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Current trends in electronics are toward the use of reduced voltages. In the past, 5 V and higher voltages have been the standard, however, currently, 3.3V and 2.5V circuits are becoming increasingly common. While the operating voltage is decreasing, electronic systems are becoming more complex. The net result is that in many, cases, the current required by the next generation of electronics will be far greater than in the past. These increased currents and low voltages pose dramatic problems for designers not the least of which is the effect of electronic packaging and circuit implementation on the overall power supply performance. In addition, for many applications, space and weight are at a premium and converters are needed to power low voltage circuit assemblies that are highly efficient, low in weight, and small in total height and foot print. This dissertation addresses these trends and needs through the design, fabrication and evaluation of a 3.3V DC/DC converter. Designs of 3.3V, 2.5V, and 1.5V are presented and evaluated while a 3.3V, 100 watt converter with a power density of 157 watts/in³ has been fabricated and evaluated in a miniature form. This converter utilizes a implementation strategy developed by the author which was selected due to its ability to handle the current levels required and its compact size. Specific contributions of this work include: • Analysis of the effects of packaging on low voltage high current converters in order to provide a guideline for converter implementation. This analysis has been performed for 3.3 V, 2.5 V, and 1.5 V designs, respectively. • Development of high efficiency 2.5 V, 100 watt and 1.5 V, 75 watt designs based on previously reported half bridge topologies. • Development of a packaging strategy which allows the fabrication of low voltage compact converters with high efficiency. A 3.3 V converter has been fabricated and with the simulated data validated these experimental results. For very low (less than 50 watts and / or less than 10 amps) and high power levels (hundreds of amps or kilowatts), the implementation strategy is normally clear; PCB/IMS, and DBC respectively. However, for applications in the middle range of power or current level, the optimum implementation is often unclear. The question that this work seeks to answer is under what conditions are different implementation schemes most suitable. / Ph. D.

The purpose of this study was to determine the effects of storage temperature and film oxygen transmission rate (OTR) on toxin development by Clostridium botulinum in refrigerated raw vacuum packaged croaker fillets, and to determine if toxin development precedes microbiological and/or organoleptic spoilage. Raw croaker fillets were vacuum packaged in oxygen-permeable films (OTR of 10,000 cc/m2/24hr or 3,000 cc/m2/24hr) and stored at either 4ºC or 10ºC. Type 83F, 17 Type B, Beluga, Minnesota, and Alaska nonproteolytic strains of C. botulinum were used to inoculate fish prior to vacuum packaging. At both temperatures, microbial spoilage preceded toxin production in fillets vacuum packaged in both film types. At 4ºC microbial spoilage occurred after approximately 7 days for fillets vacuum packaged in the 10,000 cc/m2/24hr OTR film and after 8 days for fillets vacuum packaged in the 3,000 cc/m2/24hr OTR film. However, toxin was not detected until day 8. At 10ºC microbial spoilage occurred after approximately 3 days for fillets vacuum packaged in the 10,000 cc/m2/24hr OTR film, while toxin production occurred on day 5. For fillets vacuum packaged in the 3,000 cc/m2/24hr OTR film microbial spoilage occurred after 4 days. However toxin production did not occur until day 6. In contrast, at both temperatures toxin production preceded or coincided with organoleptic spoilage in fillets vacuum packaged in both film types. At 4ºC organoleptic spoilage occurred after 10 days for fillets packaged in the 10,000 cc/m2/24hr OTR film and after 9 days in the 3,000 cc/m2/24hr OTR film, while toxin production occurred on day 8. At 10ºC organoleptic spoilage occurred after 6 days for fillets packaged in the 10,000 cc/m2/24hr OTR film, and toxin was detected on day 5. For fillets packaged in the 3,000 cc/m2/24hr OTR film and stored at 10ºC, organoleptic spoilage occurred after 6 days, while toxin production occurred on day 6. Although toxin production preceded or coincided with organoleptic spoilage in both film types, this may have been because samples were presented on ice, which could have masked potential odors. This study shows that there are not significant differences between these film types when it comes to microbial and organoleptic spoilage. Therefore lower OTR films, such as 3,000 cc/m2/24hr film, may be used to vacuum package Atlantic croaker. / Master of Science in Life Sciences

Power electronics is a constantly growing and demanding technical field. Consumer demand and developing technologies have made the improvement of power density a primary emphasis of research for this area. Power semiconductors present some of the major challenges for increasing system level power density due to high loss density and interconnection requirements. Advanced cooling schemes, such as double-sided, forced liquid convection or multi-phase flow, can be implemented with non-wire bond packaging to improve thermal management while maintaining proper electrical performance. Embedded power is one such packaging technology, which provides a compact structure for interface of power semiconductor to fluid flow. The objective of this work was to identify the potential of implementing embedded power packaging with double-sided forced liquid convection. Physics based, electro-thermal models were first used to predict the improvement in heat transfer of double-sided, forced liquid convection with embedded power packaging over single-sided liquid cooled wire bond based packaging. A liquid module test bed was designed and constructed based on the electro-thermal models, which could be interfaced with high power MOSFET based samples implementing various packaging technologies. Experiments were used to verify the model predictions and identify practical limitations of high flow rate, double-sided liquid cooling with embedded power. An improvement of 45% to 60% in total junction to case thermal resistance is shown for embedded power packaging with double-sided liquid cooling for water flow rates between 0.25 and 4.5 gal/min. / Master of Science

Silicon carbide (SiC) is a wide bandgap material capable of higher voltage and higher temperature operation compared to its silicon (Si) counterparts due to its higher critical electric field (E-field) and higher thermal conductivity. Using SiC, MOSFETs with a theoretical high temperature operation and reliability is achievable. However, current bottlenecks in high temperature SiC MOSFETs lie within the limitations of standard packaging. Additionally, there are reliability issues relating to the gate oxide region of the MOSFET, which is exacerbated through high temperature conditions. In this thesis, high temperature effects on current-generation SiC MOSFETs are studied and analyzed. To achieve this, a high temperature package is created to achieve reliable operation of a SiC MOSFET at junction temperatures of 300 °C. The custom, high temperature package feasibility is verified through studying trends in SiC MOSFET behavior with increasing temperature up to 300 °C by static characterization. Additionally, the reliability of SiC MOSFETs at 300 °C is tested with accelerated lifetime bias tests. / M.S. / Electrical devices that are rated for high temperature applications demand a use of a material that is stable and reliable at the elevated temperatures. Silicon carbide (SiC) is such a material. Devices made from SiC are able to switch faster, have a superior efficiency, and are capable of operating at extreme temperatures much better than the currently widely used silicon (Si) devices. There are limitations on SiC certain structures of SiC devices, such as the metal oxide semiconductor field effect transistor (MOSFET), have inherent reliability issues related to the fabrication of the device. These reliability issues can get worse over higher temperature ranges. Therefore, studies must be made to determine the feasibility of SiC MOSFETs in high temperature applications. To do so, industry standard tests are conducted on newer generation SiC MOSFETs to ascertain their use for said conditions.

Currently, pallets are designed assuming that the load is distributed evenly on the top of the pallet. When pallets are loaded with packages such as corrugated boxes or returnable plastic containers, due to their physical shape, packages, are not capable of deforming freely with the pallet and a bridging phenomenon occurs. During this load bridging phenomenon, a portion of the vertical forces are redistributed as horizontal forces which causes the redistribution of the vertical compression stresses on the pallet towards the support. As a result, the deflection of the pallet can decrease and the load capacity of the pallet can increase significantly. The second chapter of this paper investigates the effect of package content on pallet deflection. The study concluded that package content did not have a significant effect on pallet deflection within the boundary conditions of the experiment. The third part of this paper considers how a specific pallet characteristic could affect the way a corrugated box performs. Standard box design procedures include adjustments of estimated compression strength for relative humidity, overhang on pallets, vibration, and alignment of boxes. However, there is no adjustment factor for pallet stiffness. The objective of the study described in this thesis is to find an answer for how the compression strength of a box is affected by pallet stiffness and top deckboard twist. The study concluded that the pallet stiffness and top deckboard twist do not have an effect on the compression strength of the box until less than 12% of the area box is supported. / Master of Science / Within the United States alone, there are more than 2 billion pallets in service daily. These pallets transport and store a wide variety of products. There are many factors that could effect the performance of a pallet, and it is still unknown which design factors and possible package interactions will or will not effect pallet performance. The first objective of this thesis is to investigate the effect of package content on pallet deflection. The study concludes that the package content does not have an effect on pallet deflection. With about 1300 manufacturing plants that produce corrugated in the Unites States and Canada, the industry alone provides $26 billion to economies. Corrugated paperboard boxes are used daily for distribution and packaging, allowing products to easily and safely travel the globe. A majority of the time, these boxes are transported and stored on wooden pallets. Currently, there is no safety factor for box design that takes pallet stiffness into consideration. The second objective of this thesis is to investigate the effect of top deckboard twist on box compression strength. The results from the study concluded that the pallet stiffness and top deckboard twist do not have an effect on the compression strength of the box until less than 12% of the area box is supported.