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• 1. [Article] Making Gains in Rwanda: It Will Take New Business Models, not Small Donations, to Provide Meaningful Development

  Nearly a billion people in the world drink dirty water. Two billion don't have a sanitary toilet. Three billion use campfires every day. Governments and charities spend billions of dollars every year to ...

  Citation × Citation Citation Abstract Copy Title: Making Gains in Rwanda: It Will Take New Business Models, not Small Donations, to Provide Meaningful Development Author: Thomas, Evan A. Year: 2015 Nearly a billion people in the world drink dirty water. Two billion don't have a sanitary toilet. Three billion use campfires every day. Governments and charities spend billions of dollars every year to address these problems. And there are big successes in some places, but more innovation is needed. Title: Making Gains in Rwanda: It Will Take New Business Models, not Small Donations, to Provide Meaningful Development Author: Thomas, Evan A. Year: 2015 Nearly a billion people in the world drink dirty water. Two billion don't have a sanitary toilet. Three billion use campfires every day. Governments and charities spend billions of dollars every year to address these problems. And there are big successes in some places, but more innovation is needed. Close

• 2. [Article] Slip, Crystal Orientation, and Damage Evolution During Thermal Cycling in High-Strain Wafer-Level Chip-Scale Packages

  Wafer-level chip-scale package samples with pre-cross-sectioned edge rows were thermally cycled to study microstructure evolution and damage development. Electron backscattered diffraction (EBSD) and high-energy ...

  Citation × Citation Citation Abstract Copy Title: Slip, Crystal Orientation, and Damage Evolution During Thermal Cycling in High-Strain Wafer-Level Chip-Scale Packages Author: Zhou, Bite, Zhou, Quan, Bieler, Thomas R., Lee, Tae-Kyu Year: 2015 Wafer-level chip-scale package samples with pre-cross-sectioned edge rows were thermally cycled to study microstructure evolution and damage development. Electron backscattered diffraction (EBSD) and high-energy x-ray diffraction were used to obtain Sn grain orientations and the average coefficient of thermal expansion normal to the board in every joint of the package for samples in the as-fabricated and thermally cycled conditions. The results indicated a near-random distribution of joint orientation. Optical, scanning electron microscopy, and EBSD methods were used to characterize microstructure changes in pre-cross-sectioned samples due to thermal cycling. Slip trace analysis and Orientation Imaging Microscopy™ (OIM) show that slip systems with high Schmid factors (estimated global shear stress based on the package neutral point) are responsible for the observed microstructure evolution during thermal cycling, which provides information about slip systems that are more easily activated. Two joints were analyzed in detail to evaluate slip activity at different stages of their thermal history. The first case showed that a solidification twin grain boundary misorientation deviated from the twin relationship due to slip activity during thermal cycling, which can influence damage development and the path of crack propagation. The second case showed a new grain orientation developing due to gradual lattice rotation about the Sn [110] axis by a continuous recrystallization mechanism. This rotation was correlated with the operation of slip system {110)⟨001]. Small tin whiskers emerged from the initially polished chip interface and grew with increasing thermal cycles until a crack developed in the solder that relieved the stress. As the local stresses are not known experimentally, this analysis provides observations that can be compared with a crystal plasticity model simulation. Title: Slip, Crystal Orientation, and Damage Evolution During Thermal Cycling in High-Strain Wafer-Level Chip-Scale Packages Author: Zhou, Bite, Zhou, Quan, Bieler, Thomas R., Lee, Tae-Kyu Year: 2015 Wafer-level chip-scale package samples with pre-cross-sectioned edge rows were thermally cycled to study microstructure evolution and damage development. Electron backscattered diffraction (EBSD) and high-energy x-ray diffraction were used to obtain Sn grain orientations and the average coefficient of thermal expansion normal to the board in every joint of the package for samples in the as-fabricated and thermally cycled conditions. The results indicated a near-random distribution of joint orientation. Optical, scanning electron microscopy, and EBSD methods were used to characterize microstructure changes in pre-cross-sectioned samples due to thermal cycling. Slip trace analysis and Orientation Imaging Microscopy™ (OIM) show that slip systems with high Schmid factors (estimated global shear stress based on the package neutral point) are responsible for the observed microstructure evolution during thermal cycling, which provides information about slip systems that are more easily activated. Two joints were analyzed in detail to evaluate slip activity at different stages of their thermal history. The first case showed that a solidification twin grain boundary misorientation deviated from the twin relationship due to slip activity during thermal cycling, which can influence damage development and the path of crack propagation. The second case showed a new grain orientation developing due to gradual lattice rotation about the Sn [110] axis by a continuous recrystallization mechanism. This rotation was correlated with the operation of slip system {110)⟨001]. Small tin whiskers emerged from the initially polished chip interface and grew with increasing thermal cycles until a crack developed in the solder that relieved the stress. As the local stresses are not known experimentally, this analysis provides observations that can be compared with a crystal plasticity model simulation. Close

• 3. [Article] Development and Training of a Neural Controller for Hind Leg Walking in a Dog Robot

  Animals dynamically adapt to varying terrain and small perturbations with remarkable ease. These adaptations arise from complex interactions between the environment and biomechanical and neural components ...

  Citation × Citation Citation Abstract Copy Title: Development and Training of a Neural Controller for Hind Leg Walking in a Dog Robot Author: Hunt, Alexander J., Szczecinski, Nicholas, Quinn, Roger Year: 2017 Animals dynamically adapt to varying terrain and small perturbations with remarkable ease. These adaptations arise from complex interactions between the environment and biomechanical and neural components of the animal’s body and nervous system. Research into mammalian locomotion has resulted in several neural and neuro-mechanical models, some of which have been tested in simulation, but few “synthetic nervous systems” have been implemented in physical hardware models of animal systems. One reason is that the implementation into a physical system is not straightforward. For example, it is difficult to make robotic actuators and sensors that model those in the animal. Therefore, even if the sensorimotor circuits were known in great detail, those parameters would not be applicable and new parameter values must be found for the network in the robotic model of the animal. This manuscript demonstrates an automatic method for setting parameter values in a synthetic nervous system composed of non-spiking leaky integrator neuron models. This method works by first using a model of the system to determine required motor neuron activations to produce stable walking. Parameters in the neural system are then tuned systematically such that it produces similar activations to the desired pattern determined using expected sensory feedback. We demonstrate that the developed method successfully produces adaptive locomotion in the rear legs of a dog-like robot actuated by artificial muscles. Furthermore, the results support the validity of current models of mammalian locomotion. This research will serve as a basis for testing more complex locomotion controllers and for testing specific sensory pathways and biomechanical designs. Additionally, the developed method can be used to automatically adapt the neural controller for different mechanical designs such that it could be used to control different robotic systems. Title: Development and Training of a Neural Controller for Hind Leg Walking in a Dog Robot Author: Hunt, Alexander J., Szczecinski, Nicholas, Quinn, Roger Year: 2017 Animals dynamically adapt to varying terrain and small perturbations with remarkable ease. These adaptations arise from complex interactions between the environment and biomechanical and neural components of the animal’s body and nervous system. Research into mammalian locomotion has resulted in several neural and neuro-mechanical models, some of which have been tested in simulation, but few “synthetic nervous systems” have been implemented in physical hardware models of animal systems. One reason is that the implementation into a physical system is not straightforward. For example, it is difficult to make robotic actuators and sensors that model those in the animal. Therefore, even if the sensorimotor circuits were known in great detail, those parameters would not be applicable and new parameter values must be found for the network in the robotic model of the animal. This manuscript demonstrates an automatic method for setting parameter values in a synthetic nervous system composed of non-spiking leaky integrator neuron models. This method works by first using a model of the system to determine required motor neuron activations to produce stable walking. Parameters in the neural system are then tuned systematically such that it produces similar activations to the desired pattern determined using expected sensory feedback. We demonstrate that the developed method successfully produces adaptive locomotion in the rear legs of a dog-like robot actuated by artificial muscles. Furthermore, the results support the validity of current models of mammalian locomotion. This research will serve as a basis for testing more complex locomotion controllers and for testing specific sensory pathways and biomechanical designs. Additionally, the developed method can be used to automatically adapt the neural controller for different mechanical designs such that it could be used to control different robotic systems. Close

• 4. [Article] Development of a National Anthropogenic Heating Database with an Extrapolation for International Cities

  Given increasing utility of numerical models to examine urban impacts on meteorology and climate, there exists an urgent need for accurate representation of seasonally and diurnally varying anthropogenic ...

  Citation × Citation Citation Abstract Copy Title: Development of a National Anthropogenic Heating Database with an Extrapolation for International Cities Author: Sailor, David J., Georgescu, Matei, Milne, Jeffrey M., Hart, Melissa A. Year: 2015 Given increasing utility of numerical models to examine urban impacts on meteorology and climate, there exists an urgent need for accurate representation of seasonally and diurnally varying anthropogenic heating data, an important component of the urban energy budget for cities across the world. Incorporation of anthropogenic heating data as inputs to existing climate modeling systems has direct societal implications ranging from improved prediction of energy demand to health assessment, but such data are lacking for most cities. To address this deficiency we have applied a standardized procedure to develop a national database of seasonally and diurnally varying anthropogenic heating profiles for 61 of the largest cities in the United Stated (U.S.). Recognizing the importance of spatial scale, the anthropogenic heating database developed includes the city scale and the accompanying greater metropolitan area. Our analysis reveals that a single profile function can adequately represent anthropogenic heating during summer but two profile functions are required in winter, one for warm climate cities and another for cold climate cities. On average, although anthropogenic heating is 40% larger in winter than summer, the electricity sector contribution peaks during summer and is smallest in winter. Because such data are similarly required for international cities where urban climate assessments are also ongoing, we have made a simple adjustment accounting for different international energy consumption rates relative to the U.S. to generate seasonally and diurnally varying anthropogenic heating profiles for a range of global cities. The methodological approach presented here is flexible and straightforwardly applicable to cities not modeled because of presently unavailable data. Because of the anticipated increase in global urban populations for many decades to come, characterizing this fundamental aspect of the urban environment – anthropogenic heating – is an essential element toward continued progress in urban climate assessment. Title: Development of a National Anthropogenic Heating Database with an Extrapolation for International Cities Author: Sailor, David J., Georgescu, Matei, Milne, Jeffrey M., Hart, Melissa A. Year: 2015 Given increasing utility of numerical models to examine urban impacts on meteorology and climate, there exists an urgent need for accurate representation of seasonally and diurnally varying anthropogenic heating data, an important component of the urban energy budget for cities across the world. Incorporation of anthropogenic heating data as inputs to existing climate modeling systems has direct societal implications ranging from improved prediction of energy demand to health assessment, but such data are lacking for most cities. To address this deficiency we have applied a standardized procedure to develop a national database of seasonally and diurnally varying anthropogenic heating profiles for 61 of the largest cities in the United Stated (U.S.). Recognizing the importance of spatial scale, the anthropogenic heating database developed includes the city scale and the accompanying greater metropolitan area. Our analysis reveals that a single profile function can adequately represent anthropogenic heating during summer but two profile functions are required in winter, one for warm climate cities and another for cold climate cities. On average, although anthropogenic heating is 40% larger in winter than summer, the electricity sector contribution peaks during summer and is smallest in winter. Because such data are similarly required for international cities where urban climate assessments are also ongoing, we have made a simple adjustment accounting for different international energy consumption rates relative to the U.S. to generate seasonally and diurnally varying anthropogenic heating profiles for a range of global cities. The methodological approach presented here is flexible and straightforwardly applicable to cities not modeled because of presently unavailable data. Because of the anticipated increase in global urban populations for many decades to come, characterizing this fundamental aspect of the urban environment – anthropogenic heating – is an essential element toward continued progress in urban climate assessment. Close

• 5. [Article] Synthesis of Large-Scale 2-D MoS2 Atomic Layers by Hydrogen-Free and Promoter-Free Chemical Vapor Deposition

  As one of the two-dimensional (2-D) transition metal dichalcogenides, atomically thin molybdenum disulfide (MoS2) has attracted significant attention and research interests for micro and nanoelectronic ...

  Citation × Citation Citation Abstract Copy Title: Synthesis of Large-Scale 2-D MoS2 Atomic Layers by Hydrogen-Free and Promoter-Free Chemical Vapor Deposition Author: Nguyen, Hung, Huang, Chih-Fang, Luo, Weijun, Xia, Guangrui (Maggie), Chen, Zhiqiang, Li, Zhiqiang, Raymond, Christopher, Doyle, David, Zhao, Feng Year: 2016 As one of the two-dimensional (2-D) transition metal dichalcogenides, atomically thin molybdenum disulfide (MoS2) has attracted significant attention and research interests for micro and nanoelectronic applications. Significant efforts have been made to develop different approaches in order to obtain atomic layer MoS2, such as exfoliation, chemical synthesis, and physical or chemical vapor deposition (CVD) processes. In this paper, we report a hydrogen-free and promoter-free CVD growth to synthesize large-area MoS2 atomic layers. A variety of techniques including optical microscopy (OM), atomic force microscopy (AFM), photoluminescence (PL) mapping, Raman and x-ray photoelectron spectroscopy (XPS), high resolution electron microscopy (HREM) and scanning transmission electron microscopy (STEM) were applied to characterize the film quality, uniformity and layer numbers. High quality centimeter-sized MoS2 atomic layers were demonstrated, which form a foundation to develop wafer-sized material platform for device fabrication and production. Title: Synthesis of Large-Scale 2-D MoS2 Atomic Layers by Hydrogen-Free and Promoter-Free Chemical Vapor Deposition Author: Nguyen, Hung, Huang, Chih-Fang, Luo, Weijun, Xia, Guangrui (Maggie), Chen, Zhiqiang, Li, Zhiqiang, Raymond, Christopher, Doyle, David, Zhao, Feng Year: 2016 As one of the two-dimensional (2-D) transition metal dichalcogenides, atomically thin molybdenum disulfide (MoS2) has attracted significant attention and research interests for micro and nanoelectronic applications. Significant efforts have been made to develop different approaches in order to obtain atomic layer MoS2, such as exfoliation, chemical synthesis, and physical or chemical vapor deposition (CVD) processes. In this paper, we report a hydrogen-free and promoter-free CVD growth to synthesize large-area MoS2 atomic layers. A variety of techniques including optical microscopy (OM), atomic force microscopy (AFM), photoluminescence (PL) mapping, Raman and x-ray photoelectron spectroscopy (XPS), high resolution electron microscopy (HREM) and scanning transmission electron microscopy (STEM) were applied to characterize the film quality, uniformity and layer numbers. High quality centimeter-sized MoS2 atomic layers were demonstrated, which form a foundation to develop wafer-sized material platform for device fabrication and production. Close

• 6. [Article] Reliability Physics Behind the QFN State of Stress

  A physically meaningful analytical stress model is developed for the explanation of the reliability physics underlying the relief in the thermally induced interfacial shearing stresses in a typical Quad ...

  Citation × Citation Citation Abstract Copy Title: Reliability Physics Behind the QFN State of Stress Author: Suhir, Ephraim, Ghaffarian, Reza, Yi, Sung Year: 2017 A physically meaningful analytical stress model is developed for the explanation of the reliability physics underlying the relief in the thermally induced interfacial shearing stresses in a typical Quad Flat No-lead (QFN) assembly. The stress relief in a QFN design is, in effect, an implementation of the general concept developed and quantified by the first author about a decade ago of using inhomogeneous bonds for lower thermal stresses in adhesively bonded or soldered assemblies. It is shown also that the maximum stress in the QFN design can be minimized, if the lengths of the peripheral zones are established based on the requirement that the stresses at the ends of the assembly are made equal to the stresses at the ends of its mid-portion. In the carried out numerical example the gain in the relief in the maximum interfacial shearing stress owing to the application of a bond with an elevated compliance is 9.94 %. When the optimized inhomogeneous bond is applied, the gain is 16.87 %. The gain in the stress relief owing to the optimized inhomogeneous bond (with respect to the homogeneous compliant bond) is 10.66 %. The computed interfacial stresses are below the yield stress of the solder material. © 2016, Springer Science+Business Media New York. Title: Reliability Physics Behind the QFN State of Stress Author: Suhir, Ephraim, Ghaffarian, Reza, Yi, Sung Year: 2017 A physically meaningful analytical stress model is developed for the explanation of the reliability physics underlying the relief in the thermally induced interfacial shearing stresses in a typical Quad Flat No-lead (QFN) assembly. The stress relief in a QFN design is, in effect, an implementation of the general concept developed and quantified by the first author about a decade ago of using inhomogeneous bonds for lower thermal stresses in adhesively bonded or soldered assemblies. It is shown also that the maximum stress in the QFN design can be minimized, if the lengths of the peripheral zones are established based on the requirement that the stresses at the ends of the assembly are made equal to the stresses at the ends of its mid-portion. In the carried out numerical example the gain in the relief in the maximum interfacial shearing stress owing to the application of a bond with an elevated compliance is 9.94 %. When the optimized inhomogeneous bond is applied, the gain is 16.87 %. The gain in the stress relief owing to the optimized inhomogeneous bond (with respect to the homogeneous compliant bond) is 10.66 %. The computed interfacial stresses are below the yield stress of the solder material. © 2016, Springer Science+Business Media New York. Close

• 7. [Article] Board Level Drop Test: Exact Solution to the Problem of the Nonlinear Dynamic Response of a PCB to the Drop Impact

  An analytical predictive model has been developed for the evaluation of the nonlinear dynamic response of a printed-circuit-board (PCB) to the drop impact during board-level testing. The hypothesis of ...

  Citation × Citation Citation Abstract Copy Title: Board Level Drop Test: Exact Solution to the Problem of the Nonlinear Dynamic Response of a PCB to the Drop Impact Author: Suhir, Ephraim, Ghaffarian, Reza Year: 2016 An analytical predictive model has been developed for the evaluation of the nonlinear dynamic response of a printed-circuit-board (PCB) to the drop impact during board-level testing. The hypothesis of “heavy-and-flexible” PCB is used in the analysis: the surface-mounted-devices (SMDs) are assumed to be small enough not to affect the PCB’s flexural rigidity, but their masses have been considered and accounted for by “spreading out” the SMD total mass over the PCB surface. The analysis is restricted to the fundamental mode of vibrations, and the method of principal coordinates is used to evaluate the response. The exact solution to the nonlinear differential equation for the principal coordinate has been obtained. Another important finding is that the nonlinear amplitudes were determined even without solving the nonlinear differential equation of motion. The main objective of the analysis is to provide design guidelines for constructing a feasible experimental setup. A simply supported board is suggested as the most appropriate structure for an adequate test vehicle: the experimental data for such a board, as far as the behavior of the solder material in the second level of interconnections is concerned, can be easily and reliably interpreted and extrapolated for the practical use. The developed model enables one to predict the induced bending moments and the in-plane (membrane) forces that could be applied in the subsequent analyses to the PCB areas in the proximity of the package and its solder joint interconnections. Title: Board Level Drop Test: Exact Solution to the Problem of the Nonlinear Dynamic Response of a PCB to the Drop Impact Author: Suhir, Ephraim, Ghaffarian, Reza Year: 2016 An analytical predictive model has been developed for the evaluation of the nonlinear dynamic response of a printed-circuit-board (PCB) to the drop impact during board-level testing. The hypothesis of “heavy-and-flexible” PCB is used in the analysis: the surface-mounted-devices (SMDs) are assumed to be small enough not to affect the PCB’s flexural rigidity, but their masses have been considered and accounted for by “spreading out” the SMD total mass over the PCB surface. The analysis is restricted to the fundamental mode of vibrations, and the method of principal coordinates is used to evaluate the response. The exact solution to the nonlinear differential equation for the principal coordinate has been obtained. Another important finding is that the nonlinear amplitudes were determined even without solving the nonlinear differential equation of motion. The main objective of the analysis is to provide design guidelines for constructing a feasible experimental setup. A simply supported board is suggested as the most appropriate structure for an adequate test vehicle: the experimental data for such a board, as far as the behavior of the solder material in the second level of interconnections is concerned, can be easily and reliably interpreted and extrapolated for the practical use. The developed model enables one to predict the induced bending moments and the in-plane (membrane) forces that could be applied in the subsequent analyses to the PCB areas in the proximity of the package and its solder joint interconnections. Close

• 8. [Article] A Proposed Integrated Data Collection, Analysis and Sharing Platform for Impact Evaluation

  Global poverty reduction efforts value monitoring and evaluation, but often struggle to translate lessons learned from one intervention into practical application in another intervention. Commonly, data ...

  Citation × Citation Citation Abstract Copy Title: A Proposed Integrated Data Collection, Analysis and Sharing Platform for Impact Evaluation Author: Kipt, Andreas, Brunette, Waylon, Kellerstrass, Jordon, Podolsky, Matthew, Rosa, Javier, Sundt, Mitchell, Wilson, Daniel, Borriello, Gaetano, Brewer, Eric, Thomas, Evan A. Year: 2015 Global poverty reduction efforts value monitoring and evaluation, but often struggle to translate lessons learned from one intervention into practical application in another intervention. Commonly, data is not easily or often shared between interventions and summary data collected as part of an impact evaluation is often not available until after the intervention is complete. Equally limiting, the workflows that lead to research results are rarely published in a reproducible, reusable, and easy-to-understand fashion for others. Information and communication technologies widely used in commercial and government pro- grams are growing in relevance for international global development professionals and offer a potential towards better data and workflow sharing. However, the technical and custom nature of many data management systems limits their accessibility to non-ICT professionals. The authors propose an end-to- end data collection, management, and dissemination platform designed for use by global development program managers and researchers. The system leverages smartphones, cellular based sensors, and cloud storage and computing to lower the entry barrier to impact evaluation. Title: A Proposed Integrated Data Collection, Analysis and Sharing Platform for Impact Evaluation Author: Kipt, Andreas, Brunette, Waylon, Kellerstrass, Jordon, Podolsky, Matthew, Rosa, Javier, Sundt, Mitchell, Wilson, Daniel, Borriello, Gaetano, Brewer, Eric, Thomas, Evan A. Year: 2015 Global poverty reduction efforts value monitoring and evaluation, but often struggle to translate lessons learned from one intervention into practical application in another intervention. Commonly, data is not easily or often shared between interventions and summary data collected as part of an impact evaluation is often not available until after the intervention is complete. Equally limiting, the workflows that lead to research results are rarely published in a reproducible, reusable, and easy-to-understand fashion for others. Information and communication technologies widely used in commercial and government pro- grams are growing in relevance for international global development professionals and offer a potential towards better data and workflow sharing. However, the technical and custom nature of many data management systems limits their accessibility to non-ICT professionals. The authors propose an end-to- end data collection, management, and dissemination platform designed for use by global development program managers and researchers. The system leverages smartphones, cellular based sensors, and cloud storage and computing to lower the entry barrier to impact evaluation. Close

• 9. [Article] Development of 3D Accelerometer Testing System

  Accelerometers are used in numerous industries including aircrafts and missile navigations systems, rotary machines, and electronic devices such as tablets, cell phones, and cameras. Accelerometers of ...

  Citation × Citation Citation Abstract Copy Title: Development of 3D Accelerometer Testing System Author: Alsaedi, Mohammed Abbas Soudai Year: 2016 Accelerometers are used in numerous industries including aircrafts and missile navigations systems, rotary machines, and electronic devices such as tablets, cell phones, and cameras. Accelerometers of different purposes and specifications are being produced in large quantities. The large demand for accelerometers forces the need for accelerometer testing methodology that is more convenient and accurate. Inertial Micro-Electromechanical Systems Accelerometer (MEMS) require a series of tests that include physical stimuli. One of the key challenges is the cost associated with testing. Therefore, the accurate prediction of the sensor functions not only reduces the testing time but also more importantly contributes to reducing testing cost. Shaker accelerometer calibrators are widely used to test accelerometers. Shakers use sinusoidal acceleration input, and their testing acceleration range could be as small as 0.1 g1 and as high as 20 g. These devices test accelerometers in one axis at a time. In this study, the 3-D MEMS accelerometer testing method and system have been developed to reduce the testing time cycle significantly by testing 3D axes simultaneously. The theoretical study shows that an acceleration sensor is rotating about a fixed axis experiences tangential and normal accelerations. The objective of this project is to develop a testing methodology and equipment to test accelerometers along all three axes simultaneously over a range of ± 50 g while reducing testing time. These accelerations are related to the distance from the center of rotation and the angular velocity. The angular velocity can be controlled by the amount of the voltage that is given to the DC motor from the power supply which is adjusted by a speed controller. By varying either the angular velocity with the speed controller or varying the distance from the axis of rotation, it is possible to expose an accelerometer to the desired acceleration value. The equipment uses a rotating turntable where the center of the table marks the axis of the rotation. The accelerometer being tested was mounted at a known distance from the center of the table. The resulted normal and tangential accelerations were calculated from the angular velocity of the turntable and the position of accelerometer from the axis of rotation. A high precision encoder was used to determine the angular velocity of the turntable. The range of the angular velocity that can be measured accurately by the encoder affects the range of acceleration amplitude the system can be used to test. The encoder used can sense an angular velocity as low as 0.0144º/s. This corresponds to the normal acceleration value of 2.32 x 10-9 g. The accelerometer mounted on a turntable in a way that all three of its axes are exposed to the input acceleration to test an accelerometer in all three axes at the same time. A program written in LabVIEW operated the system and collected the test data. This program was able to collect acceleration readings along all three axes of the accelerometer with position and velocity information of the input motion. The collected data set were processed by MATLAB. This testing methodology provides a way to use multiple input accelerations unlike traditional accelerometer testing method. The test methodology developed in this study provides a way to use a constant acceleration input over a wide range (± 50 g). Its lowest acceleration range is 2.32 x 10-9 g. This reduces the time it takes to align the accelerometer in different axes and eliminates errors that may result during a manual repositioning of the accelerometer to align it in a different axis. Error models for MEMS accelerometer sensors have used Kalman filters to perform complete accelerometer sensor test. The accelerometer error model must be constructed, and the coefficients in the error equations must be determined. Therefore, Kalman filter in the analysis of visual motion has been documented frequently. The filter is constructed as a mean squared error minimizer. The purpose of filtering is to extract the required information from a signal, ignoring everything else. Title: Development of 3D Accelerometer Testing System Author: Alsaedi, Mohammed Abbas Soudai Year: 2016 Accelerometers are used in numerous industries including aircrafts and missile navigations systems, rotary machines, and electronic devices such as tablets, cell phones, and cameras. Accelerometers of different purposes and specifications are being produced in large quantities. The large demand for accelerometers forces the need for accelerometer testing methodology that is more convenient and accurate. Inertial Micro-Electromechanical Systems Accelerometer (MEMS) require a series of tests that include physical stimuli. One of the key challenges is the cost associated with testing. Therefore, the accurate prediction of the sensor functions not only reduces the testing time but also more importantly contributes to reducing testing cost. Shaker accelerometer calibrators are widely used to test accelerometers. Shakers use sinusoidal acceleration input, and their testing acceleration range could be as small as 0.1 g1 and as high as 20 g. These devices test accelerometers in one axis at a time. In this study, the 3-D MEMS accelerometer testing method and system have been developed to reduce the testing time cycle significantly by testing 3D axes simultaneously. The theoretical study shows that an acceleration sensor is rotating about a fixed axis experiences tangential and normal accelerations. The objective of this project is to develop a testing methodology and equipment to test accelerometers along all three axes simultaneously over a range of ± 50 g while reducing testing time. These accelerations are related to the distance from the center of rotation and the angular velocity. The angular velocity can be controlled by the amount of the voltage that is given to the DC motor from the power supply which is adjusted by a speed controller. By varying either the angular velocity with the speed controller or varying the distance from the axis of rotation, it is possible to expose an accelerometer to the desired acceleration value. The equipment uses a rotating turntable where the center of the table marks the axis of the rotation. The accelerometer being tested was mounted at a known distance from the center of the table. The resulted normal and tangential accelerations were calculated from the angular velocity of the turntable and the position of accelerometer from the axis of rotation. A high precision encoder was used to determine the angular velocity of the turntable. The range of the angular velocity that can be measured accurately by the encoder affects the range of acceleration amplitude the system can be used to test. The encoder used can sense an angular velocity as low as 0.0144º/s. This corresponds to the normal acceleration value of 2.32 x 10-9 g. The accelerometer mounted on a turntable in a way that all three of its axes are exposed to the input acceleration to test an accelerometer in all three axes at the same time. A program written in LabVIEW operated the system and collected the test data. This program was able to collect acceleration readings along all three axes of the accelerometer with position and velocity information of the input motion. The collected data set were processed by MATLAB. This testing methodology provides a way to use multiple input accelerations unlike traditional accelerometer testing method. The test methodology developed in this study provides a way to use a constant acceleration input over a wide range (± 50 g). Its lowest acceleration range is 2.32 x 10-9 g. This reduces the time it takes to align the accelerometer in different axes and eliminates errors that may result during a manual repositioning of the accelerometer to align it in a different axis. Error models for MEMS accelerometer sensors have used Kalman filters to perform complete accelerometer sensor test. The accelerometer error model must be constructed, and the coefficients in the error equations must be determined. Therefore, Kalman filter in the analysis of visual motion has been documented frequently. The filter is constructed as a mean squared error minimizer. The purpose of filtering is to extract the required information from a signal, ignoring everything else. Close

• 10. [Article] Stress Analysis for Chip Scale Packages with Embedded Active Devices under Thermal Cycling

  One of the main challenges in the electronics manufacturing and packaging development is how to integrate more functions inside the same or even smaller size. To meet the demand for higher integration, ...

  Citation × Citation Citation Abstract Copy Title: Stress Analysis for Chip Scale Packages with Embedded Active Devices under Thermal Cycling Author: Yeo, Hyunwook Year: 2014 One of the main challenges in the electronics manufacturing and packaging development is how to integrate more functions inside the same or even smaller size. To meet the demand for higher integration, the interest toward passive and active component embedding has been increasing during the past few years. One of the main reasons for the growing interest toward embedded active components, in addition to demand for higher packaging density, is the need for better electrical performance of the component assemblies. However, it is little known how embedded IC and passives affect the reliability of IC packaging. Solder joints have been used in the electronic industry as both structural and electrical interconnections between electronic packages and printed circuit boards (PCB). When solder joints are under thermal cyclic loading, mismatch in coefficients of thermal expansion (CTE) between the printed circuit boards and the solder balls creates thermal strains and stresses on the joints, which may finally result in cracking. Consequently, the mechanical interconnection is lost, leading to electrical failures (such as hard/intermittent open, parametric failure), which in turn causes malfunction of the circuit or whole system. When a die is embedded into a substrate, Young's modulus of the die is larger than one of the core of the substrate and the CTEs of the die is smaller than those of the substrate. As a result, mismatch in coefficients of thermal expansions (CTE) between the substrate with the embedded device and the solder balls may increase. In the present study, the stress of chip scale packages (CSP) with an embedded die under thermal cycling conditions is evaluated using the finite element method. The viscoplastic model for solders including matrix dislocation mechanism and grain boundary sliding model developed by Yi et al. (2002) is employed. Title: Stress Analysis for Chip Scale Packages with Embedded Active Devices under Thermal Cycling Author: Yeo, Hyunwook Year: 2014 One of the main challenges in the electronics manufacturing and packaging development is how to integrate more functions inside the same or even smaller size. To meet the demand for higher integration, the interest toward passive and active component embedding has been increasing during the past few years. One of the main reasons for the growing interest toward embedded active components, in addition to demand for higher packaging density, is the need for better electrical performance of the component assemblies. However, it is little known how embedded IC and passives affect the reliability of IC packaging. Solder joints have been used in the electronic industry as both structural and electrical interconnections between electronic packages and printed circuit boards (PCB). When solder joints are under thermal cyclic loading, mismatch in coefficients of thermal expansion (CTE) between the printed circuit boards and the solder balls creates thermal strains and stresses on the joints, which may finally result in cracking. Consequently, the mechanical interconnection is lost, leading to electrical failures (such as hard/intermittent open, parametric failure), which in turn causes malfunction of the circuit or whole system. When a die is embedded into a substrate, Young's modulus of the die is larger than one of the core of the substrate and the CTEs of the die is smaller than those of the substrate. As a result, mismatch in coefficients of thermal expansions (CTE) between the substrate with the embedded device and the solder balls may increase. In the present study, the stress of chip scale packages (CSP) with an embedded die under thermal cycling conditions is evaluated using the finite element method. The viscoplastic model for solders including matrix dislocation mechanism and grain boundary sliding model developed by Yi et al. (2002) is employed. Close