Techniques for cleaning flux off PCBs


#1

What are other DIY’ers doing for board cleaning? No-clean flux and forget it? Rosin-core and IPA? Ultrasonic baths?

My practice in the past has been to use 99% IPA, a tupperware tray for soaking, and an old toothbrush, but I recently switched to this Sparkfun lead-free solder with a water-soluble flux.

IPA doesn’t do a very good job on this, and I finally tracked down the manufacturer recommendations on the flux, which is to water-wash without cleaning agents:

http://documents.indium.com/qdynamo/download.php?docid=373

I’m going to try doing the same tupperware/toothbrush strategy that I used with IPA, plus drying with compressed air and/or a heatgun. But I see people online using ultrasonic cleaners, special PCB spraying equipment, even dishwashers(!!) Anyone have good anecdotes?


#2

Oof:

http://www.circuitinsight.com/programs/50203.html

We have seen people try to use DI-water, for example, on the bench top. This is futile. If the water is pure enough to be an aggressive cleaner, it instantly will become contaminated as soon as the bottle or container is opened, and at that point you might as well be cleaning with distilled water and save some money… The only viable option is a tightly-sealed, closed-loop system which purifies the water, performs the cleaning task, and then recycles the water. These tend to be expensive, energy-hungry, and relatively slow in through-put.


#3

Here at LZX we use 99.9% isopropyl and an ESD safe brush (toothbrush style) for just about anything that needs cleaning up. For production soldering though, it’s an MG Chemicals SAC305 lead free no clean solder that doesn’t require cleanup.


#4

Thanks, those are great tips! The no-clean MG SAC305 looks very tempting, I will probably try a roll of that when I use up my Sparkfun rolls.

I went ahead and cleaned my Castle boards with distilled water; Sparkfun wasn’t kidding about the flux being water soluble, the mess washed up very easily. Some gentle squirts of distilled water and scrubbing with a denture brush (stiffer than a toothbrush, with a wide-bristle side and a long narrow side, but I should upgrade to an ESD-safe one) did a really nice job cleaning up the boards. Used a hot air gun at low temp to dry them out. Putting water on electronics felt VERY WEIRD and uncomfortable… but so far, so good.

I asked the same question over on lines, it turns out monome uses this Sparkfun lead-free also. https://llllllll.co/t/state-of-the-art-smd-diy-best-practices/6772/30