JP2001036260A - Electronic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress a rise in the temperature of an electronic component which is lower in guarantee temperature than a high heat generating element without making a housing large-sized. SOLUTION: The electronic device 1 has a wall surface 2a, a 2nd circuit board 12, and the inside surface of the high heat generating element 14 covered with resin 18 of low heat conductivity to suppress heat radiation from the wall surface 2a, 2nd circuit board 12, and high heat generating element 14 to the space in the housing even when the high heat generating element 14 reaches a high temperature and further suppress heat conduction from the high heat generating element 14 to the atmosphere of the space in the housing. Consequently, the heat radiation from the high heat generating element 14, etc., to a low guarantee temperature electronic component 8 and the heat conduction through the atmosphere in the space in the housing are suppressed to suppress a rise in the temperature of the low guarantee temperature electronic component 8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic device in which an element generating a large amount of heat (a high heat generating element) and an electronic component having a lower guaranteed temperature than the high heat generating element are provided on mutually different wall surfaces of a housing. About.

[0002]

2. Description of the Related Art Conventionally, functions of electronic devices mounted on, for example, automobiles have been advanced and diversified.
As the electronic circuits become more and more complicated, the amount of heat generated tends to increase, and it is important to efficiently dissipate heat. In a high heat generating element (for example, a power transistor) that generates a large amount of heat, the temperature rises to about 130 ° C. during operation, so that it is necessary to further improve the heat radiation efficiency.

Therefore, the high heat generating element is disposed directly on the wall surface of the housing constituting the outer shape of the electronic device, or “an electronic component having a lower guaranteed temperature than the high heat generating element” (for example, an IC element, etc.). However, in the present specification, the electronic component is mounted on a circuit board different from the circuit board on which the “low guaranteed temperature electronic component” is mounted, and the circuit board is placed in close contact with a wall surface of the housing. By doing so, it is conceivable to use the wall surface of the housing as a heat radiating plate to achieve efficient heat radiation. This is to prevent the occurrence of such an adverse effect because mounting the low-guaranteed-temperature electronic component and the high-heat-generating element on the same circuit board is likely to adversely affect the operation of the electronic circuit due to the influence of heat.

[0004] Specifically, for example, a configuration as shown in FIG. 3 can be considered. That is, the electronic device 10 shown in FIG.
In 1, a housing constituting the outer shape is composed of a metal lid 2 and a first circuit board 4 made of resin, and a low-temperature-guaranteed electronic component 8 and the like are provided on the first circuit board 4. Electronic components. Then, the second circuit board 12 on which the high heat generating element 14 is mounted is heat-conductive on the wall surface facing the first circuit board 4 (that is, the surface facing the wall surface on which the low-guaranteed temperature electronic components 8 are provided). Adhesion is performed in an intimate contact state with an adhesive having excellent properties. In this way, most of the heat generated by the high heat generating element 14 can be dissipated to the outside of the electronic device via the wall surface 2a as a heat sink.

[0005]

However, in addition to heat conduction through the wall surface of the housing, heat radiation from a high-heat-generating element and heat conduction through the atmosphere (air, etc.) inside the housing cause the guaranteed temperature to be reduced. It cannot be denied that the temperature of a low electronic component rises, which may affect its operation performance. In order to eliminate such a problem, it is conceivable to make the housing as large as possible to increase the distance between the high heat generating element and the electronic component having a low guaranteed temperature. However, there is a limit in terms of space saving.

SUMMARY OF THE INVENTION The present invention has been made in view of such a problem, and it is an object of the present invention to suppress an increase in the temperature of an electronic component whose guaranteed temperature is lower than that of a high heat generating element without increasing the size of a housing in an electronic device. And

[0007]

Means for Solving the Problems and Effects of the Invention In order to solve the above-mentioned problems, an electronic device according to the present invention (described in claim 1) has a high heat generating element provided on a wall surface as a heat sink. , With a material having low thermal conductivity.

That is, according to the electronic device according to the first aspect of the present invention, since the surface of the high heat generating element is covered with the material having low thermal conductivity, the temperature of the high heat generating element becomes high. However, heat radiation from the high heat generating element to the internal space of the housing is suppressed, and heat conduction from the high heat generating element to the atmosphere in the internal space of the housing (that is, gas that fills the housing, for example, air). Is also suppressed.

As a result, heat is radiated from the high heat generating element to an electronic component having a lower guaranteed temperature than the high heat generating element (low guaranteed temperature electronic component), and the heat is reduced from the high heat generating element through the atmosphere in the internal space of the housing. Guaranteed (limited) heat conduction to electronic components
As a result, it is possible to suppress a rise in temperature of the low-guaranteed temperature electronic component.

In order to dispose the high heat generating element on the wall surface as the heat radiating plate, the high heat generating element may be provided in direct contact with the wall surface as the heat radiating plate, or via a circuit board on which the high heat generating element is mounted. It may be indirectly provided on a wall surface as a heat radiating plate, and the former is superior in terms of heat radiation. However, considering the ease of connection with other electronic components (including low-guaranteed-temperature electronic components), it is indirectly provided on the wall surface as a heat sink via a circuit board, and via the wiring of the circuit board. It is preferable to connect to other electronic components.

As described above, when the high heat generating element is provided on the wall surface (of the housing) as a heat radiating plate via the circuit board, the heat generated by the high heat generating element during the operation of the electronic device also depends on the temperature of the circuit board. Will rise. In this case, the effects of heat radiation and heat conduction from the circuit board on which the high heat generating element is provided to the low-guaranteed-temperature electronic components cannot be ignored.

In the case where the high heat generating element is mounted on a circuit board provided in close contact with a wall surface as a heat radiating plate and provided on the wall surface via the circuit board,
It is preferable that the surface of the circuit board is coated with a material having low thermal conductivity in addition to the high heat generating element.

According to the electronic device according to the second aspect, in addition to the surface of the high heat generating element mounted on the circuit board, the surface of the circuit board is covered with a material having low thermal conductivity. Therefore, even if the temperature of the circuit board becomes high due to the heat generated by the high heat generating element, heat radiation from the circuit board to the internal space of the housing is suppressed, and furthermore, Heat conduction to the atmosphere of the space is also suppressed.

As a result, heat radiation from the circuit board to the low-guaranteed-temperature electronic components and heat conduction from the circuit board to the low-guaranteed-temperature electronic components through the atmosphere in the internal space of the housing are limited. The temperature rise of the guaranteed temperature electronic component can be further suppressed. In addition, as a circuit board on which the high heat generating element is mounted, it is preferable to form the circuit board with a material having a high thermal conductivity as much as possible in terms of improving heat dissipation of the high heat generating element. For example, when a ceramic wiring board or a metal core board is used. good. Only when the thermal conductivity of the circuit board is high as described above, the temperature of the circuit board on which the high heat-generating element is mounted easily rises and becomes high when the electronic device is operated. It is desirable to obtain a remarkable effect if applied.

By the way, the wall surface as the heat radiating plate is preferably formed of a material having a high thermal conductivity such as a metal (for example, aluminum) for the purpose (that is, the purpose of radiating heat of the high heat generating element). Temperature rises easily,
During operation of the electronic device, the temperature is high. Therefore, there is a high possibility that heat radiation and heat conduction from the wall surface as the heat sink to the low-guaranteed temperature electronic component also contribute to the temperature rise of the low-guaranteed temperature electronic component.

Therefore, the inner surface of the wall as the heat radiating plate (that is, the surface exposed to the inner space of the housing; the same applies hereinafter) may be further coated with a material having a low thermal conductivity. . According to the electronic device of the third aspect configured as described above, the surface of the high heat generating element (in the case of claim 2, the surface of the high heat generating element and the surface of the circuit board on which the high heat generating element is mounted). In addition, since the wall on which the high heat generating element is provided is also covered with a material having a low thermal conductivity, even if the heat generated by the high heat generating element raises the temperature of the heat radiating wall to a high temperature, the wall is Thus, heat radiation from the inside to the internal space of the housing is suppressed, and heat conduction from the wall surface to the atmosphere in the internal space of the housing is also suppressed.

As a result, heat radiation from the wall surface as the heat radiating plate to the low-guaranteed-temperature electronic component and heat conduction from the wall surface to the low-guaranteed-temperature electronic component via the atmosphere in the internal space of the housing are limited. Thus, the temperature rise of the low-guaranteed-temperature electronic component can be further suppressed.

When a low-guaranteed-temperature electronic component is disposed at a position facing a wall surface as a heat sink provided with a high-heat-generating element, heat radiation from the high-heat-generating element to the low-guaranteed-temperature electronic component is provided. Is particularly strong. Therefore, the inventions according to claims 1 to 3 are preferably applied to such a configuration, because the above-described effects can be more remarkably exhibited.

[0019]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing an electronic device 1 for controlling an external device (such as an engine) as one embodiment of the electronic device of the present invention. The housing constituting the outer shape of the electronic device 1 includes a metal lid 2 formed by casting aluminum, and low-temperature-guaranteed electronic components 8 such as IC elements.
And a printed wiring board made of resin (hereinafter, referred to as “first circuit board 4”) on which is mounted. That is, the mounting surface of the electronic component, which is one surface of the first circuit board 4 (that is, the surface on which the electronic component is mounted, of the front and back surfaces of the first circuit board 4) is used for the metal lid 2. The housing of the electronic device 1 is configured by covering.

The first circuit board 4 is provided with a connector 6 for exchanging signals between the electronic device 1 and an external device. The connector 6 includes a metal cover 2 and the first circuit board 4.
Is disposed between the metal lid 2 and the first circuit board 4 so as to close the opening of the housing composed of Then, the internal space of the housing is sealed by the metal lid 2, the first circuit board 4, and the connector 6.

The connector 6 has a connector terminal 6a for connecting to a predetermined circuit board. The connector 6 is connected to the first circuit board 4 via the connector terminal 6a. A control circuit is formed on the first circuit board 4 by various electronic components including a low-guaranteed temperature electronic component 8 such as an IC element, and the connector 6 is electrically connected to the circuit.

On the other hand, the metal lid 2 has a wall surface 2a having substantially the same shape as the first circuit board 4. This wall surface 2 a faces the first circuit board 4 when the housing of the electronic device 1 is configured by the metal lid 2 and the first circuit board 4. A printed wiring board made of ceramic (hereinafter, referred to as a “second circuit board 12”) is closely adhered to the inner surface of the wall surface 2 a via an adhesive 10 having excellent thermal conductivity. The second circuit board 12 includes a high heat generating element 14 that generates a large amount of heat.
(For example, a power transistor).
That is, the high heating element 14 is provided on the inner surface of the wall surface 2a via the second circuit board 12.

The second circuit board 12 on which the high heat generating element 14 is mounted is connected to the connector terminal 6 via a flexible board 16.
a, and is connected to the first circuit board 4 via the connector terminal 6a. That is, the high heating element 14 mounted on the second circuit board 12 is connected to the first circuit board 4 via the flexible board 16 and the connector 6 (connector terminal 6a), and is mounted on the first circuit board 4. A predetermined circuit is configured together with the electronic components (including the low-guaranteed-temperature electronic components 8).

In the electronic device 1 according to the present embodiment, the high heating element 14 and the second circuit board 12 on which the high heating element 14 is mounted are mounted.
In addition, the entire area of the inner surface of the wall surface 2a on which the second circuit board 12 is disposed is covered with a material having low thermal conductivity.
In the present embodiment, the material having a low thermal conductivity is sufficient for the thermal conductivity (about 90 W / (m · K)) of the metal material (aluminum in the present embodiment) constituting the metal lid 2. The resin 18 having a low thermal conductivity (about 0.2 W / (m · K)) is used. This resin 18 has about 10 to 5
It is laminated with a layer thickness of 0 μm.

When the high heat generating element 14 operates and its temperature rises, heat is transmitted around the high heat generating element 14 through various paths as shown in FIG. 2, for example. That is,
The heat generated by the high heat generating element 14 is mainly “high heat generating element 1”.
4 → the second circuit board 12 → the adhesive 10 → the wall surface 2a → the outside of the electronic device 1 ”.

Some of the heat generated by the high heat generating element 14 is, for example, “high heat generating element 14 → resin 18 → (atmosphere inside the housing →) low guaranteed temperature electronic component 8”, “high heat generating element 1
4 → second circuit board 12 → resin 18 → (atmosphere inside casing →) low guaranteed temperature electronic component 8 ”,“ high heat generating element 14 → second circuit board 12 → adhesive 10 → wall 2a → resin 18 → ( Atmosphere inside the housing →) low-guaranteed-temperature electronic component 8 through heat radiation and heat conduction.

That is, the heat generated by the high heat generating element 14 is not only the high heat generating element 14 but also the second circuit board 12 and the wall surface 2a.
And the heat is transmitted to the low-temperature-guaranteed electronic component 8 by heat radiation from these (the high-heat-generating element 14, the second circuit board 12, and the wall surface 2a) and heat conduction through the atmosphere in the housing. is there. However, in the electronic device of the present embodiment, as described above, the high heat generating element 14 and the second circuit board 12
Since the surface of the wall surface 2a is covered with the resin 18, heat radiation and heat conduction from these are suppressed.

The inventor conducted a comparative experiment to confirm the effect of this embodiment. That is, the electronic device 101 (FIG. 3) in which the high heat generating element 14, the second circuit board 12, and the wall surface 2a are not coated with the resin 18 and the electronic device 1 of the present embodiment in which the resin 18 is coated are energized and operated. The temperature near the low-guaranteed temperature electronic device 8 was measured (measured with a thermocouple), and the two were compared. As a result, in the electronic device 1 of this example, it was confirmed that the temperature near the low-guaranteed-temperature electronic device 8 was reduced by approximately 2 ° C. as compared with the electronic device 101 to be compared.

As described above, according to the electronic device 1 of the present embodiment, the surface of the high heat generating element 14 is covered with the resin 18 having a low thermal conductivity.
Therefore, even if the high heat generating element 14 becomes high temperature, heat radiation from the high heat generating element 14 to the internal space of the housing is suppressed. Heat conduction to the atmosphere is also suppressed.

As a result, heat radiation from the high heat generating element 14 to the low assurance temperature electronic component 8 and heat conduction through the atmosphere in the internal space of the housing are suppressed, and the low assurance temperature electronic component 8 Temperature rise can be suppressed. Also,
Since the surface of the second circuit board 12 is also covered with the resin 18 in addition to the high heat generating element 14, even if the second circuit board 12 becomes high temperature due to the heat generated by the high heat generating element 14, Heat radiation from the second circuit board 12 to the internal space of the housing is suppressed, and heat conduction from the second circuit board 12 to the atmosphere in the internal space of the housing is also suppressed. As a result, it is possible to further suppress the temperature rise of the low-guaranteed-temperature electronic component 8.

Further, since the inner surface of the wall surface 2a is also covered with the resin 18 having low thermal conductivity, even if the wall surface 2a becomes high temperature due to the heat generated by the high heat generating element 18, the wall surface of the wall surface 2a is not heated. Heat radiation from 2a to the internal space of the housing is suppressed, and heat conduction from the wall surface 2a to the atmosphere in the internal space of the housing is also suppressed. As a result, it is possible to further suppress the temperature rise of the low-guaranteed-temperature electronic component 8.

Although one embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment and can take various forms. For example, in the above embodiment,
Although the description has been made on the assumption that the resin 18 is used as the material having a low thermal conductivity, the present invention is not limited to this, and various materials can be used as long as the material has a low thermal conductivity. In addition,
As a preferable resin to be used as a material having a low thermal conductivity, for example, a silicon resin (0.2 W / (m · K))
And an epoxy resin (0.7 W / (m · K)) are preferred because of their low thermal conductivity.

In this case, since the temperature of the second circuit board 12 and the wall surface 2a is higher as the temperature is closer to the high heat generating element 14, at least the inner surface near the high heat generating element 14 should be covered with a material having low thermal conductivity. However, preferably, as in the above embodiment, the wall surface 2a, the second circuit board 12, and the high heat generating element 14
When the entire inner surface (surface exposed to the internal space of the housing) is covered, heat radiation and heat conduction through the atmosphere can be surely suppressed.

In the above embodiment, the thickness of the resin 18 is set to 1
Although described as 0 to 50 μm, the thickness is not limited to this, and it is preferable that the thickness is larger because heat radiation and heat conduction can be suppressed. However, the thicker the film, the more difficult it is to dry and the more troublesome the handling.

Since the temperatures of the second circuit board 12 and the wall surface 2a are higher as they are closer to the high heating element 14, the second circuit board 1
The inner surface of the wall 2 or the wall surface 2a is preferably coated with a material having a low thermal conductivity so as to become thicker as it approaches the high heating element 14. This is preferable because heat radiation and heat conduction through the atmosphere in the housing can be more effectively suppressed, and the temperature rise of the low-guaranteed-temperature electronic component 8 can be reduced.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram illustrating a configuration of an electronic device according to an embodiment.

FIG. 2 is an explanatory diagram showing a heat transfer path near a high heat generating element.

FIG. 3 is an explanatory diagram illustrating a configuration of an electronic device of a comparative example.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Electronic device, 2 ... Metal cover, 2a ... Wall surface, 4 ... First circuit board, 8 ... Low temperature temperature electronic component, 12 ... Second circuit board, 14 ... High heat generation element, 18 ... Resin.

Claims (3)

[Claims] 1. A high heat generating element and an electronic component whose guaranteed temperature is lower than that of the high heat generating element inside a housing in which at least one of the wall surfaces is configured as a heat sink, wherein the high heat generating element is In an electronic device provided on a wall surface as a heat radiating plate, the surface of the high heat generating element is coated with a material having low thermal conductivity, so that heat radiation from the high heat generating element to the electronic component and the inside of the housing are formed. An electronic device characterized by suppressing heat conduction through an atmosphere. 2. The electronic device according to claim 1, wherein the high heat generating element is mounted on a circuit board provided in close contact with a wall surface as the heat sink, and provided on the wall surface via the circuit board. In addition to the high heat-generating element, the surface of the circuit board is further coated with a material having low thermal conductivity, so that heat radiation from the circuit board to the electronic components and the atmosphere inside the housing are achieved. An electronic device characterized by suppressing heat conduction through the electronic device. 3. The electronic device according to claim 1, wherein an inner surface of the wall surface as the heat sink is coated with a material having a low thermal conductivity, so that heat from the wall surface to the electronic component is transferred to the electronic component. An electronic device, wherein radiation and heat conduction through an atmosphere inside the housing are suppressed.