Highly reliable die-attach bonding with etched brass flakes

Highly reliable microparticle sinter paste based on etched brass flakes is developed. A low temperature $(275^{\circ}\mathrm{C})$, low pressure (10 MPa) and fast (5 min) die-attach process resulting in sintered interconnects with an average shear strength of 60 MPa is realized. The use of polyethylene glycol 600 (PEG600) in the sinter paste formulation allows an in-situ reduction of copper oxide and sintering in an open bond chamber under a constant nitrogen flow with no influence of residual oxygen. Even under high stress thermal shock cycling, the sintered interconnects realized by the etched brass flakes show no drop in shear strength after 1000 cycles. Porosity of the interconnect affects the oxidation with time. In pure Cu flakes, stacking over each other, a preferential growth in (220) grain orientation is observed.