Washing A PCB

[justDIY]

the temp I recommend is commonly specified by semiconductor manufacturers as a drying temperature.

it's well within the storage specs of most any microelectronic component. look at your datasheets, most parts have an operational ceiling of 70-90C and a non-operating ceiling of 150C+

I thought we were talking about a PCB assembly, not a plastic case, not an LCD ... isn't the title of this post "Washing a PCB"?

The temperature needs to be higher than the boiling point of water so you can be sure the water will turn to gaseous form and leave the assembly. heating to to less than the boiling point will accelerate evaporation but will take a lot longer.

 

[justDIY]

Whats the average time? Ive never done this before.

you have to worry about thermal stress damaging your solder connections and the delicate multilayer circuit board.

I'd aim for no less than 15 and probably closer to 30-45 min

I don't know about your oven, but my toaster oven takes quite a bit of time to heat to a low temperature (dial goes down to 150F) ... so I'd put the board in, close the door, turn it on and let it sit for 30 min, then turn it off, leave the door closed another 15-20 min for everything to cool slowly

heating the assembly to 100C and then taking it out every 5 min to inspect it is just asking for thermal shock.

edit: oh, if you are using a toaster oven, make sure to use the indirect heating method (heating rods under the tray) instead of the broiler method (heating rods over the tray). direct heating of the board will cause irregular heating of the various components.

 

[ParkingLotLust]

I thought we were talking about a PCB assembly, not a plastic case, not an LCD ... isn't the title of this post "Washing a PCB"?

Im talking about the PCB of an iPod Video.

 

[Marks256]

I don't mean to hijack this thread, but would any of these techniques work on a cell phone? My brand new cell phone went through the wash, too...

It doesn't turn on, and i have my old phone re-activated, so there really is nothing to loose...

 

[ParkingLotLust]

Dont see why not. Pull the PCB, wash 'er down, and bake it, and see if it works.

I went to the Hardware Store, and couldnt find anything under the name of 'denatured alcohol', so I picked up some 99.9% Methanol (Methyl Alcohol). Thatll work, right?

 

[mramos1]

Way back when, we would take a device that went into water. NOT power it up and put it in a vacuum. That would boil the moisture off. Sure it still works

The oven idea just sounds like a bad idea. LCD, plastics, etc. Maybe broil it .

Marks256, is there a little pink blur on the battery now? Now they have pink dots on the battery, and it it hits water, and you send it back (even after you clean it) they know it went in water since the pink dots become one big pink dot..

EDIT: fixed vacuum

 

[Marks256]

Yeah, the battery has been pinkified... he he, is that even a word?

I personally think the thing is frenchfried... it was on when it went in the wash, and it was off when it came out... duh...

 

[ParkingLotLust]

Checked the battery cable, and it looks like right where it plugs into the motherboard, it has been burned, so it needs a new battery. Checked the hdd pcb, and there wasnt any sign of soap residue, so Id bet that it still works. But my original question still stands - will the Methanol I picked up work?

 

[justDIY]

according to wikipedia, methanol is corrosive to some metals. they didn't mention copper, but I don't think anything corrosive is a good idea when used with electronics

One of the drawbacks of methanol as a fuel is its corrosivity to some metals, including aluminium. Methanol, although a weak acid, attacks the oxide coating that normally protects the aluminium from corrosion

have you checked the drug store for 90+ percent "isopropyl alcohol" ... it may be called "rubbing alcohol" - the weak stuff is used as a massage fluid, the strong stuff used as an astringent and disinfectant.

or if you've got a radio shack or something similar, check for electronic board cleaner or tv tuner cleaner.

 

[3v0]

I think the vaccum vacuum (funny word) is a much better idea. If you can not find one local I would be glad to do it for you. I have one of the tables used to degass/debubble investment for casting.

3v0

 

[ParkingLotLust]

have you checked the drug store for 90+ percent "isopropyl alcohol" ... it may be called "rubbing alcohol" - the weak stuff is used as a massage fluid, the strong stuff used as an astringent and disinfectant.

The highest I could find was 70%, which I picked up anyways since I was out. I only picked up the Methanol because I was told near the beginning of the thread to "Use denatured alcohol from a hardware store, NOT pharmacy stuff. The stuff you get at a drug store is 10-30% water and will just makes things worse if it gets trapped anywhere." Thats why I picked up the 99.9% pure methanol (the 70% isopropyl being 30% water).

To 3v0, thanks, but Im already broke as it is, and that would cost me to ship the board to you and back. Id check around here, but I know no one would have anything like that, because we're all hick farmers around here.

 

[Sceadwian]

Be very very careful how you store methanol. Basically if you have any kids a cat or a dog return it immedatly or store it in a locked cabinet at all times, a small amount will kill or severly sicken household pets or livestock, or people if ingested. It's also corrosive (especially to aluminum) and for that reason probably no recommended for cleaning PCB's =\

 

[ParkingLotLust]

So its useless then? Would I be able to use the 70% Isopropyl?

 

[Marks256]

I use isopropyl all the time to clean components... I NEVER have ran into ANY problems so far... As a matter of fact i spilt pepsi all over my nice wireless keyboard last night, so before i hit the sack tonight, i am going to swab down a few of the keys that are sticking. I would say go for it, but i am not an expert, and maybe i have just been lucky...

 

[Sceadwian]

Try it on an Ipod though Marks, the problem is the isopropyl disolves in water and evaporates very fast, but the water doesn't. It sneaks underneath the leads of surface mount chips and once the alcohol is gone the surface tension keeps it from getting out. You need a pure non-corrosize solvent. You might be able to freeze distill the Iso-propyl but I'm not sure. All in all AGAIN this is WAY more effort than possible benefit... If you're really hard up, use the 70% isopropyl, but don't be surprised if it works for a while and corrodes again later, oxides tend to be auto-catalytic, if any is left more will form.

 

[ParkingLotLust]

So why not submerge it in isopropyl, then heat it up to boil off any remaining water? Would that work?

 

[Sceadwian]

Submergence isn't required, in fact the goal is to flush away corrosion. Try Isopropyl in a squirt bottle (away from heat!!!) flush it with dry compressed air, then bake, with plenty of ventiliation.

 

[ParkingLotLust]

Sounds easy enough. Only thing, we only have one of those bagel toasters, so using the oven wont be a problem right? What setting should it be on? Bake? Broil? Convection?

 

[Sceadwian]

convection

 

[ParkingLotLust]

Didnt work Ahwell, lesson learned. Thanks for the help!