An approach to the low cost flip-chip technology development with punched-out solder disks by micro-press punching method

Abstract

A new low cost bare-chip LSI inter-connection lead-less-chip technology was installed by Au ball-bump (1976) and Ag-Sn solder on the printed wiring board under none flux condition. Au ball-bumps were made on the LSI Al pads directly by conventional wire bonding method and Ag-Sn bumps on the leads of the build-up processed PWB by the solder micro-press punching technology less than 120 microns pads-pitch. This micro-press punching technology has reached the higher stability of 500,000 times continuously at nearly 0.1 sec/piece speed with 50 /spl mu/m thickness soft solder tape. And the diameter of punched-out solder disk was realized at 50 /spl mu/m level on the tips of the PWB pads directly. This lead-less-chip technology of the flip-chip assembly on MCM-L, has the high reliability and the low cost possibility.