Advanced flip chip bonding techniques using transferred microsolder bumps

For future high-speed and high-density opto-electronic multi-chip module (OE-MCM) packaging, we developed two advanced transferred microsolder bump bonding techniques. One uses 80% Au-Sn, which allows module packaging using processes at various temperatures because it has a higher melting temperature 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 techniques will thus be very useful in developing high-speed and high-density OE-MCM's for multi-functional board-level interconnection in future optical communication systems.