In computing and electronics, thermal pads (also called thermally conductive pad or thermal interface pad) are a pre-formed square or rectangle of solid material (often paraffin or silicone based) commonly found on the underside of heat sinks to aid the conduction of heat away from the component being cooled (such as a CPU or another chip) and into the heatsink (usually made from aluminum 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 firm at room temperature, but become soft and well able to fill gaps at higher temperatures.
For special applications, non-silicone thermal pad may be required. Most commonly seen is Acryl-based non-silicone thermal conductive pad. The applications may include electronic components: IC、CPU、MOS、LED、M/B、P/S、Heat Sink、LCD-TV、Notebook PC、PC、Telecom Device、Wireless Hub、DDR II Module、DVD Applications、Hand-set applications, etc.
Reference: Wikipedia & T-Global Technology Research Team