Accelerated Life Test And Failure Analysis Of LED Plate COB Light Source

In the paper,LED plate COB light source was taken as the object of the study.Accelerated life test was designed to project life of the light source. Blackened failure and delamination failure that occur on plate COB light source in the application was analyzed,and the improvement measures were put forward.. The main work and conclusions are as follows:Firstly, accelerated life test theory of LED including accelerated life test concept and test program was elaborated.And life theory and life theoretical model used for accelerated life test was highlighted.Secondly, accelerated life test was designed.The test results show that optical properties of the light source were degraded gradually with aging time under constant current stress accelerated conditions.But these properties were still stable, and it means no catastrophic failures appeared. The average life of the light source calculated based on test data and life theory is about 21591 hours.Furthermore, a process of blackened failure test and analysis of LED lighting source was put forward to study the blackened phenomenon near the chip surface of plate COB light source.Scanning electron microscopy(SEM) and other detecting instrument were used to achieve that the position of the black zone was phosphor glue.X-ray photoelectron spectroscopy was used to analyze the change of chemical bonds before and after phosphor glue was blackened.Then the essence of blackened failure from the material level was determined that C=C bond and C=O bond in silicone was broken and the free C enriched on the surface of the chip, in other words,the silicone was carbonized.And the improvement measure that reduce the light source power to 0.8W was put forward.Finally, according to the theoretical analysis, the most important factor of delamination failure was welding thermal process and working thermal process.Bymeans of the finite element simulation,the effect of thermal process on delamination failure was researched. Results show that the welding thermal process had a greatinfluence on delamination.So light source connectivity solutions need to be optimized.The effect of delamination failure on heat dispersion of plate COB was researched. Results show that delamination had little impact on heat dispersion of it due to structural advantage of self-cooling.