Stripping solder masks

[Wyndham]

I just came into a large batch of pc boards, about half were ISA sound cards. They look like there's a good bit of gold on some of the boards but there's the solder mask barrier.

I saw in the tutorials about using lye solution to dissolve the solder mask from pc boards. I have a large quantity of Soda Ash and I know it is less caustic than sodium hydroxide but wondered if it is still strong enough to strip the mask.
I was unable to see the video on Steve's page, everything downloaded and I had the plugin but it never played.

If the soda ash won't work, what are the ratio's of lye in water and what is the temp to heat to.
Thanks, this is my first batch of boards to start working with. Is there enough gold beside the fingers to go to the trouble of stripping these?
I thought I'd strip first then AP then HCL/Clorox if it's worth it.
Thanks for any help
Wyndham

 

[JHS]

http://goldrefiningforum.com/~goldrefi/phpBB3/viewtopic.php?f=37&t=3874

 

[patnor1011]

Do it if you have nothing else to do. It is not worth the hassle in my opinion.

 

[rickbb]

I think you'll find that under that green mask is copper. They only put the gold where it is needed to save money, not everywhere on the board.

 

[shmandi]

I think you'll find that under that green mask is copper. They only put the gold where it is needed to save money, not everywhere on the board.

that information is not correct. I have hundreds of boards that are covered with gold, same as on fingers. Many older sound cards, some RAMs and other.

 

[lazersteve]

The solder mask video can be viewed on my youtube channel : search lazersteve, solder mask

Steve

 

[rickbb]

I think you'll find that under that green mask is copper. They only put the gold where it is needed to save money, not everywhere on the board.

that information is not correct. I have hundreds of boards that are covered with gold, same as on fingers. Many older sound cards, some RAMs and other.

I stand corrected then. But in my defence I did say "I think",,,

I am new to stripping boards, and of the few hundred I've done so far, have yet to see a fully gold plated board under the masking.

 

[shmandi]

Here are just few samples. two sound cards, modem and RAM. On RAM plating under mask looks very pale comparing to fingers, but on others is same color. However fingers on those sound cards look very pale already.

 

[rickbb]

The modems and PCI video cards I do, have a few bits of gold plate here and there all over the board, but none under the green that I've found.

I cut the fingers off and sell the board along other mixed PCB's that I've cut the easier to deal with fingers and such off of.

You can try stripping the masking off with lye as suggested to see whats under there, but IMHO, there won't be gold plate in any quantiy to justify the dangers involved.

 

[Wyndham]

thanks for the link to youtube
I'll try a few boards and see what they look like.
Wyndham

 

[Shaul]

Whenever processing cards, always scrape away some of the solder mask first, to see what's underneath. Many times the boards are completely plated on both sides. With Medical equipment, many boards (like some makes of Glucometers or even small items like digital thermometers) are gold plated on one or both sides. Once you get into the habit of checking, you'll check every board you come across. Save them separately.

Shaul

 

[NobleMetalWorks]

Ultimately the best way to deal with boards, and soldering mask for that matter, is to incinerate. Once everything is ashed it's easy to remove much of the base metals with a magnet, and then process using a wet process for values.

If I need to remove a soldering mask, I usually do so with a lye past I make, it works, but it's been awhile since I have done this. It's not really profitable to play around removing soldering masks from sound cards if you are making this a business. If however, it's just a hobby and you are only recovering the values to save, and don't care about how much labor, or money you are putting into what you are getting out then it doesn't really matter.

Scott