Multifunctional Interfaces for Combined Mechanical, Thermal and Electrical Properties

Abstract

Interfaces between heterogeneous materials exist in many applications and affect properties such as mechanical integrity during thermal cycling, heat transport and electrical transport due to the inherent disparate properties such as coefficient of thermal expansion (CTE), density and bonding strength. Multifunctional interfaces are developed to bridge the desired properties and functionality. These interfaces are comprised of an alloy of zirconium and copper which are common materials compatible with electronics industry processes. A magnetron sputtering deposition system with dual deposition is utilized to perform the functional deposition. The functionally varied layer is placed at the interface between a high coefficient of thermal expansion material and a low CTE material and bridges the material property differences. Materials selection is driven by comparing CTE differences, elastic moduli and geometric averaging. Thermal cycling is performed to investigate mechanical integrity for extreme cycle ranges of order -55 °C to 300 °C. Additionally thin buffer zones using atomic layer deposition (ALD) are investigated for adhesion improvement. Orthogonal to the mechanical properties, thermal and electronic properties need to be maintained. Both thermal and electrical transport are investigated for the effect of the alloy gradient on them. Theoretical modelling is utilized to find the proper alloy to simultaneously provide the best mechanical, thermal and electrical properties.