A Self-Aligning Flip-Chip Assembly Method Using Sacrificial Positive Self-Alignment Structures

A self-aligning flip-chip assembly method is described. The method is capable of correcting up to 150 μm (five times the radius of solder balls used) of initial misalignment during flip-chip assembly. Critical components of the self-alignment are four polymeric positive self-alignment structures (PSASs), which are fabricated on a substrate, and four inverted pyramid pits, which are etched on a silicon chip in corresponding positions. The PSAS is removed using solvent after the assembly. Resistance of the solder joints is measured to be below 9 mΩ.