Research On Environmental Stress Screening Technology Of Circuit Board Assembly

Research shows the fact that there are a large number of early failures in the CNC system hardware are one of the important factors affecting the reliability of the CNC system.In order to provide the basis for solving the early failure problem of CNC system,based on the analysis of the reliability test method,from the point of view of the failure physics,this paper investigates circuit board assembly environmental stress screening techniques and proposes recommendations for optimizing environmental stress screening profiles,by using the finite element method and taking the circuit board assembly with the SOP packaged device as the object.The main contents are as follows:1.For the problem of fatigue life of solder joints under temperature cyclic load for circuit board assemblies with a SOP device assembled,the temperature distribution and stress-strain response of the solder joints under load are calculated using numerical simulation methods,and a modified Coffin-Manson model is used to predict the time to fatigue failure of solder joints.Based on this,the influence of temperature cycling parameters on the fatigue life of solder joints is studied.The results show that: improving the high temperature endpoint temperature is the most helpful to reduce the solder joint fatigue life.Secondly increasing the temperature change rate can also accelerate the solder joint fatigue failure.The low temperature endpoint temperature,high temperature insulation and low temperature insulation time will reduce the screening efficiency.2.For the problem of fatigue life of solder joints under random vibration loads for circuit board assemblies with a SOP device,the modal analysis of the circuit board assemblies is performed by using the finite element method,and the stress conditions and stress power spectrum responses under random vibration loads are calculated.Based on Miner linear cumulative damage theory and Dirlik model,the fatigue life of solder joints under random vibration loads is estimated.The results show that the larger vibration intensity,the vibration signal at the first-order natural frequency and the excitation perpendicular to the direction of the circuit board can significantly reduce the fatigue life of the solder joint and improve the test efficiency.Taking the control board of a certain type of servo drive unit as the test piece,the modal analysis and random vibration fatigue life test of the test piece are performed by adopting the orthogonal test design method.Analysis of the test results shows that the increase in the root mean square value of the random vibration acceleration and the frequency range close to the first-order natural frequency of the component can significantly reduce the fatigue life of the solder joint.The conclusions of the test and simulation analysis are basically the same.In this paper,numerical simulation methods are used to study the effects of various parameters of temperature cycling and random vibration profile on the fatigue life of solder joints.Based on the analysis results,suggestions for optimizing the environmental stress screening profile are proposed in environmental stress screening.A random vibration fatigue life test is performed on a certain type of drive control board,and it is found that the conclusion is basically consistent with the simulation analysis.The research results of this paper have important practical significance for the development of environmental stress screening technology of circuit board assembly.