"harrogate" wrote in message
...
"Chris Isbell" wrote in message
...
On Thu, 4 Sep 2003 12:14:31 -0700, "jim"
wrote:
Solder is very bad. It contains lead. This kills people. A whole
generation
died in Latvia digging it up. Solder also contains tin. Years ago,
Cornish
miners were killed by the thousand looking for it... The newsreels
tell
us
these people were only available in black and white, as well. I now
use
3/8" nuts and bolts for all connections......
Don't worry about the solder, worry about power semiconductors stuffed
full of beryllium oxide (beryllia). This stuff is really toxic. (See:
http://www.mcga.gov.uk/msn/msn0646.pdf.) So don't go sawing-off the
tops of your amplifier's output transistors to let the sound out
unless you know exactly what you are doing or you have a death wish!
An engineer I knew years ago did cut off the tops of power transistors
(after checking that they did not contain beryllia) and produced an
oil-cooled amplifier. Again, not recommended for your average hi-fi
enthusiast.
--
Chris Isbell
Southampton
UK
I suppose you can read anything you want into that link - it is a bit
(deliberately?) vague.
Beryllium Oxide powder - usually in a paste form - has been used for over
30
years in radio frequency (RF) power transistors. It has the near unique
capabilities of being an excellent heat conductor whilst being an
essentially pefect insulator.
In transistor fabrication there are two opposites: the higher the power
rating of the device the bigger the junctions of the chip need to be, and
the bigger they are the higher their capacitive coupling and thus the
lower
the maximum frequency at which they will work. There is also need to
dissipate heat from the junction. Manufacturers thus came up with the
commonly used method of construction for RF transistors of having one
collector, one base, and multiple emitters - we're talking dozens if not
hundreds here. This permits low capacity and thus high frequency per
junction, but high current capability of the parallel emitters. When
you've
gone to all this trouble to get the power at the frequency you still need
to
get rid of the heat and research showed that Berryllium Oxide was the best
substance to use in this application.
AIUI it is most toxic in dust form as it caused paralysis - in most RF
powers transistors there is a very small quantity directly underneath the
chip in a sort-of paste form, so unless the device has been open to the
air
for some considerable time and had time for part of that paste to dry out,
and you go sniffing immediately around it - in general use the risk it
presents is minimal enough to be ignored. Not to say that you should not
still take care when handling devices.
RF power devices are usually in a round plastic case with four equispaced
radial leads, mounted on either a screw (making what is commonly called a
'capstan' case) or onto a small flat 'rounded diamond' metal base that has
two screws on opposite sides to mount it - this heatsink is often gold
coloured, even gold plated, to aid heat conduction. Many such devices are
made by Motorola and the plastic case is white, for most other
manufacturers
the plastic case is grey.
Most people not in the radio communications industry will rarely come
across
these devices.
--
Woody
when I worked at Gardners Electronics 89-97 (Christchurch, Dorset),
we used Beryllium Copper crinkle washers by the thousands,
they were lovely and dusty and nobody ever warned us about the danger.
in 94 when new owners came in we went over to Stainless Steel fastners.
so out went the Beryllium Cuprle! and the Zinc plated Cadmium coated machine
screws / nuts.
one benefit Stainless fastners dont dry your fingers.............!!!
regards malcolm
Is solder bad for music?
Linear Mode
