Sea of polymer pillars: compliant wafer-level electrical-optical chip I/O interconnections

An electrical-optical chip input-output (I/O) interconnection technology called sea of polymer pillars (SoPP) is presented. SoPP provides highly process-integrated and mechanically flexible (compliant) electrical-optical die-to-board interconnections that mitigate thermo-mechanical expansion mismatches. The I/O density of SoPP exceeds 10
⁵
/cm
²
. The compliance of the polymer pillars is shown to be 3-5 μm/mN. Approximately 50% input optical coupling efficiency into a volume grating coupler through a set of polymer pillars is demonstrated.