This sounds stupid, but I need a little advice, Lapping 101......

SammieC

Platinum Member
Apr 24, 2000
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Got me a BP6 and a few celerons, if I decide to keep it, but wanted to give it a better chance of doing the 366@550, and 400@600, and 466@whatever, But I am totally unfamiliar to this lapping procedure....

Can you guys help me out......I have two Alphas- pfh-6035's to put on 'em

Thanks!
 

raptor13

Golden Member
Oct 9, 1999
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Basically, you need to go out and get some wet/dry sandpaper in various grits. Then, take masking tape and mask off the entire CPU, except for the core which obviously has to be exposed. ;)

That done, grab a little dish of water and the roughest sand paper that you got. Wet the core a very tiny bit and set to work on it with the sandpaper. Make sure you move in a figure-8 pattern, as that will ensure you evenly sand down the entire core. After not too long, you should start to see some copper peeking through the silvery metal on top of it. Use the heavy sandpaper until all of the silver is gone.


After you've got the copper showing itself, move down to a finer grain of paper and keep working in the same figure-8 pattern. You might want to rotate the CPU 90 degrees every so often as you sand, again ensuring even sanding all around. When you've got the CPU down to the smoothest it will be with that grain of paper, go finer. You want to eventually move down to the finest grain of paper you can find, which almost feels like it doesn't have sand on it. Take your time doing the job as you certainly don't want to mess up. You can keep taking copper off the CPU until is is almost flush with the ceramic part around it. When all of that is done, you've got yourself a lapped CPU. :D


NOTES: Keep wiping the CPU off as you go and reapplying fresh water. You want to keep as clean as you can through the whole process. Remember, this is a detail job, not one you can just attack full force. Good luck!
 

SammieC

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Apr 24, 2000
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Huh, a little more than I expected, but I'm sure its worth the results..

Thanks for the enlightment and the extra typing:)

I appreciate it!

I will get to work!
 

raptor13

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Oct 9, 1999
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I forgot to add that when you're all done, clean the entire CPU with rubbing alcohol as best you can. You certainly don't want copper dust laying around on the CPU or in your case. Let that dry and you're good to go! Just don't forget the thermal paste when you slap those Alpha's on. ;)
 

SammieC

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Apr 24, 2000
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You really want it almost flush with the other surface.....? thats a lot of sanding down....the heatsink won't interfere if its that low will it?

Thanks!
 

Jwyatt

Golden Member
Mar 22, 2000
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<< You can keep taking copper off the CPU until is is almost flush with the ceramic part around it. >>




That doesnt mean you should. Taking it down that far would pose problems keeping the heatsink flat on the slug. Its hard enough to keep it on there as it is. Take off as little as you can to get the results you want. Make sure you keep the cpu level so the end product the cpu wont be off kilter with the wafer of the processor.

The only one i lapped turned out pretty good, but i did notice that the edge of the slug was rounded a little, thus loosing some surface contact area. When the sand paper starts wrinkling i would suggest getting a new area and start there.


Good luck


Edit: Just thought about something. You should get a shim and put it on there as you lap. That might help keep it flat. Im going to try that on my next lapping job.
 

ericd

Senior member
Oct 8, 2000
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One thing that I have seen others suggest that I think makes a lot of sense. Put the sandpaper flat on a piece of glass and wet it down so that it sticks to the surface of the glass. This way you are ensured of a flat sanding surface which will give you a flat lapped core.

Eric