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new material for a heat sink

new material for a heat sink

new material for a heat sink

(OP)
hi there

at the moment we use a copper chrome disk (concave and convex lens shaped) to transfer the heat from a cast iron base to a pyrex cap, the curvature of the cap and the base are different so the copper has a varying thickness.

what is happening is that the caps are cracking, and the coppers expansion is a consideration.

what im looking for are aternatives to the copper chrome, i need a high thermal conductivity and a low thermal expansion.

the caopper insert has at the moment a

COE = 18x10-6/degC
Thermal conductivity = 300w/m degC

any help would be greatly appereciated :)

RE: new material for a heat sink

Maybe use something softer than the copper, such as lead or heat-conductive putty. Might not stress the Pyrex as much.
Both are easy to form, so can make thinner than the copper to compensate for lower conductivity.

RE: new material for a heat sink

looks like you are generating a hot spot in the glass. in that case what you need is to reduce(not increase) the thermal contact.

basically use a lower conductiviy material than copper.

RE: new material for a heat sink

If the Pyrex cap is breaking due to thermal stress, switch to fused silica glass [it can withstand a quench from 850oC into icewater].

If the Pyrex cap is breaking due to mechanical stress, i.e., from the male copper part expanding inside a female cap, maybe you should change the design.  Would a porcelein coating on the cast iron satisfy your requirements (chemical resistance? electrical insulator)?

RE: new material for a heat sink

(OP)
thanks for the replies,

kenvlach, is fused sillica not quite expensive?  and porcelin i have not thought about that. interesting

RE: new material for a heat sink

Metals:                COE (ppm/C)     TC (W/mK)
Molybdenum                 5           150
Tungsten                   5.5         200
copper-tungsten            8.5         210
copper-molybdenum          7.0         150

Ceramics:

aluminum nitride            4.6        190
silicon carbide             3          130

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