Foreign Material on White Polyimide

摘要

I HAVE AN LED application where I need my flex tohave white solder mask or white polyimide. When Ireceived my first prototypes, there seemed to be a lotof small specks of “stuff” on the outer surface. I haveused flex circuits in the past, but they all used amberpolyimide covers. I never noticed these specks before.Is there something different in processing white polyimide that would cause these spots?