ELECTROLESS TIN-SILVER ALLOY PLATING BATH AND FILM CARRIER OF TAB, OR THE LIKE, COATED WITH TIN-SILVER ALLOY FILM BY THE PLATING BATH

摘要

PROBLEM TO BE SOLVED: To increase the secular stability of an electroless tin-silver alloy plating bath, to surely precipitate tin and silver, furthermore to low suppress the compositional ratio of silver in the film and to improve its joining strength. ;SOLUTION: This bath contains a mixture of a primary tin salt and a silver salt, at least one kind of organic acid such as an organic sulfonic acid and a aliphatic carboxylic acid, and an inorganic acid such as hydrofluorboric acid, hydroluorosilic acid and sulfamic acid, a nitrogen-contg. compd. (thiourea or a derivative thereof and amines) and a sulfide based compd. having basic nitrogen atoms. Since it jointly uses the nitrogen-contg. compd. and sulfide compd. as complexing agents, by the synergistic effect thereof, silver ions in the bath is stabilized, and tin is also smoothly precipitated. Thus, the objective electroless plating bath is excellent in the secular stability at high temp and the compositional ratio of silver in the tin-silver alloy film is low suppressed, and the joining strength and the appearance of the film not inferior to those of a tin film can be secured.;COPYRIGHT: (C)2000,JPO