Author Topic: OT: Heatsinks for processors (Read 607 times)

AKDejaVu · « **Reply #30 on:** March 18, 2001, 01:00:00 PM »

Packrat and Wardog, I think you are both talking about different things.

Wardog, the whole packaging is not the chip. The tiny little peice of silicon at the center of the packaging is the chip.. the rest is simply packaging. Packrat is absolutely correct.. if you sand all the silicon (let me know what kind of sandpaper you use for that... I've very curious) down to the metal, you've effectively destroyed every transistor on the processor.

I believe these refferences are more along the lines of sanding the PACKAGING (ceramic, not silicon) and coming to metal structures in side of the PACKAGING.

IF you can get one completely smooth and flat surface to mate with another completely smooth and flat surface you are going to have optimal heat transfer.

In any other case, a good heat transfer compound LIGHTLY applied is an excellent solution. It should be applied only to fill in the voids and non-flat areas, but not to bridge the gap between surfaces that would be touching had it not been applied. The heat trasnfer pastes' main shortcoming is in its common misapplication. People treat it like glue with a 1/32" layer of it actually separating the heat sink from the ceramic.

AKDejaVu

AKDejaVu · « **Reply #31 on:** March 18, 2001, 01:03:00 PM »

BTW, any "wet sanding" using anything other than a flat granite block as a backstop is pretty much worthless. You're simply replacing one version of not very flat with another version of it.

AKDejaVu

Lephturn · « **Reply #32 on:** March 18, 2001, 01:31:00 PM »

Deja,

As I understand it that little square slug is not the CPU itself, but rather a slug of ... well something ... that sits directly on top of the die to help transfer heat. A little wet sanding will not kill it, but you have to use a very fine grain and be very careful.

BTW, a good way to do the sanding is with a piece of glass as a backing for the fine paper. You can normally get glass that is as close to "perfectly flat" as you can find easily. The main reason to do anything at all to the heat slug on the CPU is to remove some of the lettering and such that you do find on these CPU heat slugs. The only thing that typically needs to be smoothed and flattened to any degree is the heatsink part of the combination.

All of that aside, this isn't something I would recommend unless you are experienced, very careful, have the right tools, and are willing to buy a new CPU if you botch it.

For most folks, a $7 tube of Arctic Silver applied properly is a far better solution.

Wardog,

Have you had much experience mating the HSF and CPU with no grease without sanding anything? That would make me nervous, but I've never tried it that way. If you have I'd love to hear your results.

------------------
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http://www.flyingpigs.com

Check out Lephturn's Aerodrome for AH articles and training info!

PakRat · « **Reply #33 on:** March 18, 2001, 01:44:00 PM »

Nope - that square in the middle of the new processors *is* the die itself. It is the back side - the side that wasn't etched or had circuitry deposited on it. It is silicon. Very brittle and if you look at a reflection on one you will see it is very flat. That is a very fragile part and the reason the CPU manufacturers say to be very careful when attaching the heatsink. Put it on crooked and you can overstress and crack the die. But it is definitely the silicon die itself.

The manufacturers went to this style of packaging because it allows better heat transfer out of the die - the die itself is what makes contact to any heat sink.

Glue/compound/phase change material - it's all pretty much the same (except maybe the foams). All help to get better heat transfer than just chip/heatsink contact itself.

The CPU die flatness is not the problem anyway. As was pointed out (over and over) it is exceptionally flat. The surface that needs to be smoothed out otherwise generally is the heatsink. The extruded parts have little ridges in them that limit the direct contact area. All sanding the chip does is shorten the thermal path by a millimeter if that. Whoo hoo! Distance being a factor in removing heat, this will help the heat transfer.

But sanding (or lapping) the CPU die is bad advice. Really bad advice. Not using any thermal compound is also bad advice.

But hey, they are your CPUs - do what you want.

---
PakRat
http://www.jump.net/~cs3" TARGET=_blank>63rd FS, 56th FG
"Zemke's Wolfpack"

"Juggies, dance us back in history!"

AKDejaVu · « **Reply #34 on:** March 18, 2001, 02:04:00 PM »

Leph, glass is not a very smooth surface. A common misconception.

I haven't seen the latest packaging material, but I do believe PakRat to be correct. If you are seeing a little square in the middle that is about 10mm x 11mm, then it is actually the processor.

I'm not sure if gold is dep'd on the back of the processor anymore since what PakRat is describing eliminates the need for it (cost savings too). But the back of the microchip is essentially glass and is much smoother than anything you will find virtually anywhere.

Also, it is important to remember what adheres the chip to the packaging. Solder bumps (actually lead).. and that is all. Little 80um bumps on the top of the chip that are heated to bond with the packaging. Sure there's a ton of them on the top of the chip, but it doesn't really take that much to break one of the bonds.

Also, the chip has been ground down. The silicon portion shouldn't be too much more than .3 mm thick. It doesn't take much to cleave that thin of a glass surface.

AKDejaVu

Thorns · « **Reply #35 on:** March 18, 2001, 10:40:00 PM »

I have a 1GHz T-bird with a Cooler Master fan and heatsink. I looked at Arctic Silver compound, and it was $13.00 for compound and $12.00 for shipping. I picked up some good old heatsink compound from Radio Shack for $1.97 plus tax. My temp after an afternoon of Aces High is 105 degrees F with an inlet and exhaust fan in my Enlight 7237 box, and the fan is quiet...........I like it!

Thorns

Raubvogel · « **Reply #36 on:** March 18, 2001, 11:28:00 PM »

Using a Chrome Orb from ThermalTake on my 1ghz Athlon. Seems to keep it fairly cool. Never seen it over 109 F. I also have 2 intake fans and 2 exhaust fans plus a slot fan in my case. It starts out a bit warm in Hawaii, so I've found that I need it. I tried letting the sides off, but my cats wouldnt cooperate with that

I also used the cheapo thermal compund from Radio Shack. I think this is my 4th PC using it, and never had any problems.

------------------
Raubvogel
LuftJägerKorps

Wardog · « **Reply #37 on:** March 19, 2001, 02:34:00 AM »

Dejavu got it right

Your sanding the sealant on the center of the CPU.

Pakrat is part right concerning Thermal Glue. After you sand/lap the CPU put a little thermal glue on a cloth to clean the dust off the CPU, as the glue is non conducting. Then thoughly clean all the Thermal glue off.

Deja, i started as the article i was reading said to use 400, 600, 800 and 1000 grit. I now use the 400 to break through the sealant only, 2 to 3 strokes. Ive got a piece on machined Steel i use. Just think of it like an anvil.

I ran into a web site last year and will go through my papers and email you the link.

They did this with a PIII-700 running fine at 980mhz...

Ive built about 50+ machines, its a hobbie. About 14 or 15 i O/Ced as i have parts around the house i can experiment.

Dog out...........

PakRat · « **Reply #38 on:** March 19, 2001, 07:38:00 AM »

Wardog-

Deja said the same thing I did. The square in the middle *IS* the CPU die itself. That is silicon - not a slug of metal.

I did not say anything about thermal glue other than that it was similar to thermal grease. It is just a high heat transfer material.

It sounds like all you are doing is sanding off the polished surface and getting to the bare silicon. This does nothing more than roughen the surface (scratch marks are very visible in the bottom photo). Every scratch mark is decreased surface area over which to make thermal contact.

Do what you want. There are really nice white papers at both Intel and AMD websites about proper heatsinking of these types of CPUs. None say to omit thermal compound and none recommend sanding the surface.

They do recommend phase change over other transfer compounds. The whole deal about phase-change thermal compound is as the CPU heats up, the phase change material thins and flows. Under spring tension it adjusts to give the closest possible contact between CPU and heat sink.

I still say this is really bad advice. But again, it's your CPU.

Wardog · « **Reply #39 on:** March 19, 2001, 03:25:00 PM »

There are many way of dealing with heat when over clocking a pIII 700 to a 980.

This is one way, not adiving anyone to do this, i do it because i can afford the parts

Dog out.........

Staga · « **Reply #40 on:** March 19, 2001, 03:34:00 PM »

My SL45Y is running 933 with Majesty heatsink/fan; Havent tried bigger speeds yet. Too lazy to hone it

AKDejaVu · « **Reply #41 on:** March 19, 2001, 04:44:00 PM »

Thanks for the pics wardog.. I hadn't seen any flip-chip processors... didn't know they were that much different from the old ceramic packaged ones. I can see why we went to them? Err.. wait.. did I say "we".. I ment Intel.

I wouldn't sand much on that chip. And it won't matter how flat of a sanding surface you use.. you'll just be scratching the glass, not smoothing it out.

I can see the purpose if it means removing the adhesive/protectant from the back of the processor, but I think that NOBODY posting these articles has any idea of all the ramifications.

AKDejaVu