Gainclones and fans, a bad mix ?

[TwoSpoons]

Has anyone considered a Peltier device as a heat pump to keep the chip cool no matter what the heatsink temp is

A Peltier is not going to help, only make your heat problem worse.
The COP of peltiers is poor, so if you're pumping 50W out of the cold side, its likely you'll have to get rid of more than 100W on the hot side! Remember also the pumping ability of peltiers drops as the temperature differential increases - usually dropping to zero at a temp diff of about 60C ( single stage )

 

[Oborous]

A Peltier is not going to help, only make your heat problem worse.
The COP of peltiers is poor, so if you're pumping 50W out of the cold side, its likely you'll have to get rid of more than 100W on the hot side! Remember also the pumping ability of peltiers drops as the temperature differential increases - usually dropping to zero at a temp diff of about 60C ( single stage )

Yup! Peltiers do put out alot of heat by themselves.

However, the Peltier is a heat pump, and so if you're extremely constrained for space/air-flow, you could use a combination of Peltier/heat pipe to force the heat away from the chip, then disappate it elsewhere.

I've just been trying to suggest the various wacky cooling that I've tried over the years (and I do mean wacky).

Potting the electrically insulated chip inLow Melting Point Alloys to increase surface area also could work. The joules/cm/second heat transfer isn't that great (nor can I remember the proper notation for the speed of heat exchange), but it gives you a massive surface area to work with.

Safety warning I do not suggest low melting point alloys, they have high concentrations of various heavy metals with some nasty side effects. MSDS sheets & proper handling proceedures are required.

Most low melting alloys have a high percentage of lead... that would damp any vibration...

 

[Vikash]

That was just WD40 and a disc sander?? Would you mind telling me a bit about what technique you did, any difficulties you encountered? I lap by hand, that looks way better than the other 'mechanically aided' lapping that I've seen. That would save so much time.

Hi Oborous, nothing special about the method. I have a cheap belt and disc sander machine to which I stuck wet and dry 1200 grit directly onto the metal wheel with some pva (which makes it easy to remove and clean afterward). Then as it's sanding just keep lubricating with WD40 and it comes out like in the pic. Also keep cold bowl of water nearby to cool the copper between sides