Re: getting rid of gold on pcb

Martin Griffith mart_in_medina@xxxxxxxx posted to
sci.electronics.design:

On Sat, 13 Oct 2007 12:48:34 -0700, in sci.electronics.design D from
BC <myrealaddress@xxxxxxxxx> wrote:

On Sat, 13 Oct 2007 19:29:52 GMT, Rich Grise <rich@xxxxxxxxxxx>
wrote:

On Sat, 13 Oct 2007 01:57:46 -0700, D from BC wrote:
On Sat, 13 Oct 2007 00:59:13 -0700, Robert Baer
<robertbaer@xxxxxxxxxxxx>
D from BC wrote:
On Fri, 12 Oct 2007 11:35:02 -0700, a7yvm109gf5d1@xxxxxxxxxxx
wrote:

We have boards that inadvertently ended up with hard gold
finish. As a result we have 50 microinches of gold causing all
kinds of headaches at assembly.
We asked to have the extra gold stripped off but I was told it
was not possible.
Is there no way to dissolve the gold off? Otherwise we have to
get another batch made and they're expensive. Mercury bath? Hot
cyanide? Microtome? Have an immersion silver finish over the
gold!!! Argghgghgh anything!!

I have no experience in this area so I'll just rattle off the
wacky ideas:

1) Sandblasting (copper microspheres?) 2) Planar (as with
lumbar) 3) Wet abrasive and lapping (mirror polishing) 4) Air
blasting at 1063C (Au melting point) (Cu melts at 1083C and Ni
at 1455C..but PCB will burn) 5) EDM engraving
6) 3:1 HCL:HNO3 etching
7) Chlorine gas etching or Chlorine in solution

...and do not forget environmentally and people friendly Mercury
as well as acidic Cyanides...

Wouldn't chlorine would be the choice toxin. If it gets loose,
it's heavier than air and will find something to react with. It's
far from being an inert gas and isn't found naturally in it's
elemental form. I'm guessing the resulting chlorine compounds are
going to be more friendly than mercury compounds or cyanide just
sitting around not reacting with objects.

If chlorine etching is used on the gold..it should be checked out
what temperature should be used.
The colder the temperature...the less reaction to copper. D from
BC

How about Aqua Regia?

Thanks,
Rich

That's item #6 on my list.. HCL and HNO3 3:1 ratio which is called
Aqua Regia..


D from BC
What else would aqua regia disolve? BTW in WW2 one nobel prize
winner dissolved his medal in AR to stop the nazis getting it. The
gold was recovered after the war are re-cast into the medal, neat.


Martin

Most certainly any local metal.

.

Relevant Pages

  • Re: getting rid of gold on pcb
    ... We asked to have the extra gold stripped off but I was told it was not ... Chlorine gas etching or Chlorine in solution ... How about Aqua Regia? ...
    (sci.electronics.design)
  • Re: getting rid of gold on pcb
    ... We asked to have the extra gold stripped off but I was told it was not ... Chlorine gas etching or Chlorine in solution ... ...and do not forget environmentally and people friendly Mercury as well ...
    (sci.electronics.design)
  • Re: getting rid of gold on pcb
    ... We asked to have the extra gold stripped off but I was told it was not ... Chlorine gas etching or Chlorine in solution ... ...and do not forget environmentally and people friendly Mercury as well ...
    (sci.electronics.design)
  • Re: getting rid of gold on pcb
    ... We asked to have the extra gold stripped off but I was told it was not ... Chlorine gas etching or Chlorine in solution ... ...and do not forget environmentally and people friendly Mercury as well ...
    (sci.electronics.design)
  • Re: getting rid of gold on pcb
    ... We asked to have the extra gold stripped off but I was told it was not ... Sandblasting (copper microspheres?) ... Chlorine gas etching or Chlorine in solution ... I know scotchbrite scuffs copper which means something in the ...
    (sci.electronics.design)
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