Heat sink lapping (sanding)

Does anyone know much about this?

Long story short, I have a heat sink that I need to get clean and smooth.

Can ANY heatsink be lapped? Does it matter if the heatsink has a black finish (that will be removed from the sanding)?

It's for an old Socket 370 Celeron machine (Dell)

PK

 

See

http://forums.majorgeeks.com/showthread.php?t=117684

 

Uhhh....thats does not really directly answer my question.

Though it does have some interesting info.

PK

 

Sanded or lapped?
You haven't said what you are trying to achieve. An objet d'art or a plant pot?
Lapping is aprocess to create two closely mating surfaces. and can be applied to anything that is hard enough. Why do you want to do this?

Studio T

 

Removing the black finish wont hurt, it's probably just some crappy paint with poor thermal qualities.
I'd sand the HS to minimum of 800 grit & no more than 1200, then use some good Thermal Paste like AS5 or AS Ceramique (I prefer Ceramique)

 

WTF, you know what the poster wants, Why be a Butt Hole

If you truly dont know Read the Thread again starting with the Title, then the following post :booger

 

Major Geek or not I strongly resent the implications here.

Surely no one is proposing to lap a processor against a heatsink for computer purposes?
If Allochthonous wants a superfine finish on his heatsink, or other Dell parts that's OK by me. I do believe certain computer assemblages have fetched fabulous prices in NY and other art galleries.

Studio T

 

What Ever
Nothing personal here!


I want to help the poster I think I did exactly that
Did you?

 

I'll grant that lapping the processor die is likely to be highly prejudicial to the chip if not done very carefully. But some do it.

Lapping the contact surface of the heatsink is much safer, and makes sense if it's still got milling ridges in it, or is otherwise on the rough side, or has bulges or hollows in it that prevent contact with the entire surface of the CPU chip or its heat spreader.

Lapping is the name for the process used for flattening and smoothing a surface by abrasion using appropriate grits and a lapping surface that is flat within very close tolerances, rigid, and softer than the grit used. The grit embeds itself in the lapping surface and forms what is effectively a rigid sandpaper. For most of us, a thick sheet of plate glass covered with a heavy self-adhesive Mylar sheet is sufficient. The Mylar embeds the grit quite satisfactorily and can easily be replaced when it's no longer flat, with the result that truing the lapping surface does not become an issue. For more info on lapping, see the Wikipedia article.

The better the contact between the base of the heatsink and the CPU chip, the more heat the heatsink can remove from the CPU die. Ideally, one would want a mirror-smooth finish on the contact surfaces, but for most people, the incremental improvement gained by going that far isn't worth the trouble. O/Cers sometimes find it worthwhile. You'll find that some reviewers will report on the smoothness of the heatsink base -- for instance, see here.

Allochthonous, lapping is a subject that is often pursued in some detail by those concerned with cooling and/or modding their machines. You might find more info in that forum. You might also try a discussion group that concentrates on those issues. OverClockers is one such.

 

Damn! I thought this was a fairly easy to understand question.

I was trying to spare everyone by keeping the details short and to the point.

Yes, Rob M, that is what I meant by "lapping." However, I am not looking to polish like an overclocker, but just to prepare the surface a little better.

Here's the whole story:
Someone suggested I read the instructions from Arctic Silver.com
http://www.arcticsilver.com/pdf/appinstruct/as5/ins_as5_singlecore_expsd.pdf on how to prep the heat sink.
I thought that my local shop might have some of that Arctic Cleaner I could use or could maybe recommend an isopropyl alchohol cleaner to clean the bottom of my heatsink to remove the residue of the thermal pad (I am pretty sure it was a pad).

The first guy just started grabbing cans and saying they would work, but I was reluctant since one was citrus based and the other did not have ingredients.

I got my glob of Arctic Silver from him and on my way out, asked another guy for his opinion. He quick grabbed a can of "Blow Off Cleaner" and said while spraying my heatsink "this will work." I just looked at him in disbelief and asked what was in that stuff. He said "I don't know, but its safe for electronics, so it should be OK." Duh!

Now I am worried that it left God knows what behind on the painted metal surface of my heatsink.

I cleaned what was left of the thermal pad with some 91% alcohol, but will that also remove whatever may have been left by the "Blow Off?" I did not want to have to worry about it, so a friend of mine suggested sanding.

Research revealed this as "lapping" in the overclocking world.

But then I wondered if the fact that the heat sink has a black finish on it would make a difference. Most folks I talk to say go for it, but one user on the Dell forum was reluctant to say so. I have since learned that this may have just been a personal preference in maintaining the original "aesthetics" of the heatsink.

So there ya go...good story eh?

Does this help clarify my motives?

I have sandpaper from 400 to 1500.

PK

 

has no-one plucked up the question why do you want to lap a cpu/heatsink that old anyway, it would proberbly survive if you just give it a quick waft with the newspaper once and a while, lapping is an art for hardcore enthiusiasts to get the best possible thermal connection for there heavily overclocked cpus running phase-change cooling, its really not needed, if the surface is rough, then clean it, and apply a fresh blob of paste, that'll do it! :major i-CONICA:major over and out!

 

If you're just wanting to remove whatever materials have been applied to the base of your heatsink, and it's otherwise smooth, I'd say that lapping may be an unnecessarily laborious process to do that.

You've seen Arctic Silver's instructions. They're the best I've seen on the topic, though I'm not 100% convinced that you really have to have the Arcticlean 1 and 2 products -- and Arctic Silver itself says that you need them only if you want to do an "optimal" job of cleaning the heatsink base. See section 4 (Heatsink Preparation) of the Arctic Silver instructions.

I've used isopropyl alcohol with satisfactory results. You should be able to get 99.9% pure isopropanol (same stuff, slightly different name) at your local pharmacy. Don't use rubbing alcohol, even if it's based on isopropyl alcohol. It contains additives, some of which may not evaporate quickly or at all.

Isopropanol did a good job of removing the thermal pads and thermal pastes I've run across so far. A xylene-based cleaner may be easier, but I didn't have a problem without it.

As for the black stuff you refer to: if it were mine, and it's coating the contact surface, I'd get rid of it unless it's metallic or is otherwise known to have good heat transfer properties. Lapping may be the best way to do that without contaminating the metal surface with something that you can't afterwards remove from the pores of the metal.

If it's not on the surface that contacts the CPU chip, I'd leave it be.

 

Isopropyl alcohol or isopropanol is a common name for 2-propanol, an alcohol which is the main component of rubbing alcohol. Its chemical structure is: Its formula is C3H8O or more descriptively, CH3.CHOH.CH3, an absolutly pointless piece of info and far too indepth for the point of this thread, but it sounds clever and does a weewee all over the bloke below this' techie fire!, lol i can be serious sometimes i swear! hushhh, dont tell anyone i just googled "isopropyl" lol :major i-CONICA:major

 

Seems like we are now into the general hardware discussion I suggested in my earlier thread.

I am glad to have Allochthonous' aims clear now. I have seen serious modders chrome plate and illuminate their heatsinks, cutting holes in their cases to view. Sanding is obligatory, pre chrome plating.

However for present purposes it is not only uneccessary, it could be long term harmful. You have to be very very careful not to bring in (microscopic)
particles of metal or abrasive when you have done. This is because as a chip heats and cools it expands and contracts. This cause small gaps under it in the socket. If a gritty particle get in between when hot, problems can arise when the chip tries to relax again on cooling. Why take the risk?

Dell are usually pretty well specified and built; their design will be fine for normal use.

Asus mentioned in another thread the use of plastic (credit card) scrapers to remove the bulk of the old material. This is a very good idea. There are many suitable solvents to finish the job, the only ones you need avoid are those which are definite plastics solvents, such as acetone, found in nail varnish remover.

lapping - ?flat? Many toolroom apprentices will have had to lap a spherical joint. Any motor enthusiast will probably have lapped in his curved valve heads to his cylinder head ports. Lapping is the creating of two mating surfaces but rubbing them together with and abrasives cutting medium between, usually in successively finer stages until the desired finish is achieved. Sometimes one of the surfaces is sacraficial as in the case of lapping against a glass plate. These processes chieve no more in computer terms than gofaster stripes painted on the side of a car.

Much research has been done, and many learned textbooks written, concerning the efficiency of heatsinks and whether their fins should be vetical or horizontal, painted or bare, thick or thin etc etc.

I should just rely on Dell, clean up sensibly well, and remember what I said in the other thread about grease v paste and future removal of components.

Good re-assembling

Studio T

 

Well....it's done. I did my best at sanding the heat sink. It's not perfect, but I think it will do. My only fear now is whether I applied enough Arctic Silver. I followed the instructions to the letter, applying half a grain of rice blob of grease on the processor core and spreading in a thin layer over its surface.

The heat sink still seemed tight enough, so I think i have good contact.

I booted up and the 1.0 ghz processor seems to be working fine. Both the BIOS splash on boot and Windows detect it as 1000 mhz (or 996) and the bus speed as 100 mhz (or 99).

However, after upgrading to BIOS A14, i can't seem to figure out how to get into the actual BIOS setup screen!!

I can see a definite speed improvement.


PK

 

This was too funny to let it go unnoticed.:cry

 

I figured it out...i just had to time DEL just right.

Part of the problem was the "quick boot option."

Last night I was running a beanchmark program and it froze up on me. Should I be alarmed?

I am going to leave the machine working on Folding@Home today and see what happens.

PK