A MEMS-based compliant interconnect for ultra-fine-pitch wafer level packaging

A novel compliant flip-chip interconnect in the form of a planar microspring is presented in this paper. Different spring geometries are evaluated and compared in terms of compliances and electrical parasitics. It is shown that the J-shape spring design gives a better balanced performance. Further numerical studies reveal the geometric dependence of the compliances of J-shape spring interconnects, and also the influence of the sacrificial material upon the electrical performance of the interconnects. The wafer-level process flow for fabrication of the planar microspring interconnects is described and discussed. Prototype interconnects are fabricated by combining planar technology and 3D surface micromachining technology