Simulation Research On Electronic Package Board Level Solder Joint Under Multiphysics Load

With the rapid development of the electronics industry,people have entered the information age,and electronic information technology plays an increasingly important role in the defense,transportation,and medical industries.People are pursuing the development of electronic devices in a smaller,lighter,and thinner direction.The advancement of electronic packaging technology has contributed to the development of electronic products.The sizes of the board-level interconnect solder joints also decrease sharply with the miniaturization of the product.Solder interconnects often experience thermal,mechanical,electrical loading simultaneously during the actual service,which inevitably leads to higher and higher requirements for the reliability of electronic products.Therefore,the response characteristics of PCB and interconnected solder joints under thermalmechanical coupling and thermal-mechanical-electrical coupling are characterized by vibration experiment and finite element simulation.The failure modes and life of board-level solder joints under coupling conditions are studied.In the thermal-mechanical coupling test,the reliability of the board-level solder joints under vibration loads at different temperatures(25 °C,65 °C,105 °C)was studied.When the test board is subjecting to the harmonic vibration at the first eigenfrequency of 25 °C,the first eigenfrequency of the PCB board decreases as the temperature raises,because of the offset of eigenfrequency at elevated temperature,the resonance effect is weakened at high temperatures.This phenomenon leads to the decrease of the deformation of PCB,which furtherly results in the decrease of load intensity as well as the reduce of stress level of solder joint.When the vibration frequencies are set at the eigenfrequency of different temperatures respectively,as the temperature increases,the PCB deformation increases,the load strength of PCB increases,while the solder joint stress decreases,the plastic strain of solder joints increases,and the stress of solder joints is relieved by deformation.The temperature dominates the crack propagation path of the solder joint,and the temperature rises,which improves the plastic deformation ability of the solder joint,and promotes the deformation of solder joints through bulk solder to alleviate the interface stress of solder joints.The crack position changes with the change of the high stress region.The crack migrates from the interface IMC / Cu layer to the bulk solder,and the crack is more likely to change from brittle fracture to ductile fracture,and the life of the solder joint is improved.The solder joint life curve is fitted by the solder joint stress in the numerical simulation and the life data in the experiment.The results show that the temperature raises,the solder joint stress level decreases,and the solder joint life increases.In the thermal-mechanical-electricity coupling test,the effect of current on the reliability of board-level solder joints under vibration loads at different temperatures(25 °C,65 °C,105 °C)was studied.After applying current,the temperature of the electrified position is higher,the temperature of the edge position of PCB is lower,and the temperature distribution of PCB is not uniform.Compared with the thermal-mechanical coupling condition,the change of the PCB temperature reduces the first eigenfrequency of the PCB board,the strain peak of the PCB board decreases,and the stress level of solder joint decreases with the decrease of load intensity.The temperature of solder joint is further increased and the plasticity is further improved after electrification.The crack sites are mainly bulk crack and interface-bulk mixed crack.Therefore,PCB strain reduction and solder joint plastic properties increase the solder joint life.Further increase the current intensity,the solder joints are served at higher temperatures,the PCB board load strength is reduced,the solder joint plasticity is better,and the solder joints are not broken.When the ambient temperature drops sharply,the strain of the PCB increases,and the vibration load strength increases.The plastic strain of the solder joint increases sharply in a short time,and cracks are easily generated,resulting in immediate failure of the solder joint.