Validation of Forward Voltage Method to Estimate Cracks of the Solder Joints in High Power LED

Abstract

The Light Emitting Diode (LED) has many advantages compared to traditional lamps, such as a long lifetime, color rendering and energy saving. It requires good thermal management, since as the temperature increases, the lifetime decreases. Furthermore, the presence of cracks in the Solder Joint of an LED (SJL) compromises the correct dispersion of heat and causes the joint fatigue. This can lead to a decrease in the lifetime of the assembled LED. In this study, we validated that an SJL can be considered faulty if the Forward Voltage (Vf) acquired before and after thermal cycles increases by more than 2%. The voltage measurement method was validated by comparing the results with the techniques commonly used to evaluate the defects of a solder joint as the X-ray analysis and the metallographic section. The failure analysis results present the probability of failure and the lifetime of the SJL achieved by analyzing the data using the Norris–Landberg Model. The lifetime calculated over 1800 SJLs considered in the validation process is greater than 20 years for 95.9% of the tested LEDs.

Analysis of LED Lamps’ Sensitivity to Surge Impulse

“…With a proper failure distribution model, the failure rate, MTBF/MTTF, reliability and lifetime can be represented as a function of the parameters of the specific distribution model [7,8]. When estimating the MTBF/MTTF, the real factors that have a significant impact on the operating time are temperature, humidity in the surrounding of the lamp and change in voltage and current supplying LED in the lamp [9]. The fact that they have a measurable impact on the operation of lamps and the duration of their serviceability was presented in publications [9][10][11], where their selected types were tested under extreme conditions.…”

“…When estimating the MTBF/MTTF, the real factors that have a significant impact on the operating time are temperature, humidity in the surrounding of the lamp and change in voltage and current supplying LED in the lamp [9]. The fact that they have a measurable impact on the operation of lamps and the duration of their serviceability was presented in publications [9][10][11], where their selected types were tested under extreme conditions. The authors' experience shows that the declared and estimated durations of correct operation of LED lamps in many cases differ significantly from those observed in reality.…”

Challenges and New Trends in Power Electronic Devices Reliability

“…A reliability forecasting model that targeted the insulation of power components subjected to varying harmonics was presented in [12]. The model focused on the role played by low percentiles of time to failure, typically selected as the rated life in the framework of the modern probabilistic design of components, and it treated all the odd voltage harmonics from the fifth to the twenty-fifth; • LED lamps were investigated in [13,14]. The design of a new LED lamp concept, with attention to energy-saving, comfort and reliability purposes was presented in [13].…”

“…The lifetime of LED lamps was considered in [14], with a Norris-Landberg model that analyzed the probability of failure and the lifetime with reference to solder joint cracks. Over 1800 events were considered in the experimental validation process; • A review of the state of the art of the condition monitoring of power electronics devices is in [15].…”

Challenges and New Trends in Power Electronic Devices Reliability

“…On the basis of the outcomes, an improved topology was then developed to damp the surge energy and to mitigate the reverse recovery currents; • A reliability forecasting model that targeted the insulation of power components subjected to varying harmonics was presented in [12]. The model focused on the role played by low percentiles of time to failure, typically selected as the rated life in the framework of the modern probabilistic design of components, and it treated all the odd voltage harmonics from the fifth to the twenty-fifth; • LED lamps were investigated in [13,14]. The design of a new LED lamp concept, with attention to energy-saving, comfort and reliability purposes was presented in [13].…”