Study On Reliability Of Laminated Solder Joints Under Thermal-Random Vibration Composite Loading Conditions

In the field of microelectronic packaging,solder joint reliability is an important part of overall reliability,so it is necessary to systematically study solder joint reliability.Based on finite element simulation analysis,the reliability of stacked BGA solder joints under temperature cyclic conditions,random vibration conditions and thermal vibration composite loading conditions is studied.Firstly,based on ANSYS APDL finite element analysis software,the finite element model of the interconnection structure of the stacked solder joints is established,and the stress-strain distribution and time variation law of the stacked solder joints under this load are analyzed by applying the temperature cyclic load.The results show that under the temperature cyclic load,the stress and strain is concentrated in the four corners of the solder joint array,the stress and strain of the outermost solder joint is greater than that of the inner solder joint,and the maximum stress and strain occurs on the solder joint at the most corner.For a single stacked solder joint,the stress-strain is approximately symmetrically distributed vertically.In the heating and cooling stages,the stress and strain of stacked welding joints showed an increasing trend,and in the high temperature and low temperature insulation stages,the stress and strain showed a decreasing trend.The maximum stress and strain occurs at the onset of the low temperature hold.Under random vibration load applied to the interconnected structure,The results show that the stress and strain is concentrated in the four corners of the solder joint array;The maximum stress data of the stacked solder joint obtained based on the orthogonal design simulation test was regressed and the maximum stress prediction model of the stacked solder joint was obtained,and the Average prediction error less than 3%.Secondly,the vibration characteristics of the stacked solder joint interconnection structure in the key temperature field environment are analyzed.The maximum stress values of stacked solder joints obtained based on orthogonal experimental design and simulation test were analyzed for range and variance,and univariate analysis was carried out for significant factors.The results show that the natural frequency of the interconnection structure of the stacked solder joint increases to a certain extent under the condition of thermal vibration composite loading.The stress and strain is concentrated in the four corners of the solder joint array,and the maximum stress and strain occurs at the corner solder joint,which is the connection surface with the PCB.At 95% confidence,the diameter of the solder ball,the height of the solder joint and the diameter of the pad have significant effects on the maximum stress of the solder joint.The maximum stress and strain of the stacked solder joint increases with the increase of the solder ball diameter,decreases with the increase of the solder joint height,decreases with the increase of pad diameter,and the change of PCB thickness has little effect on the maximum stress and strain of the stacked solder joint.Finally,based on the orthogonal design simulation test data,the gray correlation analysis method is used to carry out multi-factor single-objective gray correlation analysis and multi-factor dual-objective optimization.The results show that the correlation between the four factors and the maximum stress of the stacked solder joint is as follows: solder ball diameter> solder joint height> pad diameter> PCB thickness.The order of correlation with the maximum strain of the stacked solder joint is: solder ball diameter> solder joint height>pad diameter> PCB thickness.The horizontal combination of double-target optimal structural parameters is solder joint diameter 0.61 mm,solder joint height 0.52 mm,pad diameter 0.50 mm,PCB thickness 2.0mm,The maximum stress of the corresponding stacked solder joint is 26.9MPa,which is 40.88% lower than the 45.5MPa before optimization.The maximum strain is 0.625E-3,which is 38.73% less than the 1.020E-3 before optimization,and the optimization effect is well.