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MEK to Remove Solder Mask from PCB

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magic:

--- Quote from: T3sl4co1l on January 03, 2020, 12:38:58 pm ---I mean... acetic acid has a complex for copper, it might dissolve that faster. :P  And it looks formic does as well.

--- End quote ---
Why is nobody etching PCBs in vinegar then?

It's not actually that aggressive against copper. I tried it once and got slightly bluish solution after a week of soaking and nothing visible on copper. Don't remember if it was 10% or 100% acid. Actually, 100% concentration may be weaker against metals if it behaves anything like nitric/sulfuric.

It will get worse with added salt, however. This seemingly innocent mixture can even etch aluminium in a matter of days.

T3sl4co1l:
Vinegar is weak (5%).  I didn't say it would be fast, but we're talking epoxy here, so, there's probably some time for it to happen. ;D

OTOH, hot glacial acetic acid, isn't very pleasant to work with.  Keep that away from my mucous membranes, please!  Given some oxygen (or H2O2), and indeed chloride and other ligands will help further, and you're likely to see some effect.

Tim

SeanB:
Hot tricholrethane is very good at stripping the soldermask, and after around a minute more you start to lose the board as well. Was the only way to remove some of the more robust conformal coatings, though it would wreak havoc on anything with a rubber seal, and would remove all markings from components, making all the resistors and glass encapsulated components a uniform colour, though if you left a resistor in too long it came out with shiny metal end caps and a very easy to see carbon or metal film.

Did nothing to epoxy that IC's are made from, though we did lose a fair number of ceramic package lids in it, all of them the cemented type. Soldered and glass frit survived no problem.

AJ3G:
I thought this may not be as straightforward as I thought. I was terrible at Chemistry in University.  I looked at some videos, ad I saw someone using a teaspoon of lye, and boiling water to accomplish the job. 

What I have done is purchased 4 of the boards, and will try a few approaches before doing the one I want to keep. The boards are $1.50 a piece, and no, I am not mining for precious metals, but intend on using the board but need the mask removed to implement/modify the board for my application. 

Typically I would just have some boards made, but I cannot purchase the boards from any vendor after designing them for the price this vendor is dumping a board that will work.  Kind of a odd request I know..

magic:
OP gave up so let's hijack the thread :)

I got some 85% formic acid for other purposes and tested what happens to a piece of PCB immersed in it.

Three days later:
FR4 soaked it up and increased in thickness from 1.2mm to 1.55mm :scared:
Soldermask is easily scratched off from copper but still adheres to the laminate.

A small trace in the corner of the sample separated from the substrate and the soldermask. Copper wasn't appreciably dissolved, but one side carries some dark residue. No obvious loss of mechanical strength in either of the separated pieces.

Effective but not without side effects :P

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