Trivia for the Day

From: Marvin <>
Date: Wed Dec 30 02:07:40 1998

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.
Received on Wed Dec 30 1998 - 02:07:40 GMT

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