Soldermask, Tombstoning and Solder balls
This is an update to a prior post about solder mask and tombstoning. In that post I wrote about how having your solder mask too thick up in the pad or poorly registered can cause tombstoning with 0201 and 0402 parts. It can even cause the problem with larger parts like 0603s.
Further, I've also been told that thick soldermask like this can cause solder balls. The solder can get trapped by the part and a small opening in deep solder mask. It has no place else to go, so it can spit out and land someplace near as a solder ball. Not a good thing.
He shoots. He scores. He shorts!