Quasi-Coaxial Through-Hole Integrated Additively Manufactured Antenna-in-Package Lid Substrates

The heterogeneous integration of small antennas into semiconductor packages offers an efficient approach to enhancing impedance matching and signal transmission efficiency in wireless communication. Conventional antenna-in-package (AiP) implementations have employed through-mold vias (TMVs) to electrically feed antennas vertically stacked on top of molded flip-chip dies. However, these TMV structures suffer from impedance mismatch, parasitic loss, and fabrication complexity that involve multiple steps such as TMV etching, molding, and substrate grinding, leading to high manufacturing costs. In this work, we propose an additively manufactured AiP lid substrate featuring quasi-coaxial through-holes, a chip cavity, and an integrated patch antenna to improve signal transmission while simplifying fabrication. The quasi-coaxial through-via structure, where a signal via is surrounded by ground vias, prevent undesirable electromagnetic radiation from the vertical signal line thereby reducing insertion loss compared to conventional TMVs. The AiP lid substrate was fabricated using 3D printing technology, producing a $5 \times 7 ~\text{mm}$ polymer structure with a 1.6 mm thickness and $200 \mu ~\mathrm{m}$ via diameter. After passing through the coplanar waveguide and quasi-coaxial through-hole, which were designed based on EM simulation, the resonance frequency of patch antenna slightly shifted by +0.1 GHz, exhibiting an $S_{11}$ of -26.0 dB. These results demonstrate that the 3D-printed AiP lid substrate provides a cost-effective and scalable alternative to conventional AiP designs for next-generation wireless communication.