High Density Optoelectronic Interconnect using Micro-machined Spring Arrays

摘要

We report on a novel flip-chip packaging technology capable of interconnecting devices packed at very high density. The process utilizes micro-machined cantilevers for establishing electrical contact, where package assembly is performed at room temperature without solder. The cantilevers, called micro-springs, are fabricated by sputtering, masking, and releasing a stress-engineered conductive thin film on a quartz substrate. The film is patterned into electrical routing wires whose ends are released from the substrate. Upon release, the film stress forces the ends to curl up into compliant springs. Packages are formed by pressing the micro-springs against a set of device contact pads, much like probing pads using tungsten needle probes. The connections between springs and contact pads are anchored by an encapsulating acrylic adhesive. We utilize this packaging technology to interconnect 200-element arrays of independently addressable VCSELs with 4 μm-wide pads on 6 μm pitch to silicon CMOS driver chips with equally dense output lines. Tests show the technology produces good contacts with excellent robustness.