The effect of solder alloys and surface finishes on the thermal cycling reliability of different electronic packages

Electronic products have become essential in modern society, powering everything from communication devices to critical infrastructure. Eutectic SnPb (Tin-Lead) solder has been used in electronics since the early days due to its excellent mechanical and electrical properties, making it a reliable choice for soldering applications. However, by the late 20th century, the harmful effects of lead were recognized, prompting a shift towards lead-free electronics. In response to these issues, the industry engaged in extensive research to find suitable alternatives, ultimately leading to the development of near-eutectic alloys based on tin (Sn), silver (Ag), and copper (Cu), known as SAC solder alloys. In everyday applications, solder joints endure thermal and mechanical stresses, causing the microstructure to evolve and the mechanical properties to degrade, ultimately leading to component failure. Over time, solder materials have shifted from traditional SnPb alloys to lead-free alternatives, later incorporating dopants like Bismuth (Bi), Antimony (Sb), and Nickel (Ni), which have been shown to enhance thermal and mechanical performance. While the literature has examined solder alloys and their function, the reliability of solder joints, particularly in an extensive context based on joint shape and surface finishes under thermal cycling conditions, remains unexplored. This research focuses on the reliability analysis of a series of electronic packages (CABGA, CVBGA, MLF, and SMR) subjected to thermal cycling using various solder alloys, and surface finishes. The study is designed to evaluate how these factors influence the characteristic life and failure mechanisms of solder joints for different components under harsh environmental conditions. A combination of traditional methods, such as Weibull analysis, along with advanced machine learning techniques, is employed to identify the most critical factors affecting reliability. Furthermore, a novel approach based on the Maximum Entropy Principle is developed and tested to create a more accurate predictive model. Moreover, this research develops and utilizes a new algorithm and software to monitor data in thermal cycling tests. This research aims to contribute to understanding solder joint reliability and provide improved models for predicting the lifetime of electronic components in industrial applications

Interfacial Damage Mechanics and Reliability at Multiple Electronic Interfaces under Harsh Environments

Advanced electronic assemblies are expected to perform with greater reliability in mission-critical applications under harsh environmental conditions, including high G-shock loads (up to 25,000 g), thermo-mechanical stresses, and long-term exposure to elevated temperatures (up to 150°C) and humidity in various defense, aerospace, and automotive underhood applications. The interfaces at critical junctions Potting/PCB, Resin/Copper, Chip/Underfill, and EMC/Substrate) degrade much faster than the bulk materials. It is necessary to understand these critical interfaces to predict the failure mechanisms, develop mitigation strategies, and optimize material selection for long-term reliability. Through this understanding, this dissertation embarked on a holistic investigation into the degradation of interfacial properties at board-level and component-level assemblies, with particular emphasis on potting material, PCB resin, underfill, and EMC interfaces. In this regard, the cohesive zone parameters used in the finite element simulations are determined by experimental test techniques and predictive modeling to investigate the interfacial fracture behavior. These efforts have been made to assess interface reliability, besides making predictions of failure modes due to harsh mechanical and thermal conditions, thereby helping design reliable electronics. The investigation starts with high-temperature-aged potting/PCB interfaces at 100°C and 150°C from 30 to 360 days and is tested under dynamic four-point bend loading. Stress intensity factors (KI & KII) and energy release rates in a steady state were measured at different aging intervals. The results reveal the degradation in interfacial properties with time due to thermal exposure and an increased tendency for delamination at extended durations of harsh environment exposure. The extracted fracture toughness parameters were used to calculate cohesive zone parameters and validation through finite element modeling. Additionally, shock load orientations at 0°, 30°, and 60° were also investigated, bringing out the sensitivity of the drop orientation to the reliability of potted electronic assemblies. The developed predictive finite element model was validated using experimental data for which high-speed imaging and 3D-Digital Image Correlation (DIC) techniques were employed. This predictive model successfully captured the behavior of potting/PCB interfaces, emphasizing the importance of cohesive zone parameters in understanding damage propagation in potted assemblies. Pad cratering failures at the resin and copper layer of the PCBs due to multiple reflow conditions have been discussed at board–level interfaces. The research characterizes the evolution of bulk resin properties and resin-copper interfacial strength through multiple reflow cycles and their interaction in determining the susceptibility of pad cratering. The interfacial fracture toughness was measured using four-point bend tests for various resin-copper-glass fiber combinations. The results show that multiple reflows degrade bulk resin properties, accelerating the loss of resin-copper interface strength and increasing pad cratering. A predictive regression model to identify material combinations offering superior pad cratering resistance was developed to improve board-level reliability. In flip-chip ball grid array (FCBGA) packages used in automotive applications, the primary focus was the delamination in chip/UF and EMC/substrate interfaces. The thermo-mechanical loads in automotive underhood environments, such as engine control units, advanced driver assistance systems, and safety and critical systems, could degrade the FCBGA interfaces, which have not been studied widely yet. The research reported here has investigated the monotonic and fatigue behavior of chip/UF interfaces after aging at 100°C and 150°C using bi-material specimens aged up to 360 days. The interfacial fracture toughness and Paris law constants are determined to characterize the interfacial strength. Results show that the properties of the cohesive zone evolve with aging, which plays a vital role in crack growth rate and long-term reliability. The presented research follows up with a predictive finite element modeling of the FCBGA packages, the cohesive zone parameters developed from the experiments. To model the interfacial fracture behavior of the FCBGA under thermal cyclic loading (-40°C to 125°C), cohesive elements were used in critical interfaces such as chip/UF, substrate/underfill, and TIM/Cu. The SDEG parameters show that the TIM/Cu interfaces have the highest degradation among the other FCBGA interfaces. These simulations offer predictive insights into possible failure mechanisms occurring during long-term operations. This dissertation embodies significant contributions toward understanding the mechanisms of interfacial degradation and failure in complex electronic assemblies under harsh environments. These findings give critical insights into the evolution of interfacial properties under mechanical and thermal loads, bringing out the importance of cohesive zone modeling for accurately predicting failure behavior. The predictive models developed in this work would go a long way toward being useful to designers and manufacturers for optimizing material selection to ensure electronic component reliability in such a harsh environment. The practical impact of this research is extensive in defense, aerospace, and automotive applications, where long-term electronics reliability is crucial. Herein, a state-of-the-art advance is made in investigating the interfacial fracture toughness and its predictive modeling to enable the development of next-generation electronics for extreme environmental conditions

Examining sleep extension as a feasible strategy for improving cardiometabolic health in emerging adults with habitual short sleep

The purpose of this dissertation was to determine the feasibility and efficacy of a two-week sleep extension intervention (increasing time in bed for 1 hour/night) to improve metrics of cardiometabolic health in emerging adults. In Aim 1 we sought to determine whether sleep extension (habitual/extension) in emerging adults who self-reported sleeping <7 hours/night improves in-laboratory resting brachial and central blood pressure and peripheral vascular function compared to a control group (habitual/habitual).We had 32 emerging adults complete a two-week sleep extension protocol where they increased time in bed by 1 hour/night. In Aim 2 the purpose was to determine whether sleep extension (habitual/extension) in emerging adults who self-reported sleeping <7 hours/night could lead to improvements in health behaviors such as hydration, appetite regulation and metabolic health assessed via 24-hour urine collection, an ad libitum breakfast, and a fasting blood draw compared to a control group (habitual/habitual). Individuals in the intervention (sleep extension) group showed an increase in sleep duration by 29.5 minutes and self-reported better sleep quality. In our cohort of emerging adults, we did not find the sleep extension intervention to influence any of the measures of blood pressure or vascular function. Furthermore, we found that sleep extension did not improve several of the health behaviors. In the present study we highlight that sleep extension is feasible in emerging adults, however, the efficacy for this intervention to improve health outcomes needs to be further tested in future studies and could specifically target emerging adults or other individuals with pre-existing risk factors for cardiometabolic diseases

Raccoon (Procyon lotor) Rabies in Alabama: Insights from Historical Trends, Oral Rabies Vaccine Bait Fate, and Spatial Epizootiology

Rabies epizootiology and management in Alabama have evolved significantly over the past two centuries, yet the influence of long-term ecological and historical factors on the effectiveness of oral rabies vaccine (ORV) programs remains poorly understood. This study synthesizes historical trends in rabies occurrence and management, emphasizing Alabama’s role as the westernmost extent of the raccoon rabies virus enzootic zone. Additionally, we investigated the effects of region, habitat, bait type, and climate on ORV bait uptake by raccoons (Procyon lotor). Our findings highlight substantial competition for baits from non-target species, particularly Virginia opossums (Didelphis virginiana), and a rapid decline in bait uptake over time as key factors limiting the success of current management efforts. These results underscore the need to tailor ORV strategies to Alabama’s unique historical context and diverse ecosystems to enhance efficiency, minimize redundancy, and reduce the economic burden associated with zoonotic disease control

Modeling hydrology and water quality in Moore's Mill Creek using the Storm Water Management Model (SWMM)

Urban development has long been known to be disruptive of the hydrological cycle and surface water quality. The change from natural vegetation to impervious materials tends to result in larger quantities of stormwater runoff because of lower surface infiltration, leading to flooding and stream bank erosion. Higher pollutant loads are also more likely and can lead to waterbody impairment for drinking water, recreation, and aquatic habitats. One of the most significant pollutants is sediment, which is especially common rapidly developing areas where construction site runoff is a greater issue. One such area is the Moore’s Mill Creek (MMC) watershed in Lee County, Alabama. Population growth in the cities of Auburn and Opelika over the past fifteen years has necessitated a reevaluation of the watershed management plan to address the persistent issue of sedimentation using best management practices (BMPs). Hydrological models are a valuable tool for assessing the effectiveness of BMPs by representing hydrologic and water quality behavior within a watershed. The Storm Water Management Model (SWMM) is one of the oldest and most popular of these models. Though it is ordinarily used for urban stormwater management, SWMM has hydrologic and water quality capabilities that allow it to be applied to a variety of watersheds. Stream flow data and water samples were collected across the northeast portion of the MMC watershed to calibrate hydrographs and total suspended solids pollutographs for several rain events. Sensitivity analyses were conducted to better understand the individual and combined effects of hydrologic and water quality parameters on model results. The results showed the significance of aquifer and surface storage representation to stream hydrograph accuracy and total outflow volume, as well as to pollutograph recession curves. Accounting for groundwater also improved modeled hydrograph recession curves compared to previous research in the watershed

Using Her Words: Marriage in Twentieth Century Advice Columns

This thesis examines the evolution of popular perceptions of marriage in the United States during the mid twentieth century through advice columns. It argues that the point at which a marriage was considered salvageable drastically shifted between the 1940s and 1950s, which directly correlated with the social markers of success within a relationship. In the 1940s, a marriage was considered successful if the couple was happy and a divorce, though not ideal, could be an option for an unhappy couple. In the 1950s, a marriage was considered a success if the couple remained married for their entire lives, even if they would prefer to be separated. This thesis focuses on “If I Were In Your Shoes,” written by self-proclaimed psychic Gene Dennis for The Seattle Star from 1940 to 1944, and the first four years of “Can This Marriage Be Saved?” which ran in The Ladies’ Home Journal using accounts of the counseling sessions conducted by the American Institute of Family Relations

Forest Structure, Composition, Basal Growth, Hydrology, and Salinity in the Lower Mobile-Tensaw Delta

Coastal wetlands, particularly tidal freshwater forested wetlands (TFFWs), are among the most vulnerable ecosystems to climate change. They face direct impacts from global sea level rise and extreme weather events, compounded by indirect anthropogenic disturbances like urban development and hydrologic alterations. This research investigates the ecological responses of TFFWs to tidal influence and salinity intrusion within the Mobile-Tensaw River Delta (MTRD), an internationally significant deltaic region along the northern Gulf of Mexico. This work is intended to serve as a baseline for current forest conditions and an initial indication of resilience within the study area. This study consisted of vegetation surveys (n = 47) conducted in forested wetland stands across a tidal gradient. Results revealed five distinct canopy communities that corresponded with river distance to Mobile Bay and plot elevation. Multivariate analyses highlighted a strong response of tidal influence on forest composition and structure, indicating community-level sensitivity to estuarine influences. Forested areas located near Mobile Bay exhibited lower basal area, species richness, higher shrub stem density, and a higher proportion of visually stressed canopy trees. To assess species-level responses, over 50 Taxodium distichum (bald cypress) trees were monitored over two growing seasons using low-cost dendrometer bands and continuous hydrologic measurements. Results showed that inundation was the best determiner of tree basal growth, and that, surprisingly, floods with low salinity levels also acted as a subsidy for basal growth across the tidal gradient. However, tidal influence did not account for differences in growth among our long-term forest transects (n = 8). In addition, during the monitoring period, a major saltwater intrusion event following Hurricane Francene in September 2024 was documented near the end of the study. Although this event was near the end of the growing season, it further emphasized the vulnerability of these forests to extreme climatic events. Together, these findings demonstrate how tidal hydrology and salinity gradients influence forest structure, composition, and productivity in TFFWs. This research underscores the importance of site-specific monitoring to inform adaptive management and conservation strategies in the face of accelerating climate change. As sea levels continue to rise and saltwater intrusion events become more frequent and intense, understanding the nuanced responses of coastal forest communities will be critical for land managers looking to predict ecosystem trajectories and mitigate coastal forest loss

Evaluation of the effects of photonic decontamination on reduction of Salmonella and Campylobacter and a comparative transcriptomics analysis following its application on Salmonella Infantis

Recently, there has been an increase in research into new methods responding to the unsuccessful efforts in reducing foodborne pathogen infections associated with poultry products such as Salmonella and Campylobacter. With the looming concern of antibiotic-resistant bacteria surviving past the current antimicrobial interventions used in poultry processing along with consumer concerns and environmental impacts of the overuse of chemicals on poultry products, novel antimicrobial intervention methods have become an increasingly popular topic of conversation. The first chapter reviews published literature on these topics. Developing an effective method for reducing foodborne pathogens in animal products while preserving meat quality and application efficiency is an important topic of research. To address this, in the second chapter, we evaluated the efficacy of photonic decontamination on whole chicken wings and tenders inoculated with Salmonella and Campylobacter. Treatments included evaluating photonic decontamination alone, the inclusion of chemical antimicrobial dips with and without photonic decontamination treatment, and photonic decontamination on multiple parts simultaneously. Photonic decontamination alone and in combination with chemical dips was able to significantly reduce Salmonella and Campylobacter on both wings and tenders. Additionally, in the third chapter, we focused on elucidating the molecular basis of photonic decontamination using comparative transcriptomics analysis of Salmonella Infantis. Comparisons were made between a 100-voltage treatment and no treatment, a 200-voltage treatment and no treatment, and between a 100-voltage treatment and a 200-voltage treatment. Our results identified the list of differentially expressed genes with identified roles relating to response to light-induced cell damage, oxidative stress response, transcriptional regulation following pulsed light exposure, and stress resistance

A Cognitive Hierarchical Framework for Multivehicle Collision-Free Traffic Management of Unregulated Intersections

Autonomous vehicles are becoming increasingly popular, requiring efficient and reliable methods for trajectory generation and path planning. A common approach is to convert the original continuous-time optimization problem into a discrete-time parametric optimization problem, but consider only a set of control/action variables, which can limit the feasibility and generality of the generated trajectories. To address these limitations, this thesis proposes an approach to autonomous collision-free vehicle trajectory optimization using model predictive control (MPC) with a continuous range of control inputs. The considered formulation enables the computation of more accurate and dynamically feasible paths for autonomous vehicles. A key challenge in path planning of autonomous vehicles is to account for not only the presence of other vehicles, but also their trajectories. More specifically, the other vehicles must be treated as dynamic obstacles and collision-free trajectories have to be generated. Naturally, one has to take into account and model vehicle-to-vehicle interactions and incorporate such interactions, in terms of state path constraints, as part of the formulation of trajectory optimization problems. We leverage Cognitive Hierarchy Theory, specifically using level-$k$ game theory, to predict the behavior of other vehicles/agents, which affects their trajectories. This framework provides a structured way to anticipate interactions and make informed decisions for designing collision-free trajectories. For testing the proposed framework, an unregulated crossroad was simulated with two vehicles approaching it at the same time. The conducted experiments were split into two sets of scenarios: with and without the level estimator enabled, which allows one vehicle to change the reasoning depth over the course of simulations. Numerical results demonstrate that the proposed approach is both feasible and effective in capturing realistic vehicle interactions and in generating collision-free trajectories. The level-k game-theoretic modeling enhances the decision-making capabilities of autonomous vehicles, leading to safer and more efficient navigation. These findings highlight the potential of expanding the set of control actions in improving autonomous vehicle trajectory planning

Colostrum-Derived Immunity Reduces Detection of Calves Persistently Infected (PI) with Bovine Viral Diarrhea Virus (BVDV) by Common Diagnostic Tests

Diagnosis, detection, and elimination of persistently infected (PI) cattle with bovine viral diarrhea virus (BVDV) is the cornerstone of control programs for BVDV. This study investigated the most reliable tests, sample types, and timing for detecting BVDV in PI calves after colostral consumption. Thirteen pregnant heifers were infected with BVDV1b to produce PI calves. Ten PI calves were born clinically normal. Two age-matched calves were used as a control group. Serum samples, nasal swabs, and ear notches were collected from before colostrum intake to 28 days after birth. Antigen-capture ELISA, RT-qPCR, virus isolation, and the IDEXX SNAP test were performed. Colostrum-derived BVDV1b antibodies suppressed BVDV detection in all sample types during the first week of age, causing false negatives. After 7 days of age, detection of BVDV using ear notch samples with RT-qPCR, ACE, or IDEXX SNAP was highly reliable, while serum-based and virus isolation methods were the least effective