Electricity: electrical systems and devices – Housing or mounting assemblies with diverse electrical... – For electronic systems and devices
Reexamination Certificate
1999-06-21
2001-05-01
Picard, Leo P. (Department: 2835)
Electricity: electrical systems and devices
Housing or mounting assemblies with diverse electrical...
For electronic systems and devices
C361S705000, C361S719000, C361S722000, C174S016300, C257S706000, C257S707000, C165S080300, C165S185000
Reexamination Certificate
active
06226183
ABSTRACT:
FIELD OF THE INVENTION
BACKGROUND INFORMATION
A conventional arrangement is described in German Patent Application No. 1 95 28 62. In this publication, as the substrate a circuit board is indicated, which on its upper side is provided with an electronic circuit, which includes at least one power component that generates waste heat. Beneath the power component, the circuit board is provided with via holes, which divert the heat generated by the power component to the lower side of the circuit board. Between lower side of the circuit board and a control unit housing functioning as a heat sink, a thermally conductive filler is arranged. During operation, the heat produced by the power components is diverted via the via holes to the lower side of the circuit board and from there is delivered via the thermally conductive filler to the housing, which functions as a heat sink. In this context, it is disadvantageous that printed circuit traces that conduct potential on the lower side of the circuit board can come into contact with the heat sink during assembly of the circuit board in the control unit. A short-circuit that is caused in this way can damage or destroy the sensitive electronic components on the circuit board.
In addition, German Patent Application No. 1 97 23 409 describes an arrangement having a substrate and a heat sink. On the upper side of the circuit board, a power component is deposited on a large-surface printed circuit trace, which is connected by via holes to a large-surface printed circuit trace on the lower side of the circuit board. On the lower side of the circuit board, a metal layer is deposited under the large-surface printed circuit trace arranged there and over an insulation layer, which in turn is deposited through a solder stop mask onto a control unit housing part that is provided as a heat sink. In this arrangement, although an electrical contact between the printed circuit traces and a heat sink is prevented by the insulation layer, it is disadvantageous that the insulation layer and the further metal layer complicate the direct heat transfer to the heat sink, increase the space requirements of the arrangement, and also make manufacturing more expensive.
SUMMARY OF THE INVENTION
The arrangement according to the present invention avoids the disadvantages arising in the conventional arrangements. As a result of spacer elements placed on the side of the substrate opposite the power components and a thermally conductive filler introduced between the substrate and the heat sink, an effective heat coupling of the substrate to the heat sink is advantageously achieved, on the one hand, and an undesirable electrical contact between the printed circuit traces carrying potential and located on the side of this substrate and the heat sink is dependably avoided, on the other hand. In addition, a particularly space-saving arrangement can be realized. Additional layers, making manufacturing more expensive, such as an additional insulating layer or a further metal layer deposited onto the insulation layer, are not necessary, so that the costs in this regard can be saved.
It is also advantageous if the spacer elements are composed of conductor surface elements on the lower side of the substrate, which are coated using a preselected quantity of solder, since for this purpose, in particular for substrates that are fitted with components on both sides, no additional manufacturing step is required. The conductor surface elements can be manufactured together with the connecting surfaces of the electronic components provided on the lower side, and can be coated with solder.
A solder resist deposited on the side of the substrate opposite the power components prevents solder from mistakenly reaching locations that are not provided therefore during the application of the solder.
If the power component and the heat sink have the same electric potential, it is advantageous to integratedly manufacture the conductor surface elements directly in the second large-surface printed circuit trace, since in this way the heat transfer is improved.
In addition, it is advantageous if the thermally conductive filler provided between the substrate and the heat sink is a thermally conductive adhesive or a thermally conductive adhesive foil, by which the substrate can also be mechanically secured to the heat sink.
The spacer elements resting on the heat sink can advantageously also be used as a ground connection of the substrate to the heat sink and for improving the EMV behavior (electromagnetic compatibility).
In addition, the present invention relates to a method for manufacturing an arrangement composed of a substrate and a heat sink. In particular, in the case of substrates having components on both sides, no additional manufacturing steps are necessary for carrying out the method according to the present invention. The conductor surface elements can be manufactured together with the printed circuit traces provided on the second side. The deposition of solder necessary for the manufacture of the spacer elements can be carried out together with the soldering of the connecting surfaces for components, which makes the method particularly economical, since scarcely any additional costs arise for manufacturing the spacer elements.
It is advantageous to imprint the solder onto the conductor surface elements in a solder paste imprinting station, since this technology is particularly well suited for depositing a defined quantity of solder and can be controlled very well. In a subsequent reflow soldering step, the solder is melted, the spacer elements being formed at a height defined by the quantity of solder deposited. The reflow solder step can advantageously take place with the reflow soldering of the SMD components provided on the substrate.
It is easy to apply a thermally conductive adhesive or a thermally conductive adhesive foil first onto the heat sink and subsequently to place the substrate onto the heat sink coated with the adhesive or the adhesive foil such that the spacer elements are impressed into the adhesive, they being able to contact the heat sink via the solder layer.
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patent: 4626478 (1986-12-01), Soerewyn
patent: 4628407 (1986-12-01), August et al.
patent: 5261593 (1993-11-01), Casson et al.
patent: 5352926 (1994-10-01), Andrews
patent: 5375039 (1994-12-01), Wiesa
patent: 5467251 (1995-11-01), Katchmar
patent: 5541450 (1996-07-01), Jones et al.
patent: 5646826 (1997-07-01), Katchmar
patent: 25 28 000 (1977-01-01), None
patent: 93 08 842 (1993-07-01), None
patent: 197 28 632 (1997-02-01), None
patent: 197 23 409 (1998-12-01), None
“Anastrophic Conductive Paste”, Toshiba Chemical Corp.
Butschkau Werner
Dittrich Thomas
Hofsaess Dietmar
Schiefer Peter
Weber Bernd
Datskovsky Michael
Kenyon & Kenyon
Picard Leo P.
Robert & Bosch GmbH
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