Nano-micro particle filled thermal interface materials: Towards materials development, characterization, assembly, and performance evaluation

Thermal interface materials (TIM) used to improve the conductivity between mating components in an electronic assembly are discussed. A variety of materials including adhesives, gels, greases, fluids were used in this study. Both greases and pastes are considered, to improve the contact resistance of stress decoupling and stress coupling interfaces, respectively. Nanoparticles, micro particles, low melting point (LMP) fillers, and mixtures of nano-micro particles were combined to obtain both decreased interparticle thermal resistance and decreased bulk thermal resistance in thermal pastes. An evaluation of thermal grease filler materials was also conducted. A steady-state conductivity test was employed to measure conductivity. Adhesive materials were tested at various fixed bondline thicknesses and had thermal impedances ranging from 170 to 53 mm² K/W. The performance of greases varied from 70 to 11 mm² K/W at low bondline with a varied load. For thermal pastes, cross section measurements were used to measure particle dispersion throughout the interface. The paper also presents a nanoparticle dispersion approach to prepare temperature and time stable nanogels. Several nanogels were evaluated after three years post-preparation, using transmission electron microscopy (TEM), to check particle distribution in the nanogel.