JPH09213852A - Heat dissipating structure of heating electronic component - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable a heat dissipating structure of a circuit unit that a printed board mounted with a heating electronic component such as a power transistor or the like is housed in a case to be easily incorporated and enhanced in heat transfer by a method wherein a flexible heat sink is used. SOLUTION: A printed board 5 mounted with a heating electronic component such as a power transistor 4 is housed in a case 3, a first heat sink 2 is provided outside the case 3, the one end of a second flexible heat sink 7 of metal whose other end is fixed coming into contact with the power transistor 4 is deflected so as to be brought into contact with the inner surface of the first heat sink 2 by resilency. Therefore, heat is transferred well through a contacting surface without using a fixing part such as a screw, and a cut/lifted part 8 is used as an engaging part, whereby a heat dissipating structure of this constitution can be very easily incorporated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat dissipation structure in an electronic component case body having an electronic component such as a power transistor which self-heats when energized.

[0002]

2. Description of the Related Art Conventionally, in a circuit unit in which an electronic circuit is housed in a case body, particularly when a heat-generating electronic component such as a power transistor is used, a resin case due to a temperature rise in the case body due to the heat generation is used. It is necessary to prevent characteristic changes and thermal destruction due to melting or excessive heat rise of the heat-generating electronic components themselves, and normally a metal plate with good heat conduction is used as a heat dissipation plate to transfer heat to the outside of the case body for heat dissipation. There is.

Generally, a heat radiating plate is contacted and fixed to a heat-generating electronic component, and if a large case body can absorb heat, it is radiated into the case body, and if it cannot be absorbed, a large heat radiating plate is exposed to the outside of the case body. A structure is adopted in which heat is radiated to the outside by fixing with pressure with screws.

[0004]

However, in the above heat dissipation structure, the pressure contact fixing structure of the heat dissipation plate which is fixed in contact with the heat-generating electronic component and the heat dissipation plate which is exposed to the outside of the case body and promotes heat dissipation is screwed in by screws. Therefore, since the heat dissipation plate is made of metal, chips may be generated due to the incisions, and there is a concern that the chips may attach to the pattern of the printed circuit board and cause a short circuit in the electric path.

Further, since the heat-dissipating plates are pressed and fixed to each other by screws, it takes time and effort to assemble the circuit unit including the heat-dissipating plates, and the fixing positions of the electronic components and the heat-dissipating plates and the heat-dissipating plates are displaced from each other. Since the stress due to the fixing deviation may be applied to the electronic component and damage the electronic component, extremely accurate alignment is required, and workability is extremely poor. It is an object of the present invention to provide a heat dissipation structure that is easy to assemble and does not have troublesome work such as positioning and screwing and fixing.

[0006]

A heat dissipation structure for an electronic component, which is connected to a circuit pattern of a printed circuit board housed in a case body and self-heats when energized, has a heat dissipation surface exposed to the outside of the case body. And a second heat radiating plate which is fixed to the heat-generating electronic component in contact with the first heat radiating plate and which has flexibility and is in pressure contact with a part of the plate surface of the first heat radiating plate to transfer heat.

Further, the first heat radiation plate to which the second heat radiation plate is pressure-contacted is provided with a locking portion for locking the pressure-contact side end of the second heat radiation plate.

Further, the first heat dissipation plate constitutes one side wall of the case body, and the heat conductivity of the first heat dissipation plate is larger than that of the second heat dissipation plate. Characterize.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION A second heat radiating plate which is fixedly contacted with a heat-generating electronic component is in surface contact with the first heat radiating plate at the other end, and its flexibility (elasticity) allows the second heat radiating plate to be attached to the first heat radiating plate. It is pressure-welded to improve heat conduction by surface contact.
This heat dissipation structure can be easily assembled without the need for fixing the second heat dissipation plate with screws. Further, since the end portion of the second heat dissipation plate can be easily locked by the locking portion of the first heat dissipation plate, the first heat dissipation plate is accompanied by the work of fixing the printed circuit board on which the electronic component is mounted to the case body. The pressure contact structure between the second heat radiation plate and the second heat radiation plate is completed. Further, the heat dissipation efficiency to the outside of the case body is improved by making the heat conductivity of the first heat dissipation plate forming one side wall of the case body larger than that of the second heat dissipation plate.

[0010]

1 is a cross-sectional view of a circuit unit showing a first embodiment of the present invention. A cup-shaped resin case 1 and a heat forming a side wall by closing the open side of the cup-shaped case 1 are shown. The case body 3 is constituted by the first heat dissipation plate 2 made of a metal having good conductivity (copper, aluminum, etc.).
A printed circuit board 5 having a power transistor 4 which is a heat generating electronic component mounted therein is housed and fixed therein.

Although not shown, a printed circuit board 5 is formed with a circuit pattern for connecting the power transistor 4 together with other electronic parts such as a capacitor and a resistor to form a circuit. It is fixed by screwing to the support pillar 6 formed in the above. The printed circuit board 5 can be fixed to the case body by fixing it to the first heat dissipation plate 2 through a spacer.

In this case, the printed circuit board 5 is arranged in parallel with the first heat radiating plate 2, and the power transistor 4 is mounted in parallel with the printed circuit board 5 in a rectangular prism type mold structure. The second heat dissipation plate 7 is fixed in contact with the heat dissipation surface side by screwing.

The second heat radiating plate 7 is made of a thin metal plate and has a flexible structure. The second heat radiating plate 7 is elastically urged toward the first heat radiating plate 2 and the other end thereof is the first heat radiating plate 2. It is fixed so as to be pressed against the inner surface of the. That is, the printed circuit board 5
One end side is contacted and fixed to the power transistor 4 parallel to
The first heat radiating plate 2 is bent halfway, and the other end side that is bent and hangs downward has its length set longer than the distance to the first heat radiating plate 2. A stable heat conduction contact structure can be obtained by a simple assembly by flexing in contact with the plate 2 and causing the end side to come into surface contact with the inner side surface of the first heat dissipation plate 2 and to make pressure contact by its elastic force. is there.

The elastic force of the second heat radiating plate 7 can be freely adjusted by arbitrarily setting the thickness of the metal plate forming the second heat radiating plate 7. Therefore, by increasing the length and reducing the thickness, the elastic force is increased. May be made smaller to have a free end by contact like a brush. By doing so, the first heat radiating plate 2 is fixed to the open side of the case 1 in which the printed circuit board 5 is internally fixed by screwing or the like. Along with the work, the free end of the second heat radiating plate 7 comes into contact with the inner surface of the first heat radiating plate 2 like a brush contact, and the heat radiating structure in the pressure contact state is easily formed by the repulsive force against the deflection. To be done.

If the thickness of the second heat radiating plate 7 is made thick and the elastic force is set to be large, the contact pressure on the inner side surface of the first heat radiating plate 2 can be increased. In order to ensure surface contact with the second heat dissipation plate 2, a cut is formed at the end of the second heat dissipation plate 7, and a cut-up is made at the contact point of the first heat dissipation plate 2.
The second heat dissipation plate 7 is formed on the cut-and-raised part 8 by forming a (locking part).
Since the notch is engaged and locked, the contact position is fixed, thereby causing the second heat dissipation plate 7 to bend, increasing the elastic force to increase the pressure contact force, and the surface contact It forms a heat conduction path.

In this case as well, the cut-and-raised portion 8 serving as the engaging portion of the first heat-dissipating plate 2 is simply engaged with the notch formed at the end of the second heat-dissipating plate 7, and then the first heat-dissipating plate 2 is engaged. Since the pressure contact structure by the deflection of the second heat dissipation plate 7 can be obtained together with the work of fixing the heat dissipation plate 2, the circuit unit having the heat dissipation structure can be assembled very easily.

In order to bring the contact end side of the second heat dissipation plate 7 into good contact with the inner side surface of the first heat dissipation plate 2, the width of the second heat dissipation plate 7 may be increased. For example, by forming a large number of cuts at the ends to form a brush shape, stable contact with the first heat dissipation plate 2 can be obtained, and the contact area for heat transfer can be increased.

The first heat radiating plate 2 and the second heat radiating plate 7 are both made of metal plates having good thermal conductivity, but the first heat radiating plate 2 exposed to the outside of the case body is It is desirable to use a metal material having a large thermal conductivity in order to increase the area and to improve the efficiency of heat radiation to the outside air.

That is, since iron, copper, aluminum or the like is easily processed as the metal material and is inexpensive, the thermal conductivity of the first heat radiating plate 2 is set to the heat of the second heat radiating plate 7 by selecting such metal material. Design each heat sink with a combination that will be larger than the conductivity. As a result, the heat generated by the power transistor 4, which is a heat generating electronic component, is generated by the second heat dissipation plate 7.
To the first heat dissipation plate 2 and the heat conduction route for radiating heat to the outside of the case body is stabilized, and the temperature rise in the case body due to heat radiation to the case body is suppressed well.

FIG. 2 shows a second embodiment of the present invention. The case body 9 is made of resin on all four sides, and the printed circuit board 10 housed inside is external to the case. The first heat dissipation plate 12 for heat dissipation of
A part of the first heat radiating plate 12 is made to face the opening 13 opened to the case body 9 so that heat can be radiated to the outside air.

A second heat radiating plate 14 is fixed in contact with a resistor 11 which is a heat generating electronic component connected to the printed circuit board 10. The other end of the second heat radiating plate 14 is the first heat radiating plate. Due to the length relationship extending to the 12 side and longer than the distance, the same bending as in the first embodiment is generated, and the repulsive force presses the surface of the first heat dissipation plate 12.

As a result, the heat generated by the heating resistor 11 is transmitted from the second heat radiating plate 14 to the first heat radiating plate 12, and is radiated favorably from the exposed surface of the first heat radiating plate 12 to the outside of the case body. It is possible to satisfactorily prevent problems such as an increase in temperature inside the case and thermal destruction of heat-generating electronic components.

Also in this embodiment, the cut and raised hooks 15 are provided at the contact points of the first heat dissipation plate 12,
The contact end of the second heat radiating plate 14 can be held at a predetermined position, and the second heat radiating plate when the heat generating resistor 11 is fixed to the first heat radiating plate 12 on the printed circuit board 10 even at the time of assembly. The 14-end locking makes it possible to easily assemble the heat dissipation structure without using a dedicated fixing part such as a screw.

[0024]

As described above, according to the heat dissipation structure of the present invention, the heat generated by the heat-generating electronic component connected to the printed circuit board housed and fixed in the case body is dissipated by the second heat radiation which is fixed in contact with this component. The heat can be satisfactorily transferred from the plate to the first heat dissipation plate exposed to the outside of the case and can be dissipated to the outside air, and the temperature rise leading to the melting of the resin material and the thermal destruction of electronic parts due to the temperature rise inside the case can be suppressed well. You can

Further, due to the flexibility of the second heat radiating plate, heat transfer is stabilized by the pressure contact structure with the first heat radiating plate in a flexed state, and a dedicated fixing part such as a screw is used for coupling the respective heat radiating plates. The case body and the printed circuit board can be brought into contact with each other without assembling work, and the number of parts can be reduced and the assembling work can be simplified.

[Brief description of drawings]

FIG. 1 is a sectional view of a circuit unit showing a first embodiment of a heat dissipation structure of the present invention.

FIG. 2 is a sectional view of a circuit unit showing a second embodiment of the heat dissipation structure of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cup-shaped case 2 and 12 1st heat sink 3 and 9 Case body 4 Power transistor 5 which is a heat-generating electronic component 5, 10 Printed circuit board 6 Supporting pillars 7 and 14 2nd heat sink 8 Cut and raised which is a locking part 11 Resistor which is a heat-generating electronic component 13 Opening 15 Hook which is a locking portion

Claims (3)

[Claims] 1. A heat dissipation structure for an electronic component, which is connected to a circuit pattern of a printed circuit board housed in a case body and self-heats when energized, having a heat dissipation surface exposed to the outside of the case body. A heat-radiating electronic component comprising a heat-radiating plate and a second heat-radiating plate which is fixed in contact with the heat-generating electronic component and has flexibility and transfers heat by pressing a part of the plate surface against the first heat-radiating plate. Heat dissipation structure. 2. The first heat dissipation plate with which the second heat dissipation plate is pressure contacted is provided with a locking portion that locks the pressure contact side end of the second heat dissipation plate. The heat dissipation structure of the heat-generating electronic component described in 1. 3. The first heat dissipation plate constitutes one side wall of the case body, and the thermal conductivity of the first heat dissipation plate is larger than the thermal conductivity of the second heat dissipation plate. The heat dissipation structure of the heat-generating electronic component according to claim 1.