Three-path electroplated copper compliant interconnects — Fabrication and modeling studies

Compliant interconnects have been studied in universities and industry over the past decade, as compliant interconnects could mechanically decouple the die from the substrate and thus could reduce the stresses in the die. In this work, we present the design, fabrication and modeling results of three-path electroplated compliant interconnect that addresses several of the challenges associated with various other compliant interconnects. Sample interconnects were fabricated on 4" wafers to enable experimental validation of the designed microstructures. There were about 8300 interconnects on each 20 × 20 mm² chip in area-array layout. The interconnects were subjected to compliance testing. In parallel to the experiments, finite-element simulations were carried out to determine the mechanical compliance and the electrical resistance of the interconnects as well as their thermo-mechanical reliability. It is seen that the out-of-plane mechanical compliance will be more than 1 mm/N, several orders of magnitude greater than solder bump interconnects, and from a reliability perspective, the interconnects will last at least 1000 thermal cycles.