On Fri, Nov 14, 2003 at 09:54:18PM -0800, Fred Townsend enlightened us
thusly
> This is a very old problem. You have what is known in the trade as wet
> boards. In other words, there is moisture trapped in the PCB
> laminate. This is typical of poorly manufactured boards. Do you have
> plated through holes? If so the plating quality is suspect too.
>
> The simple solution is to bake your boards before soldering. Use an
> oven set somewhere between 105 to 120C for 4 hours. Any hotter and you
> will damage the resin coat.
Thank you all for the helpful advice. I obviously mislead people AGAIN,
as it was a Sharp TV (Brazilian?) and I didn't manufacture it. I did
mention something about sticking my head into a TV with a beam limiting
fault; This got snipped early on and people convinvced themselves I was
manufacturing Brazilian Monitors.
The advice on heating the circuit board was about five years too late
for Sharp, but very welcome, since it answered the questions that raised
themselves in my mind. The board was not plated through, FWIW.
Interestingly, if plating through was intact and I really heated the
joints like that, I'd destroy the via, wouldn't I? I read somewhere
about water expanding to 1600 times it's own volume as it turns to
steam. It would be fun to watch - with goggles on!
The fact that I haven't met that in Ireland (a damp country) testifies
to the quality of Irish pcbs, doesn't it?
--
With best Regards,
Declan Moriarty.
--
Author: Declan Moriarty
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