Homebrew PCBs

I recently read someone here mention that they used mineral spirits
(MS) to remove flux.  Since I had some around I gave it a go.  It
seemed to work about as fast as 91% IPA, but left less flux residue
spread around the board (i.e. none).  I found a manufacturer's
reference to using mineral spirits in place of chlorinated hydrocarbon
solvents to remove non-corrosive solder flux from copper here:

http://www.fusion-inc.com/filler2.htm#anchor237100

although, since it's paste solder they're talking about, I suspect
they're taking about using MS to remove flux from copper pipe joints.

I also found another site:

http://www.logwell.com/tech/servtips/cleaning.html

which discussed a few of the substances they used in the cleaning of
electronics in general:

"Our work bench is also stocked with a MENDA dispenser full of
denatured alcohol.  Denatured alcohol is ethanol with small amounts of
methanol or other denaturing agents added to render it unfit to drink.
 ... Denatured alcohol is very good for cleaning soldering flux; it is
now our favored circuit board cleaning agent since the demise of 1,1,1
(1,1,1 Trichloroethane a/k/a methyl chloroform)... Rubbing or
Isopropyl alcohol is a considerably less efficient cleaner and it
makes your shop smell like a doctor's office.  Commonly available
"rubbing alcohol" is usually 70% isopropyl alcohol with the balance as
water.  Anhydrous or 100% isopropyl alcohol is available and is
sometimes used as an industrial flux cleaner.  Occasionally, a
stubborn stain will yield to one of the alcohols when all other
cleaning agents fail, but ordinarily they are mediocre performers. 
Both denatured ethanol and isopropyl alcohol are generally safe on
plastics, but ethanol will mildly attack a few plastics."

About denaturing agents used in denatured alcohol:

"The completely denatured alcohol formulation used in the United
Kingdom contains (by volume) 89.66% ethanol, 9.46% methanol, 0.50%
pyridine, 0.38% naphtha, and is dyed purple with methyl violet."

Other "typical additives are methanol, isopropanol, methyl ethyl
ketone, methyl isobutyl ketone, denatonium benzoate, and even aviation
gasoline."

> Other "typical additives are methanol, isopropanol, methyl ethyl
> ketone, methyl isobutyl ketone, denatonium benzoate, and even
> aviation gasoline."

BTW, methyl ethyl ketone is MEK. Denatured alcohol can have "nasties" 
albeit in small quantities. Ethanol evaporates too fast to be better 
than MS for flux removal IMO. While fast evaporation is necessary for 
cleaning surfaces like glass to prevent smearing (methanol is the best 
here), a more balanced solvent is better suited for heavy deposit 
buildup. Furthermore, MS plus compressed air will evaporate almost as 
fast as acetone, in other words you have control over the rate of 
evaporation.

--- In Homebrew_PCBs@yahoogroups.com, "wbblair3" <wbblair3@...> wrote:
>
>

--- In Homebrew_PCBs@yahoogroups.com, "derekhawkins" <eldata@...> wrote:
>
> > Other "typical additives are methanol, isopropanol, methyl ethyl
> > ketone, methyl isobutyl ketone, denatonium benzoate, and even
> > aviation gasoline."
> 
> BTW, methyl ethyl ketone is MEK. Denatured alcohol can have "nasties" 
> albeit in small quantities. Ethanol evaporates too fast to be better 
> than MS for flux removal IMO. While fast evaporation is necessary for 
> cleaning surfaces like glass to prevent smearing (methanol is the best 
> here), a more balanced solvent is better suited for heavy deposit 
> buildup. Furthermore, MS plus compressed air will evaporate almost as 
> fast as acetone, in other words you have control over the rate of 
> evaporation.

Yes, some of those ingredients surprised me.  Basically it's, "You
didn't pay taxes to the government for this booze, so we're going to
put something in it the that'll blind you or kill you."  How very
nice.  I remember reading elsewhere that there's a move to agents that
won't kill you, they just taste _extremely_ bad, like denatonium
benzoate.  

Besides being hazardous to your health, MEK is used to clean resin
epoxies off tools used with them, so I wonder what it does to the
already cured epoxy of a PCB?

At 17:55 06/02/12, wbblair3 wrote:
>...MEK is used to clean resin epoxies off tools used with them,
>so I wonder what it does to the already cured epoxy of a PCB?

MEK causes cured epoxy to swell and soften after long exposure.
As a wash or dip followed by air drying, problems are unlikely.

Regards, LenW


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At 17:55 06/02/12, wbblair wrote:
>--- In Homebrew_PCBs@yahoogroups.com, "derekhawkins" <eldata@...> wrote:
> > > Other "typical additives are methanol, isopropanol...
>Yes, some of those ingredients surprised me..

And me. IIRC a bottle of UK "Surgical Spirit" AKA "Rubbing Alcohol" had
2% castor oil, making it less than ideal as a pre-TT PCB cleaner :-(

Similarly, "nail varnish remover" (acetone) is likely to contain perfume
and oil or lanolin to make it nicer to use.

LenW




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