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Registered Member #2463
Joined: Wed Nov 11 2009, 03:49AM
Location:
Posts: 1546
Can I cool this device effectively without having to worry about a CC supply trying to force current across the submerged diode leads instead of through the diode junction? I don't want to deal with hydrogen and oxygen being produced. It would be neat to keep the thing in a little sealed container of water + some small air gap.
This part of your post makes me think of compounds that cool when they go into solution, rather than heat. Glauber salts come to mind. If the leads of the diode could act as electrodes to control the rate of solute/solution in the zone where the diode is, you might achieve your cooling.
Registered Member #146
Joined: Sun Feb 12 2006, 04:21AM
Location: Austin Tx
Posts: 1055
Getting rid of the thermal pad (electrical isolation) between the diode and the heatsink would increase the effectiveness of the heatsink tremendously. With a heatsink that size, and high air flow, id guess the total resistance is less than 1*C/W, so you could operate continuously at about 80*C heatsink temp, which would be something like 110*C chip temp (assuming the thermal resistance of the TO-247 is 0.5*C/W or so). The thermal pads usually add >1*C/W thermal resistance. often times several *C/W on a TO-247, which really cripples their performance.
Also, i would calculate the thermal performance of any fluid before just going for it, my guess is oil may not really give the desired performance especially if you had water in mind to begin with. Id also say that the 60W you need to dissipate is completely realistic with a heatsink and fan, especially a recycled CPU cooler setup with only thermal grease used between the diode and heatsink.
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Biasing a submerged diode
