Nanoporous gold bumps for low temperature bonding

Nanoporous gold bumps have been deposited on silicon wafers by electroplating a silver–gold alloy followed by etching the silver. An open-porous cellular structure of gold at meso-scale is left on top of the bumps. For flip chip bonding we found low temperature and low force bonding conditions. The porous interconnects have very promising properties, like compressibility and reduced stiffness, which should result in higher bond yield and extended reliability.

► We electroplate Ag–Au alloy into a patterned resist mask at wafer level.
► Nanoporous gold forms a open-porous sponge at wafer level by etching silver.
► Au nano-sponge bumps were flip chip bonded by thermocompression bonding.
► Low temperature bonding and low pressure bonding was achieved.
► Low pressure bonding was also achieved with anisotropic conductive adhesives.