Rolling with Solder Balls

摘要

This Month We feature one recent problem of solder balls or fines.rnDip solder paste now commonly used in package-on-package (PoP) assembly has a lower metal content, more often designed for nitrogen reflow than air, and also has smaller solder particle size. The powder may be Type 5-6, as opposed to a stencil printing grade of Type 3-4, and hence more prone to solder balling during reflow. It is fairly uncommon for standard SMT solder paste to slump and solder ball like the example, unless it has been poorly stored.