DH Guide: Lapping a Heatsink

The_Neon_Cowboy

hey areun u that guy thats always on the ground in a pool of blood?
with me pumping a fex extra rounds in lol

Roadee

This is what was wrote in my article, "Polishing the surface is not required if you have used a fine enough grade of sand paper, but really makes your work look good."

Everyone is going to have a different opinion about something, and you are going to see something a little different each place you go to. But does that make it "correct", just because you read something else.......somewhere else? Grooves in the surface TAKE AWAY contact area when collecting heat.......they add too when dissapating heat. In other words.....the smoother the surface......the more heat the metal collects.......the more fins on a heat sink.......the more surface area to dissipate heat.

FACT

Theramal compound is only used in order to aid the transfer of heat from the CPU to the heatsink. It is needed because of imperfections on the surface of a heatsink, as in, it fills in the scratches and pits. The fewer imperfections.....the less thermal compound is needed. With this in mind, lapping a heat sink ensures the surface is as close to perfectly flat as possible. Using finer and finer grades of sand paper makes more surface contact available, by removing imperfections on the surface.......as in scratches and pits.

Rubbing compound and polishing compound are forms of abrasive's.......much like sand paper and used for the same intent. To remove material. Only there "grit" factor is more like 3000 to 10,000 grit. There sole purpose is to remove imperfections. In doing this the surface will get shiny in appearance. This shine is caused by light rays bouncing off of the surface. The less imperfections that exist, the more light will bounce off of the surface without interference. Thus giving you that "mirror" finish.

The CPU's that are made do not have finely machined surfaces, so there is a need for thermal compound to aid the transfer of heat. Even if your heatsink is PERFECT........the CPU still isn't.

How much time, if any, you spend lapping a heatsink is up to you. Whether you prefer to go the extra step to polish it is up to you. Even if you get the heatsink surface perfect, the cpu die will not be. Even if you were anal enough to lap the cpu, you may or may not gain a losely measured amount. ONLY scientific, calibrated measuring devices, that measure temperature to .0000000, and are done in a controlled environment, are going to give you accurate temperatures and differences in temperature due to lapping and polishing.

Computer's are a hobby for many of us, how serious we are about the hobby is a personal choice, much like polishing a heatsink. Expand your horizon's whenever possible and remember to have FUN

Roadee

The_Neon_Cowboy

lol ...

thats why some people lap thier cpu's

Judas

you'd think that'd be a bad idea..... but.... i saw an article were someone lapped there abit NF7-S northbridge chip.... and they got a massive preformance increase do to it being alot more overclockable...

Roadee

There is so many things you can do to increase your overclock.........just depends on how far you want to go. This article was just for a simple performance increase.

Judas

... i'm willing to buy a kyrotech case in about 5 years..... $2000 just for the hardware...... but damn.. compressed liquid nitrogen.... -198 or lower cpu temps... and those kind of temps on 4 other things.. such as vid.... north...south bridges.....maybe another cpu if your running dual....

BWX

I just lapped my heatsink- it took about 6 hours- the surface was pretty big, and uneven. I started with 250 grit for about 2 hours, then went to 350 grit, then 600, then 600, then 1500, then 2000. I didn't polish it either, after 200 grit it's pretty shiny anyway.

Roadee

If you can.........post a pic of it Also......is this the first one that you have done?

BWX

My camera quit working, so I won't be able to post a pic any time soon -But it's about the fourth one I have done, including video card heat sinks. I used a piece of 3/4" mdf with a 1' x 1' mirror tile attached. I also used that 99% pure isopropyl alcohol you can get in a metal can from Home Depot. The lapped heatsink gave me allot better temps, but I was also using a 1.5v Tbred going from a Palamino, so I can't really compare the temps, but I'm sure it's a much more efficient cooler now.. I tried the way you were talking about, going back in forth in one direction as opposed to a circular motion like I used to do and it seemed to work just fine, plus I could use smaller pieces of sandpaper. I wish I did have a good camera to take some pics, the difference of the surface before and after is pretty amazing.

Roadee

I think it is great that the sanding technique in the guide worked for you and that you were happy with the results. It made doing this article well worth it. I hope you consider doing an article of your own soon, as well as other member's of DH.

The_Neon_Cowboy

By the way here are some figures for you...

Before lapping 30C W/AS3
After lapping 27C W/AS2

Rogan

Have you got a link to that? How did they get a nice flat contact on the N/B while they were lapping it?

Nice guide btw, thanks.

Zardon

I saw that guide and in fact I still have it bookmarked at home somewhere, ill hunt it out when I get home from work. im not sure I would recommend doing that to the northbridge though, unless you are an expert with these mods. you are cutting into the top of the northbridge and if you go down to far the whole chip dies. Much safer and almost as efficient taking the stock cooler off applying some good thermal paste and reseating with a better cooler.

GutterPunk

I will in about 2 weeks post about my experience w/ lapping a heatsink i havent yet, but im getting a performance heatsink sometime so well see how things go i really enjoyed reading this, and i learned something, my current heatsink has bad bad scratches, i have a p4 2.4 @ 2.8, @ 29-32C i will lap it and see how things go... this would be to experiement for my 3.0c that im gonna get

Roadee

Sounds great, just remember not to get in a hurry, on some heat sinks it can take a little while to get what you are looking for. Find something that reflects well, so you can see how your progess it going when you are getting close to finishing. Also dont forget about "cure time" for the TIM. I prefer using AS Ceramique', just because it transfers heat extrememly well, and is SAFE to use as well as clean up is easy.

Good luck.

GutterPunk

thanks for the tips, I will take pics showing my progress, if i can do it ne1 can, i am also getting a new cooling unit for my vcard i can show that too... ill look @ ceramique ive always use as3

GutterPunk

i lapped it on my r9800 but ya know what i fogot to take pics of the process but believe me it works well! when I get some AS5 then i will post a pic of my HS cuz I have cheap paste on it for now

Roadee

Sounds good bud. I even lapped my Artic Cooling HS for my 9800 Pro. I didn't take any temperature readings for before and after......but there was a very noticable difference in temperature of the fins and the air exiting the case. Not to mention that my card overclocks much better now.

Evil Techie

thats a good idea, lapping arctic cooling which is already a kick ass cooler



i lap my heatsinks differently though
i use a sanding block or some sort of blocks
and work from 600 to 1200
but ive heard that to get the best results, you are NOT suppose to lap the lines crossing
you can only lap it one direction
and its like push, lift, move back, push, lift, move back...

the motion is kind of like when you are making a bread dough

The_Neon_Cowboy

that not right... you make an L shape or you turn the heat sink as you sand.

aslo 2000 girt is were you want to sand to

Evil Techie

when i heard it, the person said that it is not suppose to give you a mirror finish but it will give you the optimal heat transfer

Roadee

Everyone has there own little ways of doing things.....no biggie.

I was tought how to lap and polish metal by an Engineer that designed and built injection mold's for plastic. The heat transfer and surface smoothness is crucial with those presses. I also do my own porting and polishing on heads and intakes for V-8 drag race engines. What I do and how I do it works for me.

The_Neon_Cowboy

well a mirror finish will create band so good and so stong, it's possable to pull your cpu out of socket! removeing your heatsink...



the finer the better, and then you have to apply the themal paste right and all is well