Microstructure and properties of Al-Si functionally graded materials for electronic packaging

Two- and three-layer Al-Si functionally graded materials (FGMs) for electronic packaging were prepared by spray deposition. The results show that dense microstructure and good interlayer bonding are obtained in the FGMs. The flexural strength of the three-layer FGMs is higher than that of the two-layer FGMs, and the flexural strength in the H-L direction with high Si content layer as the bearing surface is higher than that in the L-H direction with low Si content layer as the bearing surface. The thermal conductivity of all the FGMs exceeds 140 W/(m center dot K), and the coefficient of thermal expansion (CTE) shows no significant difference. After thermal shock treatment, more and larger cracks are found in the two-layer FGM than in the three-layer FGMs. This phenomenon is due to the high thermal stress at the interfaces and the tendency of large Si particles to rupture as a result of stress concentration.