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US 4,221,925 AGranted
Printed circuit board
AssigneeWestern Electric Company, Inc.
InventorsDonald W. Finley, Robert B. Lewis
Life of this patent
Estimating the term…
Abstract
A printed circuit board is disclosed which comprises a metal substrate having a first coating thereon and through holes through said coating and substrate with non-linear, undercut walls and a dielectric film coating over said first coating and said non-linear, undercut walls of said through hole. Electrical circuitry is then formed on the dielectric coat in conjunction with the through hole.
Claims8
A printed circuit board comprising:
- (a) a 1-7 mil thick metal substrate having a first coating thereon and a through hole with non-linear, undercut walls in said first coating and substrate wherein said undercut is from about 1 to about 3 mils;
- and
- (b) a dielectric film coating said first coating and said non-linear undercut walls of said through hole, said dielectric film having a thickness so as to resist dielectric breakdown at an applied voltage of 1500 volts.
Dependencies are inferred from the claim text.