Proper way to use thermal paste , transistors/heat sink .

[SoundOfSound]

The cheap ones are a waste of time and do quite poorly. The best ones are superior to mica. Testing one cheap thermal pad and deciding that all the rest will perform similarly is a mistake.

One of the biggest problems with mica is the variances in thicknesses. They are all over the place. A small increase in thickness means a quite large decrease in thermal conductivity. Mica sucks for conducting heat.

I realize that this may be difficult for you to understand. All I can tell you is to do your own research and come to your own conclusions.

Are these the pads you were recommending in your other post?

http://www.mouser.com/ds/2/48/PDS_SP K10_1113-519995.pdf

 

[fred soop]

Interestingly, Nelson Pass claims that by.. his.. testings: Thermal pads are 50% more insulating than simple Mica and goo.
Only discerned advantage is in ease of application.. no messy goo.
But What would He know about adequately cooling devices in High Heat Amps.

More insulating or more conductive? If "more insulating", then you are saying that the pads are not as good which is consistent with specs I have seen.

 

[fred soop]

While everyone is perusing the ON Semi site notice that the torque specs are listed as well, 6 in/oz for TO-3 and TO-220. As far as the mica/goop goes this is what I do, spread a thin even coat on the transistor then press the mica over this thin coat, remove the mica and turn it over and reinstall on the transistor. Now you have two thin coats on each side.

Craig

My reason for greasing the transistor first, then apply the mica, then grease the exposed side of the mica as opposed to doing both sides of the mica, then installing, is mess. If you start with the transistor itself, you have something to hold that isn't going to get greasy, the top of the transistor. That stuff does not wash off, it can only be wiped off and the residue worn away over time.

 

[EchoWars]

Are these the pads you were recommending in your other post?

http://www.mouser.com/ds/2/48/PDS_SP K10_1113-519995.pdf

Yep...the K-10 is good stuff. Not cheap though.

 

[avionic]

dare ya to say that real fast 3 times......

pmds,pmds,pmds.....:d

 

[JURB]

Interestingly, Nelson Pass claims that by.. his.. testings: Thermal pads are 50% more insulating than simple Mica and goo.
Only discerned advantage is in ease of application.. no messy goo.
But What would He know about adequately cooling devices in High Heat Amps.

Unfortunately, you can tell him he cannot make that claim. Simple mica needs to be defined. I have seen it so thin that I would not use it, like for a horizontal or LOPT. Or a chopper in a power supply.

The good thin but dense ones are most likely better than the plastic. But the bottom line is - how much does it matter ? Of all the thermal resistances added up between the junctions and the atmosphere, this is only one component. It is important of course, but these things can take SOME heat.

The problems arise in thermal tracking. the fedback is slowed down.

But I digress, this has to be defined, he cannot say that that really thick 2 KV insulating stuff you could use to set the points on a car is better than the gray rubber stuff. No way. But there is alot thinner out there, and of course it is rated for less voltage. Mica insulators that are only rated for like 150 volts may well be better than the rubber. Real thin.

Too many different types.