TRANSITION TO Pb-FREE ALLOYS IN CAPACITOR FILTER ASSEMBLIES
Authors: Vatsal A. Shah, Amol S. Kane, Daryl L. Santos, Mik Date Published: 1/17/2006
Pan Pacific Symposium
Abstract: This paper describes the Pb-free process development for capacitor filter assemblies of various sizes that use solder preforms in the shape of a washer. Components considered for this research are circular filter capacitors that have pins inserted into a ferrite core. SnAgCu (SAC) and SnAg alloys are considered for the replacement of the SnPb preforms currently used. The objective of this work is to study a variety of factors (including reflow atmosphere, alloy composition, platings on the capacitor array (silver-based and gold-based), and flux) on the quality and reliability of the solder joints. The reliability of Pb-free solders is evaluated by first studying the intermetallics of the control samples, those made with Pb-bearing solders, which is the baseline for the intermetallics evaluation of the Pb-free solders. Thus far, we have begun to establish a Pb-free assembly process and have made initial investigations into intermetallic determinations of species and their amounts. Process development efforts for reliability determinations, including thermal cycling are conducted with the ultimate goals being the following: reduce and control the amount of intermetallics; increase the likelihood of multiple grains of solder formed in each joint; and eliminate the voiding we have discovered due to the flux.