How to remove "SOLID ROSIN FLUX PASTE" from PCB ? - Page 1
Forum section: electronics / beginners

author: breakz
author_rank: Newbie
timestamp: August 11, 2017, 01:01:16 am
content: hey guys !good to find you !I am starting using flux and today I was trying to clean some pads from solder and I diped the solder wick into thishttp://www.ebay.com/itm/1Pc-15g-Solid-Rosin-Welding-Soldering-Flux-Paste-High-purity-Repair-Durability-J-/132274863668?hash=item1ecc323e34:g:nOgAAOSwjtNZeVecalong with the soldering iron to melt it and then the solder wick did a great job cleaning the pads from solder but the pcb has the rosin residues all over the pads,so I wanted to ask you what is the best way to remove it ,it became stable/solid.thanks !

author: edpalmer42
author_rank: Super Contributor
timestamp: August 11, 2017, 03:01:46 am
content: I prefer to use Isopropyl Alcohol and a cotton swab instead of Acetone. Acetone is too hard on some plastics. If I need something more aggressive, I use a commercial Flux Remover.Ed

author: xrunner
author_rank: Super Contributor
timestamp: August 11, 2017, 03:04:04 am
content: Quote from: edpalmer42 on August 11, 2017, 03:01:46 amRight 90% + alcohol works well.

author: dave_k
author_rank: Frequent Contributor
timestamp: August 11, 2017, 03:24:21 am
content: Chemtronics ES897BE is nice to use.

author: netdudeuk
author_rank: Frequent Contributor
timestamp: August 11, 2017, 04:18:25 am
content: Quote from: edpalmer42 on August 11, 2017, 03:01:46 amI was using IPA with a new toothbrush and found that the joints went from bright and shiny to dull and grey. I moved onto cotton buds and IPA and even now the joints loose their proper appearance. That's with decent MG Chemicals lead based solder and a Chemtronics flux pen.

author: David Hess
author_rank: Super Contributor
timestamp: August 11, 2017, 04:29:08 am
content: Isopropyl alcohol is one of the safer options. Toluene, acetone, and lacquer thinner are more aggressive but can damage some plastics. I keep dispenser bottles with isopropyl alcohol and lacquer thinner. I use the lacquer thinner with cotton swabs or paper napkins to keep from damaging anything while the isopropyl alcohol can be used with an old tooth brush.Rosin flux thinner is or was commonly 50/50 isopropyl alcohol and toluene. I still have a few bottles like this. If I had to make some though, I would probably mix isopropyl alcohol and acetone which is miscible with water.

author: netdudeuk
author_rank: Frequent Contributor
timestamp: August 11, 2017, 04:33:38 am
content: I've wondered if the IPA was dissolving the toothbrush bristles. I had an eBay PCB brush and that left a residue. I know some people use brushes with natural bristles but I'd prefer not to.

author: David Hess
author_rank: Super Contributor
timestamp: August 11, 2017, 04:39:36 am
content: Quote from: netdudeuk on August 11, 2017, 04:33:38 amNot that I have ever noticed. My old toothbrushes have put up with all of the solvents I mentioned without problems. Sulfuric acid will melt the bristles though which is consistent with them being made from Nylon.

author: BravoV
author_rank: Super Contributor
timestamp: August 11, 2017, 04:43:10 am
content: Quote from: netdudeuk on August 11, 2017, 04:33:38 amMostly the residue is from dirty bristles when using purely IPA with toohbrush from my experiences, clean it thoroughly or just use new one. IPA wont dissolve nylon brush at all.Try a drop of IPA on a clean glass surface, rub it with your brush, then blow it dry with you breath, observe the surface, if there is a haze or thin film formed when the IPA evaporated, then the brush is dirty. Assuming the IPA is not contaminated of course.Also certain natural bristles like from animal hair, will leave residue when in contact with IPA, probably some chemical left in it when the manufacturer processed the hair.

author: edpalmer42
author_rank: Super Contributor
timestamp: August 11, 2017, 05:14:06 am
content: One time I got tricked. I thought I was buying 95% isopropyl alcohol, but what I got was 95% anhydrous ethanol with a few other ingredients. I keep it for junk cleaning jobs and don't use it on circuit boards. I suspect it would leave a residue on a sheet of glass.Ed

author: rdl
author_rank: Super Contributor
timestamp: August 11, 2017, 05:34:18 am
content: Generally speaking, for anything that's soluble in alcohol, ethanol will work better than isopropanol. I don't know for certain if that's the case with solder flux or rosin.