question about lapping?

[cOnTrOl fReAk]

How do I go about lapping my SK-6 heatsink. Just switched to a Alpha Pal 8045 with a nothing 80mm fan on it and I'm about 1-2 degrees higher than my SK-6 was with a Delta 30 CFM. I am going to try a better fan on the 8045, but while it's out I thought that this would be a time to try and lap the SK-6.
What grit of wet/dry sandpaper should I use ? Do I lap it wet or dry? About how long will it take to do a reallly good job. I have plenty of time while it's just sitting on my desk. Plus we're snowed in here in NC today.

[Tek]

Most of the SK6's I've seen have a pretty good bottom. Lapping it will get you nothing but sore arms. But if you want to spend 2 hours for maybe a .5C improvement go right ahead.

[cOnTrOl fReAk]

If that's the case then I think that I'll pass. I proablly spend my time lookng for a better fan for my 8045. I am stilll curious as to how I go about lapping though.

[MadDogMe]

It probably wont get you much of a temp' drop, but all the SK6's i've seen,(mine included ), have shite awful finishes on the bottom!.IMO its not worth lapping to a high polish, but its almost 'a must!' to lap to a 'matt' finish

[Propaganda13]

There are many little different ways to lap. Just make sure you use a large flat block with the sand paper so you don't make it into a smooth, but not flat surface. I agree with the matte finish plus ASII is designed to fill in any small imperfections.

[RavenTai]

get a pice of glass bigger than than a sheet of sand paper 9x12 is good the thicker the better (I use a pice of 1/4" thickest I could find) clean it well to remove any dirt that could cause a bump in the paper set the glass on a stack of news paper to absorb all the mess u are about to make preferably on a surface that is cleanable (no bare wood)

use wet sand paper with water the paper will last better and wont "fill" as easily thsi also keeps u from breathing all the dust and keeps the mess confined to the area that gets wet and it lubricates the whole proces making it easier

I like to use soapy water it makes the paper stick to the glass better and keeps the paper cleaner, wet the back of the paper and stick it to the glass

the first stage is to make a flat surface the rest is removing the scratches from that leveling step

the selection of the first grit is a catch 22 if u use a rughf grit (80-180) it flatten faster but take longer to remove the damage from the rughf paper

if u use a fine grit to start (200-600) it will take a long time to flatten but less time to clean up

so what u start with depends on how bad the bottom is (and what u have/can get localy also) I started my sk6 with 200 then 400-600-800-1000-1500-2000

try to pass the paper under the heattsink in one direstion (north south)try to keep it flat on the paper if u put a lot of pressure on one side u will put a bevel in the bottom it will also want to grab to help with all of this hold low on the sink and let the weight do most of the work

pick it up and look often, there will be a few "low" spots that show up (they will not be sanded) when u get to the bottom of these "lows" u are done with the first step

u should now have a perfect flat surface with a bunch of scratches in one direction move up to the next highest paper u have (400) and sand in the oppisite direction (east west) when all the north south scratches are gone u are done with that step and move to the next (600) and go north south untill all the est west scrathes are gone and so on and so forth till u get to as far as u want to go

then clean off all that junk off the fins and bottom with soap and hot water and then remove all your finger prints from the bottom with alcohol (or they will be corosion in the morning and u will have to hit it with 2000 again) and never touch the bottom again

I do not know how they treated the sk6 but the original surface will not tarnish the lapped surface will tarnish where ever u touch it (thsi is not a problem as the dime sixed part we are worried about will be sealed from the air by asll soon and will never tarnish


soem say that u should not go to i mirror finish that it will accualy hurt, "u need grooves for the as to squeeze out of"

I dont buy it copper is a much better heat conductor than arctic silver u want as much direct contact between the sink and core, well mirroed heat sink need next to no compound "almost transparent" to fill the enebitable voids and u will have no squeez problem

after all this U may get a few C


there is more than one way to skin a cat, If I missed something please do tell

[subman]

I checked my SK6 with a steel ruler and found that the base was definately concave and it had circular milling lines on the base. I lapped it to get rid of this concavity and not for a mirror finish effect. It took me 4 hours to get it flat and I ended up with a mirror finish. But the difference to the temperature is a BIG ZERO. The temperatures readings have remained the same.

I wonder if the circular lines on the base would have had any permanent effect on the CPU's core.

I picked up a lot of information on lapping before I started the process. I did things "by the book" but there has been not even one iddly piddly degree in temperature difference.

[MadDogMe]

I read a article somewhere once(one of the overclocking sites i think), with this dude who worked with cooling industrial diamonds!, apparently they did a test, polishing did not create as good a contact as a matt finish!!, i know it does'nt sound right,and they were diamonds, but its gospel

[MadDogMe]

IMPORTANT!!!, when you have finished lapping a copper H/S, you MUST leave it for at least 24hours before applying Artic Silver!!, A/S ic CORROSIVE to copper unless it has had time for the surface to Oxidise!, oxidising occurs naturaly when it comes into contact with..,duh!, Oxigine/Air

[subman]

MadDogMe

NOW you mention this !!! I have lapped the SK6 3 times and each time I have immediately applied AS2 and attached it to my CPU.

But being located in this ultra humid tropical peninsula city I suppose the waiting period would be shorter here.