The fatigue life of solder balls in Ball Grid Array (BGA) packages of a Printed Circuit Board (PCB) assembly is a key factor that influences the reliability of electronic devices. This study explores three novel methods to enhance the fatigue life of the PCB assembly with BGA packages, focusing on stress reduction techniques in solder balls under random vibration.The numerical analysis of the PCB assembly examined stress distributions and identified optimal design strategies to improve resistance to fatigue under random vibration. The findings demonstrate that strategic positioning of BGA packages, the use of additional supports, and modifications to PCB assembly can significantly reduce stress on solder balls, thus extending their fatigue life 8 to 10 times that of the existing design.
With the growing demand for high-safety and high-energy-density energy storage systems, all-solid-state lithium batteries (ASSLBs) have attracted extensive attention due to their excellent safety and potential high performance. Among them, the solid electrolyte is a key component. This study systematically investigates the effects of Li3AlF6 as a sintering aid on the sintering behavior, crystal structure, microstructure, and electrochemical performance of LLNO (Li0.25La0.25NbO3) ceramics. LLNO ceramic samples with different Li3AlF6 doping levels (0-8 wt.%) were prepared via a solid-state reaction method and sintered at 1050 degrees C and 1100 degrees C. The samples were characterized by XRD, SEM, AC impedance spectroscopy, and DC polarization testing. The results indicate that Li3AlF6 significantly reduces the sintering temperature of LLNO and promotes the densification process. However, excessive doping (8 wt.%) leads to the formation of impurity phases such as AlF3, increases grain boundary resistance, and reduces ionic conductivity. The sample with 5 wt.% Li3AlF6 sintered at 1050 degrees C exhibits the best overall performance: an ionic conductivity of 2.08 & times; 10(-6) S & centerdot;cm(-1) and an activation energy of 0.340 eV. Although its conductivity is slightly lower than that of pure LLNO (4.12 & times; 10(-6) S & centerdot;cm(-1)) sintered at 1100 degrees C, the introduction of Li3AlF6 provides a feasible route for low-temperature sintering, which is beneficial for future co-sintering integration with electrode materials.
The present work investigates the long-term relaxation behavior of anomalous photovoltage and photoelectret voltage in polycrystalline CdTe:Ag thin films prepared by oblique thermal evaporation.The relaxation kinetics were studied at room temperature under controlled photopolarization conditions. Experimental results reveal a pronounced two-stage relaxation behavior, consisting of a fast initial component with characteristic times of 2-4 min and a slow long-term component extending up to 25-45 min. The short-term relaxation is attributed to shallow trapping centers located near the band edges, while the long-term relaxation is governed by deep trapping centers associated with impurity-defect complexes involving silver atoms and cadmium vacancies. The observed metastable photoelectric states are explained within a bulk trapping model combined with near-surface band bending effects, which lead to asymmetric photocarrier separation and long-lived charge retention. The obtained results provide new insight into defect-controlled relaxation processes in CdTe:Ag thin films and demonstrate the crucial role of deep trapping centers in the formation and stability of photoinduced electric states. These findings are relevant for optimizing the photoelectric performance and long-term stability of CdTe-based photovoltaic and optoelectronic devices.
