Removing solder mask from gold fingers - is it possible?

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

Peter

-- Peter & Rita Forbes Email: snipped-for-privacy@easynet.co.uk Web:

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

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?!

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

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 wrote in news: snipped-for-privacy@4ax.com:

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.

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?

Thixotropic organic paint remover?

"Homer J Simpson" wrote in news:tZbPh.29082$__3.7899@edtnps90:

Didn't have any.

Tetramethylguanidine might do the trick. I've used it in decapsulating plastic encapsulated electronic devices. It really stinks and you need a hood to use it.

Al

What is it you are agreeing with?

This is NOT Google Groups. Most people don't see what YOU see when YOU read Usenet at Google Groups. http://66.102.9.104/search?q=cache:ypHxBbi7_W8J:en.wikilib.com/wiki/USENET+follow-Usenet-customs-and-*-rules+*-a-service-for-*-*-*-*+hide-the-fact-*-*-*-they-are-*-on-Usenet+concerns-*-*-*-*-about-the-Google-interface+zzz+*-*-*-*-*-*-*-*-*-*-*-*-*-is-now-legendary+qq-qq+Google-cannot-muster-*-*-*-*-*-*-*-*-*-*-*-*-*

There is a standard way of postiing to Usenet: http://66.102.9.104/search?q=cache:iShBLj9qnZ0J:groups-beta.google.com/support/bin/answer.py?answer=46492%26topic=9253+remove-*-*-*-irrelevant+Usenet+*.*.*.*.*-*-*-*-relevant.*+2006+be.interested+your.reply+Summarize.what.you're.following.up+before.the.original.*.*+*-for-your-readers

By now

you should have recognized that paradigm and emulated what you see the majority of other Usenet users doing.

*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*+*-put-*-*-into-context+*-netiquette+completely-unintelligible+zzz+necessary-*-*-*-to-be-understood+*-*-*-someone-who-doesn't-quote+Quoting-*-*-what-you're-replying-to+qq+I-always-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-* The part in yellow is called CONTEXT. The rest of the post explains why it is important.