Question on lapping

Associate
Joined
6 Jul 2007
Posts
431
Location
Notts, UK
Ive just bought a lapping kit and was wondering if its best to lap just the heatsink or both the cpu and the heatsink. I've just put some new 120mm 1600rpm fans in to try and lower the temps but they are still around 52 idle. Im using the zalman 9700, its a Q6600 oc'ed to 3ghz.



 
I didnt buy a lapping kit i just purchased some normal wet and dry sandpaper from my local car spares shop and used that.

I have the Q6600 and the Thermalright Ultra 120 Extreme IHS and both of mine were not flat..

I lapped them and now my temperatures are 44oC idle and 66-68oC under load

This is what my cpu and IHS looked like after I lapped them.. Be patient though as these 2 took me more than 5 hours to do both...

Shiney_Lap.jpg
 
you CPU isn't flat at all. Its just shiney.

Sounds like you didn't buy rough sand paper first and only used fine wet and dry. Hence why its shiny and not flat.
 
8igdave said:
you CPU isn't flat at all. Its just shiney.

Sounds like you didn't buy rough sand paper first and only used fine wet and dry. Hence why its shiny and not flat.

Beg to differ I used wet and dry from 240 grit up to 1500 grit..

The cpu and IHS is straight as there is no light showing thru any gaps when you put a straight edge onto either of the pieces..

I have even used graph paper to check the reflection on both as well and they show perfectly straight lines...

Ive even got my m8 whos an engineer and does precision grinding to check it before i put it back into my system and he said if its out, its only by microns..

What cooler are you using and what temps are you getting?? Also what are program are you using to measure the temps?
 
Last edited:
hey... i don't know any of you personally... but i doubt that he would be lying about it... if he did it and it took him 5+ Hours... i am sure he is telling us the truth...

After all... the camera never lies...
 
Kingy1968 said:
the edge of the IHS reflecting the HS though may just be local edge rounding from rocking
If you're lapping by hand it nigh on impossible not to put a radius on the edge. To lap it dead flat would need a jig or fixture to avoid uneven pressure when you lift off. It wont effect the contact area the IHS is no where near the edge.

dscf1808cf0.jpg
 
Last edited:
fornowagain said:
If you're lapping by hand it nigh on impossible not to put a radius on the edge. To lap it dead flat would need a jig or fixture to avoid uneven pressure when you lift off. It wont effect the contact area the IHS is no where near the edge.

dscf1808cf0.jpg

Exactly, me m8 said there is no way to precision grinding the Ultra 120 as there is no way that you could hold it in place and use the machine without damaging the fins on the heatsink...
 
Last edited:
BTW lapping aint for l33t PC geeks, I did it for 15years as a engineer, we had to mate surfaces gas tight like Valves in Cylinder Heads etc.

We used Grinding Paste, rough then smooth, you can then test with a stuff called Engineers Blue, it marks the surface you put on and when you mate it to other surface and then remove you can see any high spots.

I use Wet/Dry paper same as all others but its not as easy at home and holding tall heatsinks is hard not to coggle, its also damn hard to get the diff sizes of grit paper, nobody seems to do own car body repairs these days.

All the photos in this thread look good to me, flat and shiny too, and even though they are shiny its impossbile they are too smooth and wont grip the TIM/paste, you would still see grooves through a mircoscope, you should Google for that view on a new Razor blades edge, it looks like a mountain range.
 
Last edited:
There are ways, but it would be more hassle than worthwhile.

I used to prepare metallurgical specimens for my PhD and its hard to get perfectly flat specimens even with machine polishing: it's considered a dark art even in metallurgy to get a perfectly flat surface (ask anybody who's used an atomic force microscope).

The only point of lapping is to get a flat surface. Not shiny - flat. Bevelling around the edges is not going to be make much of a difference is the majority of the contact surface is flat. It's less effort to buy a better heatsink. :)

P.S. the only lapping I've ever done is because I could, rather than I should... nothing like working in a metallurgy department.
 
Yes thats true helmutcheese... I did use some blue carbon paper as well as I read somewhere a while back that you could use this as a kind of that engineering blue stuff to check for high points... I did it but admit it wasnt very good to check for the different points but I thought I'de give it a go as I had nothing to lose..

My old temps were around the 50+ mark and now there are roughly 44'ish as shown below.. so obviously some good must have come of it.. and these temps are at 3.2ghz as well so im really pleased with the results..

Idletemp.jpg


I know the point is to get the surface flat i just wanted to polish it up a bit to make it a bit more bling... ;)
 
Last edited:
Correct, you wont polish it too much its impossible, but the point is not to get it shiny and non flat (looks nicer) but flat as possible, shiny is nice touch and gets rid of sand marks, I polish of with Brasso or Silvo then totally wash and dry it then run with ISO.

Peeps get 10-12C drop doing Heatsink and IHS, depending how badly concave/convex they were to start with.
 
Back
Top Bottom