Reliability Research And Life Estimation Of COB-LED Package Under Composite Loadingslam

As a new solid-state cold light source,COB-LED is widely used in life.The working environment is complex such as high temperature,high humidity,thermal shock,over-current and vibration,which increases the probability of failure and affects the reliability of COB-LED chips.The failure mode and reliability of COB-LED chips in complex environments is one of the key points for further promotion of COB-LED chips.Therefore,this paper mainly tests and analyzes the reliability of COB-LED package in two complex environments of heat-vibration and heatcurrent.Based on the finite element theory,the thermal characteristics and structural characteristics of COB-LED chips under thermal-vibration combined load and thermo-electric double stress load were analyzed by Workbench.The accuracy of the 3D modeling and the reliability of the simulation analysis were verified by the comparison of the steady-state thermodynamic analysis and the junction temperature of the normal temperature lighting experiment.Through simulation analysis,it is found that the vulnerable parts of the chip under both loads are package lens,circuit layer and insulation layer,because the thermal conductivity and thermal expansion coefficient of the package lens,circuit layer and insulation material are very different from other packaging materials,which will cause the heat generated by the chip to be not well conducted,and thermal stress generated between the contact faces make the chip package lens and the substrate separate,the circuit layer deform,the surface of the insulation layer lift,and failure and damage occur,thereby affecting the package reliability of the COB-LED chip.By comparison,The displacement deformation and strain of the thermal-vibration simulation analysis are significantly larger than the thermal-current simulation analysis,which provides a theoretical basis for the subsequent experimental design.The changes of optical color parameters of COB-LED chips at different temperatures and vibration frequencies were studied.Firstly,a thermal-vibration composite loading experimental platform was built,and the vibration test and the thermo-vibration composite loading test were carried out.The luminous flux maintenance rate of the chip after vibration loading and thermalvibration composite loading experiment was compared,and the thermo-vibration composite loading was found.The luminous flux maintenance rate is smaller than the vibration-loaded luminous flux maintenance rate,which corresponds to the results of the simulation analysis,and the accuracy of the simulation analysis is verified.The thermal-current double stress accelerated aging test method of COB-LED chip was studied.In this paper,three sets of double stress aging accelerated life experiments under different current-temperature were designed.The parameters of the Eyring model were obtained by multiple linear regression.The data was processed by MATLAB software and the service life under normal working conditions was estimated.The life of four different stress levels predicted by the Eyring model is used as the raw data of the gray model to construct a discrete model of the grey system theory and predict the life under normal working conditions.Compared with the two methods,the gray prediction has higher life accuracy.In this paper,the package reliability and the electro-thermal double stress lifetime characteristics of COB-LED chip under thermal-vibration composite load are studied,which provides experimental basis and theoretical basis for COB-LED chip package reliability in complex environment,enabling COB-LED more widely used in various fields.