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Electronics => Repair => Topic started by: ionbasa on April 20, 2015, 01:15:12 am

Title: Cleaning Water Damaged PCB?
Post by: ionbasa on April 20, 2015, 01:15:12 am
Hello all, I need some advice on cleaning a PCB that was exposed to rain water:

(http://i.imgur.com/kJPTE4T.jpg)

(http://i.imgur.com/fpUfXH0.jpg)

As you can see there is some corrosion going on. Any advice? Will acetic acid (vinegar) do the trick followed by an isopropyl alcohol bath?


Backstory of how this happened and what the part is:

The PCB is an automotive ECU manufactured by Bosch from my 2001 Mercedes C320. Over the winter it rained, and the drains under the windshield and wipers were clogged. Thus, water found its way in the fuse box of the car. The ECU was enclosed in a metal shielded box. But guess what? It's not water tight, there wasn't even a seal. Just a metal clamshell held together by six security screws. Engineered to fail if you ask me.
Title: Re: Cleaning Water Damaged PCB?
Post by: mengfei on April 20, 2015, 01:40:01 am
i usually clean my boards with isopropyl alcohol & a stiff toothbrush & leave it to dry., if you can get 99% isopropyl alcohol that would be better also have a well ventilated area. Or much better yet if someone has an ultrasonics PCB cleaner that would be much better.

Some of my friends have tried washing their dead motherboards & VGA cards with liquid soap + water + brush & to our amazement some came back to life  ;D

try this also
http://wiki.arcadeotaku.com/w/PCB_Cleaning_101 (http://wiki.arcadeotaku.com/w/PCB_Cleaning_101)

http://www.iultrasonic.com/cell-phone-circuit-board-ultrasonic-cleaning/water-damage-repair-on-your-samsung-galaxy-s-with-an-ultrasonic-cleaner.html (http://www.iultrasonic.com/cell-phone-circuit-board-ultrasonic-cleaning/water-damage-repair-on-your-samsung-galaxy-s-with-an-ultrasonic-cleaner.html)

BTW some electronics may die just by brushing off the dust coz of electrostatics.
Title: Re: Cleaning Water Damaged PCB?
Post by: PeterFW on April 20, 2015, 01:47:49 am
As you can see there is some corrosion going on. Any advice? Will acetic acid (vinegar) do the trick followed by an isopropyl alcohol bath?

Scrub it with ispropanol and your toothbrush, let it dry with a bit of heat for a day and test it.
I would resolder every joint with a bit of lead solder if it works after cleaning to be safe.
Title: Re: Cleaning Water Damaged PCB?
Post by: ionbasa on April 20, 2015, 01:50:59 am
Thanks for all the advice guys. Should I just give it an entire bath in Isopropyl alcohol to make sure any remaining water is also displaced? I can gently scrub while the PCB is submerged.

Regarding drying, I have a heat gun on hand. I suppose I could leave it on low and gently warm up the board and then leave it over a day to dry.

ALso, the board has a series of connectors at the top that I didn't post a picture of. I can't manually scrub these due to size constraints and the depth of the plugs. Should I just something like deox-it and call it a day on the plugs?
Title: Re: Cleaning Water Damaged PCB?
Post by: mengfei on April 20, 2015, 01:56:03 am
BTW after using your toothbrush - please do not use it any more lol  :-DD
Title: Re: Cleaning Water Damaged PCB?
Post by: ionbasa on April 20, 2015, 01:58:22 am
BTW after using your toothbrush - please do not use it any more lol  :-DD

Haha! I wouldn't dare to even think about it  :o.
Title: Re: Cleaning Water Damaged PCB?
Post by: ionbasa on April 20, 2015, 02:05:30 am
So I have some bad news. One of the legs on the chip labeled "221" was basically gone. It corroded through the leg, but only at the halfway point. I guess I may need to do some precision soldering tomorrow to fix that
Title: Re: Cleaning Water Damaged PCB?
Post by: rdl on April 20, 2015, 05:39:48 am
Water doesn't damage circuit boards. Chemicals (such as road salt) that were dissolved in the water are probably what caused the corrosion. Those will probably rinse of quicker and cleaner in plain water. Follow that with a distilled water rinse. If anything remains, then try the alcohol.
Title: Re: Cleaning Water Damaged PCB?
Post by: TimFox on April 20, 2015, 09:47:44 pm
If there is uncleaned acidic solder flux still on the board, adding water can cause corrosion.  I have seen such corrosion that almost looks like mold, but is non-organic.
Title: Re: Cleaning Water Damaged PCB?
Post by: bookaboo on April 20, 2015, 10:33:23 pm
I've yet to find anything better than warm water and washing up liquid for cleaning most PCBs. Ispropanol does work but its hard to beat a large volume of liquid to physically shift dirt and corrosion. Ultrasonic baths can also be good.
Title: Re: Cleaning Water Damaged PCB?
Post by: station240 on April 21, 2015, 02:34:49 pm
I've used a scrubbing brush (eg from floors) to clean a PCB that fell into a alligator tank, it was the temp probe to monitor things. It worked again afterwards, despite being tiny SMD.

If a toothbrush isn't cutting it, try one of those little brushes for scrubbing (under) nails. Much harder bristles, and easier to hold/exert pressure on to get out the junk right next to SMD resistors etc.
Title: Re: Cleaning Water Damaged PCB?
Post by: Scotophor on April 24, 2015, 08:14:59 am
Was the car's battery dead or disconnected when the board was wet? If not, there's a good chance that IC with the "221" sticker and/or one or more others is toast.