Passivation of metallic equipment surfaces in electroless copper deposition processes
AssigneeKollmorgen Technologies Corporation
InventorRudolph J. Zeblisky
Life of this patent
Estimating the term…
Abstract
The metallic surfaces of plating equipment in use during electroless copper deposition, such as vessels, racks supporting substrates being plated, plumbing, and the like are rendered substantially resistant to electroless copper deposition for extended periods by initially imposing on such equipment surfaces an electrical potential more positive than the mixed potential of the electroless copper solution and sufficiently positive to resist electroless deposition, electrolessly depositing copper on the substrate being plated, and while depositing such copper maintaining on the equipment surface a potential sufficiently positive to resist the formation of adherent electroless copper deposits.
Claims25
In a method for electrolessly depositing copper from an electroless copper deposition solution of known mixed potential on at least one substrate sensitive to such deposition, the improvement for rendering the metallic surfaces of plating equipment in contact with the solution substantially resistant to electroless copper deposition, comprising:
- (1) initially imposing on said metallic plating equipment surfaces an electrical potential more positive than the mixed potential of the electroless copper solution but not substantially more positive than required to render said equipment surfaces substantially resistant to electroless copper deposition;
- (2) electroless depositing copper on said substrate from said electroless copper solution;
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- (3) while electrolessly depositing copper on said substrate, adjusting said more positive electrical potential to maintain said more positive electrical potential sufficiently positive to resist electroless copper deposition.
A method for electrolessly depositing copper from a deposition solution of known mixed potential on a substrate sensitive to said deposition, comprising:
- (1) initially imposing an electrical current on the metallic surfaces of plating equipment in contact with the solution, said current being sufficient to provide an electrical potential on said equipment surfaces more positive than the mixed potential of the solution but not substantially more positive than required to render the equipment surfaces substantially resistant to formation of an adherent electroless copper deposit;
- (2) electrolessly depositing copper on said substrate from said electroless copper solution;
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- (3) while electrolessly depositing copper on said substrate, adjusting said current imposed on said equipment surfaces to maintain such electrical potential more positive than said mixed potential but not substantially more positive than required to resist electroless copper deposition thereon.
In a method for the production of printed circuit boards by electrolessly depositing copper on a substrate from a solution comprising copper ion, a complexing agent for copper ion and formaldehyde, while said solution is contained in a vessel having stainless steel retaining walls and said substrate is supported in said solution on a rack comprising stainless steel, the improvement comprising:
- (1) providing at least one cathode in the electroless copper solution and in electrical connection with said retaining walls and rack;
- (2) initially imposing a current in said electrical connection, said current being sufficient to establish an electrical potential on said retaining walls and rack more positive than the mixed potential of said electroless copper solution but not substantially more positive than required to resist formation thereon of an electroless copper deposition from said solution;
- (3) electrolessly depositing copper on said substrate from said electroless copper solution;
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- (4) while electrolessly depositing copper on said substrate, regulating said current imposed on said electrical connection to maintain said more positive electrical potential more positive than said mixed potential but not substantially more positive than required to resist formation thereon of an electroless copper deposit.
A method for rendering a steel surface in contact with metallic copper substantially resistant to electroless copper deposition from a solution in contact therewith, comprising:
- (1) initially imposing an electrical current on said steel surface sufficient to provide an electrical potential thereon more positive than the mixed potential of said solution but not substantially more positive than required to render said surface substantially resistant to electroless copper deposition from said solution;
- (2) electrolessly depositing copper from said solution on a substrate immersed therein;
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- (3) while said electroless copper deposition is taking place, adjusting said current imposed on said steel surface to maintain the electrical potential thereon more positive than said mixed potential but not substantially more positive than required to resist formation thereon of an adherent electroless copper deposit.
Dependencies are inferred from the claim text.