More on Cleaning boards (long)

[Doug Aab]

I would like to add a little chemical clarification on alcohols to the
discussion for some that may be interested; we are talking about two very
different chemicals that have some similar but some different properties, the
least of which is concentration (%) in water.

Isopropanol, commonly known as a component of rubbing alcohol, is very toxic,
has a low boiling temperature, and is very flammable.  It is available in
many concentrations, produced by industrial processes; pure (99+) isopropanol
 takes a lot more energy to produce than 70%.

"Alcohol", on the other hand, commonly refers to Ethanol, which can be
produced by fermentation or other industrial processes (Technically,
"alcohol" is a certain class of chemicals). It also is available in many
concentrations, the most pure of which also take a lot of energy to produce.
Ethanol concentration can be expressed as "proof", the proof number being
twice the concentration.  Ethanol is sometimes "denatured" for its use in
industrial applications; it is denatured by adding another toxic component
which renders it unsafe to drink (and non-taxable).  Sometimes isopropanol is
used to "denature" ethanol.  People get sick and sometimes die from drinking
denatured ethanol, thinking they are drinking everclear.  Ethanol has an even
lower boiling point and is also very flammable.

There are many other alcohols that make good solvents in industrial
applications.  Sometimes alcohols are used as a "co-solvent" to make two or
three other components stay in solution, that would ordinarily not.  A cousin
of isopropanol, n-propanol, is used in ink.  I'm aware of one large circuit
board/chip manufacture that uses very pure, very dry "butanol" to clean
silicon wafers.

Sometimes suppliers buy high concentration chemicals and then dilute them
before repackaging them for consumer use (don't have to pay for shipping
water).  It's possible that the residue left may just be hardness (dissolved
minerals) in the particular local water used for dilution.  It could also be
because the evaporating alcohol has carried off a volatile chemical that the
board or part is made of; resulting in an actual composition change in the
surface of the board or part.

So when comparing these two solvents, be aware that it is not just the
concentration that has an effect on cleaning parts, dissolving the colors off
of resistors, or the bristles off of brushes, but the type of alcohol too.  I
remember that for a while the "gasohols" that were available in the midwest
were dissolving plastic parts in car fuel systems - I think they were using
ethanol - then the auto companies started using different plastics.

I don't pretend to know which is the better solvent for cleaning. I've
enjoyed listening to everyone's experience and enjoy this list. Thanks for
the read.

Regards, Doug

Sponsored by the City of Tempe 

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