What types of parts are causing the most problems? For
parts that are very fine pitch, tsops, etc we usually do not use a HASL
finish. I prefer a immersion gold but hate osp's. HASL finishes have
too wide of a process window for these devices. I see much flatter
surfaces with alternate finishes. This is especially true with fine pitch
on both sides. Most suppliers can control one side fairly well but two
sides and it is much harder. The only supplier I have seen do this with a
mediocre yield was utilizing a horizontal HASL process. Unfortunately most
PCB houses use vertical HASL processing.
Just my $.02
Kathy