Cleaning Flux Off PCB With Ultrasonic Cleaners - Page 1
Forum section: electronics / projects

author: LaserTazerPhaser
author_rank: Regular Contributor
timestamp: August 24, 2018, 04:17:10 am
content: Would a ~35w ultrasonic cleaner with warm 99% IPA clean some reputable branded "No Clean Flux" off a PCB? I read No Clean Flux paste hardens up and becomes difficult to remove.

author: metrologist
author_rank: Super Contributor
timestamp: August 24, 2018, 04:40:47 am
content: My cleaner is larger and I had mixed results with hardened flux. About half came off with soap/water. I would expect IPA to work much better. An you may still need to brush.

author: CJay
author_rank: Super Contributor
timestamp: August 24, 2018, 09:29:23 am
content: Yes, probably but a warm bath of isopropyl alcohol that's being agitated is not something I'd want in my workshop, it's a fire hazard.There are aqueous cleaners designed for flux removal in ultrasonic baths that work really well.Thye aren't cheap but they won't burn your workshop down.https://www.chemtronics.com/flux-off-aqueousThere may well be others that are effective, the Chemtronics stuff is what I've used.

author: Cloud
author_rank: Regular Contributor
timestamp: August 24, 2018, 10:26:30 am
content: I use flux cleaner in can with brush to clean burned flux than I put PCBs in ultrasonic where is flux cleaning solution heated to 70C.If you don't clean burned flux with brush, ultrasonic cleaner won't clean properly.

author: LaserTazerPhaser
author_rank: Regular Contributor
timestamp: August 25, 2018, 08:35:11 pm
content: Quote from: CJay on August 24, 2018, 09:29:23 am

author: IconicPCB
author_rank: Super Contributor
timestamp: August 26, 2018, 12:36:50 am
content: There was an opinion in the decades past that ultrasonic cleaning does more harm than good to the internals of an IC.More specifically micro wires could fatigue and break under severe agitation.

author: CJay
author_rank: Super Contributor
timestamp: August 28, 2018, 08:32:55 am
content: Quote from: LaserTazerPhaser on August 25, 2018, 08:35:11 pmI wasn't worried about the vibration igniting it, I was more worried about the cloud of flammable vapour that's created by warming the stuff and then agitatiing it to disperse it but if you're happy with vaporising half a litre of flammable liquid in your workshop then go for it, I still recommend the aqueous flux cleaners.

author: nukie
author_rank: Frequent Contributor
timestamp: August 28, 2018, 10:35:43 am
content: IPA as a flux cleaner is a waste. I use it for final rinse.For ultrasonic cleaning flux I use a biodegradable water based solution, works surprisingly well for a biodegradable product which is always rubbish.http://www.chemtools.com.au/product/electrical-electronics/electronics-cleaning-chemicals/pcb-flux-remover/It's also a strong degreaser can be used for cleaning parts before plating. It has a very long shelf life suitable for occasional hobby use, in my case 5 years. Highly recommended.

author: IanJ
author_rank: Unknown
timestamp: August 28, 2018, 11:09:51 am
content: Here's my experience/notes in regard to pcb ultrasonic cleaners:Freon:This stuff was great, fast, no heat req'd usually, all flux removed, pcb spotless and no marks, no rinsing or forced drying req'd.We even used to filter the dirty stuff through a stocking to extend it's life.Unfortunately it's a CFC so banned.Modern water based solutions:Needs harder/longer cleaning with heat and on lower power cleaners requires brushing/agitation also. Pcb's need rinsed with water & forced dried afterwards.With work just as good final results as Freon.IPA:Too dangerous due to extremely low flash point.Can be harmful to certain components like pcb switches.Flux/Pastes:Worth experimenting with different solder fluxes & pastes to find which ones are more readily cleaned off the pcb's.Worth using IPA with a brush by hand to remove stubborn flux before ultrasonic cleaning.Vibration causing damage:I have never worried and never experienced any failures of components (small workbench type cleaners).Ian.

author: mark03
author_rank: Frequent Contributor
timestamp: August 28, 2018, 07:57:16 pm
content: Quote from: IanJ on August 28, 2018, 11:09:51 amAny thoughts on frequency-swept vs non-swept models? I have been confused by the affordable options; it's not at all clear to me whether there is a significant difference because the sweep range is often pretty narrow. The choice seems to be, get a brand-name unit marketed for electronics use ($$$), or take your chances on anything else.

author: Dr. Photon
author_rank: Contributor
timestamp: August 28, 2018, 08:32:14 pm
content: I've usually cleaned boards with either ethanol/denatured alcohol (I like to buy it in gallons and put into spray bottles) or chlorinated brake cleaner (the non-chlorinated is a bit harsh on plastics). I usually spray and wipe with a cheap toothbrush briefly, then do a final rinse off.I've usually felt that the "electronics flux cleaner" products were a bit on the harsh side, and isopropyl was too weak save for a final rise off.