Removing potting material from PCB? - Page 1
Forum section: electronics / repair

author: Fried Chicken
author_rank: Regular Contributor
timestamp: February 02, 2025, 10:46:04 pm
content: I have a car with an original amplifier from 2003 (both subwoofer and main amp), and having lost my recapping virginity I want to go and recap every board in my life.When I went to open it up, I was greeted with probably one of the most beautiful PCBs I've ever seen. Shiny, clean, beautiful.The issue is the entire thing has a light transparent covering of some sort of potting material or otherwise.I was initially tempted to just go in with heat soldering through everything, but now I'm erring on the side of doing things properly.What are the best options for tackling something like this? The PACE soldering videos only touched on PCB coverings without detail on working on them

author: jpanhalt
author_rank: Super Contributor
timestamp: February 02, 2025, 11:28:54 pm
content: That sounds like a conformal coating for protection from the elements. Some of those coatings are like an acrylic lacquer and can be removed easily with solvent. They may also be epoxy or polyurethane. Those are not so easily removed. Test a small area with acetone, MEK, or lacquer thinner. If that doesn't work, you are probably stuck doing spot removal mechanically, like with a fiberglass scratch brush.

author: Fried Chicken
author_rank: Regular Contributor
timestamp: February 02, 2025, 11:56:16 pm
content: Quote from: jpanhalt on February 02, 2025, 11:28:54 pmConformal coating! That's the word.What about the underlying plastics, PCB material, transistor plastics, etc?Are these compatible with solvents generally?

author: jpanhalt
author_rank: Super Contributor
timestamp: February 03, 2025, 12:19:25 am
content: Epoxy and polyurethane are generally pretty safe with the solvents I mentioned. Acrylic, polycarbonate, polystyrene, PVC, and ABS plastics are not. Optical windows may be made of polystyrene, acrylic, or polycarbonate (e.g., LEDs). You need to be careful with those. Just test a portion of the board where the conformal coating is. There is no need to remove all of it.

author: Fried Chicken
author_rank: Regular Contributor
timestamp: February 03, 2025, 12:29:06 am
content: Thank you for lending me clarity in this.

author: garrettm
author_rank: Frequent Contributor
timestamp: February 03, 2025, 01:14:55 am
content: The PACE instruction video series does go over removing conformal coatings--generally by using abrasion, but sometimes by simply heating with the soldering iron (e.g. polyurethane). Solvents are situational and can require good ventilation and use of gloves. I generally avoid using solvents unless absolutely required.If the board uses epoxy encapsulation, you can use a pressure cooker (with water!) to heat the epoxy to the "glass transition" temperature where hard epoxy becomes rubbery and you can scrape it off with a small screw driver (comes out in chunks). There are videos on YouTube that show this process specifically for fixing automotive controller modules.

author: tooki
author_rank: Super Contributor
timestamp: February 03, 2025, 01:39:15 am
content: FWIW, I recently had to remove potting from a PCB. It had not-quite-hard potting compound that could very slowly be cut away. Only when I was about 90% of the way through did my dumb ass think to try applying heat, which softened it immensely. It was almost certainly polyurethane.

author: tooki
author_rank: Super Contributor
timestamp: February 03, 2025, 01:41:23 am
content: Quote from: Fried Chicken on February 02, 2025, 10:46:04 pmThe soldering series does not. But the “Adventures in Repair” series they made absolutely does. It’s hokey as hell, but as usual the information quality is top notch. Here’s part 1 of 3:

author: tooki
author_rank: Super Contributor
timestamp: February 03, 2025, 01:43:40 am
content: See also this Pace video which, for some reason, is on Marc Siegel’s* personal channel instead of Pace’s:*Descendant of Pace’s founder

author: Fried Chicken
author_rank: Regular Contributor
timestamp: February 03, 2025, 02:12:39 am
content: Quote from: tooki on February 03, 2025, 01:41:23 amThis doesn't cover the conformal coating, just digging into the board. I know b/c I watched that whole series lol

author: tooki
author_rank: Super Contributor
timestamp: February 03, 2025, 03:19:33 am
content: Hmm… there may be other videos, then. I know for certain that some Pace video covered it, because I remember the demonstration of the tool used.