Effects of rolling and annealing on microstructures and properties of Cu/Invar electronic packaging composites prepared by powder metallurgy

The Cu/Invar composites of 40% Cu were prepared by powder metallurgy, and the composites were rolled with 70% reduction and subsequently annealed at 750 degrees C. Phases, microstructures and properties of the composites were then studied. After that, the amount of alpha-Fe(Ni,Co) in the composites is reduced, because alpha-Fe(Ni,Co) partly transfers into gamma-Fe(Ni,Co) through the diffusion of the Ni atoms into alpha-Fe(Ni,Co) from Cu. When the rolling reduction is less than 40%, the deformation of Cu takes place, resulting in the movement of the Invar particles and the seaming of the pores. When the rolling reduction is in the range from 40% to 60%, the deformations of Invar and Cu occur simultaneously to form a streamline structure. After rolling till 70% and subsequent annealing, the Cu/Invar composites have fine comprehensive properties with a relative density of 98.6%, a tensile strength of 360 MPa, an elongation rate of 50%, a thermal conductivity of 25.42 W/(m.K) (as-tested) and a CTE of 10.79x10(-6) /K (20-100 degrees C).