Would these work for cooling the MOSFETS?

fluxcapacitor · Dec 4, 2003

Before I post a link to these mem coolers I'm looking to put on the MOSFETs, lemme ask this...When cooling them, can I simply put one HS across all the voltage regulators or would that cause some sort of short and they need to have separate HSs? Anyways, next I'll be setting up my NF7-S system w/ TwinMOS 3700 so obviously I'm going for max FSB. Here's the mem coolers in question:

http://www.frozencpu.com/cgi-bin/frozencpu/ram-07.html
I could use these if the MOSFETs need individual HSs.

Or these if they can have one or more across all of the MOSFETs:
http://www.frozencpu.com/cgi-bin/frozencpu/ram-08.html

What are you guys' opinion on this? How feasible is it to think I can get these to stay on the MOSFETs w/ frag tape? I'd love to epoxy, crazy glue, or silicone slealant them on...but not if it means voiding my warranty.

Input appreciated here.

Korndog · Dec 4, 2003

uh.. they're pretty expensive..

if u got the tools, just cut up an alumium fan, works better because they're big and like 5 bucks

johan851 · Dec 4, 2003

Yup, use those tools and make your own. That tweakmonster stuff is way too pricey.

schismspeak · Dec 4, 2003

These are much cheaper and should work just as well.
http://1coolpc.com/ramsinks.htm

Sharkman · Dec 4, 2003

These over at 2CoolTek might even be cheaper. Buy a big one and cut into smaller ones to fit on the Mosfets.

fluxcapacitor · Dec 4, 2003

OK, and what about the the larger heatsinks extending over more than one of the regulators? Is that OK? I have a dremel and a few older Cooler Master HSFs that would probably be perfect...

JFAB199 · Dec 4, 2003

also if you have an old heatsink you don't use you could cut it up

JP_Singer · Dec 4, 2003

any of Those would be just fine

cobray · Dec 4, 2003

Your not going to gain anything by putting a ramsink on top of the plastic piece of the mosfet.
The best way to cool mosfets is to solder a piece of copper to the metal base thats sticking to the motherboard and let it stick vertical (up) to be cooled by any passing air in your case.

L337 M33P · Dec 4, 2003

cobray said:
Your not going to gain anything by putting a ramsink on top of the plastic piece of the mosfet.
The best way to cool mosfets is to solder a piece of copper to the metal base thats sticking to the motherboard and let it stick vertical (up) to be cooled by any passing air in your case.

Solder?

Mr B did some MOSFET mods here

And this guy cooled the backside of the motherboard where the MOSFETs were with a small waterblock.

WORD OF WARNING:

Do NOT allow any MOSFET cooling solution touch the copper wires wound round the ferrite rings, MOSFET legs or any part of the motherboard with solder points on it. The person doing the backside mod carefully isolated the footprint around the waterblock with thermal tape.

cobray · Dec 4, 2003

^^^, solder, YES! Just be careful d00d

L337 M33P · Dec 4, 2003

Where exactly would you put the solder? The motherboard tray or to points on the motherboard?

cobray · Dec 4, 2003

It would probably be best to just put solder on the copper piece and stick it to the mosfet "on top".
If you were looking at the mosfet on the motherboard, it would be the small metal piece that sticks out the top (the legs being on the bottom)

L337 M33P · Dec 4, 2003

That is probably dangerous - if anything comes into contact with the heatsink then either the Vcore or the PSU's supply rail may be shorted to ground. That would be bad.

Also the area of contact on the little metal tab would be tiny to say the least - much smaller than the surface area you would get using thermal adhesive on the top of the MOSFETs.

cobray · Dec 4, 2003

I would think that really the mosfet should just sit vertically rather than horizontally.
I dont think my idea can be any worse than sticking it on top of the plastic which is a poor thermal conductor as we all know.

I think it is just easier for people to sell heatsinks that sit on top of the MOSFET and be done with it. I dont think it is the most optimal way to cool it, though.

I could be wrong, though. Im not an electrical engineer.
But im not willing to just blindly believe that putting the heatsink on the plastic part of the MOSFET is the most efficent just because that is what most of the google hits shows.

cobray · Dec 4, 2003

All of the electronics books I have seen that show designs with MOSFETS have the MOSFET typically standing vertical with a heatsink attached to the opposite side of the plastic cover.

Like I said, Im not an electrical engineer. Maybe I should have spent more time actually reading the book instead of looking at the pictures, but this is what I have seen.

L337 M33P · Dec 4, 2003

The MOSFETs used to regulate Vcore actually benefit from being mounted on the motherboard as the motherboard PCB helps to conduct the heat away. If the MOSFET were to be mounted vertically then it would require heatsinking (costs more) and also the 2nd leg (cut off in photo, attached directly to the back tab) would have to handle the current going to the CPU. If you look the back of the MOSFET is attached to the inductors and capacitors that form the smoothing circuit for the Vcore. Assuming that an overclocked CPU can pull up to 50A that means up to 25A would have to go through that tiny leg. Which would melt it. Attaching the whole metal tab to the motherboard and soldering it allows for much less current density and will minimise losses and possible overheating problems.

The thermal solution provided by the motherboard is fine for Vcores up to 1.75V and wattages of about 70W (Pally XP, anyone?) but OCed CPUs can use up to 100W so it goes a bit beyond the designed margin of operation.

fhanderson · Dec 4, 2003

Get the and use a hacksaw to cut to size, the draw file the cut edges.
http://www.bestbyte.net/Product.cfm?ProductID=1314&CategoryID=6&Keyword=

Big_Baller · Dec 4, 2003

Ya just cut up an old heatsink like me. Works fine.

I used this dremal tool to sort of make little alcoves for the little beer cans on near there. So on the side you can't see it looks kinda like a key.

Aeon Flux · Dec 4, 2003

I reacently got a cheap econo biostar board and thought Id barely get anything out of it. Just figured Id use it for a couple months until I get better board. After opening the packaged though I was suprised that biostar actually cooled the mosfets. They have pretty standard 3 prong transistor heatsink on them but they work well and much better then most cooling mods for mosfets. The real heatsink thats supposed to get attached to transistors gets bolted to the metal tab above them that are sunck into the transistor. Thats what these do.

Again I was also suprised to find the northbridge was actively cooled. Looks basically like a 486 heatsink and fan but it works well. Dont need much bigger and with the stock cooling it comes with the northbridge never gets hot.

In fact the only not cooled was the southbridge. But even with the vcor jumped up over half a volt and the FSB jumped an extra 33 mhz it stays cool to the touch, room tempature actually. And the board is very easy to over clock. Basically if it posts then its stable. Ive tried and this board doesnt get unstable.

Would these work for cooling the MOSFETS?

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