Heatsink Lapping Guide

**Doctor Feelgood** · Posted: Sun, 18 Jan 2004 12:29:13 Post Subject: Heatsink Lapping Guide

You bought the pinnacle of air cooling technology, but you want to make sure you're getting the best contact possible; you want to lap and polish your heatsink. This guide will show you how to do just that and get the most from your heatsink. - The Review

Niatross · Rated PG Joined: 19 Jan 2004 Posts: 3

I've seen two views on lapping and was wondering if you've seen the one that theorizes that you shouldn't polish any finer than 600 to 800 grit. The theory is that with finer polishing there is a thin film of thermal interface material between the heatsink and core that atually prevents metal to core contact of any kind. The purpose of leaving the 600 to 800 grit scratches is so that the TIM fills the scratches and the high parts of the metal actually make direct contact with the core. I've seen this argued both ways and you seem part of the polishing group. Have you seen this and have you any thoughts on the subject? I personally don't know which is best

**Doctor Feelgood** · Posted: Mon, 19 Jan 2004 14:29:58 Post Subject:

Hi Niatross... Welcome! We'll have to wait for Dud3! to drop in and answer, but I have seen it presented both ways as well. (but, I have also seen it presented that you just use sandpaper and your fingers, which is kinda scary... Laughing

)

Dud3! · Posted: Mon, 19 Jan 2004 15:52:26 Post Subject:

And I've read a post by someone who just couldn't figure out WHY their temps went up after they "lapped" their heatsink with a 180 grit belt sander... Laughing

Anyway, TIM = stuff that makes up for imperfect heatsinks so you will have greater contact. The less TIM the better, and by lapping and polishing the heatsink you lessen the need for TIM. Metal to core contact is much better than core to TIM to heatsink contact as I'm sure you'll acknowledge.

By leaving the heatsink at a "rough" level like 800 grit, all you do is decrease the amount of metal actually touching the core, and that metal area is replaced by TIM, which isn't a very good conductor of heat compared with metal.

Soooo, the people that think a rough finish is good need to think about it a bit longer. Razz

Niatross · Rated PG Joined: 19 Jan 2004 Posts: 3

well the people I've heard say this were actually engineers but you go back to the old saying too " I can spell engineer I are one" Laughing

**Doctor Feelgood** · Posted: Mon, 19 Jan 2004 20:16:54 Post Subject:

Although I would never try this, I know some have... Lapping your cpu. Honestly, what good is a perfectly flat and smooth heatsink if the surface of the cpu doesn't match?

trekrider · Posted: Mon, 19 Jan 2004 20:47:27 Post Subject:

Dud3! · Posted: Mon, 19 Jan 2004 21:58:25 Post Subject:

I agree BB, but one's better than nothing. I'm too chicken to lap a new processor, but I *may* try it with a dead Duron 750 I have. If that works, I might lapp the Duron 900 I'm getting from Spire just for fun.

And you need to start with 30 grit on your CPU... Laughing

Niatross · Rated PG Joined: 19 Jan 2004 Posts: 3

I would probably lap a P 4 or an FX 51 , anything with a heatspreader but just thinking about grinding on the bare core of an XP gives me the willies. Laughing

BeerCheeze · Posted: Tue, 20 Jan 2004 00:57:00 Post Subject:

A old Duron would be a good start. If you hose it, not much lost.