High-throw acid copper plating using inert electrolyte

Details High-throw acid copper plating using inert electrolyte High-throw acid copper plating using inert electrolyte

1991-02-22

1992-12-29

Niebling, John

Electrolysis: processes, compositions used therein, and methods

Electrolytic coating

Coating selected area

205291, 205296, 205920, C25D 338

Patent

active

051748860

ABSTRACT:
Improved through-hole plating of printed circuit boards, wherein the ratio of the printed circuit board thickness to the diameter of at least one through hole is greater than 3 to 1, is achieved by a high-throw acid copper plating bath of this invention. The high-throw acid copper plating bath comprises an aqeuous solution of (A) copper sulfate, (B) sulfuric acid, (C) chloride ion, e.g., hydrochloric acid, (D) a carrier, (E) a brightener, and (F) an alkali metal salt; wherein the plating bath has a pH of not greater than about 1, the concentration of the hydrochloric acid is from about 6.0.times.10.sup.-4 to about 1.8.times.10.sup.-3 moles/liter, and the mole ratio of copper sulfate:sulfuric acid is not greater than about 1:25. Unlike previous high-throw acid copper plating baths, the bath of this invention contains an alkali metal salt. The use of the alkali metal salt makes it possible to maintain a lower acid concentration resulting in easier maintenance and more consistent plating. In addition this high throw process makes it possible to obtain in a substantially shorter time, plated circuits and through-holes with an acceptably high aspect ratio.

REFERENCES:
patent: 4036711 (1977-07-01), Kardos et al.
patent: 4469569 (1984-09-01), Tomaszewski et al.
patent: 4975159 (1990-12-01), Dahms
patent: 5051154 (1991-09-01), Bernards et al.
Chemical Abstracts-86:130008v.

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