First time lapping a heatsink

[Tech Tweaker]

I made my first attempt at lapping a stock AMD heatsink today, a socket 754/939 single core heatsink.

After reading some threads around here from back around 2005-2007 on the subject I thought I would make an attempt at lapping a heatsink myself. So, I started out by removing the HS from my system, cleaning off the Arctic Silver 5 I had on it, and taking some before pictures.

Then, I took a straightedge to see if it was in fact flat. Surprisingly, my original stock AMD HS was quite flat, so I didn't have to worry too much about flattening it out.

I couldn't achieve the "perfect mirror finish" that some people claim to be able to get out of their heatsinks, but hopefully I didn't do too badly, because it took me around two hours to lap this thing.

Before:



After:

 

[Crapxxas119]

Go with finer abrasive.
Ive heard of lapping taking 5 hrs so you might want to take a little more time.

 

[Tech Tweaker]

Go with finer abrasive.
Ive heard of lapping taking 5 hrs so you might want to take a little more time.

I'm not going to go much finer than 1200 grit. I would have gone to 1500, but I had to finish up so I could go fix myself some dinner.

Five hours? The heck with that, I don't have that kind of time. I've got other things to do. I'll leave that to those with nothing better to do with their time.

 

[trents]

A mirror polished finished is not so important. What's really important is that it is flat, flat, flat.

 

[tool_462]

A mirror polished finished is not so important. What's really important is that it is flat, flat, flat.

Yep.

I did a review at Xtreme CPU but can't get on there to link it (blocked at work) but going from 800 to 1200 grit netted a good improvement, 1200 to 2000 made it a little worse, and 2000 to 2200 made it worse further. It was still better than stock, but no reason to go for a mirror finish.

 

[trents]

Yep.

I did a review at Xtreme CPU but can't get on there to link it (blocked at work) but going from 800 to 1200 grit netted a good improvement, 1200 to 2000 made it a little worse, and 2000 to 2200 made it worse further. It was still better than stock, but no reason to go for a mirror finish.

Thanks. That's valuable info.

 

[Tech Tweaker]

A mirror polished finished is not so important. What's really important is that it is flat, flat, flat.

Well, that's good to know.

I can say it's definitely flatter and/or smoother than it was before.

At first running my finger over the heatsink I could feel noticeable ridges on it from the machining marks. Now it feels silky smooth though, with no noticeable differences in height from one side of the heatsink to the other.

I would imagine this would improve cooling in some fashion, and from what I have seen it does appear to have made a difference, because my average idle temp has dropped from 36°C to 33°C; not an earth-shattering change by any means, but a noticeable improvement nonetheless.

I haven't tested it for load temps yet though, so I don't know if there is any difference there.

Plus I'm using AS5, so since it obviously hasn't cured yet the temps will likely fall further over time.

 

[trents]

Load temp difference will probably also be about 3 degrees. Hey, 3 degrees is 3 degrees, especially if you are on the verge of being too hot.

 

[m0r7if3r]

Load temp difference will probably also be about 3 degrees. Hey, 3 degrees is 3 degrees, especially if you are on the verge of being too hot.

should have more drop over idle (theoretically)...I'ma guess 5C drop at load

 

[Tech Tweaker]

I tested for load temps today, the result was not encouraging.

Max load temp before lapping: 51°C
Max load temp after lapping: 51°C

Not sure why idle temps would be lower, but load temps would be the same.

 

[Crapxxas119]

hm...

I have 12000 grit emery paper.... A few days with that would make a nice lapped heatsink...
And i dont get that either...

 

[Tech Tweaker]

Heatsink lapping, second attempt

Had another heatsink lying around (heck, who am I kidding, I have nearly a dozen just lying around) and figured I'd set about trying to lap it and seeing if I could do any better than my first attempt.

So, I picked out the best looking heatsink of the bunch and the one that I thought would take best to being lapped and shined up a bit.

Four hours, along with several grits and multiple lappings on each one later these were the results.

It actually looks better than this in person, I just couldn't get the camera to focus correctly.