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US 5,626,774 AGranted
Solder mask for manufacture of printed circuit boards
AssigneeAlliedSignal Inc.
InventorJames R. Paulus
Life of this patent
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Abstract
A permanent solder mask is applied to the surface of a printed circuit board using a copper foil carrier. The solder mask preferably is one or two layers of a thermosetting resin e.g. epoxy resin. Selected circuit features are exposed by etching away portions of the copper foil and removing the underlying thermosetting resin. Then, the remaining copper foil is removed, leaving the solder mask on the surface of the printed circuit board.
Claims6
A method of forming a solder mask on the surface of a printed circuit board comprising:
- (a) applying to said surface a sheet of copper foil having a layer of partially cured thermosetting resin on one surface of the foil disposed so that the resin layer is between the copper foil and the circuit board surface and leaving the opposite face of the copper foil exposed;
- (b) applying an etch resist over the exposed surface of the copper foil;
- (c) photoimaging regions of the etch resist and removing uncured areas of the etch resist to leave copper areas exposed;
- (d) etching away the copper areas exposed in (c), leaving the resin layer of (a) exposed;
- (e) removing the exposed resin layer of (d) to expose a circuit feature which is to be soldered;
- (f) removing the cured etch resist with a suitable solvent;
- and
- (g) etching the remaining copper foil and exposing the uncured resin as a solder mask.
5 more elements
Dependencies are inferred from the claim text.