This investigation examines a novel means of integrating high-performance ZnO piezoelectric thin films with a flexible stainless steel substrate (SUS304) to fabricate a double-sided piezoelectric transducer. The double-sided piezoelectric transducer is constructed by depositing ZnO piezoelectric thin films on both the front and the back sides of SUS304 substrate. The titanium (Ti) and platinum (Pt) layers were deposited using a dual-gun DC sputtering system between the ZnO piezoelectric thin film and the back side of the SUS304 substrate. Scanning electron microscopy and X-ray diffraction of ZnO piezoelectric films reveal a rigid surface structure and highly c-axis-preferring orientation. To fabricate a transducer with a resonant frequency of about 80 Hz, a cantilever length of 1 cm and a vibration area of 1 cm2 are designed, based on the cantilever vibration theory. The maximum open circuit voltage of the power transducer is approximately 18 V. After rectification and filtering through a 33 nF capacitor, a specific power output of 1.3 £gW/cm2 is obtained from the transducers with a load resistance of 6 M£[.

This thesis focuses on the structures of plated through holes in organic substrate, and discusses the high-frequency electrical characteristics of various plated through hole structures. This thesis consists of four parts. The first part introduces various kinds of vias in multilayer substrate. This content includes substrate drilling processes and capabilities, and discussions on plated through hole structures and their manufacture concerns. The second part focuses on actual measurement of plated through holes, and introduces high-frequency double-side probing technique. The difference from traditional high-frequency coplanar probing measurement is also discussed. The third part focuses on the high-frequency simulation by full-wave software ¡V Ansoft HFSS, and discusses the effects of various excited source and model structures on simulations. Part4 focuses on developing the broadband equivalent circuit model based on the physical structures, and discusses the electrical characterization of different plated through holes, and provides the related design concept.

This research developed a double-side power electronics packaging scheme for high temperature applications exemplified by 1200 V, 150 A silicon devices. The power modules, based on both quarter and half-bridge topologies, were assembled using sintered silver device attachment rather than conventional solder alloys. Thermomechanical stresses in the double-side architecture were mitigated with a compliant layer fabricated from elliptical silver tubes. This research presents an introduction to conventional packaging techniques and their weaknesses. These shortcomings provide the basis for a module design which improves upon module thermal management while also addressing electrical and reliability requirements. The optimum package design enhances heat dissipation with the addition of a substrate bonded to the top electrical pads of the semiconductor devices. The use of sintered silver also increases the useful application temperature by avoiding the creep failure mechanisms of solder alloys. The modules were characterized extensively to quantify thermal and electrical performance. In the case of thermal characterization, the double-side architecture required multiple testing configurations to fully understand the parallel heat flow paths. These results were compared to models constructed using finite element analysis (FEA). The FEA models were also utilized for measurement of strains in multiple package designs to better determine the effects of increased compliance on the relative package cycling lifetime. These lifetimes were then assessed, in part, using experimental passive and cycling tests on functional double-side packages. The resulting power modules exhibited significant decreases in thermal resistance when they are cooled, as designed, from both sides of the module. Even single sided cooling options reveal significant advantages and transient thermal impedance was found to be significantly lower. Power module models revealed the compliant layer was successful in reducing the device shear stresses which was experimentally validated through the use of DC power stage testing. It was found, through double pulse testing and electrical modeling, that parasitic inductances were reduced by utilizing planar bonding and planar symmetrical traces. Finally, modeling of the double-side package with added tube compliance revealed a decrease in plastic and shear strains when compared to other single and double-side package designs. This reduction directly translates to increased cycling lifetime using well known strain based fatigue models. / Ph. D.

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This thesis presents the development of a double-side cooled 3.3 kV, 100 A SiC MOSFET phase-leg power module for heavy-duty traction applications. Parasitic extraction and thermal simulations of the module showed a parasitic inductance of 2.89 nH and junction temperature of 108.3 °C at a heat flux of 156 W/cm² under a typical water-cooling condition. Electric field simulations identified high electric field stress at the module's outer surface edges exposed to air, posing a risk for partial discharge. To mitigate this risk, a solution that involves covering the critical point in an epoxy was proposed, analyzed, and validated through partial discharge inception voltage tests. Steps for fabricating the module are presented. Static electrical characterization of the fabricated module showed an average on-resistance of 31 mΩ and an average leakage current of 356 nA at VDS of 3 kV, which are similar to those of the unpackaged devices. The module with a double-side cooling design achieved an exceptional power density of 116.6 kW/cm³, more than twice that of any single-side cooled 3.3 kV SiC module. This makes it highly suitable for next-generation electric transportation systems that require high power density and efficient thermal management, such as electric trucks, railways, and eVTOL aircraft. / Master of Science / This thesis presents the development of a highly efficient and compact power module designed for electric vehicles and other high power applications. By utilizing advanced silicon carbide technology and double-side cooling structure, the module achieves outstanding performance, making it ideal for heavy-duty uses such as electric trucks, railways, and eVTOL aircraft. The module operates at 3.3 kV and 100 A, with low electrical losses and excellent thermal management. Extensive simulations and testing demonstrated that the module significantly reduced unwanted electrical effects and maintained a stable temperature under high power conditions. An epoxy coating was applied to critical areas to prevent electrical discharge, enhancing the module's reliability. The fabrication process incorporated packaging techniques like silver-sintering for attaching the semiconductor chips and other components, resulting in strong and reliable connections. Static tests confirmed that the electrical performance of the packaged power module maintained consistently high efficiency compared with the bare chips. Overall, this double-side cooled power module offers more than twice the power density of traditional designs, paving the way for the development of future electric vehicle traction systems that require high power density and efficient cooling.