Novel micro-bump fabrication for flip-chip bonding

This paper describes a new bump-fabrication technique for flip-chip connection between a chip and substrate. We propose a novel idea of forming solder microbumps on the substrate and directly bonding bare chips to the substrate. We successfully achieved the new flip-chip connection by using a 0.05Au-0.95Sn solder bump and a hydrogen-plasma reflow technique. Because the method eliminates the need for any process on the chip wafer, it will be very useful in fabricating flip-chip connections for low-cost packaging.