The reliability of power semiconductor devices is an important feature when designing converter, since the semiconductors are prone to failure and a weak link in the system. Power semiconductor devices are susceptible to thermo-mechanical stresses, and should be investigated to make reliable semiconductors. The power losses inside the device resulting in thermal cycling and expanding and contracting the layers of the semiconductors with different rates, are the cause of the thermomechanical stresses. Thermo-mechanical fatigues are the most frequently encountered forms of failure in power devices, e.g. bond wire lift-off, solder cracks, and reconstruction of chip materialization. In this thesis, the end-of-life assessment of the silicon IGBT and silicon-carbide MOSFET are investigated. Specifically the power cycling test can replicate the thermo-mechanical stresses and wear out the device in a couple of weeks [8], [9]. Multple short power cycling tests are executed to find the relationship between the selected parameters and resulting thermal cycle. Furthermore, the thermal response measurements are used to study the thermal behaviour of the semiconductor devices and thermal fatigues. In addition, the thermal model for the test system is arrived, making it possible to create a testbed for the power cycling test for different thermal cycles. Lastly, the end-of-life assessment is executed for 23 days on eight silicon IGBTs.

Sensors are extremely valuable to this world. Without sensors, we would not be able to live as we do in this data-driven environment. Therefore, finding new ways to measure the matter around us is a continuous process. In this work, an addition to the new sensors is attempted, using materials that can withstand the most extreme circumstances. This work describes the process of designing, simulating, producing, measuring and validating a pressure sensor based on LPCVD Silicon Carbide.
The created sensor should be modular and back-end-of-line compatible. In addition, the sensor should measure pressures from 80Pa up to 1MPa at temperatures from room temperature to 600°C. Because of a favourable reaction to high temperatures, a capacitive sensor type that uses a sealed membrane for absolute pressure measurements is chosen.
Due to the large pressure range, the design has been split into three distinct parts, each with its specialised pressure range. A low-range for 80Pa to 100kPa, a mid-range sensor for 100kPa to 300kPa and a high-range sensor for 300kPa to 1MPa. To compensate for the nonlinearity in the device, two approaches are taken. One method splits the bottom electrodes, generating a more linear output with the correct division. This approach is used for low-and-mid-pressure devices. The other approach uses touch mode to decrease nonlinearity. After the membrane touches the bottom contact, a linear range is found. This approach is taken for the high-pressure device.
A flowchart has been developed based on the necessary layers to create the sensors. Using this flowchart, masks have been designed. During production, the process was adjusted, as delamination of the dielectric layer was observed. In addition, because of difficulty with sealing, the membrane is thicker than the original design.
During production, buckling of the membranes was observed. This causes the sensors to behave differently compared to the simulations. One effect the buckling may have caused is the reaction to temperature. This is opposite to the simulations. In addition, subjecting the sensors to a vacuum also causes behaviour opposite to what was intended. When high pressure is applied, the sensors do work as intended. Due to the design alterations and buckling effect, the sensors are less sensitive to pressure than intended. The best sensor has a sensitivity of 0.025 f F/100Pa compared to the designed 0.3 f F/100Pa. However, the output of the sensor is linear without needing the designed compensation techniques.

Today’s cars are undergoing the greatest transformation the industry has seen. Power MOSFETs play a crucial role in making electronics more energy efficient by driving down switching losses and Rdson using a combination of next-generation trench technology and ultra-thin dies. Power MOSFET dies are becoming larger ( > 5 X 5 mm ) and thinner ( < 50 μm ) to meet the high performance lifetime requirements of the automotive industry. The high aspect ratio and the new chip designs with trench technology offer challenges for assembly, packaging and testing.

The majority of the research performed in the past, aimed to reduce the risk of die crack by improving equipment and process strategies in back-end semiconductor processing. This thesis study aims at improving die
strength from a front-end approach (device fabrication process) by making dies stronger to stress from die frontside. New chip designs are presented with new metal layer layouts for improved stress distribution. Materials like polyimide are investigated as new die top material for mechanical strengthening of die frontside. Key factors which influence die strength like trench-metal interaction, wafer stress and warpage are also analyzed in this thesis report.

In this study, ultra-thin power MOSFET dies are realised on 100 mm diameter silicon wafers with dimensions of 6 X 3 X 0.050 mm. These dies are mechanical equivalent in design, robustness to commercial trench power MOSFETs. The processed wafers are grinded from the backside to realise 50 μm thin wafers which are then sawned to obtain singulated dies. The strength of the dies are characterized by three-point bending tests and analyzed using probability plots for weibull distribution.

Since the outbreak of SARS-COV-2, various virus inactivation techniques have been applied to suppress the spread of virus. Ultraviolet exposure inactivation is an efficient approach to inactivate virus, within UV band, UV-C with comparatively higher energy. UV-C has been proved to inactivate viruses efficiently, while to figure out efficient inactivation approach, virus reduction rate as a function of UV-C wavelength with different viral sensitivity and quantitative exposure dose should be measured through experiments.
On the one hand, miniatured, energy-efficient and fully-customized UV-C light-emitting diodes (LED) offer possibility of switching wavelengths and adjusting quantitative optical properties, on the other hand, UV-C LEDs have been produced with the latest technology based on Aluminium gallium nitride (AlGaN).

~\\Multifunctional UV-C LED Virus Inactivation Experimental Platform is a system designed with replaceable UV-C wavelengths, controllable light intensity and exposure time for quantitative virology experiments. The system has an initial design for standard virology experimental equipment which offers a new and consistent tool for virus researchers. The Inactivation Platform has been assembled and utilized to perform several Influenza A (ssRNA virus) inactivation experiments in order to obtain reduction rate as a function of UV-C wavelength and exposure dose with Germicidal Curve and Inactivation Curve respectively.

~\\After inactivation experiments implementation and result analysis, the inactivation mechanism on the basis of molecular dynamic research theory and simulation is supposed to be figured out. Due to the complexity of proteins in virus, the research focuses on Nucleic Acid Bases (NABs) as target genetic viral material. The absorbed ultraviolet energy results in ultrafast decay, including molecular electronic transition, virus structure variation (Dimerization) theoretically. The absorbed energy along the band is revealed with Absorption Spectrum, and the potential electronic transition depends on the initial structure NABs, together with inside chemical bonds. When absorbed energy populates the molecules to transition state, ultrafast decay takes place because of the existence of Gibbs energy of activation. In the light of molecular dynamic simulation, it proves that compared to ground state, excited state leads to lower standard Gibbs energy of activation, causing higher reaction rate (faster inactivation speed).

Heart Failure (HF) is a disease of high mortality and morbidity with huge impact on health care systems worldwide. HF is a result of decreased contraction of the heart muscle. Current treatments focus on symptoms,and only a minor portion of HF patients is eligible for surgery. Assistance devices for cardiac contractionare currently only available as bridging therapy towards heart transplantation. In this thesis, an innovativecardiac assistance device based on light-responsive Liquid Crystalline Elastomers (LCEs) is proposed. Thisbio-compatible polymer can generate a contractile force in response to a light stimulus. Theoretically, an LCEsheet wrapped around the heart could assist cardiac contraction. Light stimuli could be administered by an implanted LED panel to achieve the first fully implanted cardiac assistance device available. Therefore, parametersregarding light-LCE interaction were investigated. Among state-of-the art light sources, the best candidates foran implantable LCE device were selected. The physical mechanisms underlying LCE behaviour were explored,and LCEs in previous research were compared. Lastly, light irradiance patterns were mathematically modelledto find the optimal configuration for LCE stimulation. It was found that LCE ’MM10’ is a good candidatefor our device as it is bio-compatible, tweakable in wavelength response, has fast response times and producesa large stress. The most promising light source is µLEDs, as they are small, provide high light intensity atgood efficiency, and are relatively biocompatible. Modeling shows that the optimal formation of µLEDs is ahexagonal pattern, which provides the most homogeneous at the highest efficiency at very-nearby irradiance(tens of µms.After this literature review, experiments were performed. Optical, mechanical and thermal properties ofMM10 were tested. The optical experiments proved that MM10 acts as birefringent half-wave plate, meaningit rotates the direction of linearly polarized light. This finding could be used to visually determine the nematicdirector of MM10, with birefringence the strongest in an angle of 45◦ with the nematic director. Birefringenceis low in the wavelength spectrum of the stimulating light source (400-500nm) and highest in the 700-800nmrange. Reflection and transmission of MM10 within the 400-500nm range are resp. 5.5±0.2%and10.6±4.6%.This indicates that most of the LED light is absorbed, and thus can be converted in mechanical energy to producestress. The order parameter was found to be 0.5. The absorption coefficient was found to be 0.081±0.006.Mechanical analysis was divided in passive properties (without light stimulus) and active properties (withlight stimulus). Young’s moduli are heavily influenced by environmental temperature, where MM10 shows a>10x higher Young’s modulus in the 0.1-2% strain range and a >4x higher modulus in the 4-6% strain rangeat 25◦C compared to 37◦C (body temperature). A calibrated the main-chain LCE model showed to be a goodpredictor of this behavior.Dynamical analysis (DMA) showed that storage modulus decreases and tan δ increases heavily upon lightstimulus. This can be explained by stiffening of MM10 upon illumination due to contraction. MM10 stressgeneration is optimal in the 35-40mW/cm2irradiance range, producing a stress of up to 80mN/mm2 at 25◦C.At higher temperatures, elasticity will rapidly increase, leading to higher irradiance tolerance before break, butlower stress generation at the same irradiance compared to 25◦C. A mathematical model was built and testedon these findings for predicting maximum stress generation when sample thickness, irradiance and environmenttemperature are known.Thermal infrared analysis showed that MM10 surface temperature rises upon illumination, as an indirectresult of the incorporated azobenzene molecules, which act as micro-heaters. Surface temperature reaches themaximum after ±5s of illumination. Stress generation coincides with this temperature rise, until it reaches aplateau. While it is possible to pace MM10 at a rate of 1-3Hz without excessive heat build-up, MM10 has a tooslow response to act as an effective contractile unit at these frequencies.A demonstrator was built for homogeneous illumination of MM10 material wrapped around a balloon. Thisplatform allows live measurement of pressure, temperature, humidity and ECG signals. Also, light stimuli canbe triggered by real-time heart beat detection. Concentric pressure measurements showed a 20µm-thick MM10band could produce up to 170 Pa pressure when wrapped around a balloon and irradiated homogeneously with60mW/cm2 green light. As such, the (very thin) MM10 band generates a substantial force of 1.29N.We conclude that MM10 is a bio-compatible, versatile material able to produce large stresses in responseto LED light. Cardiac assistance by MM10 might be too complex because of the relatively slow response timeof MM10 compared to the heart rate, the large mechanical forces in the heart and the variability of the heartrate. We see multiple other potential uses for MM10 as an implant as well as outside the (human) body.

Silicon-based MEMS technology has been the standard for developing 2D and 3D
micro-structures for many years. There are 2 main classifications of MEMS manufacturing technologies, viz. bulk micro-machining, and surface micro-machining.
These techniques have its own set of drawbacks. Bulk micro-machining affects the structural integrity of the wafer because bulk silicon is being etched. Surface micro-machining is limited by the maximum thickness of the method of thin-film deposition (usually a few microns). The current silicon-based MEMS sensors can also fail when it comes to harsh environment sensing. Due to this, the sensors would require many supporting infrastructures such as radiation shield, cooling system and shock-proof packaging.
One way to circumvent this problem is by designing sensors using materials that would not require as much supporting infrastructure. Silicon carbide (SiC) has proved to be a viable candidate to be used in such harsh environments. This is
because it is found to be mechanically robust, chemically inert and with good wear resistance. However, bulk micro-machining with SiC is extremely challenging due to the high difficulty in etching. Many techniques have been tested to etch SiC, but they all have considerable drawbacks or low etch rates. Thus, to make high aspect ratio structures using SiC we will require a new technique where carbon nanotubes (CNT) can be used as a framework in the fabrication process for high aspect ratio surface micro-machining. CNTs can be grown to lengths of several micrometres to millimetres while their diameter is in the order of a few nanometres. Bundles of these tubes were found to have excellent conductance with high current densities, and their behaviour can be either metallic or semiconducting depending on their chiral vector. These unique properties make CNTs a very interesting material to be integrated into conventional MEMS technology. Although a single nanotube has excellent properties, bundles of nanotubes show a ‘foam-like’ property since they are held together by weak van der Waals’ forces. Thus, to realize mechanical structures with CNTs, we will have to coat the nanotube bundles with a filler material. This has previously been demonstrated to allow tuning of the mechanical properties of the composite. SiC would be an attractive filler candidate for harsh environment sensors. Due to the porous nature of nanotubes, it is possible to infiltrate the forest by deposition of a nanoscale coating. The deposition of the filler material is done by means of low pressure chemical vapor deposition (LPCVD) since a low pressure and deposition rate will enable the nanotube forest to get completely infiltrated and more uniformly coated. The goal of this research is to fabricate the first sensor using this technique, viz. a comb type capacitive accelerometer and test its performance and resilience to harsh environments by using SiC as coating. This technique will enable the user of a thicker layer for the proof mass and combs, resulting in a higher performance and potentially, resistance to harsh environments.

Revolutionary changes in automotive industry toward fully connected electrical vehicles is changing the world of Board Level Reliability (BLR) Vibration Testing. It is taking BLR Vibration tests beyond board level to board module application level.
In this thesis, it contains the development of a reliability test concept called Board Module level Vibration Testing that is required to cope with the challenging application driven requests.

The COVID-19 pandemic caused a shortage of Personal Protective Equipment for Healthcare personnel. This project aims to aid in this shortage by extending the lifetime of the filter material used in a mask. This is done in the form of an SPPE, a Smart Personal Protective Equipment. This face mask has two smart filter heads that are modular and contain UVC LEDs to disinfect the filter, a control system to control the LED's radiative power and an on-board power management system. The latter is the focus of this thesis.

The implementation of an on-board power management system for a smart personal protection face mask was designed in three stages: (1) researching existing theory about battery management, (2) implementing and verifying a system design in Simulink and (3) making a PCB design and selecting off-the-shelf components. The goal of this thesis is to make a complete design of a functional battery management system, that supplies required power to the rest of the system, ensuring safe battery operation and aiming to maximize battery life. In this, the design has succeeded as almost all requirements are met. The result is a PCB design that can be made and combined with two other subgroups to create a Smart Personal Protection face mask. The main findings were a different and possibly new approach to estimating the State of Charge of a battery and designing a Battery management system for low power applications in a small form factor as opposed to battery management systems for electrical vehicles, which are common today.

The Smart Personal Protective Equipment (SPPE) is proposed as a result of the COVID-19 pandemic, which has led to shortages of standard face masks. This thesis describes one of the three subsystems of the SPPE, namely the Ultraviolet Germicidal Irradiation (UVGI). The UVGI subsystem provides the SPPE with an in situ disinfection system, in order to prolong the period in which the filters of the SPPE can be used to at least 8 hours. The UVGI is implemented by the use of UV LEDs. This implementation is done in two steps. Step one is a simulation which allows for the optimization of the LED placement depending on a multitude of parameters, including: distance between the LEDs and the filter, and the LED tilt angle. The second step is the design of a driver circuit, to allow for the adjustment of the dose applied by the LEDs. The simulation resulted in an LED array which offers the most optimal irradiation of the filter surface. The driver circuit has been designed, simulated to verify its functionality, and implemented in the form of a PCB design. The UVGI subsystem provides the SPPE with an in situ disinfection system by delivering a base dose of 305 mJ/cm2 and a driver circuit which allows for adjusting this dose, should this be desired. The UVGI subsystem should be able to extend the period in which the filters of the SPPE can be used to at least 8 hours. However, due to the restriction of not being allowed to create a prototype this has not yet been verified.

The current COVID-19 pandemic shows the necessity of personal protective equipment and face masks. In the project, a filter module with an in-situ ultraviolet-sterilization technique is designed that can serve as a new kind of smart personal protective equipment (SPPE). This technique is not used in wearable devices as of yet. The project thus aims to take the next step into the future of facemasks. The complete SPPE design is split into three submodules. In this thesis, the Sensing and Control submodule is designed. The Sensing and Control submodule is divided into three parts as well. In the first part of the design, a negative feedback control loop is developed. A photodiode transimpedance amplifier circuit provides the feedback, and the controller is programmed on a microcontroller. The control parameters are derived from a model in Simulink. In the second part of the design, the temperature and relative humidity are measured to transform the control loop’s reference value into a reference function. In the third part of the design, an estimation of the filter state of health is made by measuring the pressure drop over the filter material. Additionally, the airflow in the SPPE is calculated using equations from fluid mechanics to set the maximum allowable pressure drop. At the end of the thesis, the Sensing and Control submodule allows the SPPE to measure environmental conditions, control the ultraviolet intensity accordingly, and indicate if the filter requires replacement. The design is finalized with printed circuit board designs and an algorithm. With the design of the Sensing and Control submodule, the next step is taken towards the future of face masks.