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Old 02-16-2009, 08:48 PM   #1
Rauchster
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A Guide On: Lapping your processor (with pics)

What is lapping? Why should I do it?
I only recently found out about this process myself, but have since done it on multiple CPUs, and a couple heatsinks. I actually find it somewhat stress relieving, so I really enjoy it.

The main reason people do this is is to lower their CPU temperatures. You're probably wondering how. Every CPU (and most heatsinks) is not manufactured perfectly flat. It's close, but not perfect. When you connect the heatsink on top of the CPU, the area in between in filled by thermal material. And, if you're really unlucky, air bubbles. While thermal material is made to conduct heat, it is still yet another material the heat has to travel through before it can be dissipated. And an air bubble will heat up and not transfer well at all.

The flatter the contact surface on both sides, the less thermal material or air that the heat has to transfer through before it can reach the fins of the heatsink.

Since most high-end heatsinks are already manufactured well for thermal conductivity, this will either have a small or no effect on those aftermarket solutions. However, a large part of CPU's have a significant concave or convex surface.

From my experience:
Lapping a stock heatsink = -3C to -6C temperature change.
Lapping an aftermarket heatsink = -1C to -4C temperature change.
Lapping a CPU = -6C to -12C temperature change.

IMPORTANT NOTE: Lapping a CPU WILL VOID any warranty currently on the CPU, as you are physically changing it.

What you need:
Processor (Duh?)
Sandpaper (I used 400-800-1000-1500, I'd recommend using at least three different grit levels)
Bottle of Rubbing Alcohol (I used 99%)
Container of Polish (Optional, Automotive Turtle Wax will work fine)
Lots of Paper Towels or 2-3 clean white lint-free cloth sheets. (Cloth will be more effective)
Flat surface (Anything sturdy and flat, I used my computer desktop)
Pane of Glass (From most picture frames will suffice, try to get one only a little bigger than your sandpaper sheet)
Roll of Tape (Duct works best, Electrical works well for most, Masking doesn't work good at all)
Sharpie Marker, fine tip (optional)
Access to a sink with running water and a trash can.

Step-by-Step Guide:

Step 1: Grab your pane of glass and secure it to your flat surface
(counter/tabletop). The flatter the surface/glass, the better your end results will be.

Step 2: Affix your lowest grit (lowest number) sandpaper to the pane of glass, making sure it is VERY secure.




Step 3: Cut a small piece of paper towel (two thick is preferable) or cloth that is the same size as the processor chip. Lay them on top of the pins, to help protect them from the lapping process, and any oils on your hands.

Step 4: Take a paper towel and lightly wet it with the rubbing alcohol. Blot it to make sure there are no standing pools of liquid. If liquid gets inside the CPU, even rubbing alcohol, it can easily kill it.

Step 5: WITHOUT APPLYING PRESSURE on the CPU, move it lightly across the sandpaper. You are letting the weight of the CPU evenly glide over the sandpaper, allowing it to grind down evenly. This will take a long time.

During the process, you will notice buildup from the removed material. Remove it occasionally with a small chunk of paper towel or cloth moistened with rubbing alcohol.

Also, re-apply rubbing alcohol to the sandpaper every so often (~2 minutes). This will help clean the surface of the CPU as you are grinding it down.

If the sandpaper is noticeably getting full of material, replace it. I used 2 sheets of each grit level, and 3 of the final grit level.

Not sure how level the CPU is getting? Take your Sharpie marker, and make a small dot near each corner and in the center. OR, draw a X from all 4 corners. Do a few passes, and take a look. Is the ink disappearing evenly? That means that it is wearing down evenly, and you could possibly switch up a grit level.

Step 6: After a few hundred strokes (15-20 minutes), you will notice the CPU is gliding across much easier, and the top plating is starting to come off. When the resistance isn't there, it means it is time to switch up a grit level.

Step 7: Undo the tape holding the sandpaper to the glass, and attach the new paper using new tape (The old tape usually doesn't stick as well).

Step 8: Repeat Step 4-7 through each grit level. For a really smooth finish, use as many grit levels as you can. The smoother it is at the end, the bigger impact on temperatures.

Pre-lap


Note the dull silvery exterior (probably nickel), as well as all the markings on the top plate.

Post-400 Grit


You can see the outer nickel layer being worn off on the very edges, a large chunk of the right side, and in the center, showing just how far off of a flat surface the CPU originally was.


Post-800 Grit


Note that the top silver plating is mostly gone, with the largest chunk remaining in the top right, and almost none in the bottom left.

Post-1000 Grit


99.9% of that pesky top plating is gone, the only spot left is on the bottom right corner. Those worried about the glossiness of the CPU, be reassured. It may look like it's getting more dull here, but that just means we are finally hitting the entirety of the surface and getting it all even. Shine doesn't come until smoothness is achieved.

Post-1500 Grit


After the 1500 grit sandpaper was used, you can tell that all of that top coating has been removed, and it is at long last finally even.

Wait, you want it shiny too?
You aren't gonna see it after it goes under the heatsink. What's the point?
Oh, right. Shiiiiiny.

IMPORTANT NOTE: Steps 9-11 are optional. Some people have experienced negative results when applying polish. Personally, I have not lapped a CPU (or heatsink) without polishing it to remove the leftover debris. A possible resolution might be to polish it, and then do a high grit(2000,2500) sandpaper to remove to polish.

Step 9: For this step, you can take the sandpaper off of the glass surface, and stretch out a clean white rag (paper towels don't work well for this stage) over it. Make sure it is taut, so to discourage bunching up. Duct tape works better than electrical for this section.

Step 10: Take your polish and spread it lightly, yet evenly, across a large portion of the rag. Make sure to leave a decent sized area clean of polish for the final step.

Step 11: Gripping the four corners of the CPU, and being careful not to bend any pins, rub the CPU across the polish-laden cloth. This step works best when applying a SLIGHT and EVEN pressure on the CPU. If the cloth is bunching up on the sides, you are either pushing too hard, or the cloth isn't secured tightly enough.

You will notice the cloth turning dark rapidly at first. Rub in the polish covered area until the CPU no longer leaves a gray residue behind (or a very light grey residue).

Move to the area that no polish was applied. Rub the CPU gently over this area for about 3 minutes or so, or until no residue comes off at all.

Post-Polish



Looking at it from the sides will reveal any scratches left. Obviously the fewer there are, the better the lapping job



Stupid chip fell over when I tried to prop it up for the picture, and got two scratches from the coin. Luckily this was just a demo run to take the pics.

Step 12: Install your chip carefully, applying heat transfer liquid as normal, and watch your CPU temps drop.


Ending and important notes:

Remember, lapping a CPU will void any warranty, and probably any RMA/replacement policy it may be covered under.

Do not get any liquid inside the CPU. This can easily cause chip failure.

Be careful with the pins. The reason I use the cloth laying on top of the CPU while lapping is to apply even pressure across a larger area of pins. (Think of the guy laying on a nail bed) If you bend a pin, get a pair of needlenose pliers and CAREFULLY bend it back into alignment. If you break a pin, tough luck buddy.

Be careful of polish/debris getting in between the pins, or inside that little hole on the top. If you get debris inside either spot, what I do is bend a paper clip, wrap one end in a small amount of tissue or paper towel and gently slide it between the pins or inside that little hole. If debris is inside the hole, remeber to not press very hard (if at all) against the bottom of that.

Shine DOES NOT equal flatness. Look at the post-400 grit picture above. Relatively shiny, but nowhere near flat. Don't worry about shine until you've finished with all grit levels of sandpaper.

Polishing compound (at least the brand I used) can stain black clothes rather easily. Wear white. It can also cause skin irritations, and will probably dry out your hands and make them itchy. I recommend doing the polishing stage with a small amount of water and a couple spare paper towels lying around to clean off your hands occasionally, as well as any spills.

DON'T RUSH. This process takes time. The one shown above took me about 110 minutes total time. When I did my AMD Phenom 9600, I took nearly 180 minutes (3 hours). I had a movie playing on the computer screen, and was just absently rubbing away with the CPU. Drinks help too. (Don't splash!)

I highly recommend doing a practice run on a old, working CPU to a computer that isn't needed, but still runs. This way you can practice it on a CPU that doesn't matter (Not your $1000 C2Q Extreme or Corei7 965), and see you can do the process without ruining the CPU.

Last edited by Rauchster; 02-28-2009 at 03:59 AM.
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Old 02-16-2009, 09:16 PM   #2
redout
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Nice looking guide - good final lap result.
I think you should "attach" the images rather than inserting them.
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Old 02-16-2009, 10:36 PM   #3
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what were your actual temp drops after lapping? I hear that it is typically far less than doing the cooler. Good guide tho
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Old 02-27-2009, 06:48 AM   #4
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Thanks for the great guide! Can we use the same technique for coolers?

I might lap my 5000+ BE next week. Im installing watercooling and if it can help with temps, the lower the better ^^
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Old 02-27-2009, 11:43 AM   #5
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DO NOT use the polish for that shiny finish, it actually worsens your temps. Polish is not good at transferring heat at all. All it does is take up the space that AS5 or whatever would use to us for thermal transfer, apart from the polish, spot on.

Edit - Just double checked the polish slows up the heat transfer to the HS.

Last edited by maximus7724; 02-27-2009 at 12:23 PM.
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Old 02-27-2009, 11:46 AM   #6
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Resize the pictures to 640x480 and you are good to go
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Old 02-27-2009, 11:57 AM   #7
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Does it matter which direction when sanding, like circles ,up and down?
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Old 02-27-2009, 12:19 PM   #8
maximus7724
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To get a nice even lap the most popular technique is to do a big figure of 8 on the sandpaper.
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Old 02-27-2009, 06:39 PM   #9
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Quote:
Originally Posted by maximus7724 View Post
To get a nice even lap the most popular technique is to do a big figure of 8 on the sandpaper.
ok thank you I will do this
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Old 02-28-2009, 03:43 AM   #10
Rauchster
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Quote:
Originally Posted by maximus7724 View Post
To get a nice even lap the most popular technique is to do a big figure of 8 on the sandpaper.
Forgot to mention that, thanks.

Adding now.

Quote:
Originally Posted by 4-n-zics View Post
Resize the pictures to 640x480 and you are good to go
Better? They were too big, I know.

Quote:
Originally Posted by maximus7724 View Post
DO NOT use the polish for that shiny finish, it actually worsens your temps. Polish is not good at transferring heat at all. All it does is take up the space that AS5 or whatever would use to us for thermal transfer, apart from the polish, spot on.

Edit - Just double checked the polish slows up the heat transfer to the HS.
Added a note about that.

I've never experienced negative results from adding a layer of polish. I use it, because it's amazing jsut how much debris it removes from the surface.

Possible solution might be to polish it, and then go over it again with a real high grit sandpaper to remove the polish. Or have another cloth with rubbing alcohol and clean off all the polish.

Last edited by Rauchster; 02-28-2009 at 04:05 AM.
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Old 03-08-2009, 09:36 PM   #11
MegapowerXXL
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Thanks for writing this guide. I just recently ran into lapping in few articles and posts and had no idea what it was.

Just one question since I would want to be 100% accurate with the steps. I saw this in step 5:

Quote:
Originally Posted by Rauchster View Post
Also, re-apply rubbing alcohol to the sandpaper every so often (~2 minutes). This will help clean the surface of the CPU as you are grinding it down.
Is one supposed to apply rubbing alcholol to the sandpaper before sanding the CPU and then re-appply more or just apply some after the initial sanding? Is it important?
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Old 03-08-2009, 09:41 PM   #12
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I used Rauchster's method (thx again! works **** well on my 5000+ BE) without applying rubbing alcohol on the paper and got an excellent lap job. Instead I was cleaning the IHS with a paper towel and some rubbing alcohol on it every now and then, the same way I clean thermal paste off my CPU and heatsinks.
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Old 03-09-2009, 02:56 AM   #13
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A good guide, well presented, I acheived a slightly better surface post 1600 than your post 1500 (I know I Know) and that did not need the polish at the end, some have used 2000 grit and that is almost as good as the polish withoth the heat transfer issues
If you dont care about the warrenty I highly recommend lapping
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Old 03-10-2009, 04:51 AM   #14
[GF]Duke
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You should try using the plastic backplate that your cpu shipped with instead of pushing down on the cpu pins like that. Damage is alot less likely.
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Old 03-11-2009, 07:05 AM   #15
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Well, lapped my chip and heatsink yesterday=)
Didn't follow this guide tho, but used roughly the same methods.
Started off at 240 grit, then 400, 600, and finished off with 1200.
Didn't bother doing any polishing, but the surface had a nice shine to it anyways.
Got a 8 degree celsius temperature reduction of it on my i7 920=)

Edit; added a pic of my lap=)

Last edited by Fed-Up; 03-11-2009 at 02:09 PM.
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Old 03-15-2009, 10:10 PM   #16
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very nice guide, one question though.
what if you are jumping straight to a copper heatsink.
for example, im gonna lap my old Apogee GT for kicks. its already pretty smooth but has some bad scratches, since i dont need to take off the nickel layer, can i jump straight to 1000 grit, or 1500?
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Old 03-15-2009, 10:12 PM   #17
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I guess you will want to start it from the start. It will help evening the whole CPU by grinding it with the big grit. If you use the 1000 grit at start IMO you will need alot more work for the same thing.
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Old 03-23-2009, 10:09 PM   #18
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I lapped mine and guess what....

Well I have had my q9550 for some time now and it always seemed hotter than it shoud have been at both idle and under load and this was at stock temps. I lapped my cpu and during the process, it was very concave and by very, I mean it took a long long time to get everything flat. Once completed, all temps looked better. I am most likely on of the more exterme cases as my idle temp became very even across all 4 cores (prior 7c spread) now with in 2c. My CPU is oc'd to 3.6GHZ v core of 1.375 and my temps are now 38c idle and 52c loaded for 1 hour running prime 95 vs. before lapping 45 idle and 66 loaded. I am happy with this and will most lokely do this to my I7 build next month. Thanks for the guide!

B
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Old 03-24-2009, 03:56 AM   #19
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I never thought of buffing the mating surfaces. Just the extra clenliness of them would decrease insulation. Good tip!
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Old 06-08-2009, 04:06 PM   #20
Jahova
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Things to add:

Clean the processor and glass between grits.

Clean the turtle wax off (is not easy to do) and I'd actually recommend not using wax at all. Use something called "Mothers Aluminium and Mag Polish". Also, I use a piece of printer paper taped to glass.

Push the processor across the sandpaper, pick it up and return it to start, push across again. Do this 11 times exactly. Then rotate the processor 90* and do another 11 passes. Rotate, again and 11 passes. Then a final rotation and 11 passes. Then check it.
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