Experimental strain energy density dissipated in SAC305 solder joints during different thermal cycling conditions using strain gages measurements

International audienceDespite being widely investigated for the last two decades, solder joints thermomechanical durability assessment remains a major concern for industries wishing to switch from lead-based (SnPb) to lead-free electronics. Amongst the variety of lead-free solder compositions, 96.5Sn-3.0Ag-0.5Cu (SAC305) solder alloy has become the preferred substitute to classic SnPb solders. However, unlike SnPb assemblies, the return on experience is limited and the microstructure is very different for SAC305 solder joints. The use of SAC305 solder paste requires to understand the mechanical and fatigue behaviors of the soldered interconnects. This paper presents the experimentation based on strain gages measurements, allowing the determination of the shear stress-strain response of SAC305 solder joints subjected to different thermal cycling conditions. The area of the experimental shear strain-stress hysteresis loops gives the values of the strain energy density corresponding to each thermomechanical loading. The finite element modeling of the test assembly showed a good correlation between experimental and numerical strain energy densities. The experimental shear strain-stress curves also provide the necessary data to derive SAC305 solder joints constitutive laws

Faculty of Engineering and Design. Research Review

STUDENTS AND ACADEMICS - This publication introduces you to the department or school and then each faculty member’s research areas, research applications, and their most recent activities. A comprehensive index can be found at the back of this publication to help guide you by specific areas of interest, as well as point out interdisciplinary topics and researchers. INDUSTRY LEADERS - This publication includes information regarding specific facilities, labs, and research areas of departments and schools as well as individual faculty members and researchers. A comprehensive index can be found at the back of this publication to help guide you by specific areas of interest, as well as point out interdisciplinary topics and researchers

Integrated sensors for process monitoring and health monitoring in microsystems

This thesis presents the development of integrated sensors for health monitoring in Microsystems, which is an emerging method for early diagnostics of status or “health” of electronic systems and devices under operation based on embedded tests. Thin film meander temperature sensors have been designed with a minimum footprint of 240 m × 250 m. A microsensor array has been used successfully for accurate temperature monitoring of laser assisted polymer bonding for MEMS packaging. Using a frame-shaped beam, the temperature at centre of bottom substrate was obtained to be ~50 ºC lower than that obtained using a top-hat beam. This is highly beneficial for packaging of temperature sensitive MEMS devices. Polymer based surface acoustic wave humidity sensors were designed and successfully fabricated on 128° cut lithium niobate substrates. Based on reflection signals, a sensitivity of 0.26 dB/RH% was achieved between 8.6 %RH and 90.6 %RH. Fabricated piezoresistive pressure sensors have also been hybrid integrated and electrically contacted using a wire bonding method. Integrated sensors based on both LiNbO3 and ZnO/Si substrates are proposed. Integrated sensors were successfully fabricated on a LiNbO3 substrate with a footprint of 13 mm × 12 mm, having multi monitoring functions for simultaneous temperature, measurement of humidity and pressure in the health monitoring applications

Index to NASA Tech Briefs, 1975

This index contains abstracts and four indexes--subject, personal author, originating Center, and Tech Brief number--for 1975 Tech Briefs

2020 NASA Technology Taxonomy

This document is an update (new photos used) of the PDF version of the 2020 NASA Technology Taxonomy that will be available to download on the OCT Public Website. The updated 2020 NASA Technology Taxonomy, or "technology dictionary", uses a technology discipline based approach that realigns like-technologies independent of their application within the NASA mission portfolio. This tool is meant to serve as a common technology discipline-based communication tool across the agency and with its partners in other government agencies, academia, industry, and across the world

Life Consumption Monitoring for Electronics

Life consumption monitoring is a method to assess product's reliability based on its remaining life in a given life cycle environment. The life consumption monitoring process involves continuous or periodic measurement, sensing, recording, and interpretation of physical parameters associated with a system's life cycle environment to quantify the amount of degradation. This thesis explains a life consumption monitoring methodology for electronic products, which includes failure modes, mechanisms and effects analysis (FMMEA), virtual reliability assessment, monitoring product parameters, data simplification, stress and damage accumulation analysis and remaining life estimation. It presents two case studies to estimate the remaining life of identical circuit card assemblies in an automobile underhood environment using the life consumption monitoring methodology. Failure modes, mechanisms, and effects analysis along with virtual reliability assessment is used to determine the dominant failure mechanism in the given life cycle environment. Temperature and vibration are found to be the environmental factors, which could potentially cause malfunction of the circuit card assembly through solder joint fatigue. Temperature sensor and accelerometers are used along with a data logger to monitor and record the environmental loads during the experiment. A data simplification scheme is used to make the raw sensor data suitable for further processing. Stress and damage models are used to estimate the remaining life of the circuit card assembly based on the simplified data. Performances of the test board assemblies are monitored through resistance monitoring. The life cycle environment and results for the case studies are compared with each other. The estimated results are also compared with experimental life results