A Method of Fabricating Bump-Less Interconnects Applicable to Wafer-Scale Flip-Chip Bonding

A chemical flip-chip bonding method by electroless plating process has been developed. This method positively utilizes so-called "bridge" phenomenon between metal pads in electroless Ni-B plating, and enables bump-less interconnect without loading and/or heating at lower temperature (60 degrees C). The interconnect behavior was examined using test chips and substrates with various pad-to-pad configurations. The result confirmed that effective pad width and a ratio of pad pitch to pad width determine the completeness of the interconnection under the condition that distance between facing pads arc Sufficiently close. A potential of improved method was also demonstrated for fabricating finer pitch flip-chip interconnect with a minimum pad-pitch of 20 mu m.