Micro-bump formation technology for flip-chip LSIs using micro-solder-ball

Micro-bump formation technology on advanced LSIs was investigated for flip chip interconnection. Advanced LSIs have a large number of electrode pads and a density that is continuously increasing. A novel bump formation method for these LSIs has been developed using a process that enables the fabrication of precision-sized micro-solder-balls. This process facilitates the fabrication of 100 mum balls with a diameter of 100 +/- 5 mum. The novel method consists of a solder ball arraying process in an arraying plate in conductive fluid. The static electricity in the conductive fluid is cancelled, and during the transforming process, solder balls are moved from the arraying plate to the electrode pads on the LSI. This bump formation experiment using 100 mum balls resulted in the production of approximately 4,000 micro-solder-ball bumps arranged in a 200 mum pitch area array as formed on LSIs.