Preparation And Characterization Of Kovar/Cu/Kovar Cladding Sheets

The Kovar/Cu/Kovar (K/C/K) cladding sheets with different Kovar/Copper thickness ratios were prepared and investigated in this paper. The electrical resistivities (ETs), coefficients of thermal expansion (CTEs) and mechanical properties of the laminates were measured. The Kovar/Copper interface, as-rolled microstructure and annealing rinicrostructure of the materials were observed by using optical microscope (OM) and scanning electron microscopy (SEM), energy diffraction scanning (EDS) and the results were discussed. It showed that:(1)The processing methods of the mating surfaces have a important effect on thecladding sheets. The shear strength of the cladding sheet treated with steelbrushing had the highest values.(2) The roll-bonding temperatures and the first reduction had a fundamental effect on the properties of the cladding sheets. The cladding sheets had optimal properties when rolled at 850 Cwith the reduction of 50%.(3) The annealing temperatures had an important effect on the properties of the cladding sheets such as electrical resistivity and the tensile strength.. The cladding sheet annealed at 850C had the best properties .(4)The diffusion happened between the surfaces of the Kovar/Cu/Kovar electronic packaging cladding sheets. The bonding mechanisms were the mechanic joggle and atomic diffusion of the interface.(5)The measured data of the instrument designed for the measurement of the CETs of cladding sheets showed: the CETs and tensile strength of K/C/K were slightly higher, but the Els of K/C/K were much lower, compared to those of Kovar. The properties of K/C/K manufactured in this paper meet the requirements of electronic packaging materials such as high conductivity, high TC and low CTEs.