removing conformal coating - Page 1
Forum section: electronics / beginners

author: Hendrik
author_rank: Contributor
timestamp: March 30, 2023, 01:17:57 am
content: Hello,as I am currently repairing a Fluke 335D I am now looking for an effective way to remove the conformal coating at the places I need to solder new components in.For the few places I've done so far I used a glassfiber pen to carefully scratch the coating away. But the glass fibers and dust it leaves behind are not pleasant at all. Are there better alternatives (chemicals, or just sand paper for example)? It seemed pretty resilient to IPA.Kind regards,Hendrik

author: coromonadalix
author_rank: Super Contributor
timestamp: March 30, 2023, 02:08:42 am
content: some brand dissolve with acetone, try with a cotton swab to see if it melt / dissolve ?not plunging the board in acetone loll some people forced their way with re heating the solder smell and vapors warnings

author: Terry Bites
author_rank: Super Contributor
timestamp: March 30, 2023, 10:20:16 pm
content: After many solvent fails (including satans xylene), I had some success with graffiti remover solvent on a cotton bud.If I had any I was going to have a go with DMSO, "the green" painstripper.Test before you try!

author: jpanhalt
author_rank: Super Contributor
timestamp: March 30, 2023, 11:20:30 pm
content: "Green" paint stripper used to use NMP (https://en.wikipedia.org/wiki/N-Methyl-2-pyrrolidone) as a substitute for chlorinated hydrocarbons and other aggressive solvents. It's not quite as green as originally thought, but it is a greatsolvent.As for your question, it depends on what the resist is. If it's an acrylic, then a lot of solvents, including but not limited to dichloromethane ("methylene chloride" and other names) will work, as may acetone, MEK , and lacquer thinner. If it's polyurethane , silicone, or epoxy, I recommend simply abrasion. Sulfonic acids (e.g., heptane sulfonic acid or mixed alkyl sulfonic acids) will work to denature (chemically char) the resist, but they will also damage the PCB. Think about it, anything that will dissolve an epoxy will damage the PCB.For small amounts of silicone, you can try a mixture of isopropyl alcohol and mineral spirits (I prefer VM&P Naphtha). The IPA will tend to break the adhesion and the naphtha acts as a lubricant. I have used that to remove residual silicone caulking.If you can solder through it, try that; otherwise, stick with abrasion.

author: Hendrik
author_rank: Contributor
timestamp: March 31, 2023, 06:25:39 pm
content: Thank you guys for the informations.I tried soldering through it which (with IPA cleaning after desolder) came out surprisingly clean:Not any worse than my solder with scratched of coating before:I've ordered some acetone and will try that out as soon as it arrives. But with the results from just soldering through it, aside from the smell and vapors, it's hard to beat.

author: jpanhalt
author_rank: Super Contributor
timestamp: March 31, 2023, 07:41:23 pm
content: Acetone will probably work, but real "lacquer thinner" (not the "green stuff") would probably be cheaper and maybe a little better as it evaporates more slowly than acetone.

author: MathWizard
author_rank: Super Contributor
timestamp: March 31, 2023, 09:24:21 pm
content: Don't use 2-4-5 Trioxin, it's hard on the skin and brain.

author: penfold
author_rank: Frequent Contributor
timestamp: March 31, 2023, 11:18:26 pm
content: Could you try the fiberglass pen but continuously wetted with IPA or similar to avoid airborne dust? As far as other abrasives, I think most would be too harsh on the substrate, but if you were careful with the application and focus only on the tracks, pumice powder (0 or 00 grade) might be OK (again, keep wetted as a paste). Ground walnut shells are used professionally in micro media-blasting to remove CC so might also be OK as a paste.