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           EasyPCKits Lapping Kit

Product :

  PC Lapping Kit

Manufacturer :

  EasyPCKits

Reviewed by :

  Wayne Brooker

Price :

  Various

Date :

  5th May 2004.

 

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Introduction:::...

If your experience with the whole PC scene is limited to the past twelve months then you'd be forgiven for not ever having heard the term "lapping" before. Although it seems to have faded a little in popularity, it was once one of those geeky pursuits that ranked alongside other mysterious black arts like overclocking and water cooling, and anyone who was anyone had lapped a heatsink and lived to tell about it.

Lapping, in simple terms, is the flattening, smoothing and finishing of a metal surface. It can be done by machine or by hand and almost always involves motion and some form of abrasive. But why?

Well, let's imagine the diagram below represents a highly magnified cross section of how the base of your heat sink looks when it's sat on your CPU core or the heat spreader that covers it.

Because neither surface is perfectly flat there are a few contact areas but there are also a lot of places where neither of the surfaces actually meet. As I'm sure you can imagine, heat from the core travels easily across the contact areas but, due to the relatively low thermal conductivity of air, it has a much tougher job bridging the areas where there is no contact.

Unlapped ~ No Thermal Grease

 

This is the reason why thermal compounds are so important when fitting a heat sink. The thermal compound has a much higher thermal conductivity than air and so helps heat to bridge the gaps where air would normally reside. The thermal compound filled areas still aren't as efficient at shipping heat as those in physical contact but the solution is still vastly preferable to dry mating of the surfaces.

Unlapped ~ With Thermal Grease

 

There is however a further step that can be taken to improve thermal transmission and that is to abrade away (or lap) the imperfections in one or, ideally, both mating surfaces.

As you can see, with just the heat sink base lapped, there is an increased amount of contact and a reduced volume of thermal compound. If you ever wondered why it'd important not to use too thick a layer of thermal grease, this is why. You want just enough to fill the surface pits and not so much that it forms a cushioning layer that keeps the two surfaces apart.

HSF Lapped ~ With Thermal Grease

 

Naturally, the progression to this is to lap both mating surfaces which, if done properly, would virtually eliminate the need for any kind of thermal interface between the two. That said I think I'd still use a thin smear of a very fine silver or ceramic based compound which may well still do some good on a microscopic level.

HSF and Core Lapped

 

So that's what lapping is all about, but who should do it and how?

Well the who is easy. If you've got the time and the patience and you're not expecting to see miraculous temperature gains then lapping is suitable for just about anyone.

As for the how, well, you can buy all the parts you need quite easily at any half decent hardware store, but you need a pretty good idea of exactly what you want, and you need to be ready to be sold far more of each component than you actually need.

If that idea doesn't grab you, then you could take the vastly easier route and head over to EasyPCKits to order one of their lapping kits that comes complete with everything you need including detailed instructions, the full range of grits, glass (if required) and a tube of quality thermal compound.

The glass is a cheap but effective way to provide a perfectly flat surface on which to work, but more on that in a moment.

For this review I'll be trying out the premium kit which contains one each of the following 1/4 sheets of sandpaper:

  • 400
  • 600
  • 800
  • 1000
  • 40 micron (yellow)
  • 25 micron (green)
  • 20 micron (blue)
  • 15 micron (peach)
  • 10 micron (light green)

It also came with a piece of glass and a tube of Arctic Silver Ceramique thermal compound.

Let's get started!

 

 


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