Mosfets and thermal paste

[Juddog]

I'm looking to cool my mosfets, but wondering if it's safe to apply thermal paste to them, so I figured I would check up with AT and see who has done it so far and if there was any issues before I try it.

 

[Sea Moose]

thermal paste is used between a heatsink and whatever you need to cool. <--- metal to metal
I know when i replace circuit boards i have to use paste or i get my ass kicked.

I dont see why you cant use it to cool your mosfet, but how are you going to attach the heat sink safely?

 

[sdifox]

what kind of mosfet do you have that is not attached to a heatsink?

 

[PottedMeat]

Sure it's fine. They've been doing it for decades.

Unless you mean without a heatsink... that would be just weird.

 

[DisgruntledVirus]

Originally posted by: Sea Moose
thermal paste is used between a heatsink and whatever you need to cool. <--- metal to metal
I know when i replace circuit boards i have to use paste or i get my ass kicked.

I dont see why you cant use it to cool your mosfet, but how are you going to attach the heat sink safely?

I think the first question is, outside of an industrial application or extreme OC'ing why do you need to heatsink your mosfets? I see no reason. Oh and FWIW "extreme OC'ing" I'm referring to the liquid nitrogen stuff that you boot the system long enough to get a benchmark score.

 

[Paperdoc]

Beyond the why? and how? questions above, my though is it is fine as long as you only put on enough to accomplish the main task, heat conductivity to the heatsink. Assuming your MOSFET device has a non-conductive case, there is no problem with using a heat conductor (which usually also is en electrical conductor) from case to heatsink. The problems come only when you get over-enthusiastic and put on so much it squeezes out and gets to the MOSFET leads. Then you do have a real problem because MOSFET's are designed for very low currents, and any minor electrical leakage between leads is a major disruption.

 

[bignateyk]

Depends what package it's in. If it is a TO220 I think it has a screw hole that you can easily attach a heatsink.

If it's a TO92 I don't see how you'd attach a heatsink to it.

 

[Sea Moose]

Originally posted by: bignateyk
Depends what package it's in. If it is a TO220 I think it has a screw hole that you can easily attach a heatsink.

If it's a TO92 I don't see how you'd attach a heatsink to it.

This guy obviously knows stuff.

 

[Juddog]

Well this was for a motherboard, the EVGA 790i FTW, it already has a heat sink that sits on top of the mosfets but there is no thermal paste or thermal pads from one surface to another.

 

[PottedMeat]

Originally posted by: bignateyk
Depends what package it's in. If it is a TO220 I think it has a screw hole that you can easily attach a heatsink.

If it's a TO92 I don't see how you'd attach a heatsink to it.

They've got TO92 heatsinks - basically clamp on sheet aluminum. Actually they shouldn't be using TO92 cases for power applications...

Originally posted by: Juddog
Well this was for a motherboard, the EVGA 790i FTW, it already has a heat sink that sits on top of the mosfets but there is no thermal paste or thermal pads from one surface to another.

Thats crappy of them - sure just apply some paste and you're good to go.

 

[Sea Moose]

Originally posted by: Juddog
Well this was for a motherboard, the EVGA 790i FTW, it already has a heat sink that sits on top of the mosfets but there is no thermal paste or thermal pads from one surface to another.

well, if the manufacturor didnt put it there, they didnt put it there for a reason. If the board is under warranty i wouldnt fuck around with it.

If you dont care about warranty, its not a bad idea, as a fine amount will help transfer heat away from mosfet, also putting a fan onto the heatsink will make a great addition to your mod. Be warned tho, heat transfer paste is very messy to work with, careful you dont get it on other parts

 

[esun]

MOSFETs? As in single discrete transistors? I'm not sure you'd need a heatsink on those except in rare circumstances. Anyway, it shouldn't be a problem so long as you don't touch the pins.

 

[Sea Moose]

Originally posted by: esun
MOSFETs? As in single discrete transistors? I'm not sure you'd need a heatsink on those except in rare circumstances. Anyway, it shouldn't be a problem so long as you don't touch the pins.

this, its not gay if the pins dont touch

 

[Sea Moose]

So you gonna put a fan on it? Respect to you if you do

 

[TecHNooB]

Applying thermal paste on a mosfet is perfectly fine.

 

[Sea Moose]

Originally posted by: Juddog
I'm looking to cool my mosfets, but wondering if it's safe to apply thermal paste to them, so I figured I would check up with AT and see who has done it so far and if there was any issues before I try it.

PLease take before and after pics. are you going to be awesome and add a fan to heatsink?

 

[sunzt]

Originally posted by: Juddog
Well this was for a motherboard, the EVGA 790i FTW, it already has a heat sink that sits on top of the mosfets but there is no thermal paste or thermal pads from one surface to another.

I don't know how much or what settings you're exactly overclocking, but it's not likely that the MOSFET temperature would be any sort of limiting factor. In other words, adding paste between the MOSFET and heatsink will not benefit you.

 

[PlasmaBomb]

Originally posted by: DisgruntledVirus

Originally posted by: Sea Moose
thermal paste is used between a heatsink and whatever you need to cool. <--- metal to metal
I know when i replace circuit boards i have to use paste or i get my ass kicked.

I dont see why you cant use it to cool your mosfet, but how are you going to attach the heat sink safely?

I think the first question is, outside of an industrial application or extreme OC'ing why do you need to heatsink your mosfets? I see no reason. Oh and FWIW "extreme OC'ing" I'm referring to the liquid nitrogen stuff that you boot the system long enough to get a benchmark score.

Plenty of people water cool their mosfet...

This is how not to do it.

 

[Sea Moose]

Originally posted by: PlasmaBomb

Originally posted by: DisgruntledVirus

Originally posted by: Sea Moose
thermal paste is used between a heatsink and whatever you need to cool. <--- metal to metal
I know when i replace circuit boards i have to use paste or i get my ass kicked.

I dont see why you cant use it to cool your mosfet, but how are you going to attach the heat sink safely?

I think the first question is, outside of an industrial application or extreme OC'ing why do you need to heatsink your mosfets? I see no reason. Oh and FWIW "extreme OC'ing" I'm referring to the liquid nitrogen stuff that you boot the system long enough to get a benchmark score.

Plenty of people water cool their mosfet...

This is how not to do it.

i watched the vid plas, what was wrong with how that guy set up liquid cooling?

 

[So]

Originally posted by: esun
MOSFETs? As in single discrete transistors? I'm not sure you'd need a heatsink on those except in rare circumstances. Anyway, it shouldn't be a problem so long as you don't touch the pins.

Oh, there are LOTS of uses where discrete transistors need heatsinks.

 

[PlasmaBomb]

Originally posted by: Sea Moose

Originally posted by: PlasmaBomb

Originally posted by: DisgruntledVirus

Originally posted by: Sea Moose
thermal paste is used between a heatsink and whatever you need to cool. <--- metal to metal
I know when i replace circuit boards i have to use paste or i get my ass kicked.

I dont see why you cant use it to cool your mosfet, but how are you going to attach the heat sink safely?

I think the first question is, outside of an industrial application or extreme OC'ing why do you need to heatsink your mosfets? I see no reason. Oh and FWIW "extreme OC'ing" I'm referring to the liquid nitrogen stuff that you boot the system long enough to get a benchmark score.

Plenty of people water cool their mosfet...

This is how not to do it.

i watched the vid plas, what was wrong with how that guy set up liquid cooling?

I'm just being harsh because of the mistakes.

Set up seems OK, though I don't know about the double double rad. I would have thought that would have cut the air flow a brave bit.

 

[Special K]

Originally posted by: So

Originally posted by: esun
MOSFETs? As in single discrete transistors? I'm not sure you'd need a heatsink on those except in rare circumstances. Anyway, it shouldn't be a problem so long as you don't touch the pins.

Oh, there are LOTS of uses where discrete transistors need heatsinks.

I was just about to post this. There are high-power MOSFETs that definitely require heatsinks.

 

[VashHT]

Originally posted by: Special K

Originally posted by: So

Originally posted by: esun
MOSFETs? As in single discrete transistors? I'm not sure you'd need a heatsink on those except in rare circumstances. Anyway, it shouldn't be a problem so long as you don't touch the pins.

Oh, there are LOTS of uses where discrete transistors need heatsinks.

I was just about to post this. There are high-power MOSFETs that definitely require heatsinks.

Seriously, apparently he's never opened a power supply before, the switching FET's in there are bolted to a huge heatsink. See here.

 

[frostedflakes]

It couldn't hurt to throw some thermal paste on there. Just be careful not to short the legs if you're using a conductive paste, though (these are pretty rare, I think most TIM these days are non-conductive, but just something to keep in mind).

Honestly, the MOSFET heatsinks on your board are probably more for bling than anything else, lol. Especially on newer boards with 4+ phase power circuitry, I don't think the MOSFETs really get stressed too much. As others have mentioned heatsinks might be a good idea if you're really pushing things (phase change or LN2 cooling, stuff like that), but otherwise they're probably not really necessary for this application.

 

[Howard]

Originally posted by: bignateyk
Depends what package it's in. If it is a TO220 I think it has a screw hole that you can easily attach a heatsink.

If it's a TO92 I don't see how you'd attach a heatsink to it.

Epoxy. Penny might work. Paperclip, maybe, and you might even be able to get away with not using epoxy if you could keep it from shorting the pins.