Electronic control unit

Details Electronic control unit Electronic control unit

2003-03-21

2004-11-09

Chérvinsky, Boris (Department: 2835)

Electricity: electrical systems and devices

Housing or mounting assemblies with diverse electrical...

For electronic systems and devices

C361S690000, C361S719000, C174S252000

Reexamination Certificate

active

06816377

ABSTRACT:

CROSS REFERENCE TO RELATED APPLICATION
This application is based upon, claims the benefit of priority of, and incorporates by reference the contents of prior Japanese Patent Application No. 2002-92495 filed Mar. 28, 2002.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electronic control unit which is placed in, for example, an engine compartment of a vehicle.
2. Description of the Related Art
In an electronic control unit (ECU), for example, used for control of a vehicle, a microcomputer for performing operational processing, an input/output circuit connected to an external load, a sensor, a power supply circuit for supplying power to circuits, and like components have been conventionally placed on a substrate. Then, these circuits and substrate are housed within an enclosure typically consisting of a case and a cover.
The electronic components constituting the above-mentioned circuits generate heat during their operation. An excessively increased temperature of the electronic components adversely affects the operation of the components. Therefore, in order to reduce a temperature of the electronic components, a method for transferring the heat to the substrate, and the like, so as to diffuse the heat is known.
Moreover, as shown in
FIG. 12
, for an electronic component (for example, a semiconductor chip of a power transistor) P
1
that generates a particularly large amount of heat, a method using a radiator fin P
2
or the like has been used to efficiently dissipate the heat generated from the electronic component P
1
toward a case P
3
. However, given current product demands, the electronic control unit has been required to have higher function and performance levels, while the heat generated from the electronic component P
1
increases.
Accordingly, in order to dissipate a larger amount of heat from the heat-generating electronic component P
1
, the structure as shown in
FIG. 13
has been adopted. In this structure, a large piece of copper foil P
6
is placed on the region where the electronic component P
1
(more specifically, a heat sink P
5
) is attached on a substrate P
4
. The heat is dissipated via holes P
7
to other larger pieces of copper foil P
8
and the like. In this method, however, since an effective wiring area on the substrate P
4
is decreased, the substrate P
4
in a large size is accordingly required, leading to an increase in cost.
On the other hand, miniaturization of the electronic control unit is also desirable. In order to respond to such a need for miniaturization, that is, a method for miniaturizing the components in accordance with the development of semiconductor integration techniques, a method for making a number of circuits IC-compatible and the like have been used. However, the use of such methods causes an increase in temperature of the electronic component P
1
.
As measures against the increase in temperature of the electronic component P
1
, it has been proposed to use the expensive electronic component P
1
which results in little power loss. Additionally, it has been proposed to mount the components on the radiator fin P
2
or to increase the size of the substrate P
4
to a certain degree so as to improve heat dissipation. However, these methods result in increased costs.
It is also conceivable to make the heat-generating electronic component P
1
itself highly heat resistant. However, such a measure is not necessarily preferable because peripheral components placed at a high density also have an increased temperature due to heat transferred from the substrate P
4
, whereby the size of the substrate P
4
must be increased to a certain degree or the peripheral components must be high heat-resistant components.
SUMMARY OF THE INVENTION
The present invention has been developed to solve the above problems, and has an object of providing an electronic control unit having a high heat dissipating ability, which can be easily fabricated at a low cost.
(1) A first aspect of the present invention relates to an electronic control unit. The unit includes a substrate having a mount face (i.e. first) and an opposite mount face (i.e. second), an electronic component that generates heat and is placed on a side of the mount face, and an enclosure consisting of a plurality of enclosure members to house the substrate. A portion of the enclosure members on a side of the opposite mount face is made to protrude toward a position where the electronic component is mounted, while a flexible, thermally conductive material is placed between the protrusion and the opposite mount face so as to be in contact with a side of the protrusion and the side of the opposite mount face. The enclosure member having the protrusion and the substrate are brought to be in direct contact with each other or in contact with each other through a spacer having a predetermined thickness so as to fix the assembly.
Since the flexible, thermally conductive material is provided between the protrusion of the enclosure member and the substrate in an embodiment of the present invention, it ensures close adherence between the enclosure member and the substrate on their large faces through the thermally conductive material. As a result, the heat dissipation properties are enhanced.
Moreover, since the enclosure member having the protrusion and the substrate are brought into direct contact with each other or through a spacer, the dimensional accuracy of a gap between the substrate and the protrusion can be ensured. As a result, since the thermally conductive member placed in the gap can be very small, such a structure contributes to a reduction in cost.
Moreover, even in the case where a thermally conductive material having an inferior thermal conductivity to those of the enclosure or a thermally conductive thin film layer (for example, a copper foil) on the surface of the substrate, the maximum heat dissipation properties can be ensured because the gap can be normally reduced as described above.
(2) According to a second aspect of the present invention, a thermally conductive thin film layer (for example, a piece of copper foil which is a thin, metallic film) having a higher thermal conductivity than that of a periphery thereof, is provided on the mount face so as to overlap a region obtained by projecting the electronic component thereon.
More specifically, the thermally conductive thin film layer is provided so as to (partially or entirely) overlap the region obtained by projecting the electronic component onto the substrate side, whereby the heat transfer properties from the electronic component side toward the substrate side can be enhanced. Although it is preferred that the sentence “the thermally conductive thin film layer is provided so as to (partially or entirely) overlap the region obtained by projecting” means “the thermally conductive thin film layer is provided on a half or more of the region obtained by projecting” in terms of heat transfer properties, it is more preferred that this sentence mean “the thermally conductive thin film layer is provided so as to completely include the region obtained by projecting.” The same is applied to the following.
(3) According to a third aspect of the present invention, a thermally conductive thin film layer having a higher thermal conductivity than that of a periphery thereof is provided on the opposite mount face so as to overlap a region obtained by projecting an end face of the protrusion.
More specifically, the thermally conductive thin film layer is provided so as to (partially or entirely) overlap the region obtained by projecting the protrusion thereon, thereby enhancing the heat transfer properties from the substrate side toward the enclosure side.
(4) According to a fourth aspect of the present invention, thermally conductive thin film layers, each having a higher thermal conductivity than that of a periphery thereof, are provided respectively on the mount face and the opposite mount face so as to overlap a region obtained by projecting the electronic component thereon, and the thermally c

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