Uneconomic in the US perhaps, but the world price for sheet mica was about 50 cents a pound in 2005. That doesn't seem overly expensive.
It has been supplanted by other materials that work better, are less fragile, and sometimes cheaper.
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On Fri, 29 Dec 2006 09:45:49 -0500, cmp Gave us:
That only sounds "hot" to an Italian.
On Fri, 29 Dec 2006 16:14:55 -0500, default Gave us:
Considering that the deposits of it are not overtly large, it is. Copper was that price at one time. For an insulator material to be half the price of copper tells me that it is fairly expensive.
Die cut items from sheet stock cleavings of it would seem even more expensive.
Regular virgins are OK, but the extra virgins are usually just too fussy.
John
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Well, some of the posters are starting to provide links. Where are yours? You have quacked on this twice now, but still no links of your own.
Due to physics (that i still cannot follow all of, though electron mobility is a common theme) electrical conductors make the best thermal conductors, and electrical insulators make the best thermal insulators. It is also an empirical fact. Electrical insulators that are decent thermal conductors are very difficult to find or manufacture.
The ceramics BeO and AlN are unusually good thermal conductors, both in the ballpark of aluminum.
The opposite case, electrical conductors that are thermal insulators, is even nastier. Most metals run around 160,000 degC/watt per ohm of resistance. Brass seems better, at around 230,000. Superconductors have an infinite ratio, zero resistance but finite theta.
John
On Fri, 29 Dec 2006 18:53:40 -0800, John Larkin Gave us:
would
Taken one at a time... they all end up saying...
Don't... stop... don't... stop...
I prefer a blob of solder paste under the semi, on top of a large copper heat spreader, run through an oven.to reduce thermal impedance! Rework / repair can be a bitch though.
Jeff
On Sat, 30 Dec 2006 18:43:43 GMT, "Jeff L" Gave us:
It can also be a bitch if it must be electrically insulated from the heat sink. Say... 2kV. Oooops
They don't work as well.
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