Whats the right way to lap a HSF?

[RamonGTP]

OK, I know what lapping is, but what is the best method for lapping a HSF to give best results? Anyone have step by step instructions on how-to do that?

TIA,

-Ramon

[SPEEDO]

Take a look here (http://w3.one.net/~robotech/Lapping.htm)...................:D

[leprechaun_40]

Speedo, great article, thanks:D

[RamonGTP]

Thanks for that link SPEEDO, I went ahead and followed that procedure and got about a 3-4C drop. While I was at it I also got rid of the dust on the HSF, so i'm sure that helped too. I actually could have lapped it a little better, but I was getting impatient.

-Ramon

[Bovon]

Great artical Speedo. The main thing I didn't read was about sanding away completely, the anodized finish from the aluminum. This protective finish henders heat transfer considerably. Also, when lapping an aluminum heatsink, its necessary to keep the sink bottom turned in different directions as the sanding proceeds. All of the heat sinks I have lapped have either had a concave bottom or a *kind of* warped bottom where the edges on two parallel sides will be higher than the other two parallel sides. In other words, the east and west sides will be higher than the north and south sides...this will of course need to be sanded equal so that the surface is totally flat.

[Ol'Tunzafun]

How flat are the processor surfaces? It doesn't help much to have a flat surface on the HSF if the surface of the processor does not match.

[Bovon]

I have no means of measuring the gap between the core of a cpu and a straight edge, but I just tried two Tbirds with a machinists 6" metal straight edge and blocked off the light behind the cpu. I could not see any light at all between the processor and straight edge.

But, who knows how calibrated the straight edge is?...

Anyway, I have seen a couple of aluminum heat sinks so badly warped on the bottom that a .0001 feeler guage could be run between the two. Besides the unlevel or concave heatsinks is still the anodized finish to contend with. I had the opportunity to read a heat sink engineerijng manual and that book very plainly said that any anodized finish was to be removed before the solid state devices were attached. This was mostly for large industral heatsinks, like DC welders and other such items. But, if the anodized finish is good for industrial stud mounted transistors...its surly good for a heatsink that will hopefully suck up the heat from the core of a cpu.

[Giblet Plus!]

I might have to lap my Dr. Thermal sometime soon. A 3-4 C drop sounds nice. :)

[rangeral]

Or get a copper or copper based hs/f to wick away the heat, my gladiator is solid copper and has been good from day 1 with some AS compound. Although my tbird 1.3 seemed to benefit more from it than my 1800xp.

[BFlurie]

Tunz writes:
It doesn't help much to have a flat surface on the HSF if the surface of the processor does not match.

True. Usually the CPU alum cover is pretty flat compared to many stock HSs. Lapping the HS usually brings the air-space between the two surfaces small enough so that thermal goo can fill in the remainder.

Do you want to rough-handle the CPU itself on a sanding surface, even tho it's just the alum cover? I'd rather not.

[Bovon]

Do you want to rough-handle the CPU itself on a sanding surface, even tho it's just the alum cover? I'd rather not.Well, I had forgotten that maybe somebody had the older K6-2 series processors in mind...but I was thinking about Thunderbirds and Durons with the exposed core. I have read about K6-2's having the aluminum cover removed which apparently has a core exposed like the later cpu's, but I was never brave enough to attempt to pop off the cover myself.

But, while we are on the subject of lapping heat sinks vs the flatness of the core ect...there has been a few idiots that actually tried to lap the top of a cpu core... those that I have read about wound up with one dead bird.

[tking]

He mentions in the article that some hsf's come factory lapped. Does anyone know off hand which ones do?

[BFlurie]

The CPU HS that came w/my old Powerleap adapter was factory-polished, but that's been the only one I've seen.

[SPEEDO]

AMD processors appear to have a real shiny flat surface on top of the core like they were precision ground. The intel CPU's don't seem like they have as much effort put into them, Obviously they don't require it.................:)