[sdiy] preventing corrosion on bare traces

[sasami at blaze.net.au]

You forget that some people's "natural oil" is rather 
acidic. I have seen fingerprints on PCBs that eat right 
through the copper over time. 

I always feel happier if the board is cleaned, then sprayed 
with a solder-through varnish before assembly. Mind you, now 
days I just get proessionally etched boards with tinning and 
solder masks.

Ken


>I'd still say that protecting the traces is not necessary 
for
>prevention of tarnish (copper oxide). If you have a trace 
that is
>corroded through, its a sure bet that the culprit is an 
agressive flux 
>(maybe acid core from an ignorant repair job ???) or some 
other foreign 
>agent (James Bond perhaps?).
>
>A spray coating could help protect against coffee, soda 
pop, other
>liquids... if you will encounter them, use a spray !!!
>
>H^) harry
>
>
>>From: Ingo Debus <debus at cityweb.de>
>>To: synth-diy at node12b53.a2000.nl
>>Subject: Re: [sdiy] preventing corrosion on bare traces
>>Date: Mon, 30 Apr 2001 15:34:06 +0200
>>
>>
>>
>>harry wrote:
>> >
>> > The copper oxide that forms on the boards will protect 
the rest of the 
>>copper.
>>
>>Hmmm... I've once seen a copper PCB trace corroded so 
badly that it
>>didn't conduct anymore. This was in an old electronic 
organ. The trace
>>wasn't interrupted completely, but there was loud rumble 
in the signal.
>>Soldering a wire across that trace fixed the problem.
>>
>> > Spray is unnecessary unless you think it looks ugly. 
Rework will involve
>> > scraping
>> > the copper to fresh metal... or removing the spray 
anyway.
>>
>>I've often used SK20 spray (Kontakt Chemie). It's not 
required to remove
>>the spray for soldering afterwards.
>>
>>But it's not good if really high impedances are involved 
(like in sample
>>& hold circuits).
>>
>>Ingo
>>
>>
>
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