Electricity: electrical systems and devices – Electrostatic capacitors – Fixed capacitor
Patent
1985-08-12
1987-06-23
Pellinen, A. D.
Electricity: electrical systems and devices
Electrostatic capacitors
Fixed capacitor
156295, 1563096, 361387, H05K 720
Patent
active
046757848
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Technical Field
The present invention relates to a printed circuit board, including a supporting base element in the shape of a heat removing metal plate or panel, one side of which has a laminate layer with at least one printed circuit.
2. Background Art
The manufacture of such printed circuit boards have caused problems because of the requirement that the heat removing plate must be electrically insulated. Efforts have been made inter alia to use circuit boards having a core of anodized aluminium, i.e. with an electrically insulating metal oxide film. Aluminium or steel plates covered with different types of resins have also been tested. These tests have not been very successful, for instance because of the formation of pores in the insulating film, thereby causing short-circuits between the metal plate and the electric circuit. If, on the other hand, the insulating film is made sufficiently thick in order to ensure that no pores are present, the ability of conducting away the heat from the circuit components will decrease.
SUMMARY OF THE INVENTION
The object of the present invention is, therefore, to propose a circuit board of the type described by way of introduction, in which the insulating material is a metal oxide film, which can be made relatively thin without any increasing risk of a short-circuit due to pore formation. This object is achieved by the circuit board in accordance with the invention.
The invention is based on the surprising discovery that metal oxide films--contrary to the prevailing experience--can be used as an electrically insulating film on heat removing plates in circuit boards without any risk of pore formation and short-circuit, if a glue film is provided between the metal oxide film and the laminate layer of the circuit board, the glue film suitably being of a nature or non-synthetic resin, i.e., a synthetic resin.
The invention will be described below in greater detail with reference to the accompanying drawing, which illustrates a preferred embodiment of the invention.
BRIEF OF THE DRAWINGS
FIG. 1 shows a sectioned perspective view of a printed circuit board in accordance with the invention.
FIG. 2 shows schematically a cross section of a portion of a printed circuit board in accordance with the invention, illustrating the way in which the metal plate can be used as a screening of the circuit board.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The printed circuit board includes a supporting base element 1 in the shape of a metal plate or metal panel 2 covered by an electrically insulating metal oxide film or coating 3. The metal plate 2 is, in the embodiment shown, of anodized aluminium, the anodized film of which constitutes the metal oxide film 3.
The anodized metal plate 2 has on one side thereof, that is, the lower one in FIGS. 1 and 2, a glue film 4, an insulating varnish film 5a, an electric printed circuit 6a, an electrically insulating glass fiber laminate layer 7, an electric printed circuit 6b (shown in FIG. 2 only), and an insulating varnish film 5b, the layers and films being arranged in that order.
The laminate layer 7 the printed circuits 6a and 6b, and the varnish films 5a and 5b, are of known nature, for which reason they need not be further described here.
The electric components of the printed circuit board, which are for instance in the shape of IC-circuits 8, of which only one is shown in FIG. 1, are mounted on the free side of the plate 2, that is the upper side in FIGS. 1 and 2. It is important that the electric components 8 are in close contact with the upper side of the anodized plate 2 in order to ensure a thermally satisfactory contact between the components 8 and the plate 2, and a satisfactory heat conducting and heat spreading effect.
The components 8 are electrically connected to the circuits 6a and 6b via contact members 9. The contact members 9 extend through anodized, and thus insulated apertures 10 which are formed in the plate 2. The cross section area of the apertures 10 conically as seen in the directi
REFERENCES:
patent: 3165672 (1965-01-01), Gellert
patent: 3469017 (1969-09-01), Thompson
patent: 3912849 (1975-10-01), Thomas
Dahlberg Rolf
Dahlberg Tomas
Pellinen A. D.
Thompson Gregory D.
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