Study of Relations between Several Factors in Immersion Silver Technique and Galvanic Attack Problem

To control lead pollution," Hot Air Solder Leveling "(HASL), the traditional lead-contained PCB(Printed Circuit Board) surface finish, needs to be replaced by lead- free technique. Immersion Silver (I-Ag) has many merits compared to other lead-free techniques, thereby being increasingly widely used. However, a problem named "galvanic attack", which seriously erodes copper where circuit connects pad, is a serious obstacle to I-Ag\´s popularization. According to manufacturing experience, consistency of silver ion, temperature, mircoetch rate and liquid level are four major factors in I-Ag process. In this paper, relations between these factors and galvanic attack are studied by experiments. From these relations we get inspirations to reduce galvanic attack in engineering practice.