How Is Flat Is Flat?!

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alexbruce

alexbruce

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Hey everyone,

After reading all the hype and stuff about CPU lapping I decided to jump on the band wagon and have a go, before I hit my main CPU up I decided to have a go on my media centre PC and lap my E6300, which is already pretty good with temps and stuff; So today I lapped it down to pure (pretty smooth copper) I also lapped my cheap alpine pro 7 cooler.

My main question, I sanded it with pretty even precision and measured the flatness with a razor, I can see tiny bits of light when I hold it up to the light, but I mean small gaps... Now when I saw that I used what i figured to be common sense and figure that any tiny gaps would be filled by the thermal paste and it wouldn't make one tiny bit of difference, Am I right or is PURE flatness essential?

I thought I would ask before I do my Q6600 tommorrow, I sanded using various grits on a piece of glass from a photo frame so the base was smooth.

Also, Is there a better way to check for CPU flatness? any ideas or good tricks?

I think that's all, hopefully someone will have an answer for me :)

Thanks in advance,
A.
 
customisbetter

customisbetter

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while you were lapping, was the copper showing only on the outside, then closing inwards? If so, you heat spreader was concave an needed to be lapped.

you did set the glass on a flat surface right? if not, the glass will have flexed.

if you do the glass thing and use at least 1500 grit, you should be fine.

good luck/
 
alexbruce

alexbruce

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Yeah, the IHS was uneven, i'll give it a long go with some 2000 paper tommorrow, and hopefully i'll even out the last bits, I found quite a handy guide.

For the lapping process, do you push forwards and backwards and keep rotating for even spread?
 
B-Unit

B-Unit

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lol@Blood_Raven If your careful and take your time its no more dangerous than installing the CPU.

But it is tedious, I can tell you that. Gained 2-3C when I lapped my Opty165 and AF7. A couple strokes then rotate worked well for me. Also make sure not to press down.
 
J

Just_An_Engineer

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Technically what you're doing isn't lapping, it's grinding. For the best results you want to use straight, even strokes while keeping the pressure on the CPU as evenly distributed as possible. If you try to manipulate the chip too much (i.e trying to rotate it) you will end up with low spots along the edges.

Once you have ground both the CPU heat spreader and your heatsink to a reasonable level of flatness it will be time to start the lapping process. To do this you will need to buy some lapping compound (something like Loctite Clover would work well) spread it on the CPU and then rub it against the contact surface of the heatsink. This will ensure that the surfaces are as evenly mated as possible.
 
The_Blood_Raven

The_Blood_Raven

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Too much information...
 
C

CoachB

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Lapping much beyond 600 grit has been shown to yield limited improvement. Razor blade edges can be uneven so try the "ketsup" test. Place a small amount of thinned ketsup on the heatsink and lay your piece of glass on top of it. If the ketsup spreads out evenly then you've done a pretty good job.
 
C

CoachB

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ketchup, catch-up, catsup, sumpin like at.

Anyway, the idea is to use something easily spreadable that you can gauge the thickness of (i.e. see through) when you "squish it".
 
spathotan

spathotan

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I used razor blades to check evenness when I lapped my Q6600. I check it with about 4 different blades and it was all the same. My chip was extremely convex in the middle and around the edges, but the area inbetween that was fine. Infact I didnt even get down to the copper on those spots but the IHS was completely flat. Looked like this...

cpulapped.jpg


As far as before and after temps, I saw about a 2c drop, if that, with a Xiggy S1283. Put a Enzotech Extreme-X on it and temps dropped another 2c or so.

The lapping wasnt worth it.
 
customisbetter

customisbetter

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Where your OPINION falls is when people have Intel CPUs. almost every intle heatspreader i have seen is severly concave. I don't know why, but they are. My personal cpu needed tons of thermal compound to make a seal with the hs and still didn't spread all the way to edge. So the thermal paste just pooled to the center of the cpu and led to overheating.

I also disaggree with your notion of destroying CPUs no matter what. That seems like a pretty foolish statemnt. Especially considering that a majority of people on this forum have Lapped their CPUS and had them still work afterwards.

If you take the precautions (Moisture and ESD Especially) you will be fine.

No hard feelings :)
 
The_Blood_Raven

The_Blood_Raven

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From this forum and other forums I have seen way too many people destroy a CPU because of lapping, and they even did everything right. A shaving or some water can easily find its way to the back of the CPU if you are not totally attentive, and no one is ever totally attentive. The point is that there is a GREAT chance, but not an absolute one as I already said, that you will destroy your CPU for a 1-2c drop in temps.

Whether it be slightly too much water and you get some in places you shouldn't, not enough water even from a non consistent area can cause static electricity, shavings can find there way to bad places and cause shorts, you can press to hard and do internal damage, or your HS can cause damage if the CPU can not handle the pressure.

Point is that it is a bad idea because, simply put, something could go wrong. 1-2c temp drop is not worth the possibe $100+ bill so I stand by my original statement:

DON'T LAP YOUR CPU!
 
spathotan

spathotan

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I partially agree with blood raven. I advise against lapping, but you have to be extremely careful or just clumsy to kill the CPU in the process. Soapy water+wet/dry sandpaper = no "shavings".
 
The_Blood_Raven

The_Blood_Raven

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It sounds simple, but the at least monthly sob story of a CPU lapping gone wrong get old. Oh and if your CPU is so concave that it overheats then you do not void the warranty, you send it back and get a new one.
 
customisbetter

customisbetter

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Bought it used. Plus Intel had never heard of my CPU. At least the Service people didn't.

Look up stepping "SLA5F" and see if you can find anything :)

My theory is that its a prototype CPU between the two steppings. It has the resistor layout of the first, and the Overclocking potential of the second....


Kinda off topic....
 
spathotan

spathotan

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Parts search has it as a 2ghz pentium 4, but labeled as an E4400.
 
JohnnyLucky

JohnnyLucky

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I posted this in another thread over in the heatsink and coolers section:

I lapped my heatsink and my cpu and used a high quality thermal compound. There was a drop in temperatures as expected. I just wanted to see if I could do it. My temps were well within operating range and quite respectable before lapping because of other steps I had taken to improve ventilation, airflow, and cooling.

And now for a healthy dose of reality! I am not a hardcore gamer and I am not into serious overclocking. In fact, for what I do with my pc I can't even justify upgrading from a dual core to a quad core system. Lapping was a pleasant diversion that provided a sense of personal satisfaction. I am able to say "I did it". In that respect it was worth it.

ps - I lapped the heatsink and cpu last Summer. The cpu has been in constant use ever since. Nothing bad happened. However, I have to admit there was a possibility that something could have gone wrong. The_Blood_Raven is correct about that.

 
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