Lapping the Heatsink

[joeblo123]

Does Lapping the HS help with the cooling???

I've read from different thread that it's suppose to help with the cooling...

I currently have a CoolerMaster DP5-6H51 and prefer not to buy a new HSF if I can lapp and get my temp down a few deg.

Currently running DURON 700@901 and temp under load is 49c and 45c ambient.

Also, is there any information on proper way for lapping?

 

[pbrain]

this should help.


<< Date Posted: Jul/24/2000 11:18 PM
Posted By: cautery
Rank: Senior Member

Related Threads:
Thermal Tape Selection and Thermal Interface Qualities
http://forums.anandtech.com/messageview.cfm?catid=37&amp;threadid=204693
PIII Coppermine and Heatsinks - quality of the thermal interface...
http://forums.anandtech.com/messageview.cfm?catid=37&amp;threadid=203730
PIII Coppermine Core ? Lapping it flat?
http://forums.anandtech.com/messageview.cfm?catid=37&amp;threadid=203731
FC-PGA Heatsink ?Feet? ? how to get a custom fit
http://forums.anandtech.com/messageview.cfm?catid=37&amp;threadid=203734
Heatsinks: Are they Flat? Answer here?.
http://forums.anandtech.com/messageview.cfm?catid=37&amp;threadid=203739
Thermal Interface Materials: Required Thickness?
http://forums.anandtech.com/messageview.cfm?catid=37&amp;threadid=204688

I have discussed several aspects of achieving a GOOD thermal interface in the Related Threads above, but this post contains a key ingredient to accomplishing this:

Q: Is your heatsink mating surface flat?
A: Generally?. No, it is not.

I have examined a number of commercially available heatsinks: generic (show specials), GlobalWin, Alphas, and even The Arctic Circle, and while some of them are flatter
than others, in general, NONE of them meet the generally accepted standard for flatness for use in a thermal interface (which is a runout value of 0.001?/inch).

The solution to this reality is simply to lap your processor flat and smooth? Here?s how I recommend you do it, unless you happen to have a multi-thousand dollar,
multi-axis milling machine available:

Materials:
1 each heatsink to be lapped (disassembled from fan, shrouds, etc)
1 each NEW sheets of 3M brand wet/dry sandpaper in the following grades minimum (180, 220, 320, 600, 1500) You can use progressively higher grades if desired and
continue progression to polishing compounds if desired.
1 each 8? x 10? piece of quality double thickness (or better) glass.
CLEAN, preferably distilled water. (actually, a high quality, very light grade of lapping oil is preferable)
Several lint free towels?. I use lens cleaning towelettes.

This is the general procedure. There are tons of additional ?anal retentive? measuring tools and techniques that one can use, but for the purpose of this article, you can ?get
by? with the above.

Place the glass pane on an absolutely clean and flat surface?. Please make sure you clean off your work surface and remove all extraneous materials. Lapping a top quality
heatsink should not be done on a computer workstation cluttered with McDonald?s trash, pop cans, diskettes, Cds, and paper?.

Dampen the reverse side of the 180 grit sandpaper (beginning grade of paper depends on the amount of material that needs to be removed) with a sponge and clean water?..
Make SURE there is no label/price tag on the reverse side of the paper. The damp paper will adhere to the clean glass better, thus reducing the tendency for it to slide
around. Do NOT wrap the paper around the glass, or try to tape the paper down, as this will tend to cause the paper to ?bow? up in areas which will radically increase your
chances of NOT having a flat lapping surface and causing ?rounding? of the edges of the heatsink?. This would be BAD!!!

Now, place some (amount dependent on the size of sink surface to be lapped) clean/distilled water (lapping oil is preferable since it will reduce the tendency of the sink to
?suck down? to the wet paper as the surface gets flatter?. This ?sucking down? may cause a ?hang? which in turn MIGHT cause you to ?skip? the edge over and across the
paper? possibly rounding the edge) in a single ?puddle? in the CENTER of the NEW sheet of paper now located on the glass. It is critical that you use a NEW sheet of paper
in PRISTINE condition (no scuffs, or creases?.). Any imperfections in the paper will greatly increase the chances of you getting a less than optimum result.

Place the sink, mating side down, in the center of the water ?puddle?. Grasp the sink with your hand, trying to maintain an even (light) pressure across the entire sink. Now
begin making small circular patterns with the sink on the paper. As the sink ?settles in? you can gradually increase the circle size? to no more than 1.5 times the size of the
sink, and maintain LIGHT pressure. Too much pressure, and you will ?skip? the sink, plus it?s easier to keep the sink flat with a lighter pressure.

Periodically, check your work, rinsing the paper to remove loose grit and waste material. Clean the sink off, and repeat the process until you have a flat surface. This will be
evident as the original surface will gradually ?disappear?, being replaced with a uniform circular pattern of ?scratches? consistent with the grade of paper used. Don?t remove
more material than necessary to achieve a uniform, flat surface.

The slower and more patient you are, the better your result will be (eg. Less rounding of the edges, etc.). Repeat the above procedure with progressively finer grades of
paper/compound until you get the surface quality desired. Wind up the procedure with a thorough rinsing of the bare heatsink, and clean the mating surface thoroughly with a
lint-free cloth and alcohol (use a degreaser then alcohol if you use lapping oil).

Reassemble the heatsink/processor assembly as quickly as possible after completion as the newly lapped surface will immediately begin to oxidize. Use the best
non-conductive thermal compound you can get your hands on?.

On FC-PGA heatsinks, you?ll need to remove the feet to use this procedure?..

Hope this helps?. Have fun.


-------------------------
Clay Autery >>

 

[joeblo123]

bump

 

[Supradude]

lapping, when done right, will result in a slight edge in performance, but it's not a widely used method due to the slightly tedious procedures and the precision needed to actually get the performance edge... done wrong or imperfectly, it can actually reduce your HSF's effectiveness...

 

[joeblo123]

Thanks Guys...

Since my HS is a crappy CoolerMaster and it's got lots of nicks and scratches on the bottom of it, I'll give lapping a try...if i just stay with the higher grid sandpapers, I can't do too much damage, I hope....

 

[HardwareAddicted]

Just for your info....this is what I did.

Get a 12x12 piece of marble looking stuff from Eagle or home depot...$3 (It's 1/2 in thick and real flat)
Get a pack of wet/dry 1000 and 2000 sand paper...$10
Get a roll of duct tape...cheap.

Tape a piece of 1000 to the flat marble like surface, one piece of tape on both sides. (The paper is 8x11.)
Go to town and remember to rinse the paper often to remove the alum dust.
Repeat with the 2000 and keep it wet, always rinsing...

When you are done it will be almost a mirror finish and alot flatter than any heatsink made.

Apply with Arctic Silver ($8) and check your new temps....you'll be impressed.

I use this &quot;lapping kit&quot; still and even did my mb chipset heatsink...no problem.

My Duron600 is running at 10x108 for 1080mhz....