Development of CGA-PWW Devices Based on Advanced Wafer-Level Processing Technology

This letter presents a novel air-filled post-wall waveguide (PWW) in an advanced wafer-level planting process for millimeter-wave applications. This PWW, consisting of two metal plates and numerous regular copper columns, is implemented by an improved column grid array (CGA) bonding process with a high alignment accuracy of less than
$50~\mu \text{m}$
. Since air is the only transmission medium, the CGA-PWW has a low-loss advantage over the traditional dielectric-filled substrate-integrated waveguide. For demonstration, the prototype CGA-PWW transmission lines with a standard waveguide transition are designed and fabricated by adopting the 8-inch wafer-level processing technology. An extremely low transmission loss of 0.0032 dB/mm is achieved in the entire V-band. A good agreement between the measured and simulated results verifies the process’s stability. Moreover, introducing the redistribution layer technology and the multilayer stacking process could significantly enhance the external integration capabilities. Hence, the CGA-PWW solution is appropriate for millimeter-wave radio-frequency components and system integrations.