Abstract Method of gold plating particularly suited for the gold plating of localized conductive areas such as contacts on printed circuit boards, wherein the surface to be plated is first cleaned and activated without any current being applied by rubbing onto said surface a non-displacement type of gold electrolyte solution carried by absorbent material forming part of a gold applicator assembly that includes a gold anode. A plating current is then passed through said electrolyte solution during continued rubbing to effect the plating of gold on said surface as the cathode. The preferred electrolyte is a water solution of an alkali metal gold cyanide containing substantially no free cyanide or alkali metal cyanide in excess of the cyanide bound to the gold present in said water solution. The method is self-indicating in that so long as the plating maintains a superficial dark or brownish coloration throughout the plating cycle, the gold electrodeposit is of satisfactory quality and is firmly adherent, whereas if the gold electrodeposit exhibits a clear gold color, or if no plating takes place, that indicates a poor or broken plating connection in the plating circuit. Rubbing of the electrodeposit with the applicator during the plating operation, if there are poor or broken plating connections, quickly removes the superficial dark coloration of the electrodeposit and imparts thereto a clear gold color of substantially the same clarity of gold color as that of the gold applicator used. If this occurs, it is only necessary to correct the bad plating connection and continue plating.
The method as defined by claim 1, wherein said plating circuit carries a current density of at least about 100 amps./sq. ft. and is at a voltage of from about 8 to 16 volts.
Claim 2
Dependent Claim
20 words
The method as defined by claim 2, wherein, the current density is from 400 to 700 amps./sq. ft. and higher.
Claim 3
Dependent Claim
45 words
The method as defined by claim 1, wherein said surface area to be gold plated includes many discrete area portions, and all of said area portions are simultaneously electrically connected during plating by a flexible mass of steel wool held thereagainst and contacting said areas.
Claim 4
Dependent Claim
96 words
A non-displacement type of gold plating electrolyte solution consisting essentially of an aqueous solution of an alkali metal gold cyanide moiety containing substantially no free cyanide and substantially no free alkali metal cyanide not bound to the gold present in a concentration molecularly equivalent to from about 2.5 grams to about 10 grams of sodium gold cyanide, (Au Na (CN)2), per 16 fluid ounces, said aqueous solution containing substantially no free cyanide and substantially no free alkali metal cyanide, and substantially all of the cyanide present including the alkali metal cyanide being bound to said gold.
Claim 5
Independent Claim
219 words
The method of electrodepositing gold on an area of an electrically conductive metal surface to provide a firmly adherent high quality gold plate over said area, which comprises establishing a plating current of at least 400 amps./sq. ft. density between said surface and a manually guided, effectively pure gold anode through a gold electrolyte solution carried by a nonconductive, absorbent fabric enveloping said anode and maintained in pressure contact with both said anode and said surface, effecting wetting and rubbing contact between said absorbent fabric and said surface with said surface constituting the cathode to effect gold plating of said area, said anode having a backing of a more rigid metal than gold incapable of codepositing with the gold from said gold electrolyte solution; said electrolyte solution consisting essentially of an aqueous solution of an alkali metal gold cyanide moiety containing substantially no free cyanide and substantially no free alkali metal cyanide not bound to the gold present in said gold cyanide moiety, and containing no addition agent of any kind, and continuing said gold plating to produce a gold plate having a superficial brownish coloration in contrast to the clear gold coloration characteristic of gold, said brownish coloration persisting during such continued plating, and stopping said plating when the desired thickness of said gold plate has been reached.