thermal pads (also called thermally conductive pad or thermal interface pad)are a pre-formed square or rectangle of solid material (often paraffin wax or silicone based) commonly found on the underside of heatsinks to aid the conduction of heat away from the component being cooled and into the heatsink (usually made from aluminium or copper).Thermal pads and thermal compound are used to fill air gaps caused by imperfectly flat or smooth surfaces which should be in thermal contact they would not be needed between perfectly flat and smooth surfaces. Thermal pads are relatively firmed at room temperature, but become soft and well able to fill gaps at higher temperatures.