Large strain with enhanced energy-storage and temperature stable dielectric properties in Bi0.38Na0.38Sr0.24Ti(1-x)(Mn1/3Nb2/3)xO3 ceramics

© 2020 Elsevier Ltd and Techna Group S.r.l. A series of novel Bi0.38Na0.38Sr0.24Ti(1-x)(Mn1/3Nb2/3)xO3 lead-free ceramics (BNST-100xMN) were designed and fabricated. The dielectric, ferroelectric, energy-storage, electrostrain properties, and impedance performance of these materials were systematically investigated. A large strain response under low driving electric field was obtained that benefits from the enhanced relaxor-to-ferroelectric phase transition. The optimum piezoelectric stain coefficient d33* of 930 pm/V (under 40 kV/cm) was achieved in BNST-1MN composition. The substitution by MN dopant gave rise to a homogeneous micro-morphology with small grains that gave rise to an enhanced high breakdown strength (BDS). Slim and slanted ferroelectric hysteresis was obtained by introducing a larger amount of MN, and hence the BNST-2MN ceramic exhibits a high energy-storage density of 1.30 J/cm3 at 110 kV/cm, accompanied with an excellent fatigue-free behavior. The dielectric response exhibited a stable high temperature dielectric property with low dielectric loss. These results indicate that BNST-100xMN ceramics are promising candidates for the actuator and energy storage applications

Thermal Induced Interface Mechanical Response Analysis of SMT Lead-Free Solder Joint and Its Adaptive Optimization.

From PubMed via Jisc Publications RouterHistory: received 2022-05-17, revised 2022-06-01, accepted 2022-06-06Publication status: epublishFunder: National Natural Science Foundation of China; Grant(s): 51975447Funder: National Defense Basic Scientific Research Program of China; Grant(s): JCKY2021210B007Funder: Wuhu and Xidian University Special Fund for Industry-University-Research Cooperation; Grant(s): XWYCXY-012021012Funder: Scientific Research Program Funded by Shaanxi Provincial Education Department; Grant(s): 21JK0721Funder: Natural Science Foundation of Shaanxi Province; Grant(s): 2020JQ290Surface mount technology (SMT) plays an important role in integrated circuits, but due to thermal stress alternation caused by temperature cycling, it tends to have thermo-mechanical reliability problems. At the same time, considering the environmental and health problems of lead (Pb)-based solders, the electronics industry has turned to lead-free solders, such as ternary alloy Sn-3Ag-0.5Cu (SAC305). As lead-free solders exhibit visco-plastic mechanical properties significantly affected by temperature, their thermo-mechanical reliability has received considerable attention. In this study, the interface delamination of an SMT solder joint using a SAC305 alloy under temperature cycling has been analyzed by the nonlinear finite element method. The results indicate that the highest contact pressure at the four corners of the termination/solder horizontal interface means that delamination is most likely to occur, followed by the y-direction side region of the solder/land interface and the top arc region of the termination/solder vertical interface. It should be noted that in order to keep the shape of the solder joint in the finite element model consistent with the actual situation after the reflow process, a minimum energy-based morphology evolution method has been incorporated into the established finite element model. Eventually, an Improved Efficient Global Optimization (IEGO) method was used to optimize the geometry of the SMT solder joint in order to reduce the contact pressure at critical points and critical regions. The optimization result shows that the contact pressure at the critical points and at the critical regions decreases significantly, which also means that the probability of thermal-induced delamination decreases

Thermal Induced Interface Mechanical Response Analysis of SMT Lead-Free Solder Joint and Its Adaptive Optimization.

From Europe PMC via Jisc Publications RouterHistory: ppub 2022-06-01, epub 2022-06-08Publication status: PublishedFunder: Natural Science Foundation of Shaanxi Province; Grant(s): 2020JQ290Funder: National Defense Basic Scientific Research Program of China; Grant(s): JCKY2021210B007Funder: Wuhu and Xidian University Special Fund for Industry-University-Research Cooperation; Grant(s): XWYCXY-012021012Funder: National Natural Science Foundation of China; Grant(s): 51975447Funder: Scientific Research Program Funded by Shaanxi Provincial Education Department; Grant(s): 21JK0721Surface mount technology (SMT) plays an important role in integrated circuits, but due to thermal stress alternation caused by temperature cycling, it tends to have thermo-mechanical reliability problems. At the same time, considering the environmental and health problems of lead (Pb)-based solders, the electronics industry has turned to lead-free solders, such as ternary alloy Sn-3Ag-0.5Cu (SAC305). As lead-free solders exhibit visco-plastic mechanical properties significantly affected by temperature, their thermo-mechanical reliability has received considerable attention. In this study, the interface delamination of an SMT solder joint using a SAC305 alloy under temperature cycling has been analyzed by the nonlinear finite element method. The results indicate that the highest contact pressure at the four corners of the termination/solder horizontal interface means that delamination is most likely to occur, followed by the y-direction side region of the solder/land interface and the top arc region of the termination/solder vertical interface. It should be noted that in order to keep the shape of the solder joint in the finite element model consistent with the actual situation after the reflow process, a minimum energy-based morphology evolution method has been incorporated into the established finite element model. Eventually, an Improved Efficient Global Optimization (IEGO) method was used to optimize the geometry of the SMT solder joint in order to reduce the contact pressure at critical points and critical regions. The optimization result shows that the contact pressure at the critical points and at the critical regions decreases significantly, which also means that the probability of thermal-induced delamination decreases