Lapping Heatsinks and You

Joe_B_Me

I've decided to make a simple, easy to follow write up on how to lap your heatsink to get the most out of it.

To put this whole "lapping" in a nutshell, its basically just a lot of sanding. Lapping your heatsink(s) will create a flatter surface (more surface area), resulting in better heat transfer. Will it reduce your temps several degrees C? Probably not (unless your heatsink is that bad). CPU heatsinks, videocard heatsinks, chipset heatsinks, waterblocks etc... you name it, you can lap it.

Lapping can also be used to take regular finished aluminum, such as what you see with Lian Li cases, and make it in to a polished, mirror finished aluminum, changing the whole look of the part you are working with.

Part I - What you'll need

-water sandpaper
For really rough heatsinks, I'd start with 300-400 grit.
For something like a stock AMD heatsink, 600 grit is a good starter.

a hard, flat surface.. a piece of glass is perfect.

-water
Water will act as a buffer, allowing you to sand only the areas that are uneven. This will help ensure a flat surface. Wet sanding will help get rid of scratch marks. You can also use a drop of liquid soap on the sandpaper, along with the water, to make the sanding a little easier

-lots of free time
A good lapping will take more than 10 minutes. This could take a couple hours if you really do a nice job.

Part II - Techniques

There are only a few things you need to keep in mind when your sanding
1) tape your sandpaper to a perfectly flat surface, that is hard - like a small piece of glass or mirror
2) sand the surface evenly and do not be impatient!
3) do not apply any pressure when sanding, let the weight of the heatsink/waterblock do the work
4) it can get messy, clean off your sandpaper and heatsink often
5) sand in a circular motion, and every little while, rotate the piece you are sanding about 90 degrees - this will give you the best finish.
6) when you are satisfied with your lapping job, be very sure to clean the heatsink/waterblock very well as it will have lots of minute metal particles all over it from the sanding.
7) once done, you can use a nice metal/aluminum polish to complete the look and give it a mirror like finish - any automotive metal/aluminum polish will do (yes, aluminum polishes work just as well on copper) such as AutoSol, Mother's Mag and Aluminum Polish... and numerous others. This will give it a brilliant shine and finish, but keep in mind, it probably will not do anything to help with cooling, but will give you a big ego and braggin' rights LOL :)


When I lap my heatsinks, this is the process I normally go through
320 grit (if the heatsink is really bad)
600 grit
600 grit wet sand
1200 grit
1200 grit wet sand
1500 grit
1500 grit wet sand

You can go to a higher grit if you want (2000 ftw).

Part III - Pretty Pictures

^ This is the surface of a stock amd heatsink. Yuck, look at those machine marks!


^Here's a close up of the machine marks. As you can probably guess, that is not the kind of surface you want.



I dry/wet sanded at both 600 and 1200 grit on this heatsink. Probably spent a total of 15-20 minutes on it. That is the result. Don't let the reflection fool you. There is still a lot of room for improvment.



^If I zoom in, you can still somewhat make out the machine marks. Which means I should have spent more time on a lower grit sand paper. When I'm in the mood I'll finish this heatsink and get some nice pics up and such.

And now for a different example, a chipset heatsink.

Stock
1200 Grit Wet Sanded
Polished w/ turtle wax polishing compound.
Messy hand FTL, but the chipset heatsink looks great

Another great example by leojharris, he used a figure 8 motion for sanding.



Here are some of my (~NortH~) lapping jobs and what the finished product can look like -
In the first 2, I just used a cheap picture from a flyer for the local drag strip here and put the blocks by it so they would reflect the picture - you can see how well it reflects :)
Danger Den A64 TDX waterblock-


Silverprop Fusion HL GPU waterblock-


Asetek HDD waterblock (modded for 1/2" tubing systems)


and these are the Xoxide/NortHWateR Xtreme BGA Heatsinks... they are all lapped and polished to a mirror finish as well -

Xoxide & NorthWater Xtreme BGA Heatsinks (8 pack)

Sure hope this guide helps... if you have any questions or comments... or even additions, let us know.

The Cooling Section Staff (with help from others too)

BlackKoala

Nice Heatsink, Joe! ;). Oh, and if you use a piece of glass af a flat surface, it works lovely. Put some blue ink on the bottom of the heatsink and place it on the glass. Where the blue is NOT on the glass, is fine. Lap the HS until the HS makes full contact with the sheet of glass.


BTW blue ink, mechanical (Used for injection molding).

jfkfhhfj

great guide joe, very helpful! Guide like these will be stickied if they are unique and offer valuable info.

NortHWizarD

I have done tons of lapping, especially since i have gotten into the business of water blocks and stuff... and would like to add a few things to your guide...

The guide is correct, and very good... but there are a few small things that should be added....

you should always tape your water sandpaper to a piece of thick glass or something similar... it will have excellent rigidity and will also be as close to perfectly flat as you are going to get... putting the sandpaper on a counter, in the sink... anything other than something very very smooth and extremely flat can and will cause imperfections and/or warps.
(as pc-modda said) and yes, you can use machinist's die if you want... but normally it is quite easy to see when working with copper or aluminum.

When lapping... do NOT apply any pressure... let the weight of the block/heatsink do the work... it may take a little longer, but the results are worth it.

Always go in a circular motion and at frequent intervals, rotate the block 90* and go again... also always move it around the sandpaper... do not keep using the same area... it wears down and gets clogged up even with water running.

you can use a drop of liquid soap (dish detergent) on teh sandpaper with teh water to make it slide around better and easier and it does not affect the sanding of the material, just makes it easier on the arms/hands :)

Always make SURE to clean the heatsink/block very very well after lapping as there is a lot of very tiny metal particles all over it when you are done.

after it is all done, you can take an automotive polishing/cutting (needs to be very fine) compound (mother's aluminum polish... autosol... stuff like that... and yes.. works just as well on copper) and get a super nice finish on the base... but keep in mind.... this will not actually help the performance... but it will give you braggin' rights and make ya feel good about the sexy shiny base and lapping/polishing job ya did!

Great Guide... very informative and accurate

~NortH~

MDSarcasm

Great guide Joe...proved ouselves useful again now have we?

And by us i mean you

:)

Grez

Nice guide, man...good advice. We need more stuff like this in the forums. Whiteboy and I have plans to get more content like this in the modding forum, so that we can direct people to standardized answers to questions instead of answering the same ones over and over again. +rep, bro.

(and good appendix material from North!)

WhiteBoy88

Awesome, the first of our new XFN guides! There will be many more to come......

I say go ahead and edit NortH's additions into the guide to make it more...guided .

Joe_B_Me

I wont be around till like 9:30 tonight (est), so if north of jfkhffhj could edit that stuff in, that would be great,

NortHWizarD

it has been editted and updated... additions made as well as some more pics added.

~NortH~

WhiteBoy88

Hehe, waterblocks and drag racing.....that's NortH for you

NortHWizarD

fast cars, hot women, cold CPU's

that's what ~NortH~ is all about!

~NortH~

trsroller

goood write up im going to lap my thermalright when i get it.

Joe_B_Me

Thanks for adding all of that stuff north, looks like a pretty complete guide, excpet for me finishing that heatsink i started on. Well, i'm going to see if i can get off work tonight, relax a little, and get back to sandin :)

@ trsroller, which thermalright heatsink do you have?
If its the XP-90 (aluminum version), get like 200 grit sand paper and grind that base down till you reach the copper, then lap lap lap!!!

montypythizzle

well i didnt exactly lap one today i used steel wool on an aluminum and made a pretty good finish eh its not perfect eh but its aluminum who cares

Burton560

thanks for the guide :)

Joe_B_Me

I added a small update, using a chipset heatsink as an example. I actually pulled out some polishing compound for this one.

WhiteBoy88

You should point out that copper will allow a better reflection (from sanding) than aluminum, to keep people from sanding their Al sinks to nothingness.

opie_77

Add a note that not all polishes that work with AL will work on copper.

illustrious

nice tut
and lmfao I love the thread name :P

JimShorts