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Cleaning dirt/dust from PCB

Discussion in 'Electronics & Electrics' started by DRAGONKZ, Dec 2, 2018.

  1. Aetherone

    Aetherone Member

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    Adelaide, SA
    I've resurrected more than a few beverage drowned keyboards with this protocol. Laundry sink full of painfully hot water and dishwashing detergent (I like Morning Fresh Lemon scented) for a soak, then a scrub, then a rinse in equally painfully hot plain tap water, followed by a liberal spray bottle distilled water rinse and finally a super generous alcohol spray bottle rinse. 99% IPA is expensive when bought in the Jaycar 125/250ml bottles but cheap in a 5/20lt tank.

    ProTip: Don't use a scrubbing brush on your LGA socket...

    Without active power, water isn't instantly harmful to electronics.
     
  2. merlin13

    merlin13 Member

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    Aaaah, the 1.1.1 Trichloroethylene - Liquid Paper Sniffers of the World, Unite... from memory I vaguely recall some mutterings that they were going to ban that shit a few years ago?

    Anyway, be VERY careful using that on assembled boards.

    Story Time...

    Back in the dim dark days caused a major (!) shitfight in a company yonks ago where the design engineers and production actually starting making a new product with polycarbonate high-voltage isolation panels attached to it.

    1.1.1 Trico doesn't eat polycabonate, it actually perishes it into a brittle material that breaks off into small chunks and a fine powder.

    At the time I was using spray tins containing the stuff in high percentage in the R&D hardware lab, Production were buying it in 10 and 20 litre bottles for board cleaning in the ultrasonic baths. Not exactly healthy for the lungs etc either, but again this was back in the dim dark days.

    Used it to clean some reworked boards and it promptly borked the isolation panels. Took 'em to the QA and design engineers to point out a slight (!) problem (hey, it was only 5kV isolation, orright?...), pointed and said" You've got a slight problem".

    Had the design team, production engineers, purchasing group and the QA department panicking for DAYS until the team leader and his designers all finally wandered back up to the workshop to ask me just WTF had I done.

    Showed them the tins of bog-stock electronics spray cleaner cleaner the Company was using, demonstrated how it ate the polycarb and said "Told you lot when I started here about this nasty stuff, and THIS is why I wanted the air booth up here, but Nooooo, you all said I was full of shit. Do I get one now?".

    R&D Manager wasn't impressed. The Company Directors thought it was funny as hell, until they worked out what it had actually cost them in delays and manpower... didn't get my air booth either (bastards).

    For some funny reason all stocks of the cleaner were thrown out and they went to Isopro. And when the Production staff started getting high on the fumes from that (and the curious incident of a couple of staff in the lunch room with the bottle of orange juice...) THEY got a good air booth (bastards).
     
  3. mtma

    mtma Member

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    IPA is relatively benign on the whole, that's one of the reasons why it's so ubiquitously recommended as a solvent. The increasingly exotic solvents often have some material compatibility issues that result in exactly those similarly exotic results.

    Speaking of exotic has anyone ever tried CO2 dry cleaning? :leet:
     
  4. Technics

    Technics Member

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    I do genuinely have a drum of the stuff in the shed but I don't really use it to clean PCBs. It's a phenomenally good degreaser that leaves no residue. It's funny that a lot of chlorinated solvents were replaced with brominated ones (I.e. bromopropane) because of health and safety concerns. Those alternatives turned out to be more dangerous and have now been pulled from the market. Most remaining alternatives are flammable. Aqueous solutions seem to be the way things are heading for PCB cleaning though. I use TCE for cleaning mechanical watches but will only use it when aqueous solutions in an ultrasonic cleaner can't finish the job.

    I have a CO2 bottle and have always wanted to try it on optics but the Venturi nozzles designed for the job were very expensive when I looked into it.
     
  5. merlin13

    merlin13 Member

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    Speaking of toxicity, I'll top your drum of 1.1.1 with my gallon tin of creosote lurking in one of the sheds somewhere. My shit doesn't evaporate, terrible for cleaning as well... :)

    Remind me and I'll ask a watchmaker mate of mine what he uses in his 'sonic bath when I see him later in January...
     
  6. elvis

    elvis Old school old fool

    Joined:
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    https://www.jaycar.com.au/conductive-brush/p/TH1775

    Get one of those, attach a ground wire to it. Winning.

    Just watched it. Brilliant stuff.

     
    Last edited: Dec 27, 2018
  7. Technics

    Technics Member

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    It's getting a bit off the PCB topic but I've experimented with the traditional (some allegedly used for well over 100 years) DIY watch/clock cleaning solutions. Other than solvents like acetone, strong ammonia and oleic acid are common ingredients because they form ammonium oleate soap which does a great job of picking up the oils and the excess ammonia dissolves the oxidation and brightens everything up. Apparently cast brass can suffer from stress corrosion cracking in the presence of ammonia so it's avoided on anything with cast plates.

    Even some modern solutions designed for ultrasonic cleaning (such as L&R 111) still contain those two ingredients. It would probably work quite well if you had some old tarnished PCB blanks or perhaps older finished but unpopulated boards that had only been protected with OSP. Oxalic acid is another interesting chemical because it happily dissolves iron oxide. I haven't tried it on anything rusty yet but it is tempting.

    The challenge with watches is cleaning well while not dissolving the shellac holding some of the jewels in place.

    Just watched it too. Very informative. Now I remember the HF I have in the shed as well. I might get strange looks from the other half if i don the PPE required and use it to do the dishes though.
     

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