A heatspreader is an external casing used to cover memory modules in order to dissipate heat. They are usually made of copper or aluminium and are usually attatched using a conductive adhesive or with a clip system. Although the adhesive approach reduces the pressure on the individual memory chips, it makes removing the heatspreaders a lot more troublesome, and usually the stock heatspreaders will be impossible to reattach due to the loss of a lot of the adhesive.

Heatspreaders vary in the designs of their cooling systems. Some manufacturers have simplistic heatspreaders that simply cover the modules and draw heat from the memory chips. Other companies encorporate holes or grooves in the surface of the heatspreader to increase its surface area and therefore improving its ability to cool the modules. In extreme cases, heatsinks have been added to heatspreaders to increase cooling ability further. This can be seen in the case of the Corsair Dominator modules, the OCZ Reaper HPC (Heat Pipe Conduit) or the Thermalright HR07 aftermarket memory cooler.

Crucial Ballistix with typical heatspreader

OCZ Reaper HPC module

Corsair Dominator module