[time-nuts] beryllium oxide

[v. Bonhorst]

BeO furthermore had been used in some types of RF attenuators, especially
for higher power, as a insulating washer for transistors (High voltage power
transistors, RF terminating resistors, Thermal studs and so on. Although it
is replaced nowadays in most cases by different materials, Beo can be found
easily in older equipment. 

Hubert
DB 7 ME 

-----Ursprüngliche Nachricht-----
Von: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] Im
Auftrag von Robert Atkinson
Gesendet: Freitag, 16. Januar 2009 19:59
An: Discussion of precise time and frequency measurement
Betreff: [!! SPAM] Re: [time-nuts] beryllium oxide

I've personally seen three applications of BeO in electronics. Two,
including the most common, are a possible hazzard.
The most common application is RF power devices (transistors and terminating
resistors). These hace a "washer" or slab of BeO between the semiconductor
device and the mounting stud or flange. Asthis is trypically below the
electrical connecting leads (often wide strips or tabs), application of
excessive force between heatsink and PCB can fracture the BeO causing dust
an chips/splinters. Splinters onder the skin or in the eye can cause
problems as well as inhaled dust. force can be applied during manufacture /
service or in an accident or if the item containing the unit is crushed.
Next most common is the use in metal can semiconductors. One example are
early LM78Hxx TO3 regulators. These are fairly safe as the can has to be
ruptured. The third is as a block of solid BeO bonded to metal plates used
to insulate conduction cooled vacuum tubes. Some power tubesmay use it
internally. A big problem is that it looks like any other ceramic. In some
UK equipment
 devices containing BeO will be marked with "cornflower blue" paint dot. A
non-electronic application is in some (eg argon-ion) lasers.
on a side note some vacuum tubes (especially cold cathode types) contain
various radioactive materials.

Robert G8RPI.


--- On Fri, 16/1/09, Mike S <mikes at flatsurface.com> wrote:

> From: Mike S <mikes at flatsurface.com>
> Subject: Re: [time-nuts] beryllium oxide
> To: "Discussion of precise time and frequency measurement"
<time-nuts at febo.com>
> Date: Friday, 16 January, 2009, 6:28 PM
> At 12:45 PM 1/16/2009, Lux, James P wrote...
> >More realistically, the dangeris dust when something is
> physically 
> >overstressed (dropped, mounting overtightened, thermal
> shock). That, 
> >and if it gets ground up in trash disposal... Say
> someone throws it in 
> >the shredder.
> 
> So, if some electronics have an IC with a BeO package, and
> it sits 
> undisturbed, what's the problem? It seems to me that
> most, if not all, 
> such uses would be additionally contained by heatsinks and
> compound, 
> since it's the thermal conductivity properties which
> caused it to be 
> used in the first place.
> 
> Hard to say how much dust might be produced by dropping or 
> overtightening. In my experience, ceramics tend to break
> pretty 
> cleanly. Maybe BeO is different.
> 
> Granted, the manufacturer can be expected to be biased, but
> Brush 
> Ceramics claims "Beryllium oxide (BeO), in solid form
> and as contained 
> in finished products, presents no special health
> risks." They also 
> claim "Under federal regulations and most state
> regulations, BeO 
> ceramic or products containing BeO
> ceramics that are no longer recyclable and declared solid
> wastes are 
> not classified as hazardous waste due the content of BeO
> ceramic." 
> 
> 
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