## 1 Introduction  
The exponential growth of wireless communication systems has created unprecedented demand for compact, high-performance filters capable of operating across broad frequency ranges while maintaining exceptional reliability. RF (Radio Frequency) MEMS (Micro-electro-mechanical Systems) technology has emerged as a transformative solution for next-generation wireless communication system RF front-end modules, offering significant advantages over conventional filter technologies. MEMS-based RF components, including switches [1, 2], filters [3, 4, 5, 6, 7], variable capacitors [8], inductors [9], and resonators [10], provide substantial miniaturization capabilities, reducing component volume by factors up to 1/200 compared to traditional alternatives while delivering superior performance characteristics and enhanced reproducibility [3; 5; 11; 12]. It should be noted that while the term MEMS often implies components with active mechanical movement, in the context of RF engineering, it also broadly encompasses passive devices, such as the filter presented here, which are fabricated using micro-machining techniques to create complex 3D structures that achieve performance and miniaturization not possible with conventional methods. Ultra-wideband (UWB) MEMS filters represent a critical enabling technology for emerging applications spanning 5G/6G networks, automotive radar systems, electronic warfare, satellite communications, IoT multi-protocol systems, medical imaging, and software-defined radio platforms as shown in Figure 1. These applications impose stringent performance requirements that conventional filter technologies struggle to satisfy simultaneously. Modern UWB systems typically demand fractional bandwidths exceeding 20% with center frequencies ranging from 3.1 to 10.6 GHz for commercial applications and extending to 60 GHz for specialized military and radar implementations. Achieving such wide bandwidth performance while maintaining insertion loss below 3.5 dB across the entire operating range presents fundamental design challenges, particularly as bandwidth expansion traditionally compromises filter selectivity and increases signal attenuation. The miniaturization demands of contemporary RF front-end modules necessitate filter implementations with form factors below 5 mm\({}^{2}\) while preserving critical performance metrics. MEMS technology uniquely enables this aggressive size reduction through high-precision microfabrication techniques that facilitate complex three-dimensional structures within minimal footprints. However, achieving optimal electromagnetic performance in these compact geometries requires careful consideration of packaging technologies and mechanical design constraints that significantly influence device reliability and long-term stability. Packaging represents a critical aspect of MEMS device development, directly impacting cost, size, and operational reliability [13]. RF MEMS packages must provide environmental protection while minimizing insertion loss and return loss degradation. The packaging system must prevent moisture and contaminant penetration to address common failure mechanisms including stiction and corrosion [14], while operating within temperature constraints below 350 \({}^{\circ}\)C to prevent device degradation [15]. Additionally, packaging materials must minimize thermo-mechanical stress resulting from thermal expansion coefficient mismatches to avoid performance degradation and structural deformation [15]. Wafer-level packaging has gained significant attention for MEMS applications due to its advantages in miniaturization, integration density, and mass production scalabil  
Figure 1: Ultra-wideband MEMS filter applications. ity [13; 14; 16; 17]. However, developing reliable wafer-level packaging with low-temperature processes and hermetic sealing capabilities remains technically challenging.