PCB Cleaning - Ultrasound? - Page 1
Forum section: electronics / projects

author: digsys
author_rank: Unknown
timestamp: June 09, 2013, 04:46:49 am
content: Anyone have actual experience with cleaning post-production PCBs using Ultrasound or something similar?Quantities are climbing and hand cleaning is becoming boring :-)I need them sparkling clean, especially in between all SM IC pins. I've seen plenty of options, but I just want someone's personal experience.

author: Rerouter
author_rank: Super Contributor
timestamp: June 09, 2013, 10:56:24 am
content: depending on the components your using, ultrasonic can crack dies and snap bond wires as a small fault mode, if you turn the power down you can get around it but there is always the risk,

author: IanJ
author_rank: Unknown
timestamp: June 09, 2013, 12:05:09 pm
content: Freon in an ultrasound cleaner bath was the way I used to clean all my boards, it left no residue and totally dry after a couple of minutes......but alas Freon is a big no-no these days (CFCs).So whilst there are alternatives I never could find anything as quick, easy and as good at cleaning flux off boards in the bath............but that was a few years ago right enough so I'm sure there are pretty good alternatives nowadays.Interesting point from Rerouter........I never had a problem with anything cracking.....but maybe my bath wasn't very powerful. 30secs was the minimum time we ran for most pcb's.Ian.

author: nukie
author_rank: Frequent Contributor
timestamp: June 09, 2013, 01:18:16 pm
content: Talk to Chemtools they are very helpful. I use their water based PCB cleaner in ultrasonic tank it works great.

author: digsys
author_rank: Unknown
timestamp: June 09, 2013, 02:26:04 pm
content: Yeah, I wasn't sure if cracking through cavitation was still an issue, or if others had a way around it.I can't ring anyone until Tue, so I thought I'd get a few ideas.

author: robrenz
author_rank: Super Contributor
timestamp: June 09, 2013, 03:20:05 pm
content: Just remember a ultrasonic cleaner is just an efficient unit fordislodging/dissolvingdebris from surfaces and crevices. The debris and soluable materials are still in the solution and become higher and higher in concentration as you clean more boards. You are just re-applying a more uniform coating of crap if you don't rinse with virgin/clean solvent after the ultrasonic dunk.

author: G7PSK
author_rank: Super Contributor
timestamp: June 09, 2013, 03:33:03 pm
content: Ultrasonics clean by cavitation this will also eat your boards away if left too long. I used to use ultrasonic cleaner with Toluene for watch cleaning many years ago, one day I went for lunch leaving some parts in the machine when I came back some of the cogs had holes right through them.

author: uoficowboy
author_rank: Regular Contributor
timestamp: June 09, 2013, 03:58:09 pm
content: Ultrasonic cleaning always sketched me out.A PCB assembly house that I use uses a dishwasher machine to wash PCBs. They put in a special "soap" in the machine that is targeted at the flux that they use, but the machine is just a normal every day dishwasher.My technique, which I stole from a former colleague:Get three pans with lids, each big enough to lay your PCB down flat in. Label one "dirty", one "medium", and one "clean". Associate an acid brush with each pan. Put enough IPA in each to completely cover your PCB. Drop your PCB in the dirty one and let it sit for a minute, then scrub away at it with the dirty acid brush. Remove it from the dirty container, shake out the PCB, then throw it into the medium. Same steps as before, then move it to the clean. Same steps - and then just let it dry and you should have a clean PCB. After the "clean" container starts to have some residues in it, dump the dirty, and transfer the medium to the dirty, the clean to the medium, and put a fresh bath of IPA in the clean.

author: Rufus
author_rank: Super Contributor
timestamp: June 09, 2013, 04:09:17 pm
content: Quote from: robrenz on June 09, 2013, 03:20:05 pmYou need to rinse multiple times to progressively dilute the crap. You only need (nearly) virgin/clean for the last rinse. It you are using water based cleaning you can use tap water for the initial clean and first few rinses.I processed a large batch of boards which had problems with leakage from flux residues under some large SMT passives. I used something like thishttp://store.aqueoustech.com/ProductDetails.asp?ProductCode=PCB-Washat I think 60C in an ultrasonic bath for 10 minutes followed by 4 tap water rinses and 2 in de-ionized water baths.Quote from: G7PSK on June 09, 2013, 03:33:03 pmPutting a sheet of aluminium cooking foil in a bath and checking the production and distribution of holes in it is commonly used to test ultrasonic bath functionality.You should have got one with a timer - lol.

author: digsys
author_rank: Unknown
timestamp: June 09, 2013, 04:53:09 pm
content: Well, my current process is -SWA Aqueous foam - scrubbed with a toothbrushIPA Cleaner - rinse and blow dry (compressor)FLU Fluxclene - for the sparkly effect. Where there are lot of very fine pitch ICs etc, I have to run #3 a couple times (+)Wonder if FLU is explosive in an U/Sonic cleaner :-)I'd like to TRY to avoid having pots and pans etc FULL of liquids lying around though.