marvin at west.net
Sat Jul 7 13:45:16 CDT 2007
"Wrinkles" is a rather vague description :). When using soldermask and wave
soldering the board, the soldermask itself will wrinkle and I would guess all of
us who have worked on boards have seen that one. Since a large board can pick up
a fair amount of solder during wave soldering (depending on geometry), this adds
useless cost to the assembly of PCBs. That problem was eliminated by going to
soldermask over bare copper.
The second cause of "wrinkles" (and this is probably what you are referring to)
is due to the cooling characteristics of the solder after reflow, and this is
usually far more prominent on larger circuit areas. I would not classify these
as wrinkles per se, but rather the visual boundries where the solder started to
solidify on different parts of the circuit.
> From: David Griffith <dgriffi at cs.csubak.edu>
> I haven't heard anyone discuss this yet: what causes traces on some old
> PCBs to wrinkle and not others? My guess is a combination of suboptimal
> glue and wide temperature swings.
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