Repairing water damaged electronics

[Entropia]

I recently got an Audi Navigation plus unit from ca. 2000. It's a double-DIN in-dash satnav system, pretty sophisticated for its time. Anyway, this unit's apparently seen the bottom of a pond or something like that since all the internals are pretty much covered in silt. I have to admit, it looks pretty bad. But I've not given up. I've ran some of the parts thru my ultrasonic cleaner and the silt comes off quite nicely. After that I rub the rest down with IPA. Much to my surprise a lot of the traces and solder joints look nice, but some are pretty badly corroded so I will have to "refreshen" up those.

Some pics of the unit after I opened it (viewer discretion advised! ) are here: http://entropia.1g.fi/kuvat/Autot/Passat+Variant+1.9TDI+-05/Navigation+plus/

Anyway, to the subject. What do I have to take into account when repairing water damaged electronics? Do I just assume that all X components are past it and need replacing (like electrolytics)? I was thinking of testing all the units separately, as much as I can, with a current-limited bench power supply. Does any of this make sense? :-)

I'm a realist so I'm not keeping my hopes up regarding the resurrection of this unit, but what do you think? In case it doesn't work, I have other plans waiting for the mechanics... (Read: In-dash Android system).

[Balaur]

Whoa, that sure looks challenging.

Given the state of the boards, it's difficult to trust any kind of electro-mecanical devices such as relays, switches, fans and connectors. Inductors and transformers are a big IF as well.

I would hope that most ICs, transistors, resistors and caps could be OK, as they are usually impermeable.

One major issue is the LCD. If the unit was really submerged in water, the quality of the image will take a big hit from all the deposits between the backlight diffuser and the screen.

The tuner module is also an issue, since the internals will not be easy to clean.

Just a personal note: I would not be against using some WD40 on the stuff. However, don't do that!

In all, enjoy the project!

PS: I had to clean my camera after I fell in the water. The electronic part was OK, but I've never managed to properly clean the lens assembly.

[pickle9000]

- If you are dealing with salt water wash the board. Use 1 drop per liter of sunlight liquid (yellow) soap and warm water. Blow out under chips with canned air several times during wash, change water as needed. Rinse with distilled water. A paint brush can be used to gently scrub areas, need not be anti static as long as board is wet. An anti static brush and alcohol (iso) work well on a dry board.
- Consider parts which use paper or cardboard in their construction to be bad. I most cases they are highly suspect.
- Water will stay under chips for a very long time, it need to be blown out the the board warmed (of use desiccant or both) to evaporate the rest.
- Vias and tracks under chips are the most common issue. Easy to reapir but you have to find them first.
- Never forget to dry the board regardless of the cleaning method before testing.
- Always remember it's already dead, you will gain skill from the exercise even it the end result is a non working repair.

Good luck

[N2IXK]

I work in the instrument shop of an oceanographic research lab, so as you can imagine, I get a LOT of water-damaged electronics dropped on my bench.

I always tell the boat crews that the most important thing is not to let the equipment dry out until it gets back to the shop. Assuming it was submerged in salt water or dirty water, the first thing to do ASAP (preferably still out in the field) is to disconnect power (pull the batteries out), rinse everything off as well as possible, then put the unit into a cooler or similar container filled with clean, fresh water. If the unit dries out with salt residue still coating things, the ensuing corrosion greatly complicates repair efforts.

Once a unit gets onto the bench, I unplug all the separable connectors, remove any socketed ICs or other similar components, and give everything another rinse with warm water (the tiny amount of detergent mentioned above is a good idea). Then a rinse with isopropyl alcohol, followed by a final rinse with distilled water. and a blow-dry with compressed air.

At this point, I will give everything a quick lookover for any obvious corrosion, and remove any soldered-in lithium backup batteries or other components that may not tolerate the next step--a proper drying at ~150F in a vacuum chamber for 24 hours. 

After drying, another inspection for obvious damage, and reassembly.  Mechanical parts need a complete relubrication, and I generally give all the connectors a shot of Deoxit or similar contact cleaner. Most equipment that was rescued quickly will operate properly at this point and can be returned to service.

Otherwise, standard troubleshooting techniques apply from here on out, with special attention for stuff like corroded PCB traces in hidden areas, open plated-through holes or vias, etc.

[Entropia]

Wow, great responses and a lot of tips! Thanks! I can try out most of them, except the IPA rinsing -- that stuff costs 6 euros per 100ml (haven't found any place cheaper than the local pharmacy). I'll keep on cleaning and see how it goes... I'll keep you posted. In the mean time please do share your experiences and tips. 

[sacherjj]

Wow, great responses and a lot of tips! Thanks! I can try out most of them, except the IPA rinsing -- that stuff costs 6 euros per 100ml (haven't found any place cheaper than the local pharmacy). I'll keep on cleaning and see how it goes... I'll keep you posted. In the mean time please do share your experiences and tips. 

I use denatured alcohol from the hardware store here in the US.  The have 1 gallon jugs for a resonable amount of money.  I've always done the last soak in that and then dry with a fan.  Alcohol bonds with the water and I get full drying without having to use a vacuum system.

[grumpydoc]

except the IPA rinsing -- that stuff costs 6 euros per 100ml

Shouldn't be that expensive - there's a UK seller on ebay who does it at about €24 per 5l - sadly they only deliver to UK but you should be able to find some cheaper than €60/l. Try chemicals or schools suppliers or even your local Element 14.

[Galenbo]

My expierience in cellphone-handy-gsm repair is that the components can stand water and a bit corrosion,
but after 2001 most cellphones had multi-layer boards (instead of double layer)

The new problem was that water came between the layers, make it bulge, so they tend to come microscopicly apart,
causing bad contacts in routes between the layers.

The only hypotecticly solution could be to buy a new blank board and solder the components on it.

.

[HackedFridgeMagnet]

I use bourbon alcohol from the bottle shop here in the AUS.  They have 1 gallon jugs for a reasonable amount of money.

Just use water for the electronics though.

[Balaur]

I use bourbon alcohol from the bottle shop here in the AUS.  They have 1 gallon jugs for a reasonable amount of money.

Just use water for the electronics though.

At work, I'm known as the one who's using vodka on electronics! A reasonable approximation for IPA in my views.

[eliocor]

[...] except the IPA rinsing -- that stuff costs 6 euros per 100ml (haven't found any place cheaper than the local pharmacy). [...]

RS Components sells pure (99.5%)  IPA at 16.30 Euro/liter (RS code:  227-4427)

[robrenz]

For this application why don't you just get the 90% rubbing alcohol available at the grocery store or pharmacy.  It is 90% isopropyl and only 10% water. Since the main purpose is to clean and combine with the existing water anyhow the 10% water is trivial.

[Entropia]

For this application why don't you just get the 90% rubbing alcohol available at the grocery store or pharmacy.

I'm not aware that such a liquid is available in Finland... not widely anyways. What is available though, is denaturated ethanol (tradenames Industol, Sinol etc.). I wonder if that would do the trick as well.

A fellow Finnish electronics tinkerer hinted me of a retailer called Cheminent who sells >=99.8% pure IPA for a more reasonable ~6 euros per liter price, but that has a lead time of five weeks. http://www.cheminent.fi/index.php?display=main&view=product&productid=17821

[SeanB]

Denatured alcohol will work, it just has either methanol or another non drinkable alcohol and a bitter taste added. The outies filter it through a loaf of bread to get the taste out, then drink the pale blue result and then eat the bread.......

[sacherjj]

Sounds really nasty.  Do you perform cleaning under liquid (pure water or alcohol) to dissolve the unknown particulates without making them airborne dust?

[Entropia]

Yeah, I take care not to touch the PCBs excessively... Most of the cleaning happens in the ultrasonic cleaner with "battery water" (not distilled but ionized (is that the right word?)). After that I clean up the harder sticking mess with cotton swabs and IPA.

Yesterday I finished cleaning and testing the front panel and its buttons and rotary encoders. All the buttons work, but couldn't get the illumination LEDs to light up in-circuit with Fluke's diode tester. I'm actually not sure if they're even supposed to light up unless they are removed from the PCB first... Anyway, I'll assume they work. They're not vital anyway, they just provide illumination for the buttons in the dark. Today I'll try to assemble the LCD and attach it back. After that I'll start inspecting the "main" PCB power supply. There's a Linear Tech buck converter which I guess supplies most of the logic voltage. A good place to start...

(I hope all the power supply capacitors are okay, since I'd hate to start changing them.. there must be a 100 electrolytic caps in this thing!)

[Rerouter]

in most cases a diode check caps out at 3V, so it may not have a high enough voltage to turn them on if they are blue or white or have a dropping resistor,

[Psi]

If all the components on the PCB are basic TH and SMT (ie, no BGA) then i would probably unsolder all of them, clean the PCB, and solder them back (using new components were needed or where easier).

Simply because it's quite hard to get water and residue out from underneath components.

[paudav]

Entropia:  Your gallery hosting software looks great!  Is it open source, by chance?

Thanks!

[nukie]

I was going to suggest industrial PCB flux wash but then it will be too expensive investment if it didn't work. I use them in ultrasonic cleaner and it works very cleaning all sorts of gunk off old boards. Some of the pcbs came from smokers for repairs are really the worst covered with yellowish layer of

Secondly, some rubbing alcohol contains medication oil, read the label carefully, avoid if not pure. IPA are available from chemical supplies search the ones close to you cause they require special courier for delivery and you pay more for the flamable liquid. The ones from pharmacy usually demand the highest cost.

I am disappointed to know that a luxury car company does not conformal coat the PCB for automotive purposes but then again its probably not their choice as they usually outsource parts from OEM such as Blaupunkt. My A4 B8 Hids ballast are made by Mitsubishi in Japan, so much for a German made. It doesn't cost much for a clear layer applied on a circuit board does it? But repairing is a nightmare, the layer can only be partially melted at lead free temperature.

Anyway, theres plenty of tips provided already, if you are unsure whether a part can be washed just lookup the datasheet. I would be removing all the IC chips to look for damage underneath. After liquid cleaning, its best to fan bake at 60-70c to drive out all the moisture. A temperature adjustable painters heat gun is very useful here.

[robrenz]

(not distilled but ionized (is that the right word?)

deionized 

[Wim_L]

If you're concerned about hazardous contamination, I do hope you're covering the ultrasonic cleaner. Ultrasonic baths are capable of aerosolising the bath liquid, including any bacteria/viruses floating in there.

[Balaur]

I am disappointed to know that a luxury car company does not conformal coat the PCB for automotive purposes ...

I helped my friend fixing the dual climate board in his rather oldish E36 BMW. While the board was coated, the assembly process consisted in grabbing a handful of components and throwing them in the general direction of the boards while hoping for the best.

[ptricks]

Remove the lcd and anything that is unlikely to be water tight and spray the whole thing down with a water hose to get the gunk out. Next rinse in distilled water. Heat up an oven to just over 220F/105C you want to be just over the boiling point of water. Turn off the oven and place the device inside and let it stay inside until the oven cools and the device cools.
It should work , if it doesn't then you got corrosion or water  inside a part like an electrolytic cap.

This works great on cell phones and other portable devices. You have to be careful with cleaners like alcohol and acetone as some plastics will degrade on contact. By using the high water hose pressure you can wash out all the cracks and crevices like under bga chips.

[ptricks]

If you're concerned about hazardous contamination, I do hope you're covering the ultrasonic cleaner. Ultrasonic baths are capable of aerosolising the bath liquid, including any bacteria/viruses floating in there.

All it takes is adding some bleach to some distilled water and rinsing if you are concerned about bacteria/viruses.  The biggest threat would probably be mold.