How bad is corrosion (liquid damage) over time?

[TheBorg]

I've recently been interested in repairing MacBooks. I have gotten a deal from someone who spilled dr pepper on his Mac 9 months ago and made it unusable. Question here is, would the dr. Pepper corrosion on the logic board eat so much of the board away as to make it unrepairable?

[marshallh]

Yes its entirely possible. Soda is extremely corrosive. I have used store brand soda on several occasions to clean off car battery terminals.

[ablacon64]

Not only soda, 9 months is enough time to practically any liquid to corrode a lot of things. I receive many dead laptops because of that. The client lets the laptop dry, it works perfectly for even months until it gets totally ruined.

Marshallh, it was your 555th post! 

[TheBorg]

So better to stay away from this one or try my hand at repair? I mean if things corroded that badly I assume everything would be permanently damaged, and pretty much unfixable. All I got's to repair it is a hot air rework and a soldering iron. Well, and some IPA and wipes and tools and crap. The usual stuff, but no ultrasonic cleaner or reflow oven.

Edit: here is a pic of the board the guy posted. Nasty looking stuff, hope the spill wasn't through the keyboard 
As a beginner project into laptop repair, good project or no?

[ablacon64]

So better to stay away from this one or try my hand at repair?

Not really, you should try anyway, if you end up with a dead board at least you'll have an opportunity to practice. Follow signals, troubleshoot, study datasheets, you'll learn a lot. Besides that, SMT hand soldering is a life saviour.

Some boards appear very bad but when you clean them up they end up looking not so bad.

As for the tools, I think you have what it's needed for a start, buy more tools as needed and when you earn some money from your work.

[marshallh]

Start by thoroughly cleaning the entier board and then baking out the moisture. My guess is it's toast. That is likely a 8-12 layer pcb and there may always be some corrosion you can never reach until it's too late.

[dannyf]

Question here is, would the dr. Pepper corrosion on the logic board eat so much of the board away as to make it unrepairable?

Possible but not probable.

Corrosiveness depends on the liquid and the material. The liquid could be corrosive, but once it dries up, it is far less corrosive.


Then you have a question on the surface - plastics is much more corrosion resistant.

I would, however, worry about the circuitry in case the liquid got into the boards or mechanical parts (hard drive, connectors, etc.)

[TerraHertz]

Since you can't (so far as I know) get circuits for Macs, and even if you could the complexity and signal speeds are above what you can usefully diagnose with a scope, this becomes purely an exercise in 'clean it and hope for the best'.

I'd say it's a gonner, but doesn't hurt to try. Take the board out, remove everything removable from it (fans etc),
then with a nylon bristle brush scrub gunked areas with hot water and detergent, and maybe alternate with alcohol/water scrubbing. Careful to not scrub parts off! Use compressed air gun to blow the water out from under parts after.
Visually inspect with magnifier looking for tracks corroded through.
Then bake gently for a day or so (just warm to touch), to get water out of plastic-metal IC leg seals, coils, etc.


The worst bits are large SMD chips with tracks and vias underneath, that are corroded.

Another problem with Macs is that there's a small CPU with non-volatile memory, that controls power sequencing and machine state. It can get into modes where it just refuses to let the machine start, even if there's currently no problem. Some info on the net about special button sequences to reset that damned thing, but I don't have a note of URLs. Apple does not provide any public information on it. Imo it's partly a 'more money for Apple' thing. Same as the fact that the keyboard is open to drink spills, dust, crumbs, etc through to the motherboard in the first place. Great way to sell more units.

[TheBorg]

Since you can't (so far as I know) get circuits for Macs, and even if you could the complexity and signal speeds are above what you can usefully diagnose with a scope, this becomes purely an exercise in 'clean it and hope for the best'.

I'd say it's a gonner, but doesn't hurt to try. Take the board out, remove everything removable from it (fans etc),
then with a nylon bristle brush scrub gunked areas with hot water and detergent, and maybe alternate with alcohol/water scrubbing. Careful to not scrub parts off! Use compressed air gun to blow the water out from under parts after.
Visually inspect with magnifier looking for tracks corroded through.
Then bake gently for a day or so (just warm to touch), to get water out of plastic-metal IC leg seals, coils, etc.


The worst bits are large SMD chips with tracks and vias underneath, that are corroded.

Another problem with Macs is that there's a small CPU with non-volatile memory, that controls power sequencing and machine state. It can get into modes where it just refuses to let the machine start, even if there's currently no problem. Some info on the net about special button sequences to reset that damned thing, but I don't have a note of URLs. Apple does not provide any public information on it. Imo it's partly a 'more money for Apple' thing. Same as the fact that the keyboard is open to drink spills, dust, crumbs, etc through to the motherboard in the first place. Great way to sell more units.

Schematics are not terribly hard to find, and the non-volatile chip is the SMC controller (my current laptop had an issue where I took it apart and the SMC refused to let it boot).

My biggest fear is that, as you said, some tracks got corroded or some vias under a chip somewhere. And after 9 months like this, I wonder if it would be worth it to try.

[Neilm]

I have seen multi-layer boards start to delaminate after being soaked in liquid. The board swelled just enough to break some of the vias on it. Assuming it uses blind vias, this is impossible to fix. So try cleaning it but be realistic - you are probably wasting time.

[Agony]

Withotu cleaning.. hard to say. The soda is acidic.. but if it dried out - it left a sugary coating there instead.

Clear it off and see if it actually has any visible corrosion/swelling.

Afterall - its covered in soldermask so it shouldnt absorb liquid that fast.

[G7PSK]

I have seen boards where soda drinks have been spilt onto them and then they are immediately dried and what stopped them working was sugar deposits in the connectors acting as insulation once the board and all connectors are cleaned they work despite the corrosion on tracks and exposed leads. If the unit is free there is nothing to be lost by cleaning it up and trying it out.

[Heribert Hechtersheim]

I would give it a try and spent at least some hours in trying to fix it. At first, try to get the board as clean as possible. Clean the motherboard with IPA and an a toothbrush first. Then inspect your motherboard and if you still find corrosion that could create shorts for example between chip pins try to remove it with a needle.
As a next step remove the main board from the body and only connect the fan and the power supply. The LED of the magsafe connector will probably not light up.
Then you have to look at the schematic of your macbook and find the location of the important components. Use an multimeter to test the various voltage rails.
Before I continue to get lost in details I would recommend you to do these steps and post some pictures after you cleaned it. Then you get a better overview of what could be damaged and if it is worth to fix it.