Department of Mechanical Engineering
Kenneth E. Goodson
Hotspot mitigation, thermal management paths, and thermomechanical degradation are key challenges for 3D integration, in particular due to the increased quantity and complexity of "thermally critical" interfaces. The semiconductor industry (ranging from low-power portables to high-power microprocessors) is deeply concerned about thermal management and related failure mechanisms in 3D packaging, particularly at the increasing number of "thermally-important" interfaces. The number of interfaces renders 3D designs particularly vulnerable to thermal cycling, which tends to increase interface resistances through void formation and chemical diffusion. There is an urgent need for thermal and thermomechanical techniques that address the specific interface challenges in TSV-enabled material systems and geometries.
We are developing a broad spectrum of nanostructured packaging materials with targeted combinations of thermal, mechanical, optical, electrical, and other properties. Our past work in this area has focused on thermal interface materials based on aligned carbon nanotube films. This work has been unique in the demonstration of excellent mechanical compliance (~ 100 MPa) together with very low thermal resistance (~0.03 m2K/W) and robustness during thermal cycling. Ongoing work in the TIM area is focused on implementation in thermoelectric generators for waste heat recovery in vehicles, as well as detailed investigations of the physics governing thermal and mechanical properties. Our latest progress in this area includes nanostructured materials serving as underfill candidates, encapsulation, and 3D chip attachment. This includes disordered mixtures of combinations of carbon nanotubes and nanoparticles with a focus on metrology for distributed thermal, mechanical, and electrical properties as well as their evolution with temperature cycling. We are extending our novel measurement strategy for the in-plane elastic modulus of nano materials based on a micromechanical resonator approach.