すず真正ホイスカの発生と成長機構

概要

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The spontaneous growth of tin proper whiskers on electroplated tin films causes a practical problem of short circuit error. In order to solve this problem, factors influencing the whiskers growth as well as the growth mechanism have been investigated by many workers. However, the basic growth mechanism has not yet been wholly explained. In the present paper, some descriptions are given on the factors influencing the whisker growth, such as tin plating brightener, thickness of tin film, metallic substrate, atmosphere, heat treatment of tin film and addition of lead atoms to tin film. Subsequently, a few method to prevent the growth of tin proper whiskers are presented, which are as follows: No use of copper and its alloys as metallic substrate, use of tin plating brightener composed of ketone compound, make tin film more than 10μm thick, and heat treatment (for example, for 3 hr or more at 125℃) of tin film after electroplating. Several experimental results for making the whisker growth mechanism clearer are presented. Whiskers contain not only tin but also copper and zinc atoms of substrate metals. When tin is plated on brass, copper and zinc atoms diffuse into the tin film, then copper atoms form intermetallic compounds and zinc form oxide on the surface of films and whiskers. The tin whiskers easily grow on tin films having irregularly shaped grains.
1981-12-15