Dear all,

I have a problem with contamination of a silicon device in a liquid nitrogen
cooled cryostat, the contamination is a white residue containing carbon +
oxygen and nothing much else except possibly hydrogen which I can not
measure by technique used.

Source of contamination could be remote source of solder flux cleaned with
acetone or by product of PTFE degraded by cleaning both seem to leave a
similar thick white residue.

Any ideas on why we get white residue or how to clean solder flux off PTFE
and not leave any volatile components (ideally with solvent that can be used
in any well ventilated room) gratefully received .

Regards and Merry Xmas!

Sarah Sharp


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