FWIW: I buy 99% pure Iso prop alcohol (anhydrous - no water) by MG chemicals from Fry's.
I have learned the hard way a long while back that dribbling or accidentally swiping the gpu leads with thermal paste can wreck a vidcard. I ruined 2 expensive (at the time) vidcards this way. Since the paste was supposed to be non conductive (or "semi conductive") it was quite puzzling. I am still not sure of the mechanism that causes this. It may be shorting and it may not. But what happens is the bios is fried. Sometimes booting to a PCI vga vid card with the other bad card also in and reflashing it can bring it back.
The first time I was kind of not thorough in removing the paste since I didnt think it mattered that much. The second time I was VERY careful to remove all traces of paste and it still happened.
So I have learned that if you have not really removed all paste then turning on the PC will wreck the card, so you better be damn sure.
Note that I am NOT saying it happens with all pastes - just some.
Were it to come up again, I would investigate ultrasonic cleaning, both aqueous and non aqueos.
There are even home units you can buy reasonably.
http://www.web-tronics.com/dopoulclt.html
One could even walk into a PCB manuf locally and ask for a favor or small charge to clean the card.
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PCB Cleaning Techniques and Tips
http://www.cam.org/~burt/circuits/clen-pcb.html
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One of the things that distinguish a professional printed circuit board from an amateur made one is the final appearance. Gobs of sticky rosin flux detract greatly from an otherwise neat circuit. Cleaning the rosin off the board is one of the more misunderstood processes in making homemade boards.
Most amateur pc board instructions refer to cleaning off the rosin with "alcohol" which to the amateur means "rubbing" alcohol or the alcohol in the alcoholic beverages he drinks. The latter is too valuable to waste on pc boards and both of them are full of water, which decidedly rejects rosin. Rubbing alcohol or Isopropyl alcohol available in the drug store or supermarket is typically 40% water and in addition typically contains 1% of a "lubricant" (usually a glycol). The alcohol content could be either isopropyl alcohol or a denatured form of ethyl alcohol. Rosin itself is insoluble in water and the water in rubbing alcohol greatly reduces the solubility of rosin.
Pure isopropyl alcohol (99%) is only available as a lab or industrial solvent, so most amateurs would not be able to acquire it. Pure ethyl alcohol is a controlled substance and expensive. Pure methyl alcohol is quite poisonous and is not particularly good at dissolving rosin (it is too close to water in chemical characteristics). If you must use alcohol as a pc board cleaner, the best bet is "2B denatured" ethyl alcohol, commonly known as methylated spirits, or shellac thinner. It is 85% ethyl alcohol (for its good solvent action) and 15% methyl alcohol (so you go blind if you drink it). It should be available in the larger home centers like Home Depot and large paint stores as the proper thinner for shellac. Don't confuse it with "lacquer" thinner with is a totally different animal.
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Note:
The link above later mentions poly-clens, however this is for UNFILLED PCB's. Vidcards have electrolytic can type filter caps that may trap some liquid inside near the crimp at bottom.