Thermal SIL PAD® Materials Bergquist Company Thermal SIL PAD® Materials are electrically and non-electrically insulating silicone thermal interface materials. These materials minimize thermal resistance from the external package of a power semiconductor to the heat sink. This is achieved by isolating the semiconductor electrically from the heat sink and providing sufficient dielectric strength to withstand high voltage. The SIL PAD® materials are made of conformable fiberglass and silicone rubber, which provides a more versatile material than mica or ceramics and grease. These materials are designed to be clean, grease-free, and flexible.