PIN TRANSFERABILITY TESTING OF DIPPABLE SOLDER PASTE FORMULATIONS

摘要

A new option to using tacky flux for BGA ball attach as well as Package on Package assembly is the use of a dippable solder paste. In BGA assembly it has proven useful in decreasing ball short defects and in PoP assembly for adding solder volume to the upper device solder connections. These dippable solder paste formulations can either be applied directly to the solder spheres in a dipping operation or to the solder pads by a pin transfer process. In order to quantify the effective transfer of these dippable solder paste formulations, a novel material test method has been developed. This method has facilitated the understanding of this relatively new solder material application process as well as supported dippable material development. This same method serves ball dipping, pin transfer and PoP dipping applications and is described in detail. The effect of paste solids for a water wash formulation as well as the development of a PoP no clean material is detailed. All work to date has been done with lead free alloys.