Stripping conformal coating off PCBs...seeking advice

[The Refiner49er]

I am new to this specific industry but have some background in metals and foundry operations.

I am currently digesting a fraction of the mass of information that is at the
Gold Refiners Forum.... a superb amalgamation of experience and data.

Hats off to all of you who make it what it is!

My question- I want to strip PCBs of their conformal coating to effect removal of Au tracings, etc.
I have a large quantity of ammonium hydroxide tech. in liquid form.
Is it feasible to use instead of sodium hydroxide + trace of salt?
Can you advise as to the strength of solution.

If there is a better method for stripping PCB's, I would like to know. :?:

I look forward to contributing to the GRF in the future as I acquire experience in this field.

Thank you for your consideration.


Honemaster

 

[macfixer01]

I am new to this specific industry but have some background in metals and foundry operations.

I am currently digesting a fraction of the mass of information that is at the
Gold Refiners Forum.... a superb amalgamation of experience and data.

Hats off to all of you who make it what it is!

My question- I want to strip PCBs of their conformal coating to effect removal of Au tracings, etc.
I have a large quantity of ammonium hydroxide tech. in liquid form.
Is it feasible to use instead of sodium hydroxide + trace of salt?
Can you advise as to the strength of solution.

If there is a better method for stripping PCB's, I would like to know. :?:

I look forward to contributing to the GRF in the future as I acquire experience in this field.

Thank you for your consideration.


Honemaster

I believe I had seen the sodium hydroxide/salt process mentioned for removing the green solder mask material? Perhaps that is what you're actually referring to? Conformal coatings are a whole different beast, usually thicker and more tenacious. It would probably require finding some suitable organic solvents. It often looks somewhat like a thick coating of age-yellowed lacquer on older boards.

macfixer01

 

[The Refiner49er]

Macfixer-

I would assume you mean something hot like lacquer thinner.
What I have is a bunch of boards with gold tracings. Some are bare,
others are coated with what you referred to as a yellowish clear coating.

I want to strip the coating to enable the AR (or other as you may suggest) to remove the gold.
Being new at this, I am inclined to consult the experts to avoid going down the irrecoverable road.

After shopping for chemicals today, I learned that household ammonia is ammonium hydroxide, diluted.
The material I have (45 gallons) is straight undiluted material.
The labeling indicate it is caustic.

Thanks!

Honemaster

 

[lazersteve]

Honemaster,

Welcome to the forum.

The guide to the forum has a link that searches out all the posts related to board processing. That would be a good starting point for you. You can get to the guide by clicking on the Guided Tour Link in my signature line. The guided tour is composed of four links which help answer some of the more common questions asked here.

The guide to the forum actually evolves as the forum grows to include new posts that fall within the query parameters that I designed the guide around.

The thin colored solder mask coatings (red, green, yellow) are removed with repeated sodium hydroxide washes or manually with a scraper. The thicker polymer coatings require specific solvents for each type. Some of the rubber coatings peel off easily with little or no effort.

The concentrated ammonium hydroxide (typically 28%) you have can be better used in other processes.

Steve