Cleaning a PCB?

[Scott Shepherd]

I bought a laptop that someone spilled water on. They took it to apple and it was diagnosed with a bad logic board, which is about a $800-900 fix from them. You can get one elsewhere for $600 or so, and there are people that repair them for a fraction of that. My initial goal was to have the board repaired. I researched it prior to buying the computer.

So I took it all apart, freeing up the logic board so I could send it in for repair, and I noticed the "damage". It's just a small bit of white corrosion on a very small area that's not densely populated. So my thought was "hey, maybe cleaning it will just make it work". In researching it a little more, I see some people have had luck with that very technique.

So my question is what do I clean it with? I know a wrong choice can be devastating to the board, so I'd like to not make that mistake.

Any help would be appreciated.

Thanks!

[Jason Roehl]

Electronics are often cleaned with alcohol.

[Ken Fitzgerald]

I used a lot of alcohol to clean electronics in my 40 year career. The white residue leads me to believe it's one of two possibilities. 1) it's residue from smoke from a component that burned when the "water" was spilled on it.....or 2)something other than water was spilled on it and this is what is left after the liquid dried.

Use regular old isopropyl alcohol and just be sure to let it completely dry before you reinstall it and apply power. (Regular isopropyl alcohol is a mixture usely of about 68% alcohol and 30% water.)

[Ben Hatcher]

If it is a small area, you may be able to use a dry acid brush trimmed very short and maybe a little isopropyl. Blow it off with compressed air afterwards to ensure it is dry before reinstalling it.

[Steve Meliza]

I've cleaned circuit boards under the running tap with a toothbrush (to remove water soluble flux), alcohol, and special PCB cleaners that come in spray cans. In your case I'd try the alcohol first, but if that doesn't work look for a spray can of PCB cleaner. I agree with Ken that the board is either fried or something other than pure water was spilled and left a residue.

[Phil Thien]

I do about 3-4 of these a year.

First, you have to get it clean. Use water or alcohol, and a toothbrush.

Now blow the area dry w/ an air compressor. Be thorough. I've had boards w/ enough moisture trapped under a surface-mounted component to prevent the unit from POSTing. You could be amazed how long it takes the moisture to evaporate when it is trapped. So use the air compressor. You don't have to go nuts on pressure. Just move the nozzle around and look for any drops coming out from under a component.

Reinstall it and give it a shot.

I can save about half of them. The other half need more work. The keyboard is often shot.

[John Coloccia]

Does it pass the sniff test? It's hard to mistake the scent of a blown up board. White residue is normally very bad, as in something went *POOF*. Find a friend who knows what he's doing and take it to him. If you're extremely lucky, maybe a good cleaning is all it will take (I think this is a low probability outcome!). If you're only very lucky, he can probe around for a minute and find an off the shelf part that has blown up. Depending what's on that board, it could be as simple as something in a power supply section, which will certainly be built with readily available off the shelf components. If he's halfway competent with a soldering iron, he can just rework the board and fix it (I've reworked many many prototype PCBs by hand under a microscope, including lifting pins on miniature packages and rewiring them. It can be done!).

[Dan Friedrichs]

You can buy 92% rubbing alcohol. I'd use that.

[Jim Koepke]

One of the problems with water in electronics is the possibility of dendrite. (2 a crystal or crystalline mass with a branching, treelike structure.) These can develop if the battery wasn't immediately removed.

If you are lucky, the procedures described by others will save you money. If you are not lucky, this could have made the board unreparable if it has developed under components or between layers of the board.

jtk

[Kevin W Johnson]

I've brought several back to life just cleaning the board with alcohol(get the highest % available, it has less water) and a toothbrush. As Ken said, just make sure it's dry (I use compressed air to help this along since water could rest under BGA and PGA chips), since rubbing alcohol has water in it. I happen to have some 99% thats for electronics useage, but you can't buy that just anywhere.

[Scott Shepherd]

Thanks for the help. I cleaned it but noticed one tiny component that had white stuff on the end of it and it wouldn't clean off with my brush and cleaner. I assume that was the part that was fried. I've sent it off to be repaired now, so my attempt to get by with no cost didn't work :) No worries, I bought it cheap, it's an expensive laptop and it's not that expensive to get the board fixed. Hopefully they can fix it. They told me they had 99% success rate, so let's hope I'm not the 1% :)

[Jim Matthews]

The inventor of the transistor, Bill Shockley, discovered that compressed smoke is a near perfect conductor of electricity on a minute scale.

When asked why his prototype was so heavily built he replied,
"It runs on smoke. When the smoke gets out, it's done for."

[Jason Roehl]

Scott, if you have an expensive laptop, you are the 1%! :D

[Rich Engelhardt]

Scott, if you have an expensive laptop, you are the 1%! :D
Actually - closer to 10.7%...
He mentioned something about taking the laptop to the Apple Store ;).

[Scott Shepherd]

Actually - closer to 10.7%...
He mentioned something about taking the laptop to the Apple Store ;).

Too funny :) It's actually a used macbook pro that someone (not me) paid $1400 for. I paid $125 for it and they'll fix it for $250, so I'm in the $375 range for it, not $1,400. I think that takes me out the 1% category :)

I didn't take it to the apple store, the previous owner did when he spilled water on it.

[Kevin W Johnson]

Scott,

Did you try the board to see if it worked after cleaning?

[Scott Shepherd]

Yes, no luck. Dead as could be.