A Substrate-less Process for Heterogeneous Integration of mm-Wave Circuits

In this paper, a new ultra-compact substrate-less approach to heterogeneous integration of millimeter wave circuits is demonstrated. In the proposed process, active and passive components are placed face down on a temporary carrier. A thick layer of benzocyclobutene (BCB) is deposited surrounding these components using aerosol jet printing (AJP). This is followed by a combination of the blanket deposition of silver conductor and perforated BCB layers. This approach allows for the placement of chips close to each other leading to heterogeneous integration. Also, the front side is made planar, which allows for subsequent processing of low-loss interconnects. Here, as a proof of concept, a simple interconnect between two chips, placed close to each other, is demonstrated.