Guidelines for Pb-free BGAs:Reballing vs. Mixed Alloy Soldering
This document will provide guidance and risk trade discussion on reballing Pb-free BGAs vs. installing them using a mixed alloy soldering method. Information will be presented relative to the risks of each method and guidance on an approach.
Rationale: It is increasingly difficult to procure advanced components in non-ROHS compliant configurations, and existing products continue to have a cost impact and risk of obsolescence. For those manufacturers that continue to build traditional SnPb products, the incorporation of Pb-free BGAs typically means the selection between two main options; reballing to convert to a SnPb ball, or soldering the Pb-free ball with SnPb solder to create a mixed-alloy solder joint.
There is lots of research in this area already but translating that into a program decision is still difficult without some guiding document or process.