Apart from a few degrees Celcius difference,
Usually the largest difference in temp results if comparing
a compond too thick to one of proper viscosity, or trying to
mate irregular heatsink (base surface) to the part. In this
latter case, the obvious solution is to reject heatsinks
with a poor base finish or if you consider it reasonable to
lap a heatsink, to do so. However, many heatsinks with poor
surface finish aren't very good in general, there may be
diminishing return in trying to polish a poor one to a
mirror shine (and in general, mirrorlike surface is not
needed).
is there much point in
getting some fancy thermal compound costing 10x more than a cheapo one?
Don't get the cheapo one. Why do people always try to
contrast and consider extremes? Of course if you consider
extermes, on the one end you get junk and on the other you
pay more than it's really worth- same as with just about any
product.
It is useful that:
- Compound is thinner (but this need not necessarily be
high-end product BUT if very low end it means a lot of
silicone oil which will separate from the solids that much
faster). This is for good mating surfaces, if your heatsink
is very rough, the compound viscosity needs be slightly
higher so it doesn't run out. Such 'sinks should be avoided
altogether (in general) but there are cases where this isn't
so easy, for example on a video card that has a special
proprietarily shaped 'sink that is either difficult to lap
or you don't want to void the warranty visually by lapping
it. If the only problem is lapping a surface that is not
entirely on the same plane (staggered such that it makes
contact with different height PCI Express to AGP bridge chip
or memory chips, etc) one possibility is using a small scrap
of heatsink with a flat base as a sanding block.
- Less is applied (goes back to prior point unless one has
plenty of experience applying, and later examining, prior
similar heatsink interfaces
- Synthetic base oil, not silicone so the solids stay in
suspension better, not pumping out and drying as much over
time and repeated thermal cycles.
I suggest Arctic Alumina. Not as expensive as Arctic
Silver, but still synthetic based, reasonably thin,
non-capacitive, and cleanup is easier as you don't have to
get every last trace of it off of parts (as with Arctic
Silver, which leaves a silvery mess unless parts are
thoroughly wiped or washed).
