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I have a question on the proper way of lapping a processor...

533 Views 14 Replies 7 Participants Last post by  Lord Xeb, 
Lord Xeb
When lapping, you go from coarsest to finest grain. But when you start off on the coarse one, you put an X on the die (corner to corner) to tell if it is flat or not. with that method, how can you tell you truely got the die flat? Also, what is the proper way of lapping. Some of the guides on the web are not really that descriptive when it says which way to turn it. Some of them say to turn it 180 and then start lapping again...
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bumsoil
Quote:


Originally Posted by Lord Xeb
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When lapping, you go from coarsest to finest grain. But when you start off on the coarse one, you put an X on the die (corner to corner) to tell if it is flat or not. with that method, how can you tell you truely got the die flat? Also, what is the proper way of lapping. Some of the guides on the web are not really that descriptive when it says which way to turn it. Some of them say to turn it 180 and then start lapping again...


what i use is a piece of glass as a surface to lap on, i usually go in circles until i have only copper exposed and then move to higher grit sandpaper until i am up to about 2k grit. the only way to make sure your hsf is flat is to lap it on a completely flat surface AKA glass.
also is is a good idea to put masking tape on your cpu's bottom.
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I feel your pain. Forget all the Internet crap you saw unless it helps. You want to flatten the surface so it makes greater contact. The one video I saw showed how it rocked back and forth. Not good. You want as many points of contact as possible.

Sorry at this point I can't help more. Hope someone else adds real world.
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Lord Xeb
I am lapping my processor (because I am going to get more of a clock out of it and go for 4g
). The s1283 doesn't lap to great (since the heat pipes are rather then (maybe 1-2 mm thick).
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R
if you wanna make sure its flat and even do the razor blade test
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Lord Xeb
That sounds like a good idea
If I were to use tooth paste (or something like it) then run the blade over the top, will that give me a good idea?
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Quote:

Originally Posted by Lord Xeb View Post
That sounds like a good idea
If I were to use tooth paste (or something like it) then run the blade over the top, will that give me a good idea?
No it will tell you if sanded enough but will tell you zero about if flat.

I don't want to seem like a jerk but flat and sanded are not the same. I will give a little more effort but they are not the same. Also lapping is about flat that toothpaste test? Come on what do you think the thermal compounds do?

Read and think. Take your time.
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Lord Xeb
No I am saying if you take the tooth paste and put it onto the die, the go and take the razor blade and run it across so that it scraps away the tooth paste. If there are any thick spots remaining, then you need to lap more (after you have used to 800 grit). would that work?
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Quote:

Originally Posted by Lord Xeb View Post
No I am saying if you take the tooth paste and put it onto the die, the go and take the razor blade and run it across so that it scraps away the tooth paste. If there are any thick spots remaining, then you need to lap more (after you have used to 800 grit). would that work?
OK sure so you have gotten beyond the flatness issue? OK sure shows low points?
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Lord Xeb
I understand the flatness thing, I am just not sure how to move the proc as I lap....
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G
Quote:


Originally Posted by redalert
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if you wanna make sure its flat and even do the razor blade test

I'm assuming he's talking about placing a razor blade, edge down, on the surface and holding it up to the light. If the surface is flat you shouldn't be able to see any light coming through gaps. I've never heard of doing anything with a razor/toothpaste.
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Lord Xeb
<.< I though it would work to show high and low areas on the die
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R
More important even than how flat the CPU and heatsink are is how well they match together. Even with a precisely flat Heatsink if the CPU does not match it's flatness (looks rounded when they are interfaced together and can be shifted around) you will not get the full increased cooling effect.

The razor blade test (without Colgate, Aqua Fresh, etc.) will do fine to check for flatness. But worry more about how well the CPU mates to the heatsink as that is far more important. The more they match the better your cooling will be. I lapped both my CPU and heatsink, and though they both appeared flat they did not match well together. I did some slight sanding on the heatsink and they match just about perfect now. I saw my temps go down another 3-4 degrees Celsius.
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billbartuska
Quote:


Originally Posted by Lord Xeb
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When lapping, you go from coarsest to finest grain. But when you start off on the coarse one, you put an X on the die (corner to corner) to tell if it is flat or not. with that method, how can you tell you truely got the die flat? Also, what is the proper way of lapping. Some of the guides on the web are not really that descriptive when it says which way to turn it. Some of them say to turn it 180 and then start lapping again...


You can tell whether the CPU or HS is flat, concave or convex by where the marker is removed, although, not holding the piece flat can remove more material from the edges and make it appear convex.

Also, if you use a magnifying glass (or even better, a microscope) you can tell when the coarser swirl marks from the previous sand paper are completely removed by the current (finer) sand paper.
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Lord Xeb
Okay, I have a 30x hand microscope so that will work for me
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