Method for coating of polyimide by electrodeposition
AssigneeWestinghouse Electric Corp.
InventorsWilliam R. Gass, Luciano C. Scala, David C. Phillips
Life of this patent
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Abstract
A method of coating a copper substrate comprises the steps of: anodically microsmoothing the copper substrate in an acid bath to provide a substantially smooth surface; electrocoating the microsmoothed substrate with a pin hole free nickel film having a thickness of between about 2.5 microns to about 12.5 microns; single step, non-aqueous electrocoating the microsmoothed, nickel coated substrate with a pin hole free polyamic acid polymer, and curing the polyamic acid coating to form a polyimide film free of copper ion contamination.
Claims14
A method of coating a copper substrate comprising the steps of:
- A. anodically microsmoothing the copper substrate surface by making the substrate surface a positive electrode in an acid bath at a current density of between 100 amp./sq. ft. to 2,000 amp./sq. ft., said acid being effectively active within the current density range to dissolve copper and to provide a substantially smooth copper surface,
- B. electrocoating the microsmoothed substrate with a pin hole free nickel film having a thickness of between about 2.5 microns to about 12.5 microns, said film being effective to prevent copper ion diffusion,
- C. single step, non-aqueous electrocoating the microsmoothed, nickel coated substrate with a pin hole free polyamic acid polymer film, and
- D. curing the polyamic acid coating to form a polyimide film free of copper ion deposits.
The method of clam 2 wherein the polyamic acid polymer is electrocoated from a composition comprising a polyamic acid polymer, a nitrogen containing base which reacts with the acid to form a salt, and a dual liquid system consisting of a liquid, organic, non-aqueous solvent for the acid and a liquid, non-aqueous, non-solvent for the salt of the acid.
A method of coating the surface of a copper substrate comprising the steps of:
- A. cleaning the substrate in a degreasing solution and rinsing with water,
- B. microsmoothing the copper substrate surface by making the surface a positive electrode in an acid bath selected from the group consisting of phosphoric acid and sulfuric acid, said bath having a pH of from about 0.25 to 2.0, at a current density of between 100 amp./sq. ft. to 2,000 amp./sq. ft. to dissolve copper and to provide a substantially smooth copper surface, and rinsing with water,
- C. placing the copper substrate in a nickel containing bath of nickel chloride, making the substrate a cathode, and applying current effective to reduce any oxides present to copper metal and to electrocoat the substrate with a nickel strike film,
- D. placing the nickel strike coated copper substrate in a nickel containing bath selected from the group consisting of nickel sulfamate solution and nickel sulfate solution, making the substrate a cathode, and electrocoating the substrate with a pin hole free nickel film having a thickness of between about 2.5 microns to about 12.5 microns, said film being effective to prevent copper ion diffusion,
- E. single step, non-aqueous electrocoating the microsmoothed, nickel coated substrate with a pin hole free polyamic acid polymer film from a composition comprising a polyamic acid polymer, a nitrogen containing base which reacts with the acid to form a salt, and a dual liquid system consisting of a liquid, organic, non-aqueous solvent for the acid and a liquid, non-aqueous, non-solvent for the salt of the acid, and
- F. curing the polyamic acid coating to form a polyimide film free of copper ion deposits.
Dependencies are inferred from the claim text.