Packaging Failure Analysis Of LED Self-cooling COB Light Source

In the paper,LED self-cooling COB light source was taken as the object of the study.Wire fracture of gold and delamination failure and blackened failure that occur on self-cooling COB light source were analyzed,and the improvement measures were put forward.The main work and conclusions are as follows:First of all,this paper introduced the structure design of LED self-cooling COB light source,standardized the packaging process,and a brief introduction to the failure analysis was presented.Secondly,according to the research and analysis of the phenomenon of self-cooling COB light source wire fracture.The X-Ray and other detecting instrument were used to achieve that the position of wire fracture was the first bonding point.By means of the finite element simulation,the effect of thermal process on wire fracture was researched.Compared to the thermal of the work process,the effect of silicon the resin curing thermal process for the light source of bonding wire was relatively large,easy to wire fracture of gold.And by using the method of orthogonal experiment to stress on the structure parameters of self-cooling COB light source to optimize the field simulation approach,which can obtain the optimal structure parameters of gold bonding scheme,in order to improve the reliability of bonding quality of COB light source.Furthermore,according to the theoretical analysis,the most important factor of delamination failure was working thermal process.By means of the finite element simulation,the effect of thermal process on delamination failure was researched.Results showed single chip edge would produce stress concentration.Thermal coupling leaded to high temperature of the middle chips on the COB light source,the middle chips thermal stress was too large.Large thermal stress may be greater than the adhesion between the chip and the fluorescent glue and lead to stratification.The choice of silicone resin and solid crystal interconnect material had a great influence on the thermal stress distribution on the surface of the chip.Finally,the fluorescent glue surface of the part of the LED chip COB appeared black material,which effected the light conversion and extraction.Field emission scanningelectron microscopy(FESEM)was used to observe the morphology of the fluorescent layer,by X-ray photo electron spectrometer(XPS)the fluorescent layer composition and chemical bonding were analyzed.The results showed that C=C and C=O by a large number of decomposition,the formation of free C and O elements,the formation of a black substance accumulation on the surface of the chip.