Joseph,

How close are your solder mask fits? Do you run solder mask fingers between 0.020-inch-pitch (0.5mm) TQFP pins? How wide?

While, with my deteriorating vision, I have difficulty in placing my 0.5mm-pitch TQFPs, I have, so far, had no difficulty with soldering them, particularly in light of the fact that I can wick off excess solder should I slip up and let it bleed two or more pads together. I seldom have to do that, despite the fact that my adapters generally lack the solder mask I'd prefer, which is a ~.010"-thick brittle dry-film mask. The guy who used to make my boards locally has been out of business for a long time, but, once upon a time, he built me a set of adapters for half-mm pitch PQFP-208's that were masked such that I could put a silastic gasket between the leads and a cover/heatsink, and it would, by means of a couple of screws, hold the part and the gasket such that the QFP didn't have to be soldered in place. That was VERY convenient. I needed very few of these adapters to test parts, or to adapt them to PGA pinout for prototypes.

I've used 'em up over the years and surely wish I could get someone to make a few more for me. Unfortunately, U.S. board makers don't believe in holding tight tolerances where mask is concerned. Most of 'em won't even attempt to run mask fingers between .020"-spaced leads.

RE