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Help w/ dislocated heatsink on circa 2003 motherboard

Rumble77

2 months ago

I'm not sure of the best place to post this. The heatsink on the Northbridge chip on my Asus P4PE, rev 1.03 motherboard has broken loose. The system was built in 2003 and I still use it occasionally due to some specialized hardware/software so I'd like to keep it running.

The heat sink is normally compressed into place with a pair of spring clips across the heat sink, hooked into loops soldered into the motherboard (links to photos later). However, those 2 of those loops pulled out of the motherboard so the spring (and therefore the heatsink) popped loose.

This could have happened a long time ago, as far as I know. The system still works OK, and maybe the heatsink on the NB was primarily for overclocking, which I'm not doing, so maybe the lack of heatsink isn't a problem. Still, I'd rather try and address it.

Looking online, these loops pulling out of the P4Pe MB is a known issue. There were several online discussions about it in the 2004-2005 timeframe. Back then, there was a kit available but that was a long time ago.

5 Photos:

https://i.postimg.cc/RFJ1G57s/p4pe-northbridge-01.jpg

https://i.postimg.cc/kgD2WNFw/p4pe-northbridge-02.jpg

https://i.postimg.cc/4NWKK2tm/p4pe-northbridge-03.jpg

https://i.postimg.cc/hPDztRXk/p4pe-northbridge-04.jpg

https://i.postimg.cc/cCZK3VX8/p4pe-northbridge-05.jpg

Photo 1 is just to give some perspective of where the heatsink is on the motherboard for the zoomed photos that follow. Photo 2 shows where the hooks for the spring clamp pulled out of the motherboard and the heatsink is essentially floating. Photo 3 shows the northbridge chip and the heatsink on its side. Photo 4 is a closeup of the northbridge chip, to figure out what to do next. Photo 5 is a closeup of the heatsink top and bottom.

What would be the best way to fix this? I was thinking I would scrape off the thermal foam (the yellowish outer square on the bottom of the heatsink, and the pink inner square, neither of which have any adhesive properties to them), and maybe buy some sort of thermal adhesive/epoxy to glue the heat sink to the top face of the NB chip?

If that sounds reasonable, do I put the thermal adhesive around the die, or actually cover the die with it?

Comments

  • 2 months ago
  • 2 points

Hi, I must not have been very clear. The original clamp-based heat sink attachment method will no longer work, so I'm trying to find out how to go about attaching a heatsink (either the original one, or a new, different one) with thermal adhesive/epoxy, and what type of adhesive/epoxy to buy for this particular application. So I don't think thermal paste is relevant any longer. As mentioned, the computer still has a special purpose, so it's a few years away from being tossed.

PS, just out of curiosity, what's the purpose of the coffee filter? To filter the high impurity isopropyl alcohol that you get in a drug store to closer to a "clean room" purity?

  • 2 months ago
  • 2 points

Q: "PS, just out of curiosity, what's the purpose of the coffee filter? To filter the high impurity isopropyl alcohol that you get in a drug store to closer to a "clean room" purity?"

A: The idea is to use a coffee filter(s) as a napkin to wipe off the old (pink) thermal paste. Put some regular isopropyl alcohol on the coffee filter and then gently rub off the old (pink) thermal past on the NB chip die, as well as the underside of the heatsink. BTW, it's okay to just use a napkin instead of a coffee filter to wipe off the old thermal paste. Some folks prefer/recommend using coffee filters instead because they are lint free and are typically readily available in most homes.

Also, as part of this repair, you will need to apply new thermal paste on the NB die (e.g. the small chip in the middle) prior to reinstalling the heatsink. This step is critically important, b/c it's this thermal paste that transfers/conducts heat from the NB die to the heatsink itself. (Note, I'm clarifying this point in response to your statement above "So I don't think thermal paste is relevant any longer." Thermal paste is relevant to this repair.)

Note: The "thermal adhesive foam?" indicated in pic #3 is not thermal foam or thermal pads... it's just foam to set the right height/spacing/distance between the NB die and the heatsink itself, as well as above the surrounding capacitors on the green PCB. This yellow foam does not conduct heat from the NB die to the heatsink--it doesn't touch the NB die at all.

Now to your original question ... on how you can fix this heatsink problem using thermal adhesive? In theory, you could remove the (yellow) foam on the heatsink and replace it with a double-sticky adhesive that's the same thickness to re-attach the heatsink, but I'm not sure how well it will work or how long it will last. You want proper pressure and distance for the re-applied thermal paste to effectively conduct heat from the NB die to the heatsink. You will also want an adhesive that is "just right" in strength...if the adhesive isn't strong enough, then it won't hold the heat sink over time, but if it's too strong, then you would risk pulling the NB PCB out of the MB if you had to repair it again. As to what type of adhesive to use...they don't really make a product for this specific purpose/repair. You will probably need to search to adapt a product from the hardware store--just thinking out loud, maybe some of those 3M or Scotch removable wall mounting strips? I don't know if they would be too thick.

If I were going to fix this myself, I would re-solder the heatsink mobo clips back onto the mobo. How comfortable are you with electronic soldering? Or do you have a friend that could solder the mobo retention clips back on for you?

  • 2 months ago
  • 1 point

Thanks for the detailed reply thunder-93. On the coffee filter...oh! just as a wipe. Boy do I feel stupid.

I'm not able to re-install the mobo loops but I did consider it. It's a long an uninteresting story that parallels the experiences people in online discussion had back in 2005, but that's the short version of it.

Anyway, I found (or I should say, Google found) Intel's thermal design guidelines for this '845PE memory controller hub part

http://application-notes.digchip.com/027/27-45789.pdf

This really helps quantify things in some respects. On pg 8, this part is only 5.6 watts max, and the "maximum case temperature" is 92 degrees C (197.6*F) which pg 15 section 2.5.1 defines as "the surface temperature at the geometric center of the die."

Now an infrared thermometer isn't really the right way to measure this, but I have one, and it should get a reading that's reasonably close to using a proper thermocouple. With the system running an application that is exercising memory, and the IR thermometer's laser spot on the center of the die, I saw temperatures that ranged from 32 to 47 degrees C (90 to 116F), hovering mostly on the low end of that range, which is way below the limit. I've been in hot tubs that were more than 116F so these aren't even skin-burining temperatures.

This is encouraging.

In part, I think the relatively low temperature readings are due to this PC only having 512MB of memory (1 out of 3 memory sticks installed). It would surely be higher with more memory in use and being controlled by this MCH part. As a sidebar, it's pretty amazing what a PC with only 512MB of memory could do 15 years ago.

So I'm thinking I could probably leave it "topless" but just as an added safety measure I think I'll add a small, 2 or 3 inch fan mounted on a bracket and blowing straight onto the die.

Does that (adding a small fan, but taking the heat sink out completely) sound like a reasonable way to address this in light of my measurements, or am I practicing a bit of wishful thinking here? It seems the heat sink is only really necessary in configurations that are beyond the way this PC is configured.

  • 2 months ago
  • 1 point

If your temps are staying at most 45 deg C, then I think you'll be fine as is. Please note that the inside of the die is likely a little higher temp than what's registering on the surface.

A fan wouldn't hurt, but I'm not sure how much it would really help without a heat sink (to draw the heat off and offer more surface area for the air to cool off the heat.

  • 2 months ago
  • 1 point

I have used a thick thermal paste to repair heatsinks on some older hardware and I haven't had any problems with them yet. I would give that a try.

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