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Some questions about heatsink lapping

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July 30, 2010 6:39:28 PM

Hi,

I want to give it a try to lap my TRUE. Now I've read through many articles on the web but I got a bit confused about the what's the best lapping technique.

These are the different techniques I came across:
- Pulling and pushing the cooler to and fro on the sandpaper. After a couple of cycles turn it 90°, and repeat.
-Only pushing (pulling) the cooler, lifting it up and putting it back at the initial position and repeat. No pulling (pushing) thus.
Again turning it 90° after some cycles.
-Moving the cooler in an 8-pattern shape.

Can someone tell me which method is the best or if there is maybe an even better one? Any advice would really be appreciated.

Thanks
a c 131 K Overclocking
July 30, 2010 6:58:55 PM

Nils said:
Hi,

I want to give it a try to lap my TRUE. Now I've read through many articles on the web but I got a bit confused about the what's the best lapping technique.

These are the different techniques I came across:
- Pulling and pushing the cooler to and fro on the sandpaper. After a couple of cycles turn it 90°, and repeat.
-Only pushing (pulling) the cooler, lifting it up and putting it back at the initial position and repeat. No pulling (pushing) thus.
Again turning it 90° after some cycles.
-Moving the cooler in an 8-pattern shape.

Can someone tell me which method is the best or if there is maybe an even better one? Any advice would really be appreciated.

Thanks


I do not think it matters. I did mine using the push pull method only because it seemed easy.

I did it with the sandpaper taped to the top of a glass surfaced coffee table.
I did not go for that perfect brilliant shine. One coarse to get things level, and one fine to polish it up a bit.
What really helped to measure the progress was to wet the base of the cooler and press it against the glass. Looking at it from the other side will tell you where you need to work. When you have it really good, you should be able to momentarily suspend the cooler upside down, held only by the suction of the water film.
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July 30, 2010 8:35:35 PM

Thanks for both replies. I also wondered if the sandpaper needs to be wet, but as you both suggested, I guess it should be.

The other question I have is about the different sandpaper types. Some say to start with something like 200 grit, others 400. Some say to go up to to 2000, others just 800 or 1000. What's best actually?
July 31, 2010 7:07:34 PM

Nobody?
a c 131 K Overclocking
July 31, 2010 7:13:07 PM

I can't remember exactly what I used. In the range of recommendations, I used a coarser grit wet/dry to get it level and then finer but not superfine to finish.
July 31, 2010 9:12:57 PM

geofelt said:
I can't remember exactly what I used. In the range of recommendations, I used a coarser grit wet/dry to get it level and then finer but not superfine to finish.

And how much much did temperatures change after lapping in your case?
a c 131 K Overclocking
July 31, 2010 9:39:36 PM

Nils said:
And how much much did temperatures change after lapping in your case?


No way to tell.

I lapped it while I was waiting for delivery of parts for a new build. In truth, I don't think it made any difference. The TRUE heat sinks come with a curve that Thermalright insists is best. I suppose they should know. You might test it first. As I mentioned earlier, put a drop of water on the heat sink, and press some glass to it. Watch how it spreads. That is what will happen with your thermal material. You want the thinnest part to be in the center over the hottest part of the cpu die. Where that point is will depend on which processor you are mating it to. Look at the arctic silver web site to get their drawings of different types of processors.
August 1, 2010 6:07:02 PM

geofelt said:
No way to tell.

I lapped it while I was waiting for delivery of parts for a new build. In truth, I don't think it made any difference. The TRUE heat sinks come with a curve that Thermalright insists is best. I suppose they should know. You might test it first. As I mentioned earlier, put a drop of water on the heat sink, and press some glass to it. Watch how it spreads. That is what will happen with your thermal material. You want the thinnest part to be in the center over the hottest part of the cpu die. Where that point is will depend on which processor you are mating it to. Look at the arctic silver web site to get their drawings of different types of processors.

That's indeed what Thermalright says, but I don't believe then to be honest. Generally Intel CPU's heatspreaders are flatter than the most TRUE's. Otherwise they would have much nicer thermal paste imprints.

Anyway, what's most easy to hold the heatsink when lapping, holding the base from both sides with both hands or sticking one hand through the gap between the base and the fins and let your hand rest on the base?
August 1, 2010 6:12:22 PM

To all people on this forum, please do not just reply to my questions, but also post any tips or hints you have on heatsink lapping.

Thanks
August 2, 2010 10:50:40 AM

BUMP. No reactions?
a c 197 K Overclocking
August 2, 2010 2:28:39 PM

My TRUE had a visible off center bulge on the base. I used wet, 400, 800, and 1000 grit paper on a scrap of plate glass. And I used the "two fingers through the opening and rotate 90 degrees when I change paper" technique.

I did not test priorr to lapping because I saw the off center bulge. And I took the base down to bare copper.
August 2, 2010 6:46:31 PM

jsc said:
My TRUE had a visible off center bulge on the base. I used wet, 400, 800, and 1000 grit paper on a scrap of plate glass. And I used the "two fingers through the opening and rotate 90 degrees when I change paper" technique.

I did not test priorr to lapping because I saw the off center bulge. And I took the base down to bare copper.

Thanks for the tip. With changing the paper do you mean going to another grit or just using a new sheet of the same paper?

I'm also confused about the rotation thing. Because some guides say you must never rotate the heatsink on the same piece of paper, others tell you have to rotate after about ten passes on the same paper. Does it make any difference?
a c 239 K Overclocking
August 8, 2010 6:29:28 PM

@Nils

Since my beginning days of heat sink lapping I've settled on my best way to do it, which has taken me from an arduous ordeal to what I call speed lapping, speed lapping is worse for the longevity of the sandpaper but seriously cuts the time involved in the entire lapping job.

I no longer wet sand because it's not necessary, and it is a mess to clean up, I dry sand which will go through your sandpaper faster, but get you where you want to go much faster.

Factors are:

You still want to use automotive grade wet/dry paper, and you don't want to start with a courser grit than the scratches already on the heat sink, and sometimes if you're lapping a HDT (Heatpipe Direct Touch) heat sink, you may need to use a finer starting grit and creep up to the finish so you don't cut any deeper than the existing machined scratches, (More work but less chance of cutting through a heatpipe.).

Always make absolutely positive the heat sink base is flat to the cutting surface, do not allow wobbling during the cutting no matter what you have to do to maintain perfectly flat stability, and some top heavy heat sinks will try to wobble, if vibration begins stop and reposition your grip.

Be sure the surface you're working on is flat and particle free, make sure the sandpaper is also particle free and flat, no folds or creases.

OK here is the speed part, do not tape the paper down to the flat surface, keep the heat sink base about a half inch from the edge of the paper, if you're right handed hold the paper at the top right edge from you with the left hand, pull the heat sink down the side towards you, rotate the paper reposition your left hand, pull towards towards you, continue this process.

After about 3 full rotations of the paper, rotate the heat sink 180 degrees and continue, if you're left handed swap your hand positions and pull the heat sink with the left hand hold the paper with the right, its very simple and very fast.

When the paper starts to build up metal content, carefully vacuum or go outside and shake it off being careful not to wrinkle or crimp the paper and it will cut like brand new.

One final tip is you can actually produce a mirror finish with only 600 grit paper, once you've cut the heat sink base to the point there are no more scratches being removed, stop removing the metal residue from the paper and you'll begin a metal on metal polishing effect, and you can continue to a mirror finish. Good Luck!

Zalman Lap


Xigmatek Lap
!