Al-Si controlled expansion alloys for electronic packaging applications

The demand for thermal management in electronic packaging (EP) and its allied industries, especially in high-power electronics, has grown in the last three decades due to the continuous miniaturization of electronic components. The thermal management of EP warrants metal/alloys/composite with uniquely low thermal expansion and high thermal conductivity. Controlled expansion (CE) materials play a significant role and impart tunable thermal properties. The first and second generations of CE alloys, like Invar, Kovar, and Elinvar, are unsuitable to provide high thermal conductivity for heat sinking along with low density, which are essential for EP materials. The third-generation hypereutectic Al-Si alloys overcome these limitations. The capability to tune the CTE values of the Al-Si CE alloys combined with lower densities and high thermal conductivities has made them preferred choice for electronic applications, such as carriers and heat sinks. However, poor machinability and inability to prepare geometrically complex Al-Si CE alloy with conventional manufacturing processes pose challenges. A paradigm shift is taking place in fabricating components through additive manufacturing and friction stir processing, assisting in mitigating machining and shape complexity. The present work attempts to provide comprehensive details on the properties, microstructures, and processing techniques of hypereutectic Al-Si CE alloys and recent advancements.