green material covering gold

[snacker47]

Hi All,
Please notice that I have these fingers that have gold on the ends but that they also appear to have gold plating underneath the green layer. If i scrape away the green it appears to be gold underneath? I've tried soaking in the AP solution for a few days but the green susbstance covering what appears to be gold plating is not affected and I'm wondering what it actually is, could it be gold plating underneath and if so, what might be a good approach to getting to the heart of the matter and removing the gold underneath this green material. Here are some pix to better illustrate what I'm dealing with. I recently came by a very large number of these and would like to get the gold if it's realistic in a reasonable time frame.

Thanks all,
S47

 

[pgms4me]

The pictures you posted shows that the plating under the green solder mask does appear to be gold. It is dissolved by first soaking the boards in sodium hydroxide solution,commonly known as lye. please use the safety precautions on lye before doing this.This topic is covered here on the forum in more than one place. a quick search should get you going quickly.

 

[Smack]

Follow safety rules for using Lye, if you let it get on your skin or in your eyes you will have a very very bad day and maybe a bad rest of your life.

 

[JHS]

LYE DANGER
Lye is extremly caustic.
ONE DROP in your eye WILL BLIND you.
you must take all precautions when using it.read all the safety links before you attempt this.be very careful not to splash it.
john

 

[Lino1406]

Normally the mask is intended for avoiding gold plating. I wander?

 

[rickbb]

Freshly scraped copper does look golden.

Before you try to remove the mask, place a drop of nitric acid on the scraped area. Does it fizz and bubble? If so it's copper, if not well some board maker has made a very expensive and wasteful board.

 

[shmandi]

There are a lot of older and some newer boards that have gold plating under solder mask. But the plating should be very thin, maybe not even worth recovering. Haven't tested it myself yet.

 

[pgms4me]

My experience is that some of the premium test equipment manufacturers used gold plating as part of their claims of being the best. Hp test equipment from the 70's and 80's is a prime example. Those boards have about the thickest gold plated traces for non-military equipment ever built.Even the later HP servers such as the 1990's 9000 series have all trace and back planes on the mother board and most connector boards fully gold plated .All the plated through holes are also gold plated. They are well worth recovering. Telecom boards by Macom and some Nortel boards have excellent gold plating. What I find handy is an old 50-100x microscope. If you have samples of known thicknesses, you can easily ball park quality of unknowns by comparing them side by side with known samples under the scope.

 

[Smack]

Freshly scraped copper does look golden.

Before you try to remove the mask, place a drop of nitric acid on the scraped area. Does it fizz and bubble? If so it's copper, if not well some board maker has made a very expensive and wasteful board.

If you scrape some mask off and test with nitric it will react with the base metal regardless if it's gold plated or not. So if you do test it with nitric, you wait for the reaction to stop then look at the spot under magnification to see if there are little particles of gold floating. But you really shouldn't need to test like that, you should be able to tell by color, gold is yellow, copper is the red metal. Might just be me but I find it easy to tell if it's gold or not in regards to gold under solder mask.

 

[Geo]

they have gold plated traces, at least the ones in the picture.

 

[steyr223]

Sound testing equipment
Round boards (completely covered under mask)
2-3gr/board