Pyrolytic Graphite Sheet, high performance thermal interface material

[Conrad Hoffman]

OK, now the stuff makes more sense to me. I used to use HPOG (highly oriented pyrolytic graphite) as a target for scanning probe microscopes- you'll see a lot of the atomic scale images use that as a demo, and the stuff consists of loosely attached layers. You actually expose a fresh surface by pulling the top layer with tape. Thus, it should have only so-so thermal conductivity in the normal direction.

I'm still confused, though that's always been the case. It's because you can never get consistent conductivity numbers for all the different pads and such, to make a direct comparison. Even a single manufacturer will use different methods for their different products, just so you can't really tell at a glance what's what. I'd love for some independent person to set up a standard test and publish numbers for all the different pads, mica and different goops, to finally put some sense to it.

FWIW, I use a simple measure- the hotter the heatsink, the better. IOW, if the device is hot and the heatsink isn't, the interface needs work. If the device and heatsink are close to the same temp, life is good. Copper spreader plates are often a wonderful thing, but few people use them other than maybe for CPUs. Being an analog guy, CPUs are of very little interest to me! When you get to the conductivity level of copper, how much could possibly be gained by switching to graphite? IMO, not much.