Low-Loss Suspended Crossover Interconnects using Laser Enhanced Direct Print Additive Manufacturing

Abstract

This paper outlines a new type of versatile 3-D printed suspended coplanar waveguide (CPW) interconnects that are well suited for packaging of mm-wave systems. The design, fabrication process and characterization results are presented. 3D printing quality, namely feature size and dimensional accuracy, was improved by utilizing well-characterized laser machining techniques. The laser machining process enables the control of the dimensions of micro-dispensed conductive traces down to a few micrometers. CPW lines are printed on a fixed-fixed beam and can be extended over the bridge across devices such as a low noise amplifier MMIC chip or another interconnect layer underneath. Acrylonitrile butadiene styrene (ABS) and CB028 conductive silver paste are utilized to fabricate the CPW lines on suspended beams over an air cavity. Simulated and measured S-parameters up to 30 GHz for an interconnect are presented. The conductor width, ground width, and slot width are 160 μm, 260 μm, and 20 μm, respectively. The measured transmission line loss of the suspended CPW line is 0.26 dB/mm at 30 GHz.