Monitoring the Restoration of Interfacial Contact for Self Healing Thermal Interface Materials for Led and Microelectronic Applications

While conventional self healing materials focus on the restoration of mechanical properties, newer generations of self healing materials focus on the restoration of other functional (i.e. non-mechanical) properties. Thermal conductivity is an example of an important functional property of a Thermal Interface Material (TIM) for LED’s and microelectronics devices. Current TIMs are optimized to provide thermal conductivity for as long a time as possible, yet these materials have no self healing potential and any crack formed will only lead to a decreased or lack of thermal conductivity and will dramatically reduce life time of the component. In order to get a better insight on how, as function of time, self-healing TIM systems are able to recover structural (cracks) and interfacial (delamination, adhesion) damages, we have developed a new specific technique to monitor local heat conduction. This technique probes very locally the heat transfer through the material to monitor changes related to heat conduction. If the material is damaged (cracked), the cracking or delamination will result in a thermal impedance restricting the thermal transfer. If the material is self healing, the local thermal conduction paths will be restored in time. In order to probe the thermal transfer for conventional and our new self healing TIM materials, a dedicated silicon chip containing an array of 49 diodes spaced uniformly over a 1 cm area has been fabricated. Using this device, it is possible to map with high spatial resolution the efficiency of the local thermal transfer and to relate it to the recovery of pre-imposed damage. Such experiments will yield unique local and temporal insight into cohesion and adhesion recovery of our self-healing polymeric systems.