Aerosol-jet printed interconnects for 2.5 D electronic and photonic integration

We demonstrate a flexible face-up 2.5 D packaging technique for a hybrid electro-photonic integration. The process is based on an aerosol-jet technology to print the high-speed electrical interconnects between electronic and photonic chips as a potential alternative for the traditional bonding wires. The technology is realized by creating a transparent mechanical polymer support to bridge the gap between the photonic and electronic chips and subsequently printing the electrical interconnects on top. First, the daisy-chain test chips were used to prove the functionality of the technology by printing the electrical interconnects between the test chips. Then, a standard 85 ° C/85 RH test was performed to investigate the reliability of the printed interconnects and no failure or degradation was observed over 700 h. Afterwards, the technology was successfully applied on functional chips. An optical transmitter based on vertical cavity surface emitting lasers (VCSELs) was demonstrated at 50 Gb/s by printing 200-μm-long high-speed silver interconnects between a 4-channel SiGe BiCMOS driver and four VCSELs. In addition, the technology showed the potential to interconnect silicon photonics chips. An assembly of an electro-absorption modulator (EAM) and a CMOS driver was successfully demonstrated. Clear open eye diagrams were obtained at 40, 50, and 56 Gb/s for the EAM-driver assembly even after 2 km of a standard single-mode fiber.