Me vs NiCad battery damage on PC boards - test-drb@ccmp.vtda.org

1 Feb 2006

Hi
 Normally the PC board will have a thin layer of
nickel over the copper before the solder. This also
produces a blue-ish green oxide.
 The dark brown to black is the copper oxides and salts.
It can be removed with acid and/or mechanical rubbing.
If using any acid that does not evaporate, it needs
to be neutralized.
 If you can't find something to use, two part radiator
cleaner should do the job. They normally use oxalic
acid so handle as a toxic substance and use gloves
and face shield. I've not tried this but it should
work. You may need to heat the bath.
 One thing to consider. If it is a location the will
see high temperatures ( on the order of 100C ) during
operation, a copper to solder joint will fail with
high resistance. This is one of the reasons they put
on the nickel layer(see note). For most locations, the
temperature thing is not an issue but near regulators
and other power devices, you'll need to restore the nickel
layer.

Note: The nickel layer also simplifies the PC processing.

Dwight

...
 From: "Joe R." <rigdonj at cfl.rr.com>

 On 2/1/2006 at 9:34 AM Tim  Shoppa wrote:

>But is there some magic chemical or mechanical means that will render 
>the existing cruddy PC board solderable so I can replace these flaky 
>sockets? 
   I've seen the stuff you're talking about. Even after you clean off the
blue-green corrision the copper is black and solder won't stick to it. I
expect the black is due to copper oxide. You need to remove it by treating
it with some kind of acid that will form a water soluable salt with copper.
I expect dilute sulfuric acid may be the best. That's what they use to
clean copper circuit boards prior to assembly as well as  copper items
prior to electroplating, etc.  I'm sure you're aware of the dangers of
sulfuric acid and how much damage it can do to the board and components so
be careful!

     Joe 