Re: smd precision resistor "paint layer" peeled off while soldering *** advice needed ***


Chuck Harris
 

In short no, 99% IPA won't even touch the electrolyte,
except for that which gets removed by physical scrubbing.

The electrolyte is a water soluble mix of some sort of
glycol compound and a salt that doesn't corrode aluminum,
or aluminum oxide.... but does a job on copper. Water
and detergent is what you need to remove it.

If you don't want to dry the board over night in an oven,
blow it off with compressed air, and put it in a convection
oven at 50C for 2 hours. I use my environmental chamber.

As a drier, IPA has to be able to reach the nooks and crannies
that the water gets to, and it has to be able to move the
water through evaporation... mostly what happens is the
alcohol evaporates, and leaves the deep water behind.

You need to get the water out from under the IC's, and other
packages that almost touch the board, but not quite.

Watch the temperature! Cooking isn't exactly good for some
parts... especially the NVRAM.

And, yes, the electrolyte is a glycol based mix, and the
glycol gives the dead fish smell when it is burned with
your soldering iron.

-Chuck Harris

Richard in Edenton NC via groups.io wrote:

Chuck, would 99% isopropyl alcohol do the same thing, but without having to put it in a oven overnight? Also I assume that the electrolyte (that leaked from the caps) being heated is the cause of the smell like rotten fish? Good to know. Thanks for sharing

73 Richard W4MCD





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