Experimental Study Of PBGA Package Under The Coupling Of Thermal Cycling And Vibration Loading

Avionics will experience the temperature mutation,vibration and other harsh environment in service period,which brings huge challenge to the reliability of electronic components.The coefficient of thermal expansion mismatch in materials causes a fatigue damage of solder joints when the board-level package is subjected to temperature changes.On the other hand,printed circuit board and substrate will occur dynamic bending deformation under vibration conditions,and this high strain rate loading may cause damage in the solder joints.Considering the above issues,the 63Sn-37 Pb solder life prediction model and failure mechanism were studied under sine vibration,random vibration,thermal cycling and the coupling of thermal cycling and vibration(T-V)loading in this paper.Firstly,modal test,sine vibration and random vibration were carried out to obtain the modal parameters and solder joint fatigue life.Then,the S-N curve was established under vibration conditions through the combination of experimental results and simulation results.According to the results of the random vibration and simulation,the life prediction model was established by modifying Steinberg equation.Finally,the distribution and failure modes of failed solder joints were studied.The results show that the failed solder joints are mainly concentrated at the corner of the outer ring of the solder joint array.Due to the stress concentration of intermetallic compound at the interface,the crack initiates and propagates along the interface near the device,resulting in the failure of the solder joint.The thermal cycling test of PBGA package was carried out to obtain the fatigue life of the solder joint under thermal cycling.It is found that the critical position is located at the corner of the outer ring of the solder joint array based on the finite element simulation results,and the stress and strain data of the critical position were calculated.Then,based on the Engelmaier model,the parameters of the model were calculated by experimental and simulation results.Ultimately,the fatigue life model of PBGA solder joint under thermal cycling was established.The distribution and metallographic analysis of the failed solder joints under thermal cycling were carried out.The results show that the failed solder joints are mainly located at the corner of the outer ring of the solder joint array.The crack initiates at the interface between the solder ball and the copper pad near the device,which propagates in the solder ball,and finally leads to the occurrence of failure.The T-V experiment of PBGA package was carried out to obtain the fatigue life of the solder joints.Based on the linear cumulative damage,the random vibration fatigue life model and thermal cycle fatigue life model are linearly superimposed to construct the life model of the solder joints under the T-V load.Then,the bilinear model was used to modify the coupling model,and a better prediction result is obtained.The results of coupling failure were compared with single load failure results.The results show that the distribution of failure solder joints under coupling load is similar to that under single vibration load,which are located at the corner of the outer ring of the solder joint array.The crack has the dual characteristics of vibration failure and thermal failure.The through crack of solder joints located at the outer ring propagates along the interface of IMC,and the partial crack of solder joints located at the inner rings propagates in solder balls.