The Research Of Wire Bonding Problem Of Lateral Chip

According to the chip light-emitting area on the front or back of the electrode,LED can be divided into lateral chip and flip chip.There are many differences in packaging process between them,lateral chip need wire bonding,flip chip do not need wire bonding.Compare with lateral chip,flip chip has the advantages of higher luminous efficiency and easier packaging process,flip chip is the direction of LED development.However,as the technology of flip chip is relatively complex,it is not stable at present and needs to be further optimized and improved,so lateral chip is still the mainstream product in the market.Wire bonding problems suffer a high ratio in LED failures base on some statistics analysis,so in this paper,I did some research of wire bonding problems of lateral LED products,mainly from three perspectives,chip process,wire bonding process and packaging process.through the analysis of specific case to introduce how to identify the failure mechanism of different failure samples,then the control plan was put forward in order to reduce this kind of failure,which is very important to improve the reliability of the LED.The following phenomenon are analyzed in this paper: 1.optimize electrode structure,remove the CBL and ITO layer under the chip electrode,the electrode would not be broken by wire bonding pressure.2.We can know how to select a suitable size capillary according to electrode size and wire diameter after study the influence of different size of capillary on wire bonding quality.3.About the chip electrode get “glue gas contaminate” after chip fix baking process,we did some experiment and research,find that slight organic pollution on the surface of the electrode may induce subsequent " glue gas contaminate ",keep electrode clean is a direct solution,in addition,control baking process and ion cleaning also can avoid “glue gas contaminate”.4.Base on comparison experiment,increase the hardness of the chip fixation glue also can improve wire bonding quality.5.The thermal expansion of packaging adhesive can exert a pulling force on wire which may break the wire,so the thermal expansion property of packaging adhesive should be controlled to ensure wire bonding quality.6.A series of simulation experiment was performed to prove that poor gas tightness of packaging adhesive can bring in foreign water vapor which leads to the electrochemical reaction of the chip in the water environment,leading to electrode peeling issue.