Phase change thermal interface materials work by changing phase at a stated temperature.
When applied to an irregular surface between the heat source and heat sink, as the application temperature goes above the stated phase change temperature the material will change phase and flow. This will improve the contact between the surfaces, completely fillling air gaps and voids and thereby increasing heat transfer.
Benefits include excellent heat transfer properties, ease of storage and application. They maintain required shape and do not break down over time.
Typical applications include: high performance graphics cards and computer processors, automotive electronics, power conversion equipment, power semiconductors - MOSFET, IGBT and RF, and audio/video components.