[volt-nuts] Best cleaning procedure for precision cirquits

Chuck Harris cfharris at erols.com
Sun Sep 26 14:22:37 UTC 2010

Vapor degreasing with trichlor was definitely a nice way to clean most
everything, but alas, you can't buy trichlor in bottles bigger than about
8 oz anymore.  Sales of bulk quantities has been banned in the US for
over 30 years.

-Chuck Harris

Alan Scrimgeour wrote:
> The precision instrument production line where I used to work used old
> style fluorocarbon solvent. The cold boards are lowered into vapour
> above a boiling tank of solvent so they are washed with pure condensing
> solvent. The tank has a water cooled collar to prevent excessive loss of
> solvent to the atmosphere. The room has a very powerful extraction
> system to keep vapour levels safe to breath. After a while the boards
> heat up and no further condensation takes place so the boards are
> removed and allowed to cool. The process is repeated several times. The
> tank has a secondary smaller compartment which is also heated but
> doesn't receive the distillate from the condensing collar. All the
> solvent from the main tank is transferred to this secondary tank by hand
> occasionally to repurify the main tank solvent. The result is that flux
> and other crud collects in the secondary tank and boards are washed only
> in self condensed very pure solvent with a minimum of impure spray (from
> boiling bubbles) mixed in. This was found to be essential for instrument
> to give the highest accuracy. Presumably that was down to leakage at op
> amp inputs. Less polluting water based board cleaners where tried but
> the boards took ages to stabalise afterwards even if baked in ovens.
> I don't know if such care is necessary for a reference, but I'd choose
> to use it anyway if I could.
> Alan

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