Correlation Law Between Optical Performance Attenuation And Component Degradation In LED Package And It’s Reliability Evaluation Analyse

LED lighting products has attracted worldwide attention for its excellent optical efficiency.At present,there are some problems in reliability research of LED package,such as the effect of component degradation on optical performance is unclear and color shift does not take into account in reliability evaluation.It is of great scientific value to considering the failure mode of color shift to study the effect of sub-components on package reliability is of great scientific value.In this paper,on one hand,based on the LED package structure,accelerated tests were designed to explore the correlation law between the optical performance of LED package and component degradation.On the other,an LED package assessment model was established to evaluate the effects of different components and failure modes on package reliability and reliability life.Specific research contents and conclusions are as follows:(1)The thermal stress limit(TSL)of LED package accelerated test was explored to obtain reasonable accelerated test conditions.Based on the mutation of degenerate mechanism,the high acceleration Step-Up Stress testing was carried out and the TSL of LED package acceleration test was analyzed.The results show that the TSL of white LED package acceleration test is between 105 and 110℃,and that of blue is between 110 and 115℃.(2)The effects of degradation of LED package components on the optical properties of packaging devices were experimentally studied,and the contribution rate of components to package degradation was quantified.Design and conduct comparative analysis accelerated reliability test.Through the lens-free chip degradation data,the light source degradation data of isolated lens test and the comparison of white and blue LED package degradation data,the attenuation law and model of chip,packaging lens and phosphor degradation on package performance were obtained.Further,through the effect model of LED package components,the degradation contribution rate of LED package components and its degradation mechanism were analyzed.The results show that degradation of each LED package component(including chip,lens and phosphor)will lead to LED package luminous attenuation and color shift.The influence of LED package components on package luminous and color shift can be expressed by exponential model and linear model respectively.The main components that caused the degradation of LED package optical performance were lens and phosphor.The decrease of lens transmittance and phosphor’s optical conversion efficiency is an important failure mechanism that causes the decrease of luminous and color shift of LED package.(3)Combined with the degradation contribution rate of package components,the reliability and reliability life of LED package and package components were evaluated by modeling.Based on the theory of competing failure and the reliability distribution test method,the reliability evaluation model of LED package competing failure was established.Based on the accelerated model and distributed test method,the reliability curve and reliability life of each package component in each failure mode were calculated.Based on the acceleration model and the distribution test method,the reliability curve and the reliability life of each LED package components under different failure modes were calculated.Finally,the results of LED package reliability were obtained by the system reliability evaluation method.The results show that the suitable reliability distribution model for LED package luminous failure and color shift failure are lognormal distribution and normal distribution,respectively.The main failure mode of LED package is color shift failure,ignoring the color shift failure will lead to a large error in reliability assessment of LED package.The median life of white LED package and blue LED package at normal temperature is 12359 h and 15167 h,respectively.In this paper,the correlation law between optical performance attenuation and component degradation of LED package was studied in depth,and the reliability modeling analysis was carried out.The research results have good reference value for the design,manufacturing and reliability evaluation of LED products.