Electrical device, in particular a switching and control...

Electricity: electrical systems and devices – Housing or mounting assemblies with diverse electrical... – For electronic systems and devices

Reexamination Certificate

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Details

C174S252000, C361S715000, C361S720000

Reexamination Certificate

active

06222732

ABSTRACT:

BACKGROUND OF THE INVENTION
The invention relates to an electrical device having a printed circuit board carrying an electronic circuit and at least one power component to be cooled, particularly a switching or control unit for a motor vehicle. In these known devices, power components which heat up intensely are mounted on cooling elements which are fixed on a printed circuit board or on a housing on which the printed circuit board is secured. These cooling elements consist of special cooling profiles by which the power components are spaced from the printed circuit board or project from it. These cooling elements have the disadvantage that they consist of profiles having a complicated structure, and that the process of assembling the device with the profiles can be automated only with great difficulty. Due to the design of the cooling elements and the associated method of mounting the power components, these electrical devices have to be comparatively large, thus taking up a considerable amount of installation space.
In U.S. Pat. No. 4,811,165, an electrical device is described in which the electronic components are arranged on a printed circuit board which carries an electronic circuit. This is made from a flexible material and located on a plate of good thermal conductivity. This has the disadvantage that heat from the electronic components must be dissipated through the printed circuit board to the heat conductive plate. In addition, the (conventional) method of attaching electronic components in a wired structure can be achieved only with considerable effort, since additional insulating provisions vis-à-vis the heat conductive plate are required when the connecting wires or connection electrodes are routed through soldering apertures of the printed circuit board.
SUMMARY OF THE INVENTION
According to the invention, the electrical device comprises a printed circuit board carrying an electronic circuit and at least one power component to be cooled; a heat conductive layer applied to the printed circuit board at least in the vicinity of the at least one power component, each of the power components resting flat with their largest face in contact with the heat conductive layer; and a free-standing metallic body connected to the heat conductive layer and spaced from the power components to act as a cooling element for dissipation of heat conducted to the free-standing metallic body through the heat conductive layer from the power components.
Alternatively, instead of a free-standing metallic body the cooling element can be a part of a housing accommodating the printed circuit board. In a preferred embodiment spring means can be provided which presses the printed circuit board against an interior part of the housing to establish a good heat conduction between the heat conductive layer on the circuit board and the housing.
The heat conductive layer can advantageously be a metal cladding, a conductor track or a laminate of the circuit board. It can advantageously provide a screening for improvement of electromagnetic compatibility.
In contrast, the electrical device in accordance with the invention has the advantage that a particularly flat form of the electrical device is made possible by the arrangement of the power components. The type and form of the power components has no effect on the form and shape of the cooling elements, so that their type and method of attachment can be determined by other factors. The attachment of the power components in accordance with the invention facilitates good heat dissipation which allows a larger number of power components to be located on the printed circuit board. Good heat dissipation further allows a higher ambient temperature, such as prevails in motor vehicles, for example. The housing of the electrical device can further be automatically equipped and soldered in a small number of production steps.


REFERENCES:
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“Heat Sink Assembly For Tab-Mounted Devices”, IBM Tech. Disclosure Bulletin, vol. 31, No. 6, Nov. 1988, pp. 372-373, (361/720).

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