Lead-free BGA shock
The electronic manufacturing industry as a whole has gotten much more comfortable with lead-free processing over the last six months. We've been offering RoHS processing for a year and a half now. Still, there are some challenges in areas such as longevity and shock performance.
We tend to deal primarily with prototypes so some of the challenges are less of an issue for our customers at our stage in the NPI process then for later stages. One such issue is that of lead-free BGA shock resistance with SAC (Tin, Silver, Copper) solder. One of the solutions being explored by the industry is an adhesive underfill.
I ran across this article by Jim Hisert of Indium Corporation that covers two different methodologies. Again, we don't perform underfill here, but when you get to production, if you have a high-stress application with lead-free BGAs, you might want to consider it as an option with your production assembly house.