W-Band MMIC Chip Assembly Using Laser-Enhanced Direct Print Additive Manufacturing

In this article, the first
$W$
-band laser-enhanced direct print additive manufacturing (LE-DPAM) monolithic microwave integrated circuit (MMIC) chip-carrier assembly is demonstrated. Acrylonitrile butadiene styrene (ABS) is 3-D printed using fused deposition modeling to form substrate layers, and DuPont CB028 conductive paste is microdispensed to form transmission lines and on-chip interconnects. These processes are combined with picosecond-pulsed laser micromachining using two wavelengths in the infrared (IR) (1064 nm) and ultraviolet (UV) (355 nm) regions to create features as small as 5
$\mu \text{m}$
for printed layers with a high 6:1 aspect ratio and to improve the effective conductivity of the printed traces. The laser machining process is also adopted to fabricate vertical interconnections (vias) over multilayer substrates while also suppressing higher order modes. Four different dc-to-110-GHz transmission-line configurations have been investigated, including a coplanar waveguide (CPW), a grounded CPW (GCPW), a novel multilayer CPW-microstrip transition, and a GCPW-microstrip transition with attenuation <0.3 dB/mm and return loss >10 dB. This process is extended to embed a
$W$
-band MMIC low-noise amplifier (LNA) die inside a laser-machined cavity with a carrier-chip gap less than 5
$\mu \text{m}$
. Also, RF/dc interconnects were microdispensed to connect the transmission lines on the substrate and MMIC die. Chip-to-board transition loss as low as 0.03 dB per interconnect with return loss >7.5 dB was achieved with performance that is comparable to that of the probed MMIC die. The MMIC chip-carrier assembly provides a low-cost, versatile yet simple on-demand laser-enhanced additive manufacturing process to package a wideband MMIC die using a single automated LE-DPAM platform.