Low-temperature gold-gold bonding using selective formation of nanoporous powders for bump interconnects

We proposed low-temperature Au-Au bump interconnects bonding using nanoporous Au-Ag powders as a connective adhesion. The nanoporous powders were formed by de-alloying Au-Ag alloy in HNO
₃
solution. To optimize the pore size, the influence of the annealing temperature on the porous structures was investigated. Selective transfer of the nanoporous powders on bumps was obtained by stamping process. Bonding strength of about 2.4 MPa was achieved at 150 °C by using nanoporous Au-Ag powders. Bonding interface was evaluated by scanning acoustic microscope and scanning electron microscopy. This result indicated that the nanoporous powder is a useful material for low-temperature Au-Au bonding.