Brian Denley wrote:
Chuck Harris wrote:

Hi Mike,


The process of defluxing involved dipping or spraying the chassis
in carbon tetrachloride, or later trichlorethylene.


..and you don't want to fool with either with what we know these days.
Tricloroethylene is a carcinogen and is banned in many microelectronic
houses.


So is gasoline, but there you are pumping it into
your car every week... sniffing the fumes that waift
up to your nose, wiping the spillage from the leaky
nozzles off of your hands.

I was involved in industry back in the hay day of
trichloroethylene. It was used in careless and ridiculous
ways. We had open jugs of the stuff everywhere.
We used it in vapor degreasers to remove solder flux,
photoresist, just about anything. There was nothing
in use before, or since that works as well as it
does.

Perhaps it is a carcinogen, perhaps it isn't. In any case,
banning it was a "knee jerk" over reaction. It would have
been better to encourage safer ways of using the solvent.

Instead, we have spent the last 30 years playing cat-and-mouse
games with the needs of industry for a good general purpose
solvent, and the needs of the regulatory agencies to ban
anything that has even a remote chance of being harmful.

Carbon tet was the king, it got dethroned, so they replaced one
of the chlorines with an ethylene molecule, and trichlor came
about. It was banned, so they changed the ethylene to an ethane,
and then a butylene, and then a butane, and then ... The latest
in the chain is pentachloroethylene. It will be banned one of
these days too. It won't take off solder flux, or much of anything
else.

As far as I can tell from my casual research on the subject, not
one single human has ever contracted a case of liver cancer
proven to be caused by exposure to trichloroethylene. Plenty
of rats have, but the amounts they were exposed to, or ingested
would never happen in real life.... well, not unless you were
trying to commit suicide with the stuff.

-Chuck Harris