Wire Bonding Reliability Analysis Of High Power Light Emitting Diodes

As the fourth generation illuminant,light emitting diodes are widely used in indoor and outdoor illumination products because of the feature of long life,high efficiency,tiny volume and less heat generation.On contrast,high reliability leads to difficulty in testing.Thermal cycling and thermal shock accelerated test are the mostly used methods to test reliability of LED products,however it can't achieve online detection with expensive experiment cost and long test cycle.Firstly,the simulations of ball bonding used in LED products are done in this thesis.It includes the process of first wire bonding and comparison between copper and gold wire bonding.Explicit kinetics analysis software LS-DYNA is used to analysis whole process of wire bonding,the influence of different routes on wire pattern are investigated.In exploratory experiment,wire cracks on the neck of gold wire are found after decapsulation.This phenomenon is common within samples.Silicone used in packaging which has large coefficient of expansion has a great influence on the stress of wire during experiments.Thus,we investigated the mechanical and thermal properties by experiments and simulations to offer accuracy material parameters for the following thermal-structural coupling analysis of LED.Finally,stress concentration area located above the first bonding region is found by simulations and power cycling experiments.Life prediction is done by coffin-manson method which utilizes the data of simulation and results of power cycling test.Errors are controlled within 10 percent.A method combined Arrhenius and voltage accelerate model which used to draw accelerate factors is proposed to predict the life of LED.Low cost and satisfy precision mean significantly in reliability test of this industry.