Microstructure and thermal expansion behavior of spray-formed Al–27Si alloy used for electronic packaging

The hypereutectic Al–27Si (mass fraction) alloys are prepared by spray deposition and extrusion. The effect of thermal aging process on the coefficient of thermal expansion (CTE) and microstructure of the Al–27Si alloys are investigated. The results show that the distribution of Si particles in α-Al matrix is uniform, and the primary Si phase grows gradually during the process of thermal aging. The CTE between room temperature to 100 °C increases gradually with the ascending of aging temperature, attributed to the relaxation of residual thermal stress and the coarsening of primary Si phases in the alloys. On the other hand, the CTE increases linearly as the cycling temperature increases up to 500 °C, and the measured values are in good agreement with the Kerner model.