SMTA International Conference Proceedings


Pb-FREE PROCESS DEVELOPMENT AND MICROSTRUCTURAL ANALYSIS OF CAPACITOR FILTER ASSEMBLIES USING SOLDER PREFORMS

Author: Vatsal A. Shah et al.
Company: Binghamton University
Date Published: 9/25/2005   Conference: SMTA International


Abstract: The purpose of this paper is to describe the Pb-free process development for capacitor filter assemblies of various sizes that use solder preforms in the shape of a washer and estimating the Sn budget, before and after the reflow process, due to two different material systems, namely, gold plating and silver frit. Components considered for this research are circular filter capacitors that have pins inserted into a ferrite core. Because of the good creep and fatigue properties, good wetting characteristics with copper and nickel, and good performance at an operational temperature of 125oC, the near eutectic SnAgCu (SAC) alloys are the most promising alternatives to the traditional Sn-Pb eutectic.

Another promising alternative to SnPb solders is the eutectic SnAg alloy. The Pb-free alloys considered in this work have high temperature strength and high reliability for interconnect applications. We are studying a variety of factors (reflow atmosphere, and alloy composition) on the quality of the solder joints. The reflowed capacitors are cross-sectioned and polished up to 0.02 microns to check for the presence of any intermetallics or voids in the contact areas. The results obtained from the Pb-free test samples are compared to eutectic SnPb samples to study the differences between the Pb-free and SnPb processes.

Key words: Pb-free, SnAgCu, SnAg, Reflow profiling, Sn budget, Grain boundary, Cross polarized microscopy, Reliability.



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