Multichannel Online Lifetime Accelerating and Testing System for Power Light-Emitting Diodes

The accelerated life testing is a common tool to achieve lifetime prediction and reliability analysis for light-emitting diodes (LEDs). Currently, all popular accelerated methods, either offline or online, employ a large volume, energy-consuming temperature chamber, which will cause the instruments inside worse, and the methods are usually incapable of controlling the junction temperature online. In this paper, we propose a multifunctional online system that controls the temperature of heat sink directly by a heating plate integrated to electrical-current-stress fixture. The combinations of spectrometer with optical multiplexer and current source with electrical matrix switch are adopted to fulfill the comprehensive real-time testing of LEDs, including optical, electrical, colorimetric, and thermal properties. In particular, junction temperature is monitored and controlled online by pulse-voltage method, which raises the accuracy and reliability of lifetime analysis and prediction. A new file format-HDF5 is applied to process huge quantities of experimental data, which are helpful to analyze the failure mechanism.