Heatsink foam: keep, remove or replace?

[JingYing]

I'm recapping a M2A-VM HDMI motherboard. The chipset heatsink (passive) is known to become very hot and watching how "brownish" got the motherboard (pic. 1 & 2), I decided to (at least) renew the thermal paste, maybe add also a fan, should the mb turn on...
Unmounting the heatsink I discovered a square of foam around the central area, where the chipset stands (pic. 3 & 4); it seems to be placed over the SMDs (pic. 5).
I really have no idea how to replace the foam, so I'm carefully scratching the old paste without touching the foam and I indend to reuse it as is; in the process of unmounting, the foam got away from a little spot (pic. 3), but 95% is still there.

What's for this foam? It's just mechanical: to help place the heatsink flat?
Should I replace/remove it?
Thank you for any advice.

[ratdude747]

Re: Heatsink foam: keep, remove or replace?

I'd keep it... sure it won't cool as well, but unless you're having issues, I wouldn't sweat it. (I've done this both ways, no change either way).

[shovenose]

Re: Heatsink foam: keep, remove or replace?

I always assumed this was just to keep the heatsink straight and to prevent it from touching the chip it was cooling if it was grabbed or pushed.

[ChaosLegionnaire]

Re: Heatsink foam: keep, remove or replace?

the pad is actually to prevent too much mounting force exerted from the heatsink's mounting clips onto the smds or substrate, causing the die or smds to crack.

the pad is pretty worn and i recommend replacing it or it may not be able to cushion the mounting pressure as well and damage the nb chip.

here are just some examples u can use as a replacement tho u have to source for them urself in italy.

Phobya Special Thermal Pad for Chipset Cooling 35x35x1mm
Alphacool Double-Sided Adhesive Pad 100x100x0.5mm <- u have to cut this to desired dimensions.

also i recommend u get mosfet heatsinks for the mosfets near the northbridge that are making the board discolored as shown in the photos and maybe a bigger nb heatsink or an active nb cooler with heatpipes if the heat is really freaking u out.

[JingYing]

Re: Heatsink foam: keep, remove or replace?

Thank you all, for now I'll try to keep it, remounting the heatsink very carefully.
I'll also add a fan over the northbridge heatsink and the voltage regulators.
Regulator heatsink is also a good idea, although I have no idea how to mount one on those (a simple vertical plate somehow soldered to the tab would be effective?) and I just hate the idea of having some output voltage towering around...

[goontron]

Re: Heatsink foam: keep, remove or replace?

did anybody notice a cap next to the ram socket looks bloated.

[Th3_uN1Qu3]

Re: Heatsink foam: keep, remove or replace?

did anybody notice a cap next to the ram socket looks bloated.

Actually, a couple of them do.

[JingYing]

Re: Heatsink foam: keep, remove or replace?

Make them three! (Two near the IGP)
That's why I'm recapping those ATWY, and the KGZ, too!
https://www.badcaps.net/forum/showthread.php?t=28796

[Th3_uN1Qu3]

Re: Heatsink foam: keep, remove or replace?

Good choice. I polymodded a customer's board just a few days ago. Had all but one cap popped in the CPU VRM (TK ATWB 6.3v 1800u), and another one of the same kind above the chipset.

[ChaosLegionnaire]

Re: Heatsink foam: keep, remove or replace?

yea most likely the power guzzling nb becomes very hot and the mosfets are stressed out trying to keep the power guzzling nb fed so they overheat as well.

thus the combined heat from the power hungry nb and the stressed out mosfets combine to create a lot of heat that is conducted along the pcb traces to the caps which overheats them and kills them by bloating thru heat.

powerful cooling applied on the nb and mosfets would make the system last longer as the heat from those is no longer conducted to the caps which prolongs their life.

this is what i call indirect capacitor cooling yah~ which is what this site is about!

just like the doctor ordered: prevention (of cap failure) is better than cure! (recap)

[JingYing]

Re: Heatsink foam: keep, remove or replace?

Yeah, probably a better design (orienting cpu with stock heatsink fins toward the northbridge) and quality caps would have prolonged its life. Instead, now I have to "cure"... (still training on my old dead pentium II).

[y_not]

Re: Heatsink foam: keep, remove or replace?

The pad is actually to prevent too much mounting force exerted from the heatsink's mounting clips onto the smds or substrate, causing the die or smds to crack.

That is correct, it's mostly for short circuit protection more than anything.
However, it will not prevent the die on the bga package from cracking/chipping. That can still be done if one is careless, nothing prevents it except the use of a heatspreader.

the pad is pretty worn and i recommend replacing it or it may not be able to cushion the mounting pressure as well and damage the nb chip.

Incorrect. So long as the pad is even at least somewhat there, even say 1/4 of it on opposite sides. It's still good enough.
It is not a required item.

The adhesive TIM pads you linked to aren't necessary for this particular application. A good cleaning & some AS5 would work just fine.
Those pads are simply for thermal transfer of the die to heatsink, just like thermal grease. They are not for electrical insulation, which is what this application requires and is the very reason that foam was originally installed on the underside of the aluminum heatsink block in the 1st place.

You could just as easily cut your own little shims from some egg foam soft core type packing material, then glue it on /w high temp glue that's compatible with the 2 materials. Of course, only doing so once you have completely removed & cleaned off the old foam spacer.
I'd say glue that can handle at least 180deg F. But they can hit up to about 200-250F with lack of cooling.

Honestly, in all my years of PC repair, I have never worried about these things. If I ever had found one that was totally shot & I was worried about the end user mucking with it, I would have simply cut up a mylar sheet from an old laptop or something and glued it onto the NB/SB/IGP to insulate the SMD components from being shorted by the heatsink. But I never encountered such a situation, or at least one that I was concerned about anyway.
I have seen manufactures do the exact same thing, either glued to the mounting substrate itself, or the underside of the heatsink.

also i recommend u get mosfet heatsinks for the mosfets near the northbridge that are making the board discolored as shown in the photos and maybe a bigger nb heatsink or an active nb cooler with heatpipes if the heat is really freaking u out.

Oh, absolutely. I couldn't agree more with this.
In fact, simply use some Arctic Silver Thermal Adhesive and glue some heatsinks onto those mosfets using that. Any old heatsink will do, cut it up /w a hacksaw to make it fit & polish off the burrs on the edges. You could even lap it if you wanted. But it might not make much difference with mosfets, since they aren't an entirely flat, mirror smooth capable surface anyway.

Also, Zalman makes some good heatsink kits for this. For the mosfet heatsink mod, you could also go with some of the links that ChaosLegionnaire gave.

Those IGP chips can get pretty STUPID hot on many boards, some worse than others. I would definitely put an active cooler on there, or even a heatsink that comes with an active cooler. See my SIG for how to properly use thermal grease.

[JingYing]

Re: Heatsink foam: keep, remove or replace?

Honestly, in all my years of PC repair, I have never worried about these things.

I guess it's my first board hacking that makes me paranoid on things I'm not sure about. That's why I asked, thank you for your contribution.

In fact, simply use some Arctic Silver Thermal Adhesive and glue some heatsinks onto those mosfets using that. Any old heatsink will do, cut it up /w a hacksaw to make it fit & polish off the burrs on the edges. You could even lap it if you wanted. But it might not make much difference with mosfets, since they aren't an entirely flat, mirror smooth capable surface anyway.

Also, Zalman makes some good heatsink kits for this. For the mosfet heatsink mod, you could also go with some of the links that ChaosLegionnaire gave.

Those IGP chips can get pretty STUPID hot on many boards, some worse than others. I would definitely put an active cooler on there, or even a heatsink that comes with an active cooler. See my SIG for how to properly use thermal grease.

As for the material, I have something from an old broken PSU (sorry, no photo: it has been totally disassembled for learning purpose ). I'll probably add a 80mm-5V-powered fan over the NB heatsink and the mosfets (this is an HTPC, silence is required). I'll have to build some sort of support first, keeping in mind the little space I have between cpu and PCIe.
It lasted 4/5 years with this poor design; should it start again, maybe it will last longer...

EDIT: your link was lost in editing. Here it is https://www.badcaps.net/forum/showpo...44&postcount=7

[Pentium4]

Re: Heatsink foam: keep, remove or replace?

TK caps are horrible, they even die on the newer more efficient boards too. I measured one today off of an Intel board 820uF 6.3V, it was barely bulging at the top and the ESR measured 30.6Ω

[c_hegge]

Re: Heatsink foam: keep, remove or replace?

^
That's pretty common with those. Usually, they just bulge slightly and go way out of spec. They never seem to leak like some others do (at least not before the board gets unstable and it comes my way for fixing).

Before you go gluing heatsinks on, though, I'd see how it goes with the new caps. Bad caps can cause FETs to overheat (Although knowing ASUS, it's just as likely that they cheaped out on them). Just make sure you don't get any Arctic silver epoxy on the legs of the FETs or any other joints, though, as it is conductive.

[JingYing]

Re: Heatsink foam: keep, remove or replace?

As thermal paste I happen to have Zerotherm ZT-100 (maybe it's not like AS5, but surely better than the old-original-hard-to-scrap-away thing of the northbridge).
Probably a perfect-newbie question, but the mosfets dissipate mostly through the PCB, right? (Tab soldered to a wide copper area, etc...) Would it be efficient a heatsink "glued" on the upper side of the case?

[c_hegge]

Re: Heatsink foam: keep, remove or replace?

While it is true that they dissipate most of their heat using the tab which gets soldered to the motherboard, a heatsink on the other side will also help a lot.

[budm]

Re: Heatsink foam: keep, remove or replace?

Thermal Interface Material.
http://www.bergquistcompany.com/