a and the second ceiling wall portion 36b form a flat surface parallel to the circuit board 3.

In the second ceiling wall portion 36b, a rectangular window portion 38 is formed in a region of the circuit board 3 facing the two heat generating components 22, and the window portion 38 is made of metal so as to close the window portion 38. A heat radiating plate 39 is arranged. The metal heat radiating plate 39 has a flat rectangular shape, that is, a simple plate shape. As an example, the metal heat dissipation plate 39 is made of aluminum having excellent heat transfer properties or an aluminum alloy mainly composed of aluminum, and as described later, has a diameter deeper than the surface on both sides (in other words, the entire metal plate). It has an enlarged porous surface treatment. The peripheral edge of the metal heat dissipation plate 39 is insert-molded into the opening edge of the window 38. By this insert molding, as shown in FIG. 2, although there is a difference in plate thickness between the two, the second ceiling wall portion 36b and the metal heat radiating plate 39 are substantially along one plane. The metal heat radiating plate 39 is fixed to the window 38. Therefore, the metal radiator plate 39 is along a plane parallel to the circuit board 3.

In the assembled state of the electronic device 1, the inner surface of the metal heat sink 39 is close to the top surface of the package of the heat generating component 22, and the heat transfer member 40 having flexibility such as heat transfer grease or heat transfer sheet (FIG. 1). , Refer to FIG. 2) and is in contact with the top surface of the package of the heat generating component 22. As a result, a part of the heat generated by the heat generating component 22 is transferred to the metal heat sink 39 and radiated from the outer surface of the metal heat sink 39. The inner surface of the metal heat radiating plate 39 may be brought into direct contact with the top surface of the package of the heat generating component 22 without using the heat transfer member 40. As shown in FIG. 2, the exposed surface of the metal heat radiating plate 39 exposed inside the window portion 38 has a size capable of covering the package top surfaces of the two heat generating components 22.

The metal heat sink 39 made of aluminum or an aluminum alloy is subjected to a porous surface treatment as described above, whereby a large number of pores 41 having a shape as schematically shown in FIG. 5 are formed. The pores 41 have, for example, a diameter of μm order and a depth of at least about 10 μm, and have a tree branch shape or an ink bottle shape in which the pores are enlarged at a depth deeper than the pore diameter on the surface. The pores 41 having enlarged pores in such a deep portion contain zinc and other metals on the surface of a base material made of aluminum or an aluminum alloy, for example, as described in Japanese Patent Application Laid-Open No. 2012-415579. After forming a metal film, it is formed by immersing it in an etching solution. That is, since the etching proceeds not only in the vertical direction but also in the horizontal direction in the deep part, the pores 41 enlarged in the deep part can be obtained. The porous surface treatment in the present invention is not necessarily limited to the method described in the above publication.

By insert-molding the metal heat-dissipating plate 39 having pores 41 on both the front and back surfaces at the time of molding the synthetic resin cover 5, the synthetic resin material enters the pores 41 enlarged in the deep part, thereby exerting a strong anchoring action. Obtained, the metal heat dissipation plate 39 is securely and firmly fixed to the window portion 38. That is, bonding is possible without a reactive group for chemical bonding on the metal surface of the metal heat radiating plate 39.

Further, on the outer surface of the metal heat radiating plate 39, the surface area in contact with the outside air increases with the formation of the pores 41, and the heat radiating performance is improved accordingly. Similarly, on the inner surface of the metal heat sink 39, the contact area with the flexible heat transfer member 40 is increased by the presence of the pores 41, and the heat transfer from the heat generating component 22 is improved accordingly.

As described above, in the electronic device 1 of the above embodiment, since the cover 5 is made of synthetic resin, the weight is lighter and the parts are lighter than, for example, when the entire cover 5 is a die-cast product of an aluminum alloy. The cost is also reduced. Moreover, the cover 5 and the body 4 can be assembled by heat caulking of the caulking pin 33 instead of the screws.

Further, with respect to the heat generating component 22, since a part of the synthetic resin cover 5 is formed of the metal heat sink 39, heat can be released to the outside of the housing 2, and the cover 5 is made of metal. It can be cooled by the outside air in the same way as above. Moreover, in the illustrated example, the package of the heat generating component 22 is sandwiched from both sides together with the heat transfer members 30 and 40 by the heat sink portion 6a of the metal body 4 and the metal heat radiating plate 39. Therefore, the heat generating component 22 Is effectively cooled from both sides, and the heat of the heat generating component 22 is less likely to be dissipated into the space inside the housing 2.

Further, in the above embodiment, since the metal heat radiating plate 39 has a simple plate shape, the increase in cost and the increase in man-hours due to the addition of the metal heat radiating plate 39 are minimized. In particular, when the porous surface processing is performed by etching, a large number of metal heat radiating plates 39 can be processed together, so that a substantial increase in man-hours or complication can be suppressed.

Next, a second embodiment of the present invention will be described with reference to FIGS. 6 and 7. FIG. 6 is an exploded perspective view of the electronic device 1 of the second embodiment, and FIG. 7 is a cross-sectional view of the electronic device 1 in an assembled state.

In this second embodiment, the central wall portion 36 surrounded by the flange portions 31 on the three sides of the synthetic resin cover 5 is formed as a flat one having a constant height as a whole. That is, there is no low portion corresponding to the second ceiling wall portion 36b in the first embodiment. Similar to the first embodiment described above, a rectangular window portion 38 is formed in the region corresponding to the two heat generating parts 22 in the wall portion 36, and the window portion 38 is formed in the window portion 38. A metal heat radiating plate 39 for closing the above is arranged.

The metal heat radiating plate 39 in the second embodiment has a frame-shaped peripheral edge portion 39a supported by insert molding on the opening edge portion of the window portion 38, and a central portion recessed inward of the housing 2 with respect to the peripheral edge portion 39a. It is provided with a bottom wall portion 39b. The peripheral edge portion 39a and the bottom wall portion 39b are respectively along a plane parallel to the circuit board 3. In other words, the metal heat radiating plate 39 of the second embodiment is formed in a rectangular box shape with an open upper surface by so-called drawing processing, and has a shape in which a peripheral edge portion 39a extends like a flange from the opening edge. ..

In the assembled state of the electronic device 1, the recessed bottom wall portion 39b of the metal heat radiating plate 39 is close to the package top surface of the heat generating component 22, and is a heat transfer member having flexibility such as heat transfer grease or a heat transfer sheet. It is in contact with the package top surface of the heat generating component 22 via 40. As a result, a part of the heat generated by the heat generating component 22 is transferred to the metal heat sink 39 and radiated from the outer surface of the metal heat sink 39. The surface of the bottom wall portion 39b may be brought into direct contact with the package top surface of the heat generating component 22 without using the heat transfer member 40. As shown in FIG. 7, the bottom wall portion 39b has a size capable of covering the package top surfaces of the two heat generating components 22.

Similar to the first embodiment, the metal heat sink 39 is made of aluminum or an aluminum alloy, and the front and back surfaces thereof are subjected to porous surface treatment so as to have pores 41 having an enlarged diameter deeper than the surface. There is. Similar to the first embodiment, the metal heat radiating plate 39 is fixed to the synthetic resin cover 5 by insert molding the peripheral edge portion 39a into the opening edge portion of the window portion 38. As shown in FIG. 7, the peripheral edge portion 39a of the metal heat radiating plate 39 is located on the same plane as the wall portion 36 of the synthetic resin cover 5, and the bottom wall portion 39b of the metal heat radiating plate 39 is the wall portion 36 of the cover 5. It is closer to the circuit board 3 than.

In this second embodiment, although the metal heat radiating plate 39 needs to be drawn, the shape of the wall portion 36 of the synthetic resin cover 5 is simplified, and in particular, the aluminum electrolytic capacitor 21 is formed around the heat generating component 22. It is suitable when an electronic component having a high height from a mounting surface is arranged.

Although one embodiment of the present invention has been described in detail above, the present invention is not limited to the above embodiment, and various modifications can be made. For example, the heat generating component 22 is not limited to the FET, but may be a device having a large heat generating amount such as a CPU, and its shape is not limited to a device having a flat package as shown in the illustrated example. Further, the present invention can be applied even if the body 4 is made of synthetic resin instead of metal.

As described above, the electronic device of the present invention
A circuit board on which electronic components including heat-generating components are mounted on the first surface,
A housing including a synthetic resin cover that covers the first surface of the circuit board,
It is an electronic device equipped with
A window portion is provided in a region of the wall portion facing the first surface of the synthetic resin cover facing the heat generating component, and a metal heat radiating plate is arranged so as to close the window portion. Has been
On both sides, the metal heat radiating plate is subjected to a porous surface treatment in which holes are enlarged deeper than the surface, and the peripheral edge portion of the metal heat radiating plate is insert-molded into the opening edge portion of the window portion.

A flexible heat transfer member may be interposed between the inner surface of the metal heat sink and the package of the heat generating component.

In one preferred embodiment, the metal radiator plate is a flat plate.

In this case, in one example, the wall portion has a first ceiling wall portion having a relatively large distance from the circuit board and a second ceiling wall portion having a relatively small distance from the circuit board. Including
The window portion and the metal heat radiating plate are provided on the second ceiling wall portion.

In another aspect, the metal heat radiating plate has a central portion recessed with respect to the peripheral edge portion supported by the opening edge portion of the window portion, and the bottom wall portion relatively close to the heat generating component. It has.

Preferably, the housing comprises a metal body that accommodates the circuit board between it and the synthetic resin cover.
The metal body has a heat sink portion that is partially thickened in a region where the heat generating component is projected.
The top surface of the heat sink is in contact with the second surface of the circuit board directly or via a flexible heat transfer member.

In one example, the metal heat sink is made of aluminum or an aluminum alloy.

1 ... Electronic device, 2 ... Housing, 3 ... Circuit board, 3A ... First surface, 3B ... Second surface, 4 ... Body, 5 ... Cover, 6 ... Bottom wall, 6a ... Heat sink, 9 ... Connector, 22 ... Heat generating parts, 30 ... Heat transfer member, 36 ... Wall part, 36a ... First ceiling wall part, 36b ... Second ceiling wall part, 38 ... Window part, 39 ... Metal heat sink, 39b ... Bottom wall part, 40 ... heat transfer member, 41 ... pores.

Claims (7)

A circuit board on which electronic components including heat-generating components are mounted on the first surface,
A housing including a synthetic resin cover that covers the first surface of the circuit board,
It is an electronic device equipped with
A window portion is provided in a region of the wall portion facing the first surface of the synthetic resin cover facing the heat generating component, and a metal heat radiating plate is arranged so as to close the window portion. Has been
The metal heat radiating plate is subjected to a porous surface treatment in which holes are enlarged deeper than the surface on both sides, and the peripheral edge portion of the metal heat radiating plate is insert-molded into the opening edge portion of the window portion.
An electronic device characterized by that. The electronic device according to claim 1, wherein a flexible heat transfer member is interposed between the inner surface of the metal heat sink and the package of the heat generating component. The electronic device according to claim 1 or 2, wherein the metal heat dissipation plate is a flat plate. The wall portion includes a first ceiling wall portion having a relatively large distance from the circuit board and a second ceiling wall portion having a relatively small distance from the circuit board.
The electronic device according to claim 3, wherein the window portion and the metal heat radiating plate are provided on the second ceiling wall portion. The metal heat radiating plate is characterized in that the central portion is recessed with respect to the peripheral edge portion supported by the opening edge portion of the window portion, and the metal heat radiating plate has a bottom wall portion that is relatively close to the heat generating component. The electronic device according to claim 1 or 2. The housing includes a metal body that houses the circuit board with the synthetic resin cover.
The metal body has a heat sink portion that is partially thickened in a region where the heat generating component is projected.
The electron according to any one of claims 1 to 5, wherein the top surface of the heat sink portion is in contact with the second surface of the circuit board directly or via a flexible heat transfer member. Device. The electronic device according to any one of claims 1 to 6, wherein the metal heat sink is formed of aluminum or an aluminum alloy.

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