THERMATTACH® - The Thermattach family of thermally conductive adhesive tapes is used extensively to bond heat sinks to microprocessors and other power dissipating semiconductors. Offered with a choice of aluminium oxide or titanium diboride fillers coated on Kapton film, aluminium foil, fiberglass or expanded aluminium, these tapes combine exceptional bonding strength with low thermal impedance to effectively replace thermal grease and mechanical fasteners. 

http://www.chomerics.com/products/therm_thermattach.htm