Damaged Thermal Pads

Thermal pads are a type of thermal interface material (TIM) that acts as the heat-conducting interface between integrated circuit (IC) and heatsink. Thermal pads are phase-change materials; they soften from a firm room-temperature material into a viscous pore-filling material as the integrated circuit (IC) heats up. Thus, if you must remove a heatsink/thermal pad combination, you must replace the thermal pad with a new one or an appropriate thermal interface material (TIM) such as thermal grease. Do not try to reuse a thermal pad. You will probably be sorry.

For an excellent reference on thermal interface materials (TIM), please see AMD's Thermal Interface Material (TIM) white paper.