Research On Assessment Of Solder Joint's Reliability Based On ECPT

The electronic packaging technologies such as BGA(Ball Grid Array)and SMT(Surface Mount Technology)adapt to the demand of electronic products for function,performance,integration and size reduction,but as the circuit board's pin density increases,the pitch decreases,and the package size decreases,the reliability of electronic products is greatly affected.With the decrease of the size of solder joints and the development trend of lead-free solder joints and lead-free solder joints,solder joints are more and more prone to defects.It is quite important for the rapid development of packaging technology to detect solder joint defects and evaluate its reliability.At present,the reliability assessment for solder joints generally has the following three aspects: the occurrence and propagation of cracks during solder joint failure,the life prediction of solder joints,the influence of different package structures and material parameters on the solder joint life.This article mainly discusses the temperature cycle based prediction of fatigue life of solder joints.At this time,the life is the number of thermal cycles before solder joint fatigue failure.In this paper,BGA and SMT solder joints with small size or micro size are taken as the object for further study.A method of predicting fatigue life of solder joints based on pulsed eddy current thermal imaging is proposed based on a variety of life prediction methods and models.The content of this paper is as follows:1.Study are performed on modeling and simulation of fatigue life prediction of solder joint considering thermal-mechanical Coupling.The variation law of solder joint life with crack length,width and crack position is gained through the simulation study of solder joints with crack.Moreover,the main factor affecting the fatigue life of solder joints is identified and whether the crack length can characterize the solder joint's fatigue life is determined.2.ECPT is widely used for defect detection of solder joints and other electronic devices,so solder joints are modeled and simulated based on ECPT system.According to the principle of defect detection,experiments about different crack lengths,crack widths and crack positions are conducted to study its influence to the top surface temperature.According to the result,whether crack length can represent the average temperature of the top surface of the solder joint can be clear,and the regularity will be analyzed in detail.3.The feasibility and applicability of the method for predicting the fatigue life of solder joints based on ECPT will be studied by the data in the experiment.An eddy-pulsed-current thermal imaging test system is set up to perform defect detection tests on BGA and SMT package solder joints with different crack lengths,and image processing algorithm is used to analyze and process the thermal image to reduce interference of various factors in the test(such as lifting effect).Then the relationship between crack length and top surface temperature of the solder joint is deduced.Ultimately,the data between ECPT and fatigue life prediction is combined to analyze the relationship between temperature and solder joint's fatigue life.In this paper,solder joints of BGA and SMT are used for simulation and experimental research.The results show that the method of assessing the life of BGA solder joints based on ECPT by extracting the temperature and distribution of the top surface of solder joint thermal image is feasible.For SMT solder joints,there is need to do further study.