[Amps] Re: Beryllium Oxide (was Need info on 8874's)

[Dave Haupt]

K8GG wrote:

>>The ceramics have Beryllium Oxide so be careful when
scrubbing not to abrade them.  The hazards sheet is
big on the danger of dust or fumes from BeO.

>>Several posts on this reflector have warned people
to wash hands thoroughly after handling ceramic
amplifier tubes.  I would guess that wearing
dishwashing gloves would be a good idea if trying to
clean the tubes.<<

This is not correct.

BeO is only used in situations when you need excellent
thermal conductivity in an electrical insulator.  It
is used in the conduction-cooled 8873, and is used in
almost all of the power RF transistors that are
discussed on this email list.

It is true that Eimac's material hazards sheet, packed
with new tubes, warns about BeO.  However, that sheet
is packed with every tube.  When they still
manufactured glass tubes, you got the same sheet with
the same BeO warning.

The ceramics used in the Forced-Air Cooled tubes do
not need to be thermally conductive, and therefore do
not contain BeO.  There'd be no benefit, and it's
darned expensive stuff.

Where I work, we use BeO to bond semiconductor
substrates to Copper-Tungsten heat spreaders.  We try
to avoid it due to cost and environmental/health
hazards.  Eimac would not have been able to afford to
sell 8874s for the price they did, if that ceramic was
BeO loaded.

It's still good to take care not to damage the
ceramics, but you don't need to be worried about BeO
in those tubes.  Many ceramics involve lead in the
construction and/or processing, as well as other heavy
metals, so it's still a good idea to wash your hands
after handling.

73,

Dave W8NF

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