Eric HertzUPDATE: Ponderances of what happened and where to go from here at the bottom
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Some things were necessary... the Power-Supply PCB was held down by only two of the four screws, and the two worst-placed ones. Nearly every screw in the machine is either loose or missing.
Wherein we get down to the logic-analyzer PCB... which has a few corroded solder-joints. Alright, I'll fix 'em.
Now there's some sort of white film all over the board... could that be coming from my rubbing alcohol? A mix of that and the flux? A mix of those two and whatever weird clear coat was covering all the chips? Did I forget to rinse out the old toothbrush thoroughly enough? Alls I know is the more I try to clean it, the more it appears. Finally down to literally pouring alcohol over it, and... it's worse.
WTF. I've done my share of PCBs in my years... Alright? I mean, I hand-soldered custom PCBs for a living for years. And I've worked on countless repairs just like this... I've never seen anything like it.
It's almost like there's salt mixed in there. How the hell. 91% IPA. I've never dipped anything in it that wasn't clean (q-tips), and always poured a little into another container when I needed to reuse tools/brushes/etc that could dirty the solution, and disposed of the remainder; certainly never poured it back in... I use this same bottle for wound-care fergodsakes!
Again, this was supposed to be a one-day job. Tighten screws, resolder a couple, joints fergodsakes.
This system is possessed.
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Update: Here's my understanding of what happened:
Since I originally used the alcohol to clean up my flux only where I repaired some joints, I initially thought it was some reaction with my flux (which would've been weird, since I've done it that way on boards in the past), the flux they used originally, and maybe whatever corrosion was there. So I kept adding to the alcohol-spot-cleaning, and in a few places I think it cleared up. But, the white film seemed to expand outward in a ring/spiral... so I figured I was just pushing around the white-film outward in a spiral, and really needed to flush it off the board completely. Thus pouring the alcohol on the board, rather than brushing it around, and finding out that whatever's responsible appears not to have to do with the corrosion, nor the flux, but a chemical reaction with whatever clear-coat they put on everything(?)
The film itself can (for the most-part) be wiped-up, e.g. with a dry Q-tip. But that doesn't help between pins, etc. where it's particularly nasty-looking like it's going to short everything out. Adding alcohol makes it appear clear, again, but once it dries, it's all white.
I found this forum:
https://www.fatwallet.com/forums/technology/1335275
wherein someone suggests that the alchohol is leaching the plasticizers out of the laquer(?!)... That page is a mess of random-stuff, not at all dedicated to the topic, so I suppose I should look into how to clean leached-plasticizers, and whether I need to worry about the leaching-process having introduced conductivity...?
I'm definitely hesitant to use water to rinse it off, since it's corrosive and may have other things in it (salts) which are conductive. So, then, I suppose distilled-water? (Can I make that with the supplies/tools in my kitchen?).
Weee!
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If it has anything to do with water, it might be good to put the PCB in the oven, and bake it at about 80degC for an hour or so.
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Skip the IPA and use Acetone in open air - you don't want to breath Acetone.
IPV promotes condensation from atmospheric humidity and the conformal coating is sensitive to moisture absorption.
Some warnings. Acetone shouldn't be used with electrolytic capacitors.
Acetone could also take the marking off components that have been printed on. You can test this with some Acetone on a cotton but.
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You folks with your acetone! That stuff removes paint, melts plastic, and more... how on earth could it be safe for electronics?! And yet... you're certainly not the first to not only suggest it, but allegedly use it regularly.
Interesting point, there are no electrolytics on this board! Huh.
Just ICs, both plastic and ceramic, ceramic-caps, what looks to be a relay in an oversized plastic IC-style package, headers, and a crystal oscillator (metal can). Oh, and they decided to solder the power-leads directly to the board, almost in the middle (?!).
So, it would sound, acetone is OK on plastic DIPs (ignoring the markings, many of which are illegible through the coating)... then I guess the only other fear might be the header-plastic, and maybe screen-printing. Sounds doable, actually.
But are we trying to clean off the IPA-resultant-residue, or remove the coating altogether?
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I normally us metho to clean flux and it would have been just as bad on the board you have because metho also absorbs moisture.
It seems the coating you have there was a water or based or from an Ethylene group.
I would remove the relay first as it *will* be a plastic. IC's are normally epoxy. Just test to be sure.
If you hunt around Wikipedia then you will probably find the chemical composition of the coating.
I suggest taking it all off and using a more conventional coating.
IPV would probably work if it's in a sealed container with not too much air and left to soak for a day or so with occasional agitation.
Also - after re-reading my last post, I would like to mention that I specifically do not have a cotton but!
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I am guessing Polyurethane (not varnish). Or a hydrocarbon (turpentine or petroleum) based varnish.
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well, shee-it... I was thinking the alcohol was reacting with the coating, but you're saying it's most-likely moisture (e.g. the 9% water in the 91% IPA).
Probably a good thing I didn't dump a bunch of distilled water all over it, yet. Guess I'll try a "cotton but" first. There's a nice wide-open-space with no components I can give a go with all the chemicals.
You've mentioned IPV (not IPA) twice, now, so I assume that's not a mistype... search-fu is failing me...
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IPV was a miss type. I meant IPA. I have IPV in the mind.
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try everclear
https://forum.allaboutcircuits.com/threads/cleaning-question-white-residue-after-cleaning.52718/
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if that doesn't work make a daquri and worry about it tomorrow.
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great call!
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Hey esot.eric, man what a mess, but still may be recoverable, if you used Isopropyl alcohol remember, Isopropyl alcohol is a polar solvent, there are two routes for cleaning rosin flux residues, one is solvent cleaning the other aqueous cleaners. A blend of polar and non polar solvents has to be used so both rosin and ionic activators are dissolved and removed. Water based cleaning involves use of a biodegradable cleaner capable of saponifying rosin to form a soluble soap while ionics dissolve in the water.
Non rosin fluxes ( organic, inorganic ) require an appropriate water based cleaner.
This is a good resource on this subject;
http://www.finishing.com/library/flux.html
Hope this helps you out :)
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Haha! "It's all Greek to me!" Thanks for trying, though! I'm adding an update to this "log" to explain what I thought happened...
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No problem my man, just though I'd shoot out my 2c't :)
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Was there any sort of conformal coating ?
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there was some sort of clear-coat on the chips, and PCB (but not noticeable on the pins...?!) I just ran the IPA over another PCB and it came out fine... so that must be it.
Now what do I do?
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acetone ? oh hum.... wait...
you should have washed with something else, like water ?
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I've read someone washes PCBs with dish-soap and water... Sounds risky, but they claim good results. My theory was always to use alcohol *after* water, so as to displace it, and allow for fast-drying...
spose I could throw it in the oven at a low temperature...
(To unexperienced readers, beware! Know the oven before attempting! I once set a *digitally-controlled* oven to 125deg Farenheit and ended up with chicklets for keyboard keys!)
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