Removing oxidation from plated through holes - Page 1
Forum section: electronics / repair

author: gkmaia
author_rank: Frequent Contributor
timestamp: January 09, 2019, 09:02:54 pm
content: Hi,I got some hard encrusted blue oxidation on most of the plated through holes of my Game Gear PCB.I've been reading about ultrasonic cleaning, ammonia, baking powder. Also read that oxidation on copper/nickel is also a good thing as it builds a protective oxide layer.So I don't want to be poking into those holes and then damaging the plating.Any ideas on how to clean it NON-mechanical? With chemicals?ORShould I just leave it as it is?

author: PKTKS
author_rank: Super Contributor
timestamp: January 11, 2019, 01:40:06 pm
content: Your photo may be not the best shot.But as far as I can see IT IS **NOT** even close "BAD"But the corrosive rust already started and there is no way back.This case seems simple JUST BRUSH THE RUST W/ IPA (ISOPROPANOL)Mild brush lot of IPA brush all crappy rust with care...Dry with a lint free paper or just air.If you want to protect the corroded parts try PCB varnish in small amountsspot basedPaul

author: shakalnokturn
author_rank: Super Contributor
timestamp: January 11, 2019, 07:06:02 pm
content: Of course getting rid of the cause of oxidation would be a good thing.Those SMD electrolytic capacitors appear to be the original parts, they have spewed a good amount of their electrolyte.

author: gkmaia
author_rank: Frequent Contributor
timestamp: January 17, 2019, 10:32:26 pm
content: Quote from: shakalnokturn on January 11, 2019, 07:06:02 pmYes, they did. I got to remove them but before I want to decide how far to go with the corrosion issue. May not be worth.

author: gkmaia
author_rank: Frequent Contributor
timestamp: January 17, 2019, 10:34:27 pm
content: Quote from: PKTKS on January 11, 2019, 01:40:06 pmNice, Paul! Thanks! Ive done lots of IPA and brush already but the rust inside the holes are just impossible to remove. Can't poke them as they are hard as a rock inside those holes.What about pcb green mask those holes and isolate them from enviroment?

author: PKTKS
author_rank: Super Contributor
timestamp: January 18, 2019, 09:40:24 am
content: Quote from: gkmaia on January 17, 2019, 10:34:27 pmyep that "absorbed" rust will not just be wiped out that easy.From my trial and error procedures removing and replacing rusted parts...The only method that will remove the rust is to remove the solder joints itself.And that will vary cf. the amount of rust and oxidation of the jointMild ones you may just "wick" out with a good "RA" fluxThe bad ones... I use a very aggressive flux ... really nasty stuff - BUT WORKSRequires a lot of care to apply and ASAP to clean thatReally magical stuff when dealing with corroded joints that refuse to melt properlyand continue in blobs and residuesThe stuff I use melts the oxides and I can just wick or suck all very easy.This:http://www.soldabest.com.br/produtos_pasta_soldar.htmor the orange pot from this guys.. both are similar stuffhttp://cobix.com.br/produtos/produtosAggressive stuff. Corrosive and residual.. but works removing all oxides fast and cleanHave no better alternative than this to do a SAFE (preserve PCB from damage) and clean jobThey are soluble in IPA. Cleaning is not that bad..Paul

author: ebastler
author_rank: Super Contributor
timestamp: January 19, 2019, 10:18:54 pm
content: If it's blue, why would it be "rust"?Electrolytes or salts, maybe?Have you tried cleaning/brushing with water? If there are no sensitive mechanical parts on the board (switches etc.), immerse it in soapy water and brush gently, then rinse off with distilled water and dry in a warm place.If the residue is stubborn and you are serious (reckless?), just put the whole board in a dishwasher.

author: Clint_dk
author_rank: Newbie
timestamp: March 06, 2019, 05:10:13 pm
content: Try give a shot of deoxit contact cleaner through the holes.

author: PKTKS
author_rank: Super Contributor
timestamp: March 08, 2019, 04:42:09 pm
content: Quote from: ebastler on January 19, 2019, 10:18:54 pmMy interest in this topic is very specific.I have a board that is really hard to clean than that.VIAS are filled with that sort of "blue/white" oxidation...and even scrapping IPA over it will not clean underneath.This is not the first time I have heard some ideas of "washing" (w/water)..Sounds really weird. If IPA will not do it right ... how water should do it?Best case scenario so far is Ultrasonic bath in IPA. Or else.. other solution...Ideas welcomeBoard attachedRegardsPaul

author: ebastler
author_rank: Super Contributor
timestamp: March 08, 2019, 04:53:57 pm
content: Quote from: PKTKS on March 08, 2019, 04:42:09 pmWhile both water and IPA are polar solvents, many molecules are dissolved in water much more easily than in IPA or other alcohols.Have you ever tried to dissolve salt in alcohol? Doesn't work all that well...https://www.reddit.com/r/askscience/comments/19bwki/why_doesnt_salt_dissolve_in_rubbing_alcohol/

author: KL27x
author_rank: Super Contributor
timestamp: March 08, 2019, 11:29:36 pm
content: Blue color makes me suspect the board was exposed at some point to a base like say ammonia. Perhaps animal urine. Sorry, I have no suggestion for removing it.

author: helius
author_rank: Super Contributor
timestamp: March 08, 2019, 11:50:39 pm
content: Use a strong solution of ammonium thioglycolate (hair perm salt) with .5% benzotriazole. Allow to soak for several minutes to an hour.This chemical is being sold now in Japan for corrosion removal and is also available in the US for removing rust stains from marble.

author: wraper
author_rank: Unknown
timestamp: March 08, 2019, 11:57:02 pm
content: Quote from: PKTKS on March 08, 2019, 04:42:09 pmIPA is among the most useless solvents to clean corrosion. Almost all corrosion that comes off is due to mechanical impact, not IPA. Organic solvents in general are not good for dissolving salts and oxides.

author: StuartA
author_rank: Regular Contributor
timestamp: March 09, 2019, 12:17:44 am
content: The various comments about water and IPA are all true, but...Corrosion products are more likely to be soluble in water than in IPA, but IPA is a good wetting agent, so a mixture of say 10% IPA in water provides a good combination. You frequently hear of people talking about using lemon juice to remove corrosion products caused by old batteries, but lemon juice is really citric acid which is acting as a chelating agent, i.e. a chemical that combines with metal ions in a way that makes them very soluble, but wouldn't normally attack metal itself. So, a mix of water, IPA and citric acid (available commonly as a white powder) should make an interesting cocktail, and if you can get access to an ultrasonic bath, that should help nicely.

author: daniel444
author_rank: Regular Contributor
timestamp: March 09, 2019, 02:22:21 am
content: copper sulfate is blue in colora protective oxide layer would not be visible

author: StuartA
author_rank: Regular Contributor
timestamp: March 09, 2019, 04:23:32 am
content: Coppersulphateis blue. I thought the folks in Aus would know that. And please don't call up IUPAC.

author: ebastler
author_rank: Super Contributor
timestamp: March 09, 2019, 07:08:34 am
content: Quote from: StuartA on March 09, 2019, 04:23:32 amYou mean, as in "Sulfate is the spelling recommended by IUPAC, but sulphate is used in British English"?https://en.wikipedia.org/wiki/Sulfate

author: PKTKS
author_rank: Super Contributor
timestamp: March 09, 2019, 12:30:49 pm
content: Thanks for the helpsThe blue green white crap is not cat dog kid or other urine....Here the air is filled all daylong all year through a very saltyionic breeze (sea spray) which is impossible to avoid.Combine this (hot) air (temps are also high all year) with the faninside the electronics cases and you have a very good corrosive deviceThe ionic air spread by the FAN is corrosive by itself.I see that some kind of these ionic salts will not dilute on IPAotherwise they will on water at some degree.BUT. Don't forget to consider that other near by parts will beaffected far most from water than from IPA.So far scrapping IPA over those corroded parts works fine enoughcorrosion does get wet and fluid enough to be removed...I have heard other combinations of powerful solutions likehttps://www.all-spec.com/Catalog/Chemicals-Cleaning-Supplies/Ultrasonic-Cleaners-Accessories/Ultrasonic-Cleaner-Solutions/000-955-516-6768ORhttps://www.ebay.com/itm/Branson-EC-Electronic-Cleaner-Ultrasonic-Cleaner-1-Quart/183639687580?epid=9007302161&hash=item2ac1c7419c:g:ttMAAOSw4RZbIu0pBut they are very price and chemicals import legislation here is just insane...Anything paste with ammonia would do the magic trick but inside VIASthey will also left conductive residues...I have wonder a combination of such paste and fast IPA bath..some vent and warm rest oven to evaporate residues..Paul

author: wraper
author_rank: Unknown
timestamp: March 09, 2019, 02:00:58 pm
content: Quote from: PKTKS on March 09, 2019, 12:30:49 pmIf you use any cleaning solutions other than organic solvents, you need to clean with pure water afterwards regardless.

author: PKTKS
author_rank: Super Contributor
timestamp: March 09, 2019, 02:17:54 pm
content: Quote from: wraper on March 09, 2019, 02:00:58 pmnah I mean a regular crappy paste I use for corroded solder joints.The stuff does magic. Corrosion vanishes ..Such paste unfortunately is also corrosive and conductive.After soldering the corroded spot the residues must be cleanedIn regular THT spots there is no problem but VIAS will need special care..THIS CRAPPY STUFF DOES MAGIC ON CORRODED SPOTShttp://www.soldabest.com.br/produtos_pasta_soldar.htmbut be warned. It is corrosive and conductive and residue prone.In simple terms you apply the crappy paste (ammonia based) and heat it upAll corrosion vanishes in a nasty cloud of oxides.. the spot will be left clean withsome residues to be cleaned.e.g. No corrosion left but with the paste residues leftFortunately these residues are very easily soluble in IPA