Electroless metallization of optical fiber for hermetic packaging

摘要

An electroless process has been developed to deposit nickel and gold onto optical fibers using aqueous chemistry. The key to the process is a sensitization of a surface of an optical fiber using a dilute aqueous stannous fluoride solution in absence of oxygen. Stannous fluoride solution is prepared by dissolving crystalline SnF2 in deionized water. Subsequent treatment includes immersion of sensitized optical fiber in a palladium chloride/HCl aqueous solution and commercially available electroless nickel and electroless gold solutions. The process is compatible with either chemical or fusion lensing operations by using a strippable polymer coating to selectively metallize near the fiber end. The solder joints to the metallized fiber are hermetic as determined by helium leak testing, and solder pull-test strengths typically range from 3-5 pounds, depending on the type of solder. This electroless plating process for metallizing optical fibers makes feasible the incorporation of soldered fiber into packages which might be otherwise prohibitively expensive or mechanically infeasible with the sputtered metallization. The process is useful for all lightwave components which require either hermeticity or high reliability optical fiber attachment.