A new fluxless bonding technique using Sn-Bi-Au design is presented. Microstructure and phase growth mechanism of as deposited Au/Sn/Bi films were first studied by scanning electron microscopy (SEM), X-ray diffraction method (XRD) and X-ray photoelectron spectroscopy (XPS). It is found that the crystallites of Au-Sn intermetallics are randomly distributed in Bi-rich matrix that forms a top-capping layer. The average size of AuSn 2 and AuSn 4 crystallite are 756 and 667A, respectively. The bonding process was performed at 250 o C in air without the use of flux. The resulting joints exhibit high shear strength of 4.9kg and show only a few voids. Melting temperature of 225 o C was measured. The joint is composed of near eutectic Sn-Bi alloy with ribbon shaped AuSn 2 +AuSn 4 intermetallic compound layer embedded inside the solder joint. The fracture of the Sn-Bi-Au solder joint mainly occurs along the interface between the Au-Sn intermetallic layer and the Sn-rich regions. This facture mode is ductile. The flux-free process is compatible with many pick-and-place machines that operate in ambient air.