Lapping a CPU??

VortX · 21 Jun 2009 at 12:18

Could someone explain to me what lapping is exactly...

I understand its where you apply sandpaper to a CPU and sand away until you reach the copper base... but what I don't understand is that if it makes a good temp difference (around 5C), why isnt it done as standard, instead of Intel/AMD making a big fat metal base that collects heat?

OzZie · 21 Jun 2009 at 12:23

You use lapping paper/wet & dry, which is similar to sand paper, but is a million times finer than sand paper.

Dont use sandpaper!

VortX · 21 Jun 2009 at 12:24

OzZie said:
You use lapping paper/wet & dry, which is similar to sand paper, but is a million times finer than sand paper.

Dont use sandpaper!

oooo lol thanks

I just got the impression it was very fine sandpaper lol... same thing

setter · 21 Jun 2009 at 12:28

It would take a lot of time to ensure perfectly flat mirror finish surfaces, therefore increasing production costs that would result in hgher retail prices, its only a tiny group of end users who will lap their cpu anyway, mainly overclockers looking to eek the last few mhz from their system.

VortX · 21 Jun 2009 at 12:47

setter said:
It would take a lot of time to ensure perfectly flat mirror finish surfaces, therefore increasing production costs that would result in hgher retail prices, its only a tiny group of end users who will lap their cpu anyway, mainly overclockers looking to eek the last few mhz from their system.

True, the main reason I would do it is merely to lower my temps by that extra bit.

Is there any risk in doing it?

setter · 21 Jun 2009 at 12:58

As long as your careful when handling the cpu you shouldnt have any problems, its a good idea to cover the contact pins on the cpu with the supplied intel cover when lapping, also let the weight of the chip do the work, dont force it onto the sandpaper. I lapped my old q6600 and it helped drop about 10c of my temps.

JonJ678 · 21 Jun 2009 at 13:37

Some risk, but minor if you're careful with it, don't pour water or oil over it etc.

I'm perplexed as to why they don't come flat as standard. It would take minimal effort to run a milling bit over the surface before attaching it to the processor, and even with it then being plated in nickel one would expect the surface to remain flat.

Anyone know if they're electroplated or dip plated? If the latter, it could well explain why the surfaces are a bit hit and miss. Nickel plating is good because it's inert, copper tends to be attacked by fingerprints and the like

VortX · 21 Jun 2009 at 15:59

JonJ678 said:
Some risk, but minor if you're careful with it, don't pour water or oil over it etc.

I'm perplexed as to why they don't come flat as standard. It would take minimal effort to run a milling bit over the surface before attaching it to the processor, and even with it then being plated in nickel one would expect the surface to remain flat.

Anyone know if they're electroplated or dip plated? If the latter, it could well explain why the surfaces are a bit hit and miss. Nickel plating is good because it's inert, copper tends to be attacked by fingerprints and the like

Yeah thats what I was trying to say. Or maybe not so much to make it flat, but even to have less metal on the plate so it isn't so thick? = save money, keeps it cooler?? Or am I missing something?

MrMoses · 21 Jun 2009 at 23:05

After lapping it you wont be able to sell it as well, if you plan to

ShaolinDreams · 22 Jun 2009 at 02:20

setter said:
It would take a lot of time to ensure perfectly flat mirror finish surfaces, therefore increasing production costs that would result in hgher retail prices, its only a tiny group of end users who will lap their cpu anyway, mainly overclockers looking to eek the last few mhz from their system.

dont think intel "if they did" would lap them by hand lol doubt it would take long of cost that much using a specialized machine

Microwave · 22 Jun 2009 at 02:23

I really want to lap my next cpu, the only thing that's stopping me is that it voids the warranty.

JonJ678 · 22 Jun 2009 at 03:54

Indeed. Warranty will be void.
If its am oem cpu, the warranty is only one year anyway and may already have run out. Cpus are generally considered indestructible, though in the near future I may have an example of one which is faulty.

This is part of why I've lapped my heatsink but not processor this time around, as I'm not going to return a massive block of metal under warranty. Its better to do both, but temps aren't bothering me much at the moment.

The copper heatspreader is thick because it needs to be very stiff. It takes a lot of pressure during mounting, for a prolonged length of time. It's hardly likely to creep at 60 degrees or so, but if it were very thin it would deform and crush the core soldered behind it. This would be very bad.

Sem · 22 Jun 2009 at 21:36

setter said:
As long as your careful when handling the cpu you shouldnt have any problems, its a good idea to cover the contact pins on the cpu with the supplied intel cover when lapping, also let the weight of the chip do the work, dont force it onto the sandpaper. I lapped my old q6600 and it helped drop about 10c of my temps.

exactly the same with me
i had a good chip and after i lapped the cpu and TRUE my temps dropped a good 10c

never went above 69c with linpack 63-65c under prime

lapping is defiantly worth it

might make it hard to sell on tho

VortX · 22 Jun 2009 at 21:51

JonJ678 said:
Indeed. Warranty will be void.
If its am oem cpu, the warranty is only one year anyway and may already have run out. Cpus are generally considered indestructible, though in the near future I may have an example of one which is faulty.

This is part of why I've lapped my heatsink but not processor this time around, as I'm not going to return a massive block of metal under warranty. Its better to do both, but temps aren't bothering me much at the moment.

The copper heatspreader is thick because it needs to be very stiff. It takes a lot of pressure during mounting, for a prolonged length of time. It's hardly likely to creep at 60 degrees or so, but if it were very thin it would deform and crush the core soldered behind it. This would be very bad.

Does this mean then that by lapping a CPU you actually decrease its lifespan?

setter · 22 Jun 2009 at 22:01

Sem said:
exactly the same with me
i had a good chip and after i lapped the cpu and TRUE my temps dropped a good 10c

never went above 69c with linpack 63-65c under prime

lapping is defiantly worth it

might make it hard to sell on tho

I had no issues at all selling mine, but it was a pretty decent clocker which may have helped, 3.8ghz on air.

Mr-White · 22 Jun 2009 at 22:59

you need to lap the heatsink as well, there's no point making the heatspreader flat if the heatsink isn't

MW

setter · 22 Jun 2009 at 23:05

Yep particularly with a TRUE made a vast difference on my old q6600.

JonJ678 · 23 Jun 2009 at 08:08

VortX said:
Does this mean then that by lapping a CPU you actually decrease its lifespan?

No, this doesn't follow. Thankfully.

If you reduced the thickness of the ihs so much that there is less than a mm or so left above the core, then you run a risk of inadvertently crushing it by deforming the ihs. Risk will be reduced if your heat sink itself is flat, and increased if it is bowed.

Reducing the ihs thickness will not improve temperatures either. Heat conduction through copper occurs very quickly, its passing heat across the interfaces which reduces the transfer rate. This is why choice of paste matters, and why the cores are soldered to the back of the ihs.

It also suggests that solder would be the ideal thermal interface material, but this comes with its own risks. I quite like the look of 'liquid metal'.

Mr-White · 23 Jun 2009 at 09:56

Get your self some diamond based thermal compound, it's better than silver, copper or gold

MW