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This study investigates the degradation mechanism in the power conversion efficiency of Si solar cells under thermal cycling (TC) and explores mathematical models of the degradation curve. TC experiments were conducted for two sets of solar modules. A novel method was introduced and implemented to extract the parameters in the diode circuit model of solar cells using all experimental data points in the I-V curve. It was observed that both the series resistance and reverse saturation current increased after TC. When evaluating the increases using linear, exponential, and logarithmic functions, it was expected that the power output decreases to a range of 82 to 93 % after 5,000 TC if only the series resistance increases, while in the range of 86 to 94 % after 5,000 TC if only the reverse saturation current increases. The power drop mechanism of solar cells under TC can be attributed to the cracking of the solder layer due to TC, which increases not only the series resistance but also the reverse saturation current, resulting in drops in the power output of the solar cell. A goodness-of-fit analysis reveals that a stretched exponential model best represents the power drop function of a solar cell under TC.

This paper explores nonlinear cumulative damage models applied to Prognostics and Health Management in electronic systems, with a focus on solder joint reliability under variable vibrations. Several cumulative damage models, including the total strain energy density model, are investigated to address the limitation of Miner’s rule. The State-of-Damage (SoD) concept is introduced as a pivotal metric for evaluating Prognostics and Health Management performance within each model. A novel SoD definition with a scale factor is proposed to balance linearity and exponential behavior, meeting the demands of real-time monitoring. Furthermore, by calculating Remaining Useful Life (RUL) using the SoD metric, the RUL predictions from Miner’s rule and total strain energy density model with the scale factor are compared. The results reveal that the total strain energy density model, enhanced with the scale factor, outperforms Miner’s rule in accurately predicting SoD and RUL. This study advances Prognostics and Health Management methodologies by introducing an innovative SoD concept with a scale factor, resulting in enhanced accuracy for both SoD and RUL predictions. This innovation holds the potential for more reliable electronic systems under variable loading conditions.

In solar cell modules, thermal cycling stresses can cause cracking in the ribbon wire, leading to an increase in series resistance and a drop in the power output of the module. Quantitative analysis was conducted to study the increase in series resistance, considering two cracking models: continuous and random. In the continuous model, it was expected that if all the ribbon wires on the front side of the module cracked, the current would decrease linearly from 0 to 100%, and the series resistance would increase exponentially to infinity. In the random crack model, the current dropped slowly, and the series resistance increased less compared with that in the continuous one. A mathematical model based on the bypass mechanism of the currents was proposed to explain the differences between the two models. The study found that cracking in the solder layer under thermal cycling can be described by a combination of continuous and random models, which can represent the upper and lower levels of the series resistance increase. When the solar cell power dropped to 80%, the increase in series resistance was expected to be in the range of 200 to 250% using the continuous and random models, respectively.

Recent growth of the insulated gate bipolar transistor (IGBT) module market has been driven largely by the increasing demand for an efficient way to control and distribute power in the field of renewable energy, hybrid/electric vehicles, and industrial equipment. For safety-critical and mission-critical applications, the reliability of IGBT modules is still a concern. Understanding the physics-of-failure of IGBT modules has been critical to the development of effective condition monitoring (CM) techniques as well as reliable prognostic methods. This review paper attempts to summarize past developments and recent advances in the area of CM and prognostics for IGBT modules. The improvement in material, fabrication, and structure is described. The CM techniques and prognostic methods proposed in the literature are presented. This paper concludes with recommendations for future research topics in the CM and prognostics areas. [ABSTRACT FROM AUTHOR]

Application of electronic devices on automotive vehicles keeps increasing, and adoption of ball grid array (BGA) package is inevitable in the industry. Vibration loading to a vehicle provides another hazardous stress to the BGA assembly in addition to thermal one. In this paper, random vibration test on a daisy-chained BGA assembly is conducted with a real-time monitoring of resistance. BGA assemblies with leaded and lead-free solders are tested at once in the test. The changes of resistance before the occurrence of failure are investigated and a precursory resistance pattern before the failure of BGA assemblies is identified at the both solder types. Analyses on the failure locations confirm the localized failures on the BGA ball matrix. To investigate the generating mechanism of the precursory resistance pattern in the BGA assemblies, a numerical model of the mechanism is suggested and experimentally demonstrated. Based on the studies, a noble design of BGA assembly is suggested for the implementation of prognostics and health monitoring in vibration environment. [ABSTRACT FROM PUBLISHER]

Small induction motors, generally defined in industry as those under 100 W, are widely used, e.g., in home appliances and factory automation. Their failure could cause serious problems and increase costs, and so their reliability should be maximized. Degradation of electrical insulation is one of the main causes of failure [1]?[4]. [ABSTRACT FROM PUBLISHER]