Soaking PCBs in 99% IPA to remove dust - Page 1
Forum section: electronics / repair

author: matthuszagh
author_rank: Frequent Contributor
timestamp: November 14, 2020, 04:12:15 am
content: I bought a tektronix tds7104 oscilloscope from ebay that has a lot of internal dust. I disassembled the instrument and did my best to remove the dust with a combination of an ESD-safe vacuum and lint-less swabs with IPA. This helped a bit, but the dust is a very fine powder. The vacuum was very effective for the large dust but minimally effective for the very fine powder. The swabs were half-effective: they removed dust but also pushed it around. I'd like to be able to get the internal PCBs cleaner than that. My next plan is to remove each PCB individually and briefly soak them in 99% IPA. Then, I'd let them fully dry and reassemble the instrument. Is there any reason not to do this? I regularly clean my PCBs with 99% IPA and it's always worked well, and I've frequently seen people recommend this as a cleaner. Are there any components that could be damaged by a brief soak in IPA? For instance, would this weaken the adhesive between ICs and their heatsink? Anything else I'd want to be careful with?

author: wraper
author_rank: Unknown
timestamp: November 14, 2020, 04:21:30 am
content: You should have simply used compressed air. IPA will not "disappear" the dust by simply soaking it, it has to go somewhere. Otherwise you will have a swamp instead. Any dust that was soaked and dried will no longer be possible to be removed even by compressed air.

author: matthuszagh
author_rank: Frequent Contributor
timestamp: November 14, 2020, 04:24:52 am
content: Will a little humidity not have created that same effect anyway?

author: wraper
author_rank: Unknown
timestamp: November 14, 2020, 04:33:01 am
content: Quote from: matthuszagh on November 14, 2020, 04:24:52 amNo, unless there was condensation. In any case you should blow away as much dust as possible before soaking anything. And even then you will need not simply soaking but clean it with brush to wash everything away together with IPA. And then rinse again with clean IPA. Water could be much better for washing but there are more nuances in using it. And I do not recommend soaking any transformers, switches, relays (unless sealed without breathing hole) and trimmers in either.

author: PartialDischarge
author_rank: Super Contributor
timestamp: November 14, 2020, 04:43:29 am
content: My TDS744 once started having screen problems, like loss of sync. This is a known problem due to some big capacitors leaking a bit. I didnt have the time to replace them , so I opened the scope and with a 50/50 mix of water and alcohol I sprayed all over the boards in vertical position. I’m talking more than 1 liter sprayed. After that compressed air, and after that drying (much better in the summer). Problem solved and boards cleaned.

author: rvalente
author_rank: Frequent Contributor
timestamp: November 16, 2020, 05:55:28 pm
content: Water soap and a brush.Rub gently, rinse with a LOT of water. Compressed air, a little IPA to get the residual humidity off, let it dry at 40°C for 24h (carton box with a 60W bulb). DONEI've lost count how many industrial and T&M I've fixed from iron dust, grease, oil and other nasty stuff this way.There is not much else to do

author: duckduck
author_rank: Frequent Contributor
timestamp: November 16, 2020, 06:54:43 pm
content: Relevant:http://w140.com/Tek_Scope_Cleaning_by_C_Phillips.pdf

author: jogri
author_rank: Frequent Contributor
timestamp: November 16, 2020, 07:50:49 pm
content: iPA is next to useless when it comes to dissolving dust because there just isn't that much organic crap in it that it can dissolve. Might work well with flux or some sort of oils/greases, but that's it. (And it will probably also dissolve most water soluble minerals, but much slower than water).An ultrasonic cleaner might loosen the dust from the boards, but those things can also kill solder joints...Also, if you use water use either demineralized water from the beginning or wash your boards with A LOT of DI water after you cleaned them and when they are still wet. Otherwise, you'll get all sort of nice minerals crystallizing on your boards, and most of them form conductive solutions when they get wet (humidity)->no bueno. And no, just rinsing it with iPA/other organic solvents doesn't substitute the need for DI water.

author: med6753
author_rank: Super Contributor
timestamp: November 16, 2020, 10:12:02 pm
content: I've always been reluctant to give my Tek scopes a "wet wash". Too risky IMHO even with the accepted methods. And trust me, I've had some nasty basket cases to deal with. Due diligence with a vacuum and a stiff brush. Liquid cleaners such as "Simple Green" sparingly. But note that Simple Green does leave a residue. Follow up with plain water and wipe until dry. The covers CAN be given a wet wash. And for front panels plenty of liquid cleaners and cotton swabs to get the crap out of the slots in the knobs.Using this method you won't get ALL the dust/dirt but at least 90% of it and what's left won't affect anything.

author: MGaddict
author_rank: Contributor
timestamp: November 17, 2020, 05:46:23 pm
content: The reason alcohol is used instead of water 99% of the time, is because it evaporates faster than corrosion can set in. If you soak the board in alcohol, you'll be negating that property and it'll be no different than soaking it in water.I'm not at all recommending this, but I have washed a LOT of motherboards and add on cards in the sink with hot water and soap. I towel dry quickly then coat the whole thing in alcohol which "rinses" out the water. Then I set them in the dish strainer to my wife's disappointment. I always wait to the next day to apply any power, but I have yet (knock on wood) to make a board worse. This has even brought some boards back to life. I never SOAK any boards in anything. When I wash them in the sink, it's under running water for only a minute.

author: PartialDischarge
author_rank: Super Contributor
timestamp: November 17, 2020, 06:15:43 pm
content: Quote from: MGaddict on November 17, 2020, 05:46:23 pmExactly, water and alcohol forms a eutectic mixture with different properties to that of both, especially lower boiling point and vapour pressure.

author: Zeyneb
author_rank: Regular Contributor
timestamp: November 17, 2020, 07:04:49 pm
content: Hi,I'd recommend these foam cleaning swabs for applications like this. These big ones absorb a lots of solvent like IPA. For tiny areas there are also smaller tip cleaning swabs. These are also useful for car maintenance and repairs like cleaning a throttle body and even to apply paint. Amazon sells these but if you have some time you can also order them from an Aliexpress seller for much cheaper.