Advanced flip chip bonding techniques using transferred microsolder bumps

For future high-speed and high-density opto-electronic multi-chip module (O E-MCM) packaging, we developed two advanced transferred microsolder bump bo nding techniques. One uses 80% Au-Sn, which allows module packaging using p rocesses at various temperatures because it has a higher melting temperatur e than 100% In and 60% Sn-Pb solders. The other uses multiple transfers of bumps to achieve accurate three-dimensional flip-chip bonding with precise vertical and horizontal alignments within an error of +/-0.5 mu m. These te chniques will thus be very useful in developing high-speed and high-density OE-MCM's for multi-functional board-level interconnection in future optica l communication systems.