Cleaning off flux pen residue - Page 1
Forum section: electronics / general

author: bd139
author_rank: Super Contributor
timestamp: December 13, 2017, 09:37:08 pm
content: So I’ve got my first batch of boards from oshpark and have populated them meticulously by hand. I’ve used a Chemtronics rosin based no-clean flux pen to do the work. I’ve cleaned up with 99% IPA and a soft toothbrush then rinsed with distilled water and dried with compressed air.However the surface of the board is still slightly sticky after this process. Is there a better way or product to clean the boards with?

author: ataradov
author_rank: Super Contributor
timestamp: December 13, 2017, 10:15:38 pm
content: Just more alcohol. I typically put boards in a sealable bag or a container with a bit of alcohol and agitate them for a few minutes.Works all the time. Works much better with no-clean flux paste, since it leaves less hard residue to begin with.

author: bd139
author_rank: Super Contributor
timestamp: December 13, 2017, 10:17:24 pm
content: Excellent. Will try for longer then. Thanks for the tip.

author: Kean
author_rank: Unknown
timestamp: December 14, 2017, 01:29:11 pm
content: Yeah, generally with any solvent all you can really do is keep diluting the contaminant. And as the flux will end up contaminating the solvent bath, you probably need to go through several fresh baths of IPA/solvent to get a decent level of cleanliness. It may be better in some instances to use a spray rather than a bath - with the run-off not being used again (except maybe a first pass clean).No clean fluxes are generally a pain to clean. Something like the Electrolube Safewash SWAS works a treat as it "captures" the flux residues, rather than just diluting them. And you can rinse with distilled water.Always check your components for compatibiliy with any solvent or cleaning process. e.g. I've had expensive LEDs and sensors that were damaged by solvent cleaning. Even switches or connectors can get fouled by the dilluted flux and cause reliability issues. There are ways you can (try to) mask the parts that need protection.

author: montemcguire
author_rank: Regular Contributor
timestamp: December 27, 2017, 07:23:13 am
content: Not trying to be a jerk, but if you use no-clean flux, why do you want to clean the PCB? It sounds like more work and the possibility of driving flux or solvent into parts that don't want to see any of that. On the positive side, left-over flux can act as a corrosion inhibiter if you leave it alone, so I'm of the opinion that if you use no-clean, don't clean it. OTOH, if you need really high impedance boards or are going to conformally coat the boards after assembly, then perhaps some of the 'must-clean' fluxes would be easier overall, since they are easier to clean.I guess it depends on what kinds of components you have on the PCB and how resistant to solvents or cleaning in general they are.

author: JustMeHere
author_rank: Frequent Contributor
timestamp: December 28, 2017, 04:44:12 am
content: I find immersion does a good job. I also brush. Make sure to keep the brush immaculately clean. Use a paper or cloth towel and occasionally use it to clean the resin from the bristles. I also have some wood handle cotton swabs that I use to really polish up a board.

author: bd139
author_rank: Super Contributor
timestamp: December 28, 2017, 11:29:25 am
content: Thanks all. I just ordered some from RS and will build a board with it.Makes sense really. I’ll use no clean stuff for repairs only from now which won’t get washed.