| High frequency,high density and high reliability have become the development trend of electronic equipment.The requirements for the assembly and interconnection of modules in microwave components have become increasingly prominent.As the core component of electronic equipment,the performance indicators of microwave components directly determine whether the functions of electronic equipment meet the standards,which puts forward higher requirements for the reliability of microwave components,The reliability problem caused by the failure of the connecting part is the primary factor of the failure of the microwave components.As the most widely used and the most typical structure of the ball grid array package,the solder joint thermal force failure directly affects the reliability of the whole package,thus affecting the performance of the electronic equipment.At present,most of the researches at home and abroad focus on the reliability life prediction of the connection process,lack of research on the relationship between the structural parameters of the connection process and the reliability life,and rarely involve the reliability research on the improvement of the connection process.In this thesis,the correlation strength between connection process structure parameters and reliability is analyzed.The typical connection process of ball grid array packaging is taken as the research object.The solder joint shape of ball grid array packaging is deeply studied.Under the condition of thermal cycle,the stress-strain distribution and fatigue life of solder joints of ball grid array packaging are studied.The orthogonal experiment is carried out by using the parametric modeling method,and the ball is studied in detail Based on the particle swarm optimization algorithm,aiming at the stress-strain value of dangerous solder joints,the structure optimization of the ball grid array packaging is carried out to improve its reliability.The main work is as follows:(1)Taking the structure of ball grid array packaging as the research object,based on the engineering practice,the failure principle of solder joint is analyzed;the solder joint shape of ball grid array packaging is predicted by the principle of minimum energy;the mechanical properties of solder joint are described based on Anand unified constitutive model,aiming at the characteristics of solder joint prone to creep under the condition of thermal cycle,etc.;and the engineering is introduced Finite element method and life prediction theory of solder joints.After analyzing the symmetry of the structure and boundary conditions of the ball grid array package,the structure of the package is simplified.The slitting model of the ball grid array package is established in ANSYS.The boundary conditions are defined reasonably,the temperature cyclic load is applied,and the stress-strain values and mechanical properties of the dangerous solder joints of the ball grid array package are analyzed.Based on the theory of solder joint fatigue life prediction,the It is calculated that the life of dangerous solder joints is 2145 cycles,and the error is 16.66% by comparing 2574 test results.The correctness of the finite element analysis model is verified.(2)In order to analyze the influence of the structural parameters of the ball grid array packaging on the stress-strain distribution of the dangerous solder joints in the typical thermal environment,the advantages and disadvantages of the mainstream parametric modeling methods are analyzed firstly.The parametric model of the ball grid array packaging is established by APDL language.Taking the parametric model of the ball grid array packaging as the research object,PCB thickness,substrate thickness and solder joints are analyzed in detail The influence of thickness,diameter,spacing and pad thickness on stressstrain distribution of solder balls.The orthogonal test was designed to analyze the influence of structural parameters on the stress-strain distribution of solder balls.The correlation mechanism and strength between structural parameters and the stress-strain distribution of solder balls were determined.The key parameters selected were: solder joint diameter,pad thickness,base plate thickness and PCB plate thickness,which laid a theoretical foundation for the structural optimization design later.(3)In order to optimize the structure parameters of the ball grid array,reduce the stress-strain value in the thermal environment and improve its reliability.The main optimization methods and their advantages and disadvantages are studied.Based on the correlation mechanism,correlation strength,key parameters and other results between the structural parameters and stress-strain values of the ball grid array package in Chapter 3,combined with particle swarm optimization algorithm,a joint simulation method of MATLAB and ANSYS is proposed,which aims at the equivalent stress,equivalent strain,equivalent stress and so on The weighted sum of the effect variation is used to optimize the structural parameters.The model is established by using the obtained structural parameters,and the thermal cycle load is applied to simulate.Compared with the results of the initial model,the fatigue life is increased by 8.39%,10.77% and 13.79%,respectively.The effectiveness of the optimization method is verified,and the optimal design of the structural parameters of the ball grid array package under the thermal environment is obtained. |
