29 Dec
1998
29 Dec
'98
9:07 p.m.
Tony Duell wrote:
Certainly on some PCBs (no idea if Tandy boards do this), the current
flowing in some tracks (power and ground) gets them hot enought to make
the coating wrinkle up a bit. Some boards do this even in normal
operation (!).
The solder mask wrinkle is caused by the solder plated traces getting hot
enough to melt the solder. The result is a wrinkled solder mask. Almost
all boards I have seen with solder mask applied over reflowed solder,
stuffed with components, and then run through a wave soldering machine will
show the same thing.
Trivia for the day - One of the reasons the SMOBC (Solder Mask Over Bare
Copper) process was developed was the cost of wave soldering. I have seen
boards that were solder masked over reflowed solder that have picked up as
much as 1 pound of solder when run through the wave soldering machine (the
solder accumulates under the solder mask.) This tends to drive up the cost
of wave soldering the boards :)! SMOBC boards also do not wrinkle the
soldermask when run through the wave soldering machine.