Tin and gold plating process
AssigneeThe United States of America as represented by the Secretary of the Air Force
InventorR. Dean Hall
Life of this patent
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Abstract
A process used for plating a substrate in which the etching of the substrate's copper cladding is terminated early leaving a thin layer of copper. Resist material is then selectively placed upon this thin layer of copper in such a manner that will result in those areas of the circuit to be electroplated being connected. Etching is then resumed to completion, resulting in electrical isolation of those portions of the circuit that are not to be electroplated. Gold electroplating followed by electroless tin plating of the remainder of the circuit can then be performed followed by a final etching to remove the electrical shorts.
Claims5
A method for plating two metals onto a copper clad substrate comprising the steps of:
- a. defining, by utilizing photoresist material, a circuit pattern on the copper cladding which results in protected copper and unprotected copper;
- b. etching away the unprotected copper until only a thin layer of copper remains;
- c. applying resistive material on selected areas of the thin layer of copper in such a manner that first portions of the circuitry to be plated with a first metal are connected to one another via the resistive material while other portions of the circuitry not to be plated with said first metal are not connected via the resistive material to said first portion;
- d. etching away to completion the unprotected copper and then removing all photoresist and resistive material;
- e. applying resistive material to said selected areas of copper in order to protect them from plating;
- f. electroplating said first portions of the circuitry with said first metal;
- g. electroless plating said other portions of the circuit with a second metal by immersing the entire substrate in a plating bath;
- and
- h. removing all resistive material and then etching away the remainder of the thin copper layer.
Dependencies are inferred from the claim text.