http://en.wikipedia.org/wiki/Heat_spreader

"A heat spreader is a heat exchanger that moves heat between a heat source, and a secondary heat exchanger whose surface area and geometry are more favorable than the source."

http://www.thermacore.com/products/heat-spreaders.aspx

"Heat spreaders let you move heat from within enclosures, where space may be at a premium, to areas with a larger cross-sectional area, surface area and/or volume and a lower heat flux."

If you want to get nitpicky, "heat spreaders" you find on RAM are not fitting of that designation unless they are used in this fashion:

http://www.creationbs.com/store/index.php/watercooling/cpu-blocks/ek-ram-monarch-x4-nickel-csq.html



Anyway, I know both of my WS/PDQ CPUs (and Lombard CPU) had something between the black disk and CPU. I just forget what it was originally. The PDQ is under a pile of stuff atm and I do not remember where I put the old daughtercard.

If you look closely at the WS/PDQ & Lombard heatsinks they actually have a heatpipe extending away from the centre where they contact the CPU's spreader.

Heatpipes go between centre and left in these pics.