Fully SMT-compatible optical-I/O package with microlens array interface

A new optoelectronic package for interchip optical interconnections is presented. To make cost-effective IC-packaging and printed circuit board (PCB) assembly, we strongly emphasize the need for full compatibility with surface-mount technology (SMT). Based on the "OptoBump" interface, which couples the package and PCB by means of an array of wide, collimated beams, we developed two prototype packages: a transmitter package that contains a vertical-cavity surface-emitting laser (VCSEL) array and a driver-IC, and a receiver package that contains a photodiode (PD) array and a receiver-IC. A microlens array is integrated with each package to counteract misalignments that occur in the SMT process. All three output signals, which are E/O (O/E)-converted in the each package, exhibit clear eye diagrams at 1.25 Gb/s after the packages are surface-mounted on a PCB. The influence of polymer encapsulation on a VCSEL and an evaluation of the optical interface provided by the three optical beams on a 500-μm center-to-center spacing are also discussed.