I'm making a PCB that has a 100pin QFP pacakge microcontroller. After gaining experience with the UV photoresist process and reliably making the small, 0.5mm traces, I have a new problem: the copper traces are delaminating when soldering them. Specifically, they get stuck to the solder tip and peel off the board.
It seems this mostly happen when a large part of the trace is heated simultaneously and kept heated for > 1s. I cleaned my solder tip repeatedly to prevent a big blob of solder from accumulating, but that didn't completely make the problem go away. The boards I'm using have a copper thickness of 1 oz.
I'm also using a Weller WPS18MP, which has a tip temperature of ~900F. Is that too high?
Is there anything I can do besides using sheer soldering discipline?
Best Answer
This is a sign of too much heat in the copper strip. That you're seeing this with thin traces suggests your soldering iron temperature is too high, you're using too large a tip, or your holding it on there for too long.
Without more information, I can only suggest my parameters for your situation:
700F temperature controlled iron
Small conical tip (1mm or smaller at the tip)
Lots of flux
Small diameter solder, or paste
You should be able to solder a SMT joint in a second or two without lifting. You shouldn't keep reheating the same trace. If you must use solder wick for rework or blob removal, try to keep the iron on the wick pressing into the joint for under 15 seconds.
If after all this you still experience the problem, you might consider asking your pcb supplier about it. Poor quality copper adhesive or fabrication practices could be the culprit as well.