Design and optimization of a novel compliant off-chip interconnect One-Turn Helix

As the rapid advances in IC design and fabrication continue to challenge and push the electronic packaging technology, in terms of fine pitch, high performance, low cost, and good reliability, compliant interconnects show great advantages for next-generation packaging. A novel compliant off-chip interconnect, One-Turn Helix (OTH), is designed as an underfill-free interconnect. It has excellent compliance in all directions to compensate the coefficient of thermal expansion (CTE) mismatch between the silicon die and an organic substrate. The fabrication of OTH is similar to standard IC fabrication, and wafer-level packaging makes it cost effective. In this work, we study the effect of geometry parameters on mechanical and electrical performance of OTH. Thinner and narrower arcuate beam with larger radius and taller post are found to have better mechanical compliance. However, it is found that structures with excellent mechanical compliance cannot have good electrical performance. Therefore, a trade off is needed for the design of OTH. Response surface methodology and an optimization technique have been used to select the optimal OTH structure parameters.