JPH09102685A - Heat radiating structure of electronic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat radiating structure for an electronic equipment capable of reducing man-hours and cost for assembly and reliably radiating heat regardless of the type and loading state of electronic elements. SOLUTION: Current passes are formed and are arranged with slit-shaped intervals (insulating slit portion IS) for live part conductor pattern C1 coupled electrically and thermally to heating type electronic element PH and also to live part conductor pattern C1, and heat generated in electronic elements dispersed in a substrate 2 near the insulating slit portion IS from the live part conductor pattern C1 is led to themselves by forming heat conducting pattern C2 on the substrate 2. Then, the heat conducting pattern C2 and the shield case 1 are soldered when the substrate 2 is housed in the shield case 1, and the two elements are thermally bridged by the solder SOL.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat dissipating structure using a conductor pattern of a substrate as a heat conducting means in an electronic device having a heat generating electronic element therein.

[0002]

2. Description of the Related Art As an example of a miniaturized electronic device, there are many composite electronic components in which one functional circuit is compactly assembled and the functional circuit is housed in a package. Among them, when a heat-generating element such as a transistor is provided inside, heat dissipation measures thereof become a problem. This heat dissipation measure requires a heat dissipation means for dissipating the heat to the outside of the package, and in some cases, a heat conduction means for guiding the heat generated in the electronic element to the heat dissipation means. In many conventional composite electronic components, heat generated in an electronic element is guided to a shield case for a package and the shield case is used as a heat dissipation plate. As an example of a composite electronic component using such a shield case as a heat radiating means of an electronic element, there is one having the following heat radiating structure.

Although various heat dissipation structures are adopted depending on the element requiring heat dissipation measures, assuming a power transistor as the heat generating element, the heat dissipation structure as shown in FIG. 7 has been often used. In FIG. 7, various electronic elements PE and a heat generating electronic element PH (power transistor) are mounted on the substrate 2 to form a functional circuit. The power transistor PH is lifted to a position higher than the surface of the substrate 2 by the long lead, and the lead is bent so that the main body is parallel to the substrate 2. Then, when the substrate 2 is housed in the shield case 1, the power transistor PH is configured such that a wide surface of its main body is joined to the ceiling plate.

Here, in order to ensure good heat conduction from the power transistor PH to the shield case 1, an adhesive agent having high heat conductivity is applied between the power transistor PH and the shield case 1, or a screw and a nut are used. The measure is to tighten the power transistor PH and the shield case 1 together to bring them into close contact. In the heat dissipation structure shown in FIG. 7, the heat generated in the power transistor PH is directly conducted to the shield case 1, and is dissipated from the outer surface of the shield case 1 to the atmosphere. Illustration of the terminal pins provided on the substrate 2 and the case lid that closes the opening of the shield case 1 in order to connect the composite electronic component to the circuit pattern of the mother board is omitted. The same applies to the figures described below.

In the heat dissipation structure shown in FIG. 7, the power transistor PH needs a long lead in order to connect the shield case 1 and the power transistor PH. However, in recent years, many surface connection type devices have appeared,
The heat dissipation structure shown in FIG. 7 is not suitable for a surface connection type power transistor. Therefore, a heat dissipation structure as shown in FIG. 8 has been proposed for the surface connection type power transistor. In FIG. 8, a conductor pattern C1 forming a current path exists on the surface of the substrate 2, and the power transistor PH is formed on the conductor pattern C1.
Is mounted, the conductor pattern C1 and the power transistor P
The H collector (lower surface metal part) is electrically connected. When housing the substrate 2 in the shield case 1, the heat conducting component 4 having a spring property is sandwiched between the power transistor PH and the ceiling plate of the shield case 1. Then, the heat conducting component 4 comes into close contact with the power transistor PH and the ceiling plate of the shield case 1 due to its own restoring force.

In the heat dissipation structure shown in FIG. 8, the heat generated in the power transistor PH is conducted to the shield case 1 through the heat conducting component 4, and is radiated from the outer surface of the shield case 1 to the atmosphere. Further, as another heat dissipation structure applicable to the surface connection type power transistor, there is also a material (not shown) having a high thermal conductivity used for the substrate on which the power transistor is mounted. In this case, the heat generated in the power transistor PH is transmitted to the substrate via the conductor pattern, is further guided from the substrate to the shield case, and is radiated from the shield case.

[0007]

First, in the heat dissipation structure shown in FIG. 7, long leads are required for the power transistor. In addition to this, in order to obtain good heat conduction between the power transistor PH and the shield case 1, the following points must be taken into consideration. That is, it is necessary to accurately set the mounting length and bending position of the leads of the power transistor PH so that the contact surfaces of the power transistor PH and the shield case 1 are joined in parallel, and when tightening together with screws and nuts. In addition, the positions of the power transistor PH and the through hole for inserting the screw provided in the shield case 1 must be aligned. In actual machining, it is difficult to obtain high processing accuracy in joining and bending as compared with other machining, but the heat dissipation structure shown in FIG. 7 requires high processing accuracy in joining and bending. In addition to this, an adhesive, a screw, and a nut are required in addition to this, so that an increase in cost and assembling man-hours cannot be avoided.

Next, in the heat radiation structure shown in FIG. 8, the cost and the number of assembling steps increase due to the requirement of the heat conducting component 4 which is an independent component. In actual product manufacturing,
The heat-conducting component 4 having a spring property is brought into close contact with the shield case 1 and the power transistor PH by its own restoring force at the time of completion, but at the time of assembly, one end face thereof needs to be fixed to the shield case 1 or the power transistor PH. Normally, it will be fixed to the shield case 1 side. Here, in the case of a surface connection type element, a positional shift or the like may occur when the element is mounted on a substrate or when soldering is performed. In the extreme case, there is a possibility that contact between the heat conducting component 4 fixed to the shield case 1 and the power transistor 1 may not be sufficiently obtained, so that the heat conducting component 4 having a margin in consideration of the positional deviation of the element should be provided. Need to use.

The heat dissipation structure using a material having a high heat conductivity for the substrate is far superior to other heat dissipation structures in that the number of assembling steps does not increase. However, the unit price of the substrate itself is high due to the peculiarity of the material, which causes the cost increase of the entire product. Therefore, the present invention can be used regardless of the type of electronic element having heat generation property, and can reliably conduct heat and radiate regardless of the mounting state (positional deviation, etc.) of the electronic element on the substrate, and An object of the present invention is to provide a heat dissipation structure for an electronic device, which can suppress the increase in the number of assembly steps as much as possible and can reduce the cost.

[0010]

SUMMARY OF THE INVENTION The present invention provides an electronic device in which an electronic element is mounted on a substrate to form a functional circuit, and the substrate is housed in a shield case or a similar box body to provide a heat generating property. A first conductor pattern forming a current path electrically and thermally coupled to a terminal of the electronic element having
The first conductor pattern is provided on the same substrate surface as the first conductor pattern with a slit-shaped interval, and is electrically isolated from the first conductor pattern by the slit-shaped interval, but is thermally separated. A second conductor pattern, which is coupled to and guides heat generated in the electronic element diffused from the first conductor pattern into the substrate to the second conductor pattern, which is provided on the substrate surface opposite to the first conductor pattern. Of the third conductor pattern that guides the heat generated in the electronic element diffused in the substrate to itself, the first conductor pattern and at least one of the second and third conductor patterns are formed on the substrate, and further, It is characterized in that the second or third conductor pattern is thermally coupled to the heat radiation means.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION In order to obtain sufficient thermal coupling with the power transistor PH, the contact area of the charging portion conductor pattern C1 electrically connected to the terminal of the power transistor PH which is a heat generating element is small. It is formed on the substrate so as to be large. In the first embodiment, a narrow slit-shaped space (insulating slit portion I) is formed on the charging portion conductor pattern C1.
A conductor pattern C2 for heat conduction is provided which extends to the end of the substrate via S), and the conductor pattern C2 for heat conduction is soldered to the shield case 1 at the end of the substrate. In addition, the longer the total length of the edges of the facing portions of the charging conductor pattern C1 and the heat conducting conductor pattern C2 that separate the insulating slit portion IS, the more the heat transfer from the charging conductor pattern C1 to the heat conducting conductor pattern C2 is performed. Therefore, it is preferable that the conductor pattern C1 of the charging portion is surrounded or semi-enclosed by the conductor pattern C2 for heat conduction.

In the second embodiment, the charging portion conductor pattern C1 is formed on the substrate surface facing the charging portion conductor pattern C1.
Is provided with a heat-conducting conductor pattern C3 extending from a position facing to the end portion of the substrate.
Is soldered to the shield case 1 at the board end. In another embodiment, a heat receiving plate is provided on the shield case 1 or the case lid 3 in order to obtain thermal coupling with the above-mentioned conductor pattern C2 or C3 for heat conduction.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An outline of a first embodiment of an electronic device (composite electronic component) to which a heat dissipation structure according to the present invention is applied, in which an increase in the number of assembling steps can be suppressed as much as possible and cost can be reduced, is shown in FIGS. Indicated. 1 is a sectional view of the entire electronic device, and FIG. 2 is a plan view of the vicinity of each conductor pattern. In FIG. 1, a substrate 2 is provided with a charging portion conductor pattern C1, a heat conducting conductor pattern C2, and other conductor patterns,
In addition, various electronic elements PE and power transistors PH
(Exothermic element) is mounted to form a functional circuit.

Here, the power transistor PH is mounted so that a wide surface of its main body is bonded to the charging portion conductor pattern C1, and its collector terminal (lower body metal plate) is soldered to the charging portion conductor pattern C1 to generate electricity. Connected. The charging portion conductor pattern C1 is a power transistor P.
It has a large area equal to or larger than the junction surface of the power transistor PH so that sufficient thermal coupling with H can be obtained, and forms a current path to extend a part thereof to another electronic element. A heat-conducting conductor pattern C2 is formed with a slit-shaped space (insulating slit portion IS) separated from the charging portion conductor pattern C1 and a part of which extends to the end of the substrate. When the substrate 2 is housed in the shield case 1, the substrate receiver 1-b provided on the side wall of the shield case 1
The locking projection 1-a fixes and holds the storage position of the substrate 2. Then, the side wall of the shield case 1 and the conductor pattern C2 for heat conduction are soldered to each other at the end portion of the substrate, and the solder SO
L is used to thermally crosslink between them.

In the case of such a structure, the heat generated in the power transistor PH is first transferred to the charging portion conductor pattern C1 to which the collector terminal is soldered and one surface of which is joined, and then diffused into the substrate 2. Will be done. Then, the heat-conducting conductor pattern C2 guides the heat diffused in the vicinity of the insulating slit portion IS of the substrate 2 to itself, and further guides the heat to the shield case 1 cross-linked with the solder SOL through the solder SOL. Thereby, the heat generated in the power transistor PH is radiated from the outer surface of the shield case 1 to the atmosphere.

In general, the collector of a transistor does not always have the ground potential but has an AC potential of a predetermined voltage because of its functional circuit configuration. Therefore, shield case 1
It is necessary to electrically isolate the heat conduction conductor pattern C2 and the charging portion conductor pattern C1 which are electrically connected to each other by the insulating slit portion IS. However, charging part conductor pattern C
Considering the effect of heat transfer from 1 to the heat conductive pattern C2, it is desirable that the width of the insulating slit portion IS be as small as possible. Therefore, the width of the insulating slit portion IS is determined in consideration of the balance between the heat conducting function and the insulating function, but in practice, the width is considered to be a maximum of twice the thickness of the substrate.

In order to enhance the heat conducting effect from the charging portion conductor pattern C1 to the heat conducting conductor pattern C2, in addition to reducing the width of the insulating slit portion IS, the charging portion conductor pattern C1 and the heat conducting conductor pattern C2 face each other. It can also be achieved by increasing the length of each edge. In FIG. 2, the charging portion conductor pattern C1 and the heat conducting conductor pattern C2 are
The opposite edges are formed in a wavy shape, and the wavy edges engage each other. With such a shape, the total length of the opposing edges becomes long, and the heat-conducting action can be improved even if the areas of the charging part conductor pattern C1 and the heat-conducting conductor pattern C2 are small. In FIG. 2, the opposing edges of the charging portion conductor pattern C1 and the heat conducting conductor pattern C2 have a wavy shape, but various application examples such as an irregular shape, a key shape, a step shape, or a step shape can be considered. When the amount of heat generated by the electronic element is small and the desired heat-conducting effect is sufficiently obtained, the opposing edges may be linear.

FIG. 3 shows a second embodiment of an electronic device to which the heat dissipation structure according to the present invention is applied. Similar to FIG. 2, FIG. 3 shows a plan view of the vicinity of each conductor pattern, but in FIG. 3, the charging portion conductor pattern C1 is half-enclosed by a heat conducting conductor pattern C2 formed in a U-shape. When the wiring space on the substrate 2 has a margin, it is very effective as a means for enhancing the heat conduction effect. That is, with such a structure, the total length of the opposing edges becomes long, and at the same time, the heat diffused from the charging part conductor pattern C1 to the substrate 2 can be efficiently guided to the heat conducting conductor pattern C2. Like In addition, in FIG. 3, the conductor pattern C2 for heat conduction is formed into a U shape, and the conductor pattern C1 for the charging portion is formed.
However, the present invention is not limited to this, and may be, for example, a completely surrounding shape, or a plurality of heat conducting conductor patterns may be arranged around the charging portion conductor pattern. .

FIG. 4 shows a third embodiment (cross section) of an electronic device to which the heat dissipation structure according to the present invention is applied. In FIG. 4, the charging portion conductor pattern C1 on which the power transistor PH is mounted is formed on one surface of the substrate 2, and from the end portion of the substrate 2 to a position substantially opposite to the charging portion conductor pattern C1 on the other surface. An extended heat-conducting conductor pattern C3 is formed. When the substrate 2 is housed in the shield case 1, the shield case 1 is placed at the end of the substrate 2.
And the heat-conducting conductor pattern C3 are soldered, and the spaces between them are thermally cross-linked.

In such a structure, the heat generated in the power transistor PH is first transferred to the charging portion conductor pattern C1 and diffused from the charging portion conductor pattern C1 into the substrate 2. The heat-conducting conductor pattern C3 formed on the surface of the substrate facing the charging portion conductor pattern C1 guides the heat diffused in the substrate to itself and further conducts the heat to the shield case 1 through the solder SOL. Thereby, the heat generated in the power transistor PH is radiated from the outer surface of the shield case 1 to the atmosphere. As long as the wiring space on the substrate 2 allows, the heat-conducting conductor pattern C3 can efficiently perform heat-conducting action if it is formed wide to the entire position facing the charging part conductor pattern C1. Further, if the heat-conducting conductor pattern C2 of FIG. 1 and the heat-conducting conductor pattern C3 of FIG. 4 are used together, further improvement of the heat-conducting action can be expected.

In the examples of the embodiments of the present invention shown in FIGS. 1 to 4, solder is used as a means for bridging between the heat conductive pattern C2 or C3 and the shield case 1 and thermally connecting them. The case was explained. Although the use of this solder is the means that requires the least number of steps and cost, the heat conducting conductor pattern C2 or C3 and the shield case 1 are thermally coupled by the structure as shown in FIGS. Can also be considered.

FIG. 5 shows a fourth embodiment (cross section) of an electronic device to which the heat dissipation structure according to the present invention is applied. A part of the side wall of the shield case 1 is cut out and bent along the side wall. The structure is such that a tongue-shaped heat receiving plate 1-c, which is formed by being bent in parallel with the ceiling plate in the middle thereof, also serves as a substrate receiver. When the substrate 2 is housed in the shield case 1, the tongue-shaped heat receiving plate 1-c and the heat-conducting conductor pattern C2 on the substrate 2 are joined to each other, so that the heat-conducting conductor pattern C2 transfers heat to the shield case 1. Done.

FIG. 6 shows a fifth embodiment (cross section) of the electronic device to which the heat dissipation structure according to the present invention is applied. The case lid 3 fitted in the opening of the shield case 1 has a side wall. It has a structure in which a heat receiving plate 3-a formed by bending a part of the upper end portion in parallel with the bottom plate is provided. When the board 2 is housed in the shield case 1 and the case lid 3 is fitted into the opening of the shield case 1, the heat receiving plate 3-a and the heat conducting conductor pattern C3 on the board 2 are joined together. , The heat-conducting conductor pattern C3 and the heat-conducting conductor pattern C2 joined through the through holes TH to the case lid 3,
Heat is conducted to the shield case 1.

The tongue-shaped heat receiving plate 1-shown in FIGS.
It goes without saying that the c and the heat receiving plate 3-a can also be applied to substrates other than the substrate 2 having the heat conducting conductor patterns C2 and C3 having the illustrated shapes and structures, respectively. In the embodiments of the heat dissipation structure according to the present invention described so far, the composite electronic component is taken up as an electronic device to be applied, but the present invention is not limited to this and may be applied to other electronic devices that require heat dissipation measures. is there. Further, although the power transistor is assumed as the heat generating electronic element, it can be used for other electronic elements such as ICs, other semiconductor elements, resistive elements, etc., and is not limited to the examples. There is no.

[0025]

According to the heat dissipation structure of the present invention, the heat transmitted to the conductor pattern of the charging portion electrically and thermally connected to the electronic element, and the heat diffused from the conductor pattern of the charging portion into the substrate is transferred to the conductor pattern for heat conduction. The heat is conducted by conducting the heat from the heat conducting conductor pattern to the heat radiating means. This makes it possible to dissipate heat even with a surface-connection type element, regardless of the shape of the electronic element having heat generating properties, and the mounting state of the electronic element (positional deviation, etc.)
Regardless of, reliable heat dissipation is possible.

Since the heat-conducting conductor pattern is formed at the same time when the circuit pattern of the substrate is formed, there is no increase in man-hours and costs in product manufacturing, and the means for thermally coupling the heat-conducting conductor pattern and the shield case are In particular, if solder is used, the number of assembling steps and the cost are hardly increased. Therefore, the heat dissipation of the electronic device can be performed at a very low cost. Additionally, as a factor (positional deviation, etc.) that causes defective heat conduction is eliminated between the heat-generating electronic element and the heat radiating means, the assembly work is facilitated, the defective rate is reduced, and the cost is substantially reduced. Contribute.

[Brief description of the drawings]

FIG. 1 is a schematic overall cross-sectional view of a first embodiment of an electronic device to which a heat dissipation structure according to the present invention is applied.

FIG. 2 is a plan view of the vicinity of each conductor pattern of the first embodiment shown in FIG.

FIG. 3 is a plan view of the vicinity of each conductor pattern of the second embodiment of the electronic device to which the heat dissipation structure according to the present invention is applied.

FIG. 4 is a schematic overall cross-sectional view of a third embodiment of an electronic device to which a heat dissipation structure according to the present invention is applied.

FIG. 5 is a cross-sectional view of a fourth embodiment of an electronic device to which a heat dissipation structure according to the present invention is applied, in the vicinity of a substrate end portion.

FIG. 6 is a cross-sectional view of a fifth embodiment of an electronic device to which a heat dissipation structure according to the present invention is applied, in the vicinity of a substrate end portion.

FIG. 7 is a schematic cross-sectional view of an electronic device having a conventional heat dissipation structure.

FIG. 8 is a schematic cross-sectional view of another electronic device having a conventional heat dissipation structure.

[Explanation of symbols]

1 Shield case 1-a Locking protrusion 1-b Substrate receiving 1-c Tongue-shaped heat receiving plate 2 Substrate 3 Case lid 3-a Heat receiving plate 4 Heat-conducting component PE electronic element PH Exothermic electronic element (power transistor) C1 Charging part conductor Pattern (1st conductor pattern) C2 Heat conduction conductor pattern (2nd conductor pattern) C3 Heat conduction conductor pattern (3rd conductor pattern) TH Through hole IS Insulation slit part SOL Solder

Claims (9)

[Claims] 1. An electronic device in which a functional circuit is formed by mounting an electronic element on a substrate, and the substrate is housed in a shield case or a box similar thereto. A first conductor pattern that forms a current path electrically and thermally coupled to the terminal, and is provided on the same substrate surface as the first conductor pattern with a slit-like spacing in the first conductor pattern. , The slit-shaped space electrically isolates the first conductor pattern from the first conductor pattern, but thermally couples the first conductor pattern to the heat generated in the electronic element, which diffuses into the substrate from the first conductor pattern. A heat dissipation structure for an electronic device, which is formed by forming a second conductor pattern that leads to the second conductor pattern, and further thermally coupling the second conductor pattern and the heat dissipation means. 2. The electronic device according to claim 1, wherein the opposing edges of the first conductor pattern and the second conductor pattern are formed in a concavo-convex shape that meshes with each other. Heat dissipation structure. 3. The heat dissipation structure for an electronic device according to claim 1, wherein the second conductor pattern is formed so as to surround or semi-enclose the first conductor pattern. 4. The second conductor is provided by a conductor pattern or a through hole provided in the vicinity of the end of the substrate on the surface of the substrate opposite to the surface on which the first conductor pattern and the second conductor pattern are provided. A third conductor pattern electrically and thermally coupled to the pattern is formed,
A heat dissipation structure for an electronic device according to claim 1, claim 2, or claim 3. 5. An electronic device in which an electronic element is mounted on a substrate to form a functional circuit, and the substrate is housed in a shield case or a similar box body, wherein an electronic element having a heat generating property is provided on the substrate. A first conductor pattern that forms a current path electrically and thermally coupled to the terminal and a substrate surface that faces the first conductor pattern, and diffuses into the substrate from the first conductor pattern. A heat dissipation structure for an electronic device, wherein a third conductor pattern for guiding the heat generated in the electronic element to itself is formed, and the third conductor pattern and the heat dissipation means are thermally coupled. 6. The heat dissipation structure for an electronic device according to claim 1, wherein a shield case is used as the heat dissipation means. 7. The second conductor pattern or the third conductor pattern and the heat dissipation means are heated by soldering the second conductor pattern or the third conductor pattern to the heat dissipation means. 7. The heat dissipation structure for an electronic device according to claim 1, wherein the heat dissipation structure is electrically coupled. 8. A tongue-shaped heat-receiving plate integrally formed with the shield case is provided so as to be parallel to the substrate housed in the shield case, and the heat-receiving plate and the second conductor pattern or the third conductor pattern are provided. The heat dissipation structure for an electronic device according to claim 6, wherein the shield case and the second conductor pattern or the third conductor pattern are thermally coupled by joining conductor patterns. 9. A heat receiving plate integrally formed on a side wall of the case lid fitted in the opening of the shield case so as to be parallel to a substrate housed in the shield case,
The shield case and the second conductor pattern or the third conductor pattern are thermally coupled by joining the heat receiving plate and the second conductor pattern or the third conductor pattern. The heat dissipation structure for an electronic device according to claim 6.