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Introduction:::...
Plenty
of people have discussed the merits (or lack of) of lapping
your heatsink. Some swear by it claiming it can gain the
5 or more degrees Celsius extra cooling while others see
it as a labour-intensive way to get almost no benefit.
I
think the truth is that lapping will help increases heat
transfer from your CPU to your heat sink base, but by how
much depends on the condition of both to begin with. I have
no doubt that truly attrocious base finish can benefit to
the tune 5 or even more degrees of cooling, but a base that's
fairly true to start with isn't going to deliver you so
much.
I'm
sure you've all seen the diagrams but for the few of you
who haven't, here goes:
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.
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Unlapped
~ No Thermal Grease
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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.
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Unlapped
~ With Thermal Grease
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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.
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HSF
Lapped ~ With Thermal Grease
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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.
The
last heatsink lapping I reviews was a paper only kit. While
you can get some extremely fine grit papers, they don't
come close to the level of finish you can get from a quality
lapping compound.
The
kit I want to test today comes from PCViper, a small company
but one that clearly believes tin the personal approach
to customer service. The website, the instructions and the
whole transaction smacks of that rarest of commodities,
a freindly service from folk who obviously care about what
they sell. The
downside to being a small company is that at present, they
only accept payment by PayPal Cashiers Checks and Money
Orders but most of us have access to at least one of these
so no biggie.
Although
PCViper sell this as a kit suitable for pretty poor quality
sinks, I personally think it needs an additional sheet of
320 grit paper to cope with some of the worst sinks. Not
necessarily that you won't get deep scratches out with the
supplied three papers, but if the base has a high spot,
or worse still a low spot, there may not be enough abrasive
power to cut back that much material.
Here's
what your money buys you.
The
kit contains:
- 400,
600 and 800 grit sandpaper.
- A
single use syringe of our level 1 lapping compound.
- A
single use syringe of our level 2 lapping compound.
- A
single use syringe of our level 3 lapping compound.
- Three
alcohol soaked cotton pads.
Let's
give it a whirl!
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