In a message dated 97-11-06 16:03:17 EST, you write:

> Here is a theoretical question for you!

OK, how about a theoretical answer?

>
>  Let's assume an entirely hypothetical situation where a moderate number of
>  un-coated Assembled Circuit Cards were exposed to Ethlyene Glycol.  Just
for
>  arguements sake, lets say a cooling system dumped it's coolant on the
first
>  floor above a hypothetical basement laboratory.  The hypothetical Ethlyene
>  Glycol dripped into the theoretical basement and filled up the typical
>  anti-static bins where the hypothetical Assembled Circuit Cards are
>  typically found.
>
>  <wink>
>
>  How would you clean these boards up?  Would you need to?
>  I assume there would be an impact on the SIR, but not on the ionic
>  contamination levels.  How could you tell when the boards were clean?
>  Isn't Ethlyene Glycol a major part of many "No-Clean" solder fluxes?
>  How could these cards be demonstrated to be fine?

Well, in theory, yes you would have to clean this hypothetical glycol from
the hypothetical CCAs taken from the hypothetical basement in this
hypothetical scenario.  (Can we stop now, this is giving me a headache).

If the boards were conformally coated, a simple rinsing should work.  I will
assume that the CCAs are not coated.  What I would recommend is cleaning the
CCAs in a saponified wash with good DI water and good DI water rinsing.  I
have found that Envirosense Envirogold 816 works extremely well in rescue
cleaning cases with my customers when they have excessive HASL residues,
which usually means excessive polyglycol residues as well.  A 3%-5% solution
in DI water, 140F, in-line cleaner, 4 fpm, should do well.  There are other
saponifiers which might work, but the 816 works very well on glycol residues.

How do you tell when it is clean?  I would recommend ion chromatography per
IPC-TM-650, method 2.3.28.  It won't usually tell you if you got all the
glycols off, but it can give you an indication if you have other detrimental
residues.  In some of our analyses, we sometimes see an odd peak in IC
analysis that is an indication of polyglycols, but at present, no
chromatographic methods exist to quantify glycols.

You might also try Fourier Transform Infrared (FT-IR) analysis, using the
ethylene glycol as a base.  A competant FT-IR chemist should be able to give
you and indication when the glycols are gone.

Is ethylene glycol a constituent of low solids fluxes?  Not in any that I
have ever looked at.  Most are a weak organic acid (e.g. succinic acid or
adipic acid) in an isopropanol carrier.  There might be a small amount in
some of the VOC-free (water-borne) fluxes, but only as a wetting agent and
then in very low amounts.

How to demonstrate that they are clean?  I would suggest some burn in
testing.  If you have that implemented on current product that you build, do
the same profile.  If you don't do burn-in testing, then you should.  You
might also do some power-temp cycling.

Hope this was helpful.

Doug Pauls
Technical Director, CSL

##############################################################
TechNet Mail List provided as a free service by IPC using LISTSERV 1.8c
##############################################################
To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body:
To subscribe:   SUBSCRIBE TECHNET <your full name>
To unsubscribe:   SIGNOFF TECHNET
##############################################################
Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional information.
For the technical support contact Dmitriy Sklyar at [log in to unmask] or 847-509-9700 ext.311
##############################################################