A fully packaged D-band MIMO transmitter using high-density flip-chip interconnects on LCP substrate

In this paper, a fully packaged D-band MIMO phased-array transmitter using system-on-package (SoP) technology is presented. The transmitter chip is implemented in a 32nm CMOS SOI process and assembled on the liquid crystal polymer (LCP) substrate by flip-chip interconnects. The MIMO operation is enabled by an on-chip transformer based 4×4 Butler Matrix. The package fabrication realizes a consistent minimum feature size of 20µm on a 2-mil flexible LCP substrate. Moreover, the CMOS chip with a total of 72 RF and DC pads is well aligned with and successfully bonded onto the corresponding patterns on the LCP package. The capability of package fabrication with fine features and high-density chip-to-package interconnections enables the implementation of cost-effective and high-performance hybrid complex systems at mm-wave. Measurement results based on probing demonstrate the functionalities of the entire system.