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From: larry@kitty.UUCP (Larry Lippman)
Newsgroups: sci.electronics
Subject: Re: Rosin remover
Summary: Alcohols as flux removers...
Message-ID: <3320@kitty.UUCP>
Date: 2 Aug 89 04:05:48 GMT
References: <6236@stiatl.UUCP>
Organization: Recognition Research Corp., Clarence, NY
Lines: 36

In article <6236@stiatl.UUCP>, john@stiatl.UUCP (John DeArmond) writes:
> One of the absolute best solvents for most fluxes is 100% ethanol.  This
> is available at your friendly liquor store as PGA (pure grain alcohol).
> I've found that not only does this stuff remove roson rather well, it
> leave no residue.  I've tried other alcohols and dilute ethanol and none
> seem to work as well.  The water seems to interefer with the solvent 
> effects.  
> ... 
> One final note.  Don't get fooled at the liquor store into getting
> 196 proof votka.  The 2% water content will foul up the process.

	The small percentage of water has no practicable bearing upon
the solvent action of ethanol in this application.

	Absolute ethanol is highly hygroscopic, and will rapidly absorb
water from the atmosphere until it ultimately forms an azeotropic mixture
having a concentration of 95.6% ethanol and 4.4% water.

	I can assure you that absolute alcohol which has been sitting
around for a while after having had its container opened is no longer
"absolute".

	Rosin flux residue is NOT a single compound, but in fact a mixture
of several compounds, primarily diterpenes such as abietic acid.  In
addition, rosin flux residue contains thermal decomposition products of
these diterpenes.  These compounds all have different characteristics,
with ethanol not being an optimal, overall solvent.  Without digressing
into a discussion of the physical chemistry involved, isopropanol possesses
a structure which is more suitable as a universal solvent for these
compounds - without running risk of dissolving plastic materials on
electronic components.  95% isopropanol is just fine.

<>  Larry Lippman @ Recognition Research Corp. - Uniquex Corp. - Viatran Corp.
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