Electricity: electrical systems and devices – Housing or mounting assemblies with diverse electrical... – For electronic systems and devices
Patent
1993-05-17
1996-08-20
Sparks, Donald A.
Electricity: electrical systems and devices
Housing or mounting assemblies with diverse electrical...
For electronic systems and devices
257718, 257719, 257713, 361707, 361709, 361713, 361719, 361717, 361718, H05K 702, H05K 706, H05K 720, H01L 2336
Patent
active
055484875
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a mounting for circuit chips and the like on printed circuit boards.
2. Description of the Related Art
In planar modules or assemblies, it is known to mount unpackaged housingless chips on a surface of a module circuit board (for example a microwiring circuit board) and to place between the circuit board and the chip an elastic pressure pad which has the task of pressing a surface of the chip against a cooling plate for the purpose of heat removal. To achieve an adequate spring characteristic, it is therefore necessary to dimension the elastic pressure pad between the chip and the microwiring board of a corresponding thickness. The consequence of this is, however, that a Z shaped bend of the terminal legs of the chip must be made greater than would actually be needed for compensating for thermal stresses. The greater this Z shaped bend is, however, the greater also are the tolerances in the surface soldering area of the terminal legs and the microwiring board.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an arrangement by means of which two contradictory demands, namely the thickest possible pressure pad and smallest the possible Z bend of the terminal legs can be achieved.
To achieve this object, the invention provides for depressions for accommodating the pressure pads to be provided on the surface of the circuit board.
The result of these measures is that the tolerances are reduced in the surface soldering area without impairing the heat transfer between the chip and the cooling plate.
Another aspect of the invention provides that the multilayer boards have internal conductive layers and that the depression for accommodating the pressure pad extends to one of the conductive layers.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention is explained in greater detail with reference to the illustrative embodiment according to the FIGURE.
The FIGURE is a fragmentary cross section of a circuit chip mounted on a circuit board according to the principles of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
On the microwiring circuit board 1, depressions 6 are provided into which the elastic pressure pad 3 can be placed, the lower support area or seating surface of the pressure pad being the next copper plane 4 following in the microwiring in the circuit board. As a result, the distance between a lower surface of the component 2 and the surface of the microwiring board is reduced so that the Z-shaped bend in the terminal legs 7 can be reduced. Nevertheless, the good contact of the surface of the chip 2 with the cooling plate 8 is retained.
Although other modifications and changes may be suggested by those skilled in the art, it is the intention of the inventors to embody within the patent warranted hereon all changes and modifications as reasonably and properly come within the scope of their contribution to the art.
1. An assembly for circuit chip mounting and cooling, comprising: layers; from at least two sides adjoining said lower surface and bent in a direction toward said lower surface, free ends of said leads connected to said surface of said multi-layer circuit board; board opposite said lower surface of said circuit chip, said depression extending into said multi-layer circuit board to one of said internal conductive layers; against said lower surface of said circuit chip; and said circuit chip opposite said lower surface; against said means for removing heat from said circuit chip.
DESCRIPTION
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
On the microwiring circuit board 1, depressions 6 are provided into which the elastic pressure pad 3 can be placed, the lower support area or seating surface of the pressure pad being the next copper plane 4 following in the microwiring in the circuit board. As a result, the distance between a lower surface of the component 2 and the surface of the microwiring board is reduced so that the Z-shaped bend
REFERENCES:
patent: 3225262 (1965-12-01), Myers
patent: 4833570 (1989-05-01), Teratani
patent: 4855869 (1989-08-01), Tsuji
patent: 5184211 (1993-02-01), Fox
patent: 5389819 (1995-02-01), Matsuoka
IBM Technical Disclosure Bulletin "Heat Sink Assembly for TAB-Mounted Devices" vol. 31 No. 6 Nov. 1988.
Brabetz Berhard
Wessely Hermann
Siemens Nixdorf Informationssysteme Aktiengesellchaft
Sparks Donald A.
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