Flip chip repair process

A fluxless repair process for flip-chip multichip modules (MCMs) is demonstrated. The process includes steps for removing defective chips, reducing and leveling solder at the chip site, and retacking a new, good chip in its place. After chip removal, most of solder remained on the bonding pads. A technique has been developed to remove excess solder and to level the pads to a consistent bump height. Experimentation has shown that the wick chip reduced remaining solder bump heights to about the same height as the virgin substrate. New chips were then retacked to the leveled sites and the modules were heated in a controlled atmosphere to reflow the solder joints. Modules repaired using this technique have shown yields similar to those obtained during the initial assembly stages in electrical continuity tests.<
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