COPPER CPU SHIMS: The Definitive Answer !!

Robert Redelmeier wrote:

In comp.sys.ibm.pc.hardware.chips The little lost angel wrote:

That doesn't make much sense even if we ignore the point about
there being triple layers of compound/shim/compound to go
through. One of the key thing for the heatsink to work properly
is strong pressure pushing the sink and chip together.


The pressure is there to squeeze the thermal compound as thin
as possible. Both joints need to be good (thin and bubble-free)


What's going to be pushing the shim tight against the
side of the core?


I don't think there's much need to contact the die edge.


If there's no way to get a proper tight contact with the
shim against the core, it would be useless to transport heat
away from the core.


As I read it, the shim is sandwiched between the core and heatsink.

Unless he's doing something really strange it's a commonly available 'shim'
that sits on the chip carrier and not between the core and heatsink.

You don't want the shim near the package and those exposed jumpers
or caps.

The typical 'pre-made' shim is cutout around those areas to provide clearance.

It basically makes up for a somewhat poorly designed HS
(too thin a base).

Wishful thinking.

Lateral heat transfer matters.

What you're thinking would, at least, have a chance if you were talking
about an 1/8 inch think, or so, copper plate instead of an .027 inch thin
'shim' that could never be keep flat and in pressure contact across the
heatsink base. But, then, you wouldn't have a rat's chance in hell of
attaching the spring clip with a 1/8 inch plate under the base even after
the core was crushed flat.

The packaging sure doesn't conduct much heat since I know I can touch
the package way before it's not painful to touch the core :PpPp


True enough.

-- Robert

In comp.sys.ibm.pc.hardware.chips David Maynard wrote:
As I read it, the shim is sandwiched between the core and heatsink.

Unless he's doing something really strange it's a commonly
available 'shim' that sits on the chip carrier and not
between the core and heatsink.

Why would anyone manufacture such a useless and potentially
dangerous thing? The chip carrier has very poor thermal
conductivity and you're never going to get the thickness
right. Either a too thick carrier will prevent die-contact
(horrors!) or a thin carrier won't contact the package (doing
no good).


What you're thinking would, at least, have a chance if you
were talking about an 1/8 inch think, or so, copper plate

Yes, that's what I thought. Nice slug of copper 3-4 mm thick,
shipped with a new bale or attachment mechanism to accommodate
the extra thickness.

The OP saw some improvement -- it must have been from a flatter
HS contact. I suspect s/he must have put the HSF on backwards,
or received an HSF with the bale switched.

-- Robert

Robert Redelmeier wrote:
In comp.sys.ibm.pc.hardware.chips David Maynard wrote:

As I read it, the shim is sandwiched between the core and heatsink.


Unless he's doing something really strange it's a commonly
available 'shim' that sits on the chip carrier and not
between the core and heatsink.


Why would anyone manufacture

The original reason was the Athlon's tendency to get cracked cores from
heatsinks being 'rocked' on during installation. AMD responded by adding
rubber bumpers.

Then someone, long time before now, got the not very well thought out idea:
hey, if it's copper then maybe...

such a useless and potentially
dangerous thing? The chip carrier has very poor thermal
conductivity and you're never going to get the thickness
right. Either a too thick carrier will prevent die-contact
(horrors!) or a thin carrier won't contact the package (doing
no good).


That's been the point of the critiques.


What you're thinking would, at least, have a chance if you
were talking about an 1/8 inch think, or so, copper plate


Yes, that's what I thought. Nice slug of copper 3-4 mm thick,
shipped with a new bale or attachment mechanism to accommodate
the extra thickness.

There's a chance with a new bail but then not all heatsinks use the same
physical configuration so it's virtually impossible to make a 'universal' one.

The upshot is it's better to simply get a proper heatsink to begin with.


The OP saw some improvement -- it must have been from a flatter
HS contact. I suspect s/he must have put the HSF on backwards,
or received an HSF with the bale switched.

That's been the general speculation.