Simulation Investigation On Solder Joint Reliability Under Vibration Or Thermal Cycling For PBGA Package

The reliability problems concerning the PBGA package have drawn a constant attention due to the complexity of its own structure and the variability of its service ambient.The primary failure mode of PBGA package is the failure taking place on solder joints.To study it,this paper adopted the numerical simulation method to research on the stress status of solder joints in PBGA package under loads of vibration and thermal cycling.At first,the finite element model have been verified the accessibility and correctness by comparing with the modal test results.Secondly,numerical simulation of harmonic sweep vibration and random vibration to the finite element model of the PBGA package sample have been conducted.The result turns out that the solder joints of the PBGA package close to the center of the PCB are more likely to fail while the critical solder joint lie at the corner of the solder joint array.The maximum stress of the critical solder joint emerge on the side close to the packaging.Moreover,it is discovered by comparing the affect of simple harmonic sweep vibration and random vibration on the stress of solder joints that the resonance at first natural frequency has a greater affect on the stress of solder joints in random vibration process.Aiming at the factors that affect the stress in solder joints under vibration load,design of experiment is used to determine the best combination of parameters.And the stress of the solder joint reduce effectively.After numerical simulation of thermal cycling to the PBGA board level assembly model,the stress distribution of the solder joints is obtained,and the position of the critical solder joint is determined.Comparing the affect under vibration load and thermal cycling load on solder joints,it is found that the critical solder joint lie at the corner of the solder joint array under both loads,while the maximum stress in critical solder joint both emerge on the side close to the Component.However,there are also differences between the two situations.Under the thermal cycling condition,the stress gradient of the solder joints array is obviously smaller than that of the vibration load.The critical solder joint of the PBGA package lie close to the center of the PCB under vibration load while that away from the center under thermal cycling load.It has reached an approximate match between the numerical simulation results and the experimental results,which proves the accessibility and correctness for the finite element method to study solder joint failure issue of PBGA package.Through the above research,it offers a reference for design and application of PBGA packaging device.