Abstract: Wire bonding is still the most popular interconnect technology in the first-level packagingThe yield of wire bond mainly depends on the bondability of the bond pad which is affected by the surface charac- teristicsIn the present study,we investigated the effects of surface characteristics on the bondability of an Au-Au thermosonic bonding systemThe surface characteristics,including the Au layer thickness,surface hardness and roughness,organic contamination and metallic impurity,were compared between two specimens with different bondabilitiesIt was identified that the Au surface roughness depended on the topography of the Ni layerThe outgas from the solder mask had a negative influence on the bondabilityPlasma cleaning was effective in removing the organic contaminantsThe impurities in Au layer caused poor bondability