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From: larry@kitty.UUCP (Larry Lippman)
Newsgroups: sci.bio,sci.physics
Subject: Re: Enzyme action
Message-ID: <2100@kitty.UUCP>
Date: Sat, 10-Oct-87 00:06:40 EDT
Article-I.D.: kitty.2100
Posted: Sat Oct 10 00:06:40 1987
Date-Received: Mon, 12-Oct-87 01:38:28 EDT
References: <240@ddsw1.UUCP> <2084@kitty.UUCP> <249@ddsw1.UUCP>
Organization: Recognition Research Corp., Clarence, NY
Lines: 41
Keywords: More to the point....
Summary: Zeroing in on the problem: removing excess solder flux
Xref: mnetor sci.bio:711 sci.physics:2463

In article <249@ddsw1.UUCP>, dino@ddsw1.UUCP (Laura Watson) writes:
> >	Without considering any chemistry based upon an enzyme, there are
> >a number of solvents which will dissolve rosin: ethyl alcohol, isopropyl
> >alcohol, acetone, methyl ethyl ketone (MEK), perchlorethylene, various freon
> >degreasing solvents, turpentine, and dilute sodium or potassium hydroxide
> >solutions.
> >	The choice of solvent should be dictated by the susceptability of
> >the item being cleaned to solvent damage.
> 
> This is all very true, and the above solvents are all quite well known to
> me.  However, in the application I am thinking of, solvents will not
> do the job because of their surface tension.  On a "Surface-Mount" type
> of PC board, the chips, resistors, etc. are very close to the board.  
> Close enough to create a capillary.  Solvent removal of the rosin flux
> is possible, but very very difficult.  You have to fill the capillary
> spaces and then break the surface tension over and over again to 
> get the goo out.  
> 
> I figured with some kind of enzyme chemistry, I might only have to 
> create and break the capillaries once.  And thus, you know, like
> save money or something. 

	I now understand your problem, but don't understand why you can
find no solution [no pun intended].
	I have seen SMD production lines, and most of them use a vapor
cleaning machine to remove solder flux and solder mask (if the removeable
variety).  Vapor cleaning machines generally use a chlorinated aliphatic
hydrocarbon solvent, similar to perchlorethylene.  Such a heated vapor
will penetrate areas around SMD pins quite nicely.  What is wrong with
vapor cleaning?
	Other SMD and standard PCB production facilities use non-rosin
fluxes which are water-soluble (with detergent), and _literally_ wash the
soldered boards in a dishwasher following soldering.  Obviously, a detergent
acts as a surfactant, lowering surface tension, and allowing penetration of
the detergent and water into all areas of the PCB.  What is wrong with
using a non-rosin flux which is water-soluble?

<>  Larry Lippman @ Recognition Research Corp., Clarence, New York
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