Can surfaces be lapped TOO flat?

Kevin · 12-22-2001, 12:16 PM

What do you guys think? I've heard a bit of info arguing either way and I find it interesting so let's start a discussion... Can the surface of a waterblock or heatsink be lapped TOO flat?

Kevin · 12-22-2001, 12:17 PM

Let's not include polish... we all know that can mess things up.

WebMasta33 · 12-22-2001, 12:48 PM

Yes... (a metal worker told me this) If you eliminate most (all) of the pours of the metal, you eliminate any places for the thermal compound to reside.

When you sand it that smooth, what you end up doing is pushing fine particle of the heatsink, into the spaces in the metal, basically filling them. This metal isn't atomically bonded to the surrounding metal, so it can't transfer heat properly.

This is what a metal worker told me.

twocpu · 12-22-2001, 01:38 PM

Quote:

Originally posted by Kevin:
What do you guys think? I've heard a bit of info arguing either way and I find it interesting so let's start a discussion... Can the surface of a waterblock or heatsink be lapped TOO flat?

Check out this article

Bottom line is that you can't get too flat, but you can get too smooth. 600 grit is about as smooth as you should get the surface of a waterblock

[ 12-22-2001: Message edited by: twocpu ]

[ 12-22-2001: Message edited by: twocpu ]

BrianW · 12-22-2001, 03:38 PM

Would 600grit be ideal for processors/cores as well?

thanks

Butcher · 12-23-2001, 10:19 PM

I'm not so sure about the 600 grit, I had a very smooth heatsink, then read that and sanded it to 600, then reapplied and my temps got worse.

WebMasta33 · 12-23-2001, 11:20 PM

I found best temps at 1000 grit myself...

I was just told not to make it look polished.

redleader · 12-24-2001, 02:42 PM

Quote:

Yes... (a metal worker told me this) If you eliminate most (all) of the pours of the metal, you eliminate any places for the thermal compound to reside.

Well obviously you won't use compound on an extremely lapped surface. Its thermal conductivity is what, 1/20th that of Cu? So it would act as an insulator at that point.

I don't believe you can get too smooth. Maybe in therory, but even professionally lapped isn't going to be very smooth on the molecular level.

12-22-2001, 12:16 PM	#1
Kevin Slacking more than your weird uncle Join Date: Nov 2000 Location: San Diego, CA (UCSD) / Los Angeles, CA (home) Posts: 1,605	Can surfaces be lapped TOO flat? What do you guys think? I've heard a bit of info arguing either way and I find it interesting so let's start a discussion... Can the surface of a waterblock or heatsink be lapped TOO flat? __________________ I used to throw hot coffee all over the ass of the horse there, then whip him while he was kickin' at me. Those f***in things are crazy.

12-22-2001, 12:17 PM	#2
Kevin Slacking more than your weird uncle Join Date: Nov 2000 Location: San Diego, CA (UCSD) / Los Angeles, CA (home) Posts: 1,605	Let's not include polish... we all know that can mess things up. __________________ I used to throw hot coffee all over the ass of the horse there, then whip him while he was kickin' at me. Those f***in things are crazy.

12-22-2001, 12:48 PM	#3
WebMasta33 Cooling Savant Join Date: Dec 2001 Location: Nebraska Posts: 526	Yes... (a metal worker told me this) If you eliminate most (all) of the pours of the metal, you eliminate any places for the thermal compound to reside. When you sand it that smooth, what you end up doing is pushing fine particle of the heatsink, into the spaces in the metal, basically filling them. This metal isn't atomically bonded to the surrounding metal, so it can't transfer heat properly. This is what a metal worker told me. __________________ ========== --Soyo KT333 DRAGON Ultra (Platinum Edition) --AMD 1.4 @ 1.54 (11x) --768mb of PC2100 (@140FSB) --Asus v8200 GeForce3 @ 210/490 --Maxtor 40gb Quiet + 2 IBM 40gb 60GXPs (removable) + 8gb WD --Audigy --Maze 3, DD Gf3 block, 2x BIX, Eheim1250 ===========

12-22-2001, 03:38 PM	#5
BrianW Cooling Savant Join Date: Jun 2001 Location: Desert City in California Posts: 631	Would 600grit be ideal for processors/cores as well? thanks __________________ Water Cooled Inwin Q500 (Dual Rads: Rad1 = DTEK Pro Core \| Rad2 = Blick Ice Estreme, Hydor L30, Dangerden Maze2, Bay Res Typhoon Reservoir, 1/2 " DD Tygon Thick Wall Hose). Flow: Res, Pump, CPU watervlock, Y into both rads, both rads into res independently. Athlon XP 1800+ (@ 1731 - 150mhz fsb.), on a Asus A7N266-c, and a Radeon 9000 *waiting for RMA'd Saphire 9800 ultra from Newegg)

12-23-2001, 10:19 PM	#6
Butcher Thermophile Join Date: May 2001 Location: UK Posts: 1,064	I'm not so sure about the 600 grit, I had a very smooth heatsink, then read that and sanded it to 600, then reapplied and my temps got worse. __________________ Once upon a time, in a land far far away...

12-23-2001, 11:20 PM	#7
WebMasta33 Cooling Savant Join Date: Dec 2001 Location: Nebraska Posts: 526	I found best temps at 1000 grit myself... I was just told not to make it look polished. __________________ ========== --Soyo KT333 DRAGON Ultra (Platinum Edition) --AMD 1.4 @ 1.54 (11x) --768mb of PC2100 (@140FSB) --Asus v8200 GeForce3 @ 210/490 --Maxtor 40gb Quiet + 2 IBM 40gb 60GXPs (removable) + 8gb WD --Audigy --Maze 3, DD Gf3 block, 2x BIX, Eheim1250 ===========

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