Removing solder mask from gold fingers - is it possible?

Hello,

We have a problem with one of our circuit board vendors who applied solder
mask to the gold fingers on a lot of 100 boards. Naturally, the 100 boards
were built up and the problem wasn't discovered until test. Does anyone
know of a way to remove it without losing the gold on the fingers?
Solvent or ??

Thanks.

On Mon, 26 Mar 2007 11:34:41 -0400, JW <(E-Mail Removed)> wrote:

>Hello,
>
>We have a problem with one of our circuit board vendors who applied solder
>mask to the gold fingers on a lot of 100 boards. Naturally, the 100 boards
>were built up and the problem wasn't discovered until test. Does anyone
>know of a way to remove it without losing the gold on the fingers?
>Solvent or ??
>
>Thanks.

Try oven cleaner, have had some success with that before.

Peter
--
Peter & Rita Forbes
Email: (E-Mail Removed)
Web: http://www.oldengine.org/members/diesel

JW wrote:
> We have a problem with one of our circuit board vendors who applied solder
> mask to the gold fingers on a lot of 100 boards. Naturally, the 100 boards
> were built up and the problem wasn't discovered until test. Does anyone
> know of a way to remove it without losing the gold on the fingers?
> Solvent or ??

There might be some acid which will eat the tincoat without eating the
gold. If so it's probably nasty stuff.

--
"This, then, is the essence of Gore's complaint:
there are too many humans and they are too well off."
-- Robert Tracinski

"JW" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
> Hello,
>
> We have a problem with one of our circuit board vendors who applied solder
> mask to the gold fingers on a lot of 100 boards. Naturally, the 100 boards
> were built up and the problem wasn't discovered until test. Does anyone
> know of a way to remove it without losing the gold on the fingers?
> Solvent or ??
>
> Thanks.

If you mean that green varnish type solder resist, you could try Nitromors
paint stripper otherwise a possibly more difficult to track down solution is
Oxley Developments Resin Dissolver. A company I worked for years ago used
this stuff to dissolve thermosetting bonding mats used to stick ultrasonic
transducers to the bottom of cleaning tanks - you don't want to soak PCBs in
it though, it'll dissolve them as well!

Hold on though - cant the PCB firm tell you what'll shift it?!

JW wrote:
>
> Hello,
>
> We have a problem with one of our circuit board vendors who applied solder
> mask to the gold fingers on a lot of 100 boards. Naturally, the 100 boards
> were built up and the problem wasn't discovered until test. Does anyone
> know of a way to remove it without losing the gold on the fingers?
> Solvent or ??
>
> Thanks.


What does the board house use to clean its equipment with?


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

> JW wrote:
>>
>> Hello,
>>
>> We have a problem with one of our circuit board vendors who applied
>> solder
>> mask to the gold fingers on a lot of 100 boards. Naturally, the 100
>> boards
>> were built up and the problem wasn't discovered until test. Does
>> anyone
>> know of a way to remove it without losing the gold on the fingers?
>> Solvent or ??
>>
>> Thanks.
>
If it is the dark green probimer you have a major problem. It is
usually applied and lightly dried in an oven at low temperature. After
exposure to UV it is developed to remove the unwanted resist and then
baked at a high temperature. After the high temperature bake its
bloody difficult to remove. ( I dont know of any solvent that works
without board damage at this point, although I am not saying there is
not one) The only way that I know of would be scraping or bead
blasting which obviously is going to result in some loss of plating.

Agreed. The only thing I've seen able to remove solder mask is the
electrolyte from leaking caps, and that destroys the copper. And it
does it from the inside as it is under it, doesn't matter what you
plate it with.

Grind it off, or maybe since it is liable to be quite flat, mill it
off with a milling machine.

JURB

JW <(E-Mail Removed)> wrote in
news:(E-Mail Removed):

> Hello,
>
> We have a problem with one of our circuit board vendors who applied
> solder mask to the gold fingers on a lot of 100 boards. Naturally, the
> 100 boards were built up and the problem wasn't discovered until test.
> Does anyone know of a way to remove it without losing the gold on the
> fingers? Solvent or ??
>
> Thanks.
>

I tried acetone and strong caustic soda solution, the stuff doesn't budge.

Assuming chemical is useless, and physical is likely to wreck the bits you
want, try optical.

An IR pulsed laser should be a good match for absorption by dark green, and
the gold will reflect it, as will the copper, and the partial trasparency
of the substrate should dissipate safely what isn't absorbed by the resist
layer.

In order of rising price (and general butchness) try hair removal lasers,
tattoo removal lasers, and stone cleaning lasers. Take care not to angle
the thing such that it can reflect off gold or copper right back up the
waveguide, as that will likely damage or even instantly destroy the laser
cavity, especially if it's a direct-from-diode sort of pulsed laser.

On Mon, 26 Mar 2007 11:34:41 -0400, JW <(E-Mail Removed)> wrote:

>Hello,
>
>We have a problem with one of our circuit board vendors who applied solder
>mask to the gold fingers on a lot of 100 boards. Naturally, the 100 boards
>were built up and the problem wasn't discovered until test. Does anyone
>know of a way to remove it without losing the gold on the fingers?
>Solvent or ??

Mechanical means are going to have an impact on the plating, so (unless the
pulsed-laser trick works) I suspect you're stuck with chemical attack.

Dumb question #1: Seeing your board-fab botched their bit, have you tried
actually asking them WTF the stuff is, and then talking to an industrial
chemist?

"Lostgallifreyan" <no-(E-Mail Removed)> wrote in message
news:Xns99036EC7524E2zoodlewurdle@140.99.99.130...

> I tried acetone and strong caustic soda solution, the stuff doesn't budge.

Thixotropic organic paint remover?