Joint Healing Thermal Interface Material

Abstract

Today, thermal interface materials (TIM) are widely used between a processor die and an integrated heat-spreader (IHS) to provide a good thermal conduction path for heat transfer from the electronic package. As the current trend towards larger “die size designs” progresses, the performance and reliability of the TIM will be a greater challenge for thermal engineers. In these larger die size designs, the TIM will experience increased movement as a result of the coefficient of thermal expansion (CTE) mismatch between the die and the printed circuit board. Traditionally, indium and dispensable thermoset materials are utilized in this application. However, delamination of the TIM from one of the mating surfaces is becoming more common as these materials are unable to compensate for the increased movement. In addition, the increasing cost of indium metal is causing indium-based TIMs to become cost prohibitive while dispensable materials require frozen shipment and storage, creating logistics complications and increased costs. A recently concluded application study demonstrated that a joint-healing thermoplastic pad had better performance after thermal shock cycling, when compared to typically used TIMs. The joint-healing, thermoplastic pad maintained lower thermal resistance at the center and edges of the die. The soft thermoplastic nature of this material helps prevent delamination, or pump out, during cycling and is capable of joint-healing most delaminations that occur at operating temperatures. Data at various intervals ending at 1000 cycles will be presented. The ability to ship and store this material at room temperature as well as pre-apply it to the IHS adds additional value by simplifying logistics and reducing cost.