Skjerven, Morrill, MacPherson, Franklin and Friel
Method for forming a mounting hole in a method for forming a metallic printed circuit board
 To the end of forming a countersunk hole in a metallic printed circuit board consisting of a metallic plate, an insulating layer, and a printed circuit pattern formed on the insulating layer, for receiving a countersunk head of a mounting screw which is passed through the hole, a rough straight hole consisting of a central main part and radial extensions extending therefrom is first formed in the metallic printed circuit board, and a countersunk portion is formed around the hole by plastic deformation. Since the material of the metallic plate of the metallic printed circuit board is allowed to flow into the extensions of the hole during plastic deformation, the material of the metallic plate in the immediate vicinity of the hole is allowed to flow both radially and circumferentially, and the resulting reduction in the difference in the amount of deformation between the metallic plate and the insulating layer prevents the peeling of the insulating layer from the metallic plate. 
NHK Spring Co., Ltd.
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Hayao
Takahashi