Micro-ball bump technology for fine-pitch interconnections

Micro-ball bump technology has been developed for high density flip chip (FC) interconnections of high performance LSI chips. This technology consists of (1) the production method of fine metal balls (micro-balls) with high accuracy in size and good sphericity in shape and (2) the gang-bonding method of the micro-balls on the electrodes of chips in order to form bumps (micro-ball bumps) for FC interconnections. Gold or solder balls of 35-150 μm in diameter were prepared. After holding the balls on the through-holes of an arrangement plate by a vacuum suction method, the micro-balls are bonded onto the electrodes of the chips. Using an originally developed micro-ball mounter, the balls are successfully arranged on the arrangement plate without excess and lack of balls. The micro-gold bumps of 35 μm in size can be formed with 50 μm pitch or less.