Multiple flip-chip assembly for hybrid compact optoelectroi modules using electroplated AuSn solder Bumps

The hybrid integration of several electrical and optical chips 011 a common substrate is an important technology for merging highly functional optoelectronic modules. To fabricate such a hybrid compact optoelectronic module, it is essential to develop a multiple flip-chip assembly technique 011 a common substrate. In this study, four Si chips were flip-chip bonded successively 011 a common substrate using electroplated AuSn solder bumps. However the high thermal conductivity of the substrate and a multiple reflow process could make solder bumps formed 011 the substrate tend to be affected by neighboring ones significantly during several repeated bonding steps. As a result, it is difficult to perform an interconnection that shows high bonding strength. This paper will discuss the correlation between the successive multiple flip-chip assembly and after-bonding characteristics such as die shear strength, micro structures of remelted joints between AuSn solder bumps and chip pads.