Buying high grit sandpaper for lapping

blade52x

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Alright, I got some 600 grit and 1000 grit.

Sound good? Start with the 600 grit for a while and then finish it off with the 1000 grit? Or should I throw 800 grit into there?
 

rtierney

Limp Gawd
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i believe the right way is: start with 600 or 800 until you see all copper, then switch to 1000-1500 to finish it up. no need to polish it or give it a mirror finish.
 

bwanaaa

Weaksauce
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Dec 22, 2006
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so if u lap an ihs, how do u get all the copper dust off? how do you keep the copper/grit/water slurry from getting into the pins and messing everything up? do then dip the chip into alcohol to wash it up or do u need something like toluene?
 

cerebrex

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so if u lap an ihs, how do u get all the copper dust off? how do you keep the copper/grit/water slurry from getting into the pins and messing everything up? do then dip the chip into alcohol to wash it up or do u need something like toluene?
I never wetsand my processor. I suggested earlier using some masking tape to mask off everything but the IHS itself. As long as you give ample time for drying, I don't see any problem using alcohol to clean it off.
 

Rakinos

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I used 70% isopropyl when I wet sanded my heatspreader. After I was done, to make sure all the copper was off, I rinsed it a bit with more isopropyl over the sink (didn't submerge). Its been working great ever since.
 

rtierney

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I never wetsand my processor. I suggested earlier using some masking tape to mask off everything but the IHS itself. As long as you give ample time for drying, I don't see any problem using alcohol to clean it off.
i'm going to go this route for safety...don't want to harm my quadcore.
masking tape and iso alcohol are too cheap to not use.
 
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What are other peoples' thoughts on wet sanding CPUs? I'm going to be lapping my E6600 in a few days, and i don't know whether to use water or not. If i were to wetsand it, and water did get on the non-IHS side, is it ok to drip Arcti-Clean thermal material remover into it and let it evaporate, because i can't seem to get my hands on high-purity alcohol on the UK?
 

fe_918

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sorry for being a noob, but i have a few questions

by wet sanding... do u guys just mean to put water on sandpaper then sand it?

and, whats the point of having a glass underneath the sandpaper? for flatness?
 

NoxTek

The Geek Redneck
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sorry for being a noob, but i have a few questions

by wet sanding... do u guys just mean to put water on sandpaper then sand it?

and, whats the point of having a glass underneath the sandpaper? for flatness?
Yes, and yes
 

blade52x

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Lapping was more a pain then I thought.

I lapped my CPU, and my temps jumped 5C. What the hell! So I took it off, and looked at the heatsink - oh there was the problem. The heatsink kind of "warped" from the initial shape of the chip. So a flat chip surface was not make good contact. I lapped the heatsink, and it brought my temps back down to what I had before lapping. The heatsink wasn't perfectly flat when done, because one side was still slightly higher, and it was just taking way to long, and I ran out of sandpaper. But hey, at least now I know for a fact what the result of lapping was and it's no longer on my mind.

End: ordered a new heatsink :D
 

MajorDomo

Cat Can't Scratch It
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When lapping always use a known flat surface like a sheet of glass or a mirror and hold the heatsink in your hand and the sandpaper on the flat surface. Use a figure 8 motion or change the orientation of the heatsink every few minutes.
 

fe_918

Limp Gawd
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k i just tried to lap my thermalright ultra 120, and it wasn't a mirror like other peoples... but i read that you don't really needed it to look like a mirror.

But my question is that now the surface is turning into a light-redish color... is it getting rusted or something?... and do i actually need to clean the surface with alcohol? cuz i just wiped the surface with water and dried it lol
 

cerebrex

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k i just tried to lap my thermalright ultra 120, and it wasn't a mirror like other peoples... but i read that you don't really needed it to look like a mirror.

But my question is that now the surface is turning into a light-redish color... is it getting rusted or something?... and do i actually need to clean the surface with alcohol? cuz i just wiped the surface with water and dried it lol
it's normal, it's just the early stages of oxidation... after about 15 years copper grows a green layer which protects its almost indefinately (see: statue of liberty).
 

blade52x

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When lapping always use a known flat surface like a sheet of glass or a mirror and hold the heatsink in your hand and the sandpaper on the flat surface. Use a figure 8 motion or change the orientation of the heatsink every few minutes.
I did use a flat glass surface. It was just that making the chip flat actually caused worse contact initially, until I partially fixed the heatsink, but not completely. Heatsink still has a slight curve, but I ran out of sand paper.

Hopefully my 120 extreme will not need to be lapped, but most people seem to need to lap it. What is Thermalright doing with these heatsinks?
 

cerebrex

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I did use a flat glass surface. It was just that making the chip flat actually caused worse contact initially, until I partially fixed the heatsink, but not completely. Heatsink still has a slight curve, but I ran out of sand paper.

Hopefully my 120 extreme will not need to be lapped, but most people seem to need to lap it. What is Thermalright doing with these heatsinks?
I highly recommend anyone with more questions read the following, as I've taken the time to explain this process in great detail since obviously there is quite a bit of inexperience and questions still floating about.

Getting a perfectly flat surface is not easy for a production line. It requires an end-mill bit which is calibrated very frequently and always has a sharp bit... it's expensive to do, and hardly worth the effort for the cost of their heatsinks. Take matters into your own hand and lap them yourself.


The key to getting the benefits out of lapping is now you have the ability to use less thermal compound... a lot less. In a perfect world, 2 completely flat surfaces of copper should use no thermal compound at all... but just the damage you do in pinning the two together marrs the surface too much and also any grain of dirt, or flake of dead skin floating about in the air will lift the 2 surfaces apart in even the most micronical measurements. I myself use about 1/4 of a rice grain on my processors, and then use a perfectly clean razorblade to spread it out... the key is to keep the compound semi-transparent and then place your block (or heatsink) on the processor and press down very, very firmly, twisting slightly to remove any air bubble, and further push more paste out from between, then clip it down. If the thermal compound is correct, the block or sink should be almost glued to the processor (they are actually really hard to separate if done right) and you should see much lower temps...sometimes 10c lower... this is not due to the surfaces being flatter, but the ability to use much less thermal compound between them. Even 1/4" of rice is too much, but a necessary evil cut shorter by pushing hard and twisting to force the extra to the sides. Once you hit room temperature with water... you've done as good as you can possibly due. Which (for me) is about a 22c idle, 38c load.

For all the air cooling brethren, your objective is to get as much heat as possible into your heat sink, and then hope you can get it out as best as possible using fans, etc. The best you can hope for is about 20% over ambient idle (28c) assuming your home is 76* F.

However, I cannot stress enough to always consider what you're loosing when you lap your CPU. Basically, you are nuclear bombing your warranty... which you really should think hard about before attempting. First, the moment you consider lapping you should load fail-safe defaults in your bios, and then use the overclocking knowledge you've already accumulated to get to your previous top OC all over again. Almost every time you will use your newly acquired knowledge to find out you made a mistake earlier, and you were over-volting components that didn't need it. Only then would I recommend lapping if you are confident that your CPU is a beast.. and you cannot possibly hope for a better one... THEN lapping should be done to squeeze your already heroic CPU into the mythical dimension.

Begin by using masking tape, and masking off everything but the IHS (that's the shiny silver flat box on top of the CPU). Mask off the bottom as well, and the sides just bordering the IHS. Then, I prefer using a higher grit to begin with, since the surface is only subliminally uneven. Place a flat piece of glass on a table to make sure you're doing more good than harm, and start with 800grit, sand at 90* angles (left to right 10 times, up and down 10 times, repeat). Once the silver coating on the copper IHS is no longer visible (the entire chip is copper colored) you've succeeded in making the IHS flat. Now, move up to 1500grit, and begin the process again. Eventually the copper will build up on the 1500grit and further increase the grit for an even finer finish. You should see muddy reflections in the surface. Many people will tell you that polishing a chip is not necessary.. and that's probably certainly true, however anyone who says it does nothing would clearly be incorrect -although seeing any difference could quite possibly be immeasurable. The better your reflection, the flatter the surface is. I myself do go through the process of polishing the surface using some bluemagic metal polish.. but your mothers brass polish would work just the same for all intents and purposes. I prefer to not wet sand my processor for fear of copper being carried by the liquid into the small niche's and giving a very small slight chance of some voltage irregularities.
 

Michael Daly

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It was just that making the chip flat actually caused worse contact initially, until I partially fixed the heatsink, but not completely.
There's no point in lapping half of the system. You have to lap both to match. Unless you can demonstrate that one or the other is already very flat, then you have to flatten both.
 

netjack

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Can anyone post a pic of the amount of thermal paste (i.e as5 or sin-itsu) dropped on a lapped hsf and a 2nd pic of the paste spread on the hsf?

In the past, i've always put a whole grain of rice worth of paste and spread it enough to make sure the entire hsf has paste on it w/out any metal showing. Am I doing something wrong?

thx
 

cerebrex

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Can anyone post a pic of the amount of thermal paste (i.e as5 or sin-itsu) dropped on a lapped hsf and a 2nd pic of the paste spread on the hsf?

In the past, i've always put a whole grain of rice worth of paste and spread it enough to make sure the entire hsf has paste on it w/out any metal showing. Am I doing something wrong?

thx

Did you read my post?
 

netjack

Limp Gawd
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Did you read my post?

yes. i didn't see any links to how much paste you dropped on the hsf and what it looked like when it was spread. I understand you want to squeeze out all the air bubbles but it would be nice to see some pics.

thx
 

fe_918

Limp Gawd
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so if my cpu can't overclock very well, i shouldn't lap it so i can return it with the warranty?...... or there's just no point dropping the extra few degrees cuz its not gonna matter at low clocks lol

btw, thx cerebrex for your detailed instructions on lapping =D
 

cerebrex

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yes. i didn't see any links to how much paste you dropped on the hsf and what it looked like when it was spread. I understand you want to squeeze out all the air bubbles but it would be nice to see some pics.

thx
"I myself use about 1/4 of a rice grain on my processors, and then use a perfectly clean razorblade to spread it out... the key is to keep the compound semi-transparent and then place your block (or heatsink) on the processor and press down very, very firmly, twisting slightly to remove any air bubble, and further push more paste out from between, then clip it down."


 

cerebrex

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so if my cpu can't overclock very well, i shouldn't lap it so i can return it with the warranty?...... or there's just no point dropping the extra few degrees cuz its not gonna matter at low clocks lol

btw, thx cerebrex for your detailed instructions on lapping =D
Lapping should only be used (in my opinion) to make the real good processors the absolute best... not in hopes of making a turd into something decent... lapping won't help that much. Thanks for the compliment - I just hope people actually read my post.
 

netjack

Limp Gawd
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cereberex,

do you have any pics of the "1/4 rice grain" amount on the processor and what it looks like spread?
 

cerebrex

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cereberex,

do you have any pics of the "1/4 rice grain" amount on the processor and what it looks like spread?
I'd say for your first one, try 1/2 a grain of rice method - add if needed. Basically, get yourself a grain of rice, and then half of that. :)
 
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cerebrex, the thing you said about lapping will void our CPU's warranty probably isn't relevant to most of us. I mean, we've probably all voided our warranties by overclocking our CPUs anyway, right?

That was a very nice write-up, though. Thank you.
 
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