Effect of isothermal aging on microstructure and joint strength of Ag nanoporous bonding for high temperature die attach

The mechanical and microstructural change of Ag NPB with ENIG finished Cu and bare Cu were investigated. The results of shear test of NPB with ENIG finished Cu and bare Cu substrates show 25.7 and 26.6 MPa. The effect of surface finish became significant with increasing of aging time. In case of bare Cu substrate, the shear strength gradually decreased with increasing of thermal storage time, and it showed 11.4 MPa with the aging time of 1000 h. Contrariwise, the shear strength of NPB with the ENIG finished substrate increased to 32.2 MPa for 100 h, and then gradually decreased. After 750 h, the shear strength showed 25.3 MPa, which is similar value with the initial shear strength of NPB. These results arise from the different oxidation behavior of bare Cu and ENIG finished substrates.