What Solvent to Remove Silicone Conformal Coating? - Page 1
Forum section: electronics / beginners

author: KDoug
author_rank: Contributor
timestamp: October 15, 2018, 09:24:35 pm
content: Hi, I have made a repair to a circuit board on a power tool. I'm trying to remove the old silicone coating so I can apply a new coating. There are two different coatings, the first is a clear silicone, and the second is a potted type white silicone. Acetone has softened it up quite a bit and I was able to get the bulk off with a pick, but there is still a lot of little pieces left. What do y'all use? I'm new to this kind of stuff, any help would be appreciated.Thanks

author: vk6zgo
author_rank: Super Contributor
timestamp: October 16, 2018, 12:51:46 am
content: If you have a lot of little bits left, I'm doubtful about how useful a solvent will be.You could try mineral turpentine----it doesn't dissolve anything, but penetrates into whatever gaps there are& breaks the adhesive bond .It is horribly messy & smelly, though.Another possibility is baby oil, which seems to have similar characteristics.It will lift, in an instant, wound dressings which seem to resist any other type of encouragement to come off.

author: james_s
author_rank: Super Contributor
timestamp: October 16, 2018, 12:53:37 am
content: Silicone is extremely inert, it's very difficult to find anything that will dissolve it. Your best bet is probably soften it with acetone since that seems to work then remove it via mechanical means. Seems easier to just remove it from the spot you need to repair and leave the rest alone.

author: KDoug
author_rank: Contributor
timestamp: October 16, 2018, 02:24:40 am
content: Thanks for the suggestions, I was more curious about some of the products that are designed for stripping conformal coatings.Here's what I've found so far:https://www.amazon.com/MG-Chemicals-Conformal-Coating-Stripper-Pen/dp/B077SXSJF1(Not sure how well these pens work, but for one job it can't be that bad right?)http://siliconesolutions.com/ss-sr.htmlhttps://www.amazon.com/MG-Chemicals-Conformal-Coating-Stripper/dp/B01N5VI0KAhttps://www.alliedelec.com/techspray-2510-p/70207178/(Can be found cheaper)

author: jpanhalt
author_rank: Super Contributor
timestamp: October 16, 2018, 05:49:08 am
content: @KDougOnly checked this one:http://siliconesolutions.com/ss-sr.htmlContains dodecylbenzenesulphonic acid. Sulphonic (alternatively sulfonic) acids are strong acids (similar to sulfuric acid). A hydrophobic side chain (dodecyl + benzene = C12+benzene) is added to facilitate penetration of the silicone. Every effective remover for cured silicone I know of works on the same principle. The sulfonic acid denatures the silicone and weakens its bond to whatever.It works, but what will it to the electronics and FR4?

author: KDoug
author_rank: Contributor
timestamp: October 16, 2018, 11:07:58 am
content: Quote from: jpanhalt on October 16, 2018, 05:49:08 amThanks for deciphering that, I was wondering if it was rated for electronics. I found the data sheets on two MG Chemicals products, let me know what you think about the ingredients.https://www.mouser.com/ds/2/265/tds-8309-1154460.pdfhttps://www.circuitspecialists.com/pdf/8310-liquid.pdf

author: jpanhalt
author_rank: Super Contributor
timestamp: October 16, 2018, 11:24:04 am
content: The first is just a mixed solved that includes acetone and di-ethers. It does not denature or cause cured silicone to dissolve. it does:QuoteI have used isopropyl alcohol in a hydrocarbon solvent (e.g., VM&P Naptha) to do the same. Takes time and elbow grease, but it does help remove a thin film. Probably will not work on bulk silicone.The second includes slightly stronger organic ester solvents and "1-methyl-2-pyrrolidinone." That latter chemical has interesting solvent properties. It will dissolve/denature/soften cured enamels and is included in several "green" paint removers, including PeelAway. Unlike methylene chloride based paint removers, the enamel doesn't bubble up but rather becomes gummy and can be scrapped off relatively easily. As I recall, it is also included in one of the developers for DuPont's dry resists. (https://en.wikipedia.org/wiki/N-Methyl-2-pyrrolidone)Of the two choices, I woud try the second with the 1-methyl-2-pyrrolidinone.

author: KDoug
author_rank: Contributor
timestamp: October 18, 2018, 12:07:55 am
content: Thanks for pointing out about the first option, looks like the second option was discontinued though. Looks like I'll just have to use acetone and a black light and be patient scraping it off. I just figured there was something easier than what I was doing. I'd rather not deal with the very harsh chemicals that some of you pointed out, but I do appreciate y'all taking the time to comment.