Lapping questions

Orangey

Orangey

Orangey

Soldato
Joined
22 Aug 2008
Posts
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OK first of all to get it out the way, is it stupid to think I can use the sander attachment of my dremel (on lowest speed) to do the initial work?

And here's my problem: I just got a new CPU (rig in sig) and am sitting at 4.2GHz right now, trying to get up to 4.5 but I'm seeing core temps of 37 at idle WITH speedstep. CPU itself is only 24 right now. I used the sandwich bag trick to get a nice thin layer of TIM on the CPU but maybe too thin? The noctua cooler has seen a lot of action as I used it with my old e6420 for a while, is it safe to lap that too?

Do I need to lap? If so what website sells the sandpapers I need, a google for "sandpaper 1500 grit" only yields 1 ebay link in shopping search. Failing that can I get the type of grits you need at Robert Dyas etc?

Thanks.
 
Firstly use wet and dry paper on glass (flat), don't use a dremel attachment, it will end up 10x worse than it is.

Secondly start at a low grit (200-400 grit) then gradually go onto a finer grit until you get the finish you want (anything past 800ish only adds cosmetic effect).
 
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Dremel is a bad call. I used a lapping machine at my materials lab with great success, so machine tools do have potential. A horizontal finish with a hand held tool won't happen though, stick with glass and wet&dry.
Buy from any standard diy store :)
 
You can get the wet/dry sandpaper at Halfords (I'm pretty sure that's not a competitor :p).

I'd really advise against using a Dremel!

Regarding whether you actually need to lap - that depends on what the IHS surface is like on your chip. Can you see a visibly noticeable curve on the surface? My Q6600 was practically a cave, it took me hours to lap it flat :/
 
I'm gonna go buy the sandpaper in a bit, waiting on a delivery of a scythe 1900rpm fan. :)

Once I get back I will check it and do the job and post back with the results (if any).
 
Stick with wet and dry, its the grey one.
Safe: Use it dry, wash it under the tap, let it dry, then you can reuse that sheet.
Quick: Use it slightly damp, rinse it off now and again and pat dry

pictures always welcome :)
and dont touch the shiney copper, or you'll burn a fingerprint into it
 
Halfords £2 for four sheets and they do all the grits though 2000 is a tad of overkill you want it flat not necessarily shiny ............. shiny looks great though and you can post a picture showing it off plus all the hard work is flatting the cpu shiny takes no time at all and makes the job worth it :)
 
StevenRaith said:
Those who have lapped their CPU, did it give much of a temp drop? Anything realistically useful?
Click to expand...

It made a massive difference for me - between 8C and 12C, depending on which core. My IHS was massively concave, and temps are now much lower, and more even between the cores.
 
Hmm. Might have to clear off the kitchen worktop, tape some 40grit* down and get grinding* :cool:

Did you lap yer HSF as well?

[*yes, I know, you don't use 40 grit and you don't apply pressure - I checked a couple of tutorials out on Youtube :) ]
 
Lapping the cpu didn't really drop the overall temp much bit it did reduce the different core temps from 8-9c difference to 1-2c difference. Lapping the heatsink depends on your heat sink some work better unlapped and its not advisable to lap a heatsink where the heatpipes are exposed on the base making direct contact with the cpu :)
 
I've lapped a few CPUs now.

After some experimentation I find that using regular washing up liquid is great. Just put a drop on wet/dry paper and lap your heatsink/cpu heatspreader as normal. The washing up liquid lubricates the sandpaper, locks up the metal particles, and it also won't tarnish copper - like when you use the paper wet. When a sheet stops being useful (clogged up with metal particles) just wash it off under running water and leave the sheet to dry for reuse. You can really get rid of all the metal particles adhered to the wet/dry paper this way!! :cool:

I just use any regular (i.e. non-eco, non-antibacterial) washing up liquid brand!! :cool:

Lapping is most (only?) useful if you have a concave heatspreader or heatsink with an uneven base.

Going above 800 gritt can actually be counter productive. I have read that AS5 has a similar particle size. So getting a smoother surface means the AS5 will not enter the "micro-sized features" (technical enough for ya?? :D) in the surface of the metal.

Bob
 
Not quite AS5 have 3 main partical sizes, plus the smaller ceramic filler elements - and that way its better when used with 'micro-sized features'
It's also why it has a burn in time as the particals arrange themselfs into the best fit - improving conductitity.

Mirror - ceramic or liquid metal
concave/uneven/direct touch - AS5 or liquid metal pad (but ceramic is also v.good)

My 2p worth anyway ;)
 
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