Solder Joint Shape Prediction Of Various Devices And Vibration Reliability Analysis Of Complex PCB Assembly

Solder joint is the mechanical support between electronic components and PCB,its shape directly affects the mechanical properties of the structure.By predicting the solder joint shape,the assembly process can be effectively guided to improve the reliability of the device.At the same time,the life of PCB assemblies under vibration environment is also the focus of research.Most domestic researches on board-level random vibration reliability are based on single-axis or multi-axis random vibration loads.Few scholars have conducted research on X,Y,and Z single-axis alternating random vibration loads.The research content of this paper consists of two parts:establish the solder joint morphology model library of PLCC and SOP electronic components;explore the reliability life of solder joints of 14 printed board components under X,Y,Z single-axis alternating random vibration loads.1.The solder joint morphology of five types of PLCC and SOP electronic components are presicted using Surface Evolver software.It contain five different solder paste thickness which are 0.1mm,0.12mm,0.15mm,0.18mm and 0.2mm.It is found that the prediction result of the solder joint morphology is more reasonable,and the error is controlled within10%.As the thickness of the solder paste increases,the shape of the solder joint gradually becomes round and full,and the wetting range and climbing height of the solder joint show an increasing trend.2.14 printed board component models are Established,the solder joint fatigue life of BGA electronic components under the conditions of assemblies 1-4 on the airborne,assemblies 5-9 on the vehicle,and assemblies 10-14 on the shipboard vibration experiment is studied.The results show that:(1)Random vibration magnitude is the dominant factor affecting solder joint fatigue.Shipboard PCB components have the longest service life,followed by vehicle-mounted assembly,and airborne assembly have the lowest vibration service life.(2)Assembly 1 has the longest life when the solder paste thickness is 0.2mm,which is 34.23hours.Assembly 2 has the longest life when the solder paste thickness is 0.12mm,878.79hours.Assembly 3 has the longest life of 18382.49 hours when the solder paste thickness is0.15mm.Assembly 4 has the longest life compared to other assemblies.When the solder paste thickness is 0.15mm,the solder joint has the longest life,which is 5.00×10~8 hours.The on-vehicle random vibration life of assembly 5 to 9 are all over 1×10~9 hours,and the life is longer.The first-order natural frequencies of assemblies 10 to 14 are all higher than the upper limit of shipborne random vibration frequency,and the solder joint damage can be ignored.(3)The fatigue life of solder joints of different printed board components varies with the change of solder paste thickness.As the thickness of the solder paste increases,the fatigue life of the solder joints of assemblies 2,3,6 first increases and then decreases;assemblies 1and 8 first decreases and then increases;assemblies 5 and 7 gradually decrease;assembly 4first decreases,then increase,then decrease.3.The parametric model of assembly 1 is established,and ANSYS Workbench DesignXplorer is used to optimize the design module,and the factors that affect the reliability of its solder joints under the condition of Z-direction single-axis airborne random vibration load is analyzed.The results show that:(1)The influence of each input variable on the maximum 1?,2?,and 3?strain values of the solder ball is as follows:solder ball height>BT substrate thickness>hole edge distance?PCB board thickness>solder ball diameter.(2)The maximum 3?strain value of the solder ball decreases first and then increases with the increase of the hole edge distance.As the thickness of the PCB increases,it first slowly increases and then decreases and then increases.It increases with the increase of the BT substrate thickness and the height of the solder ball.It first increases and then decreases with the increase of the radius of the solder ball.(3)The first-order natural frequency of the modal increases with the increase of distance of edge to the hole and PCB board thickness.4.A Z-direction single-axis airborne random vibration load is applied to assembly 1,and the influence of solder joint materials and fixed restraint methods on the fatigue life of solder joints is studied through the controlled variable method.The results show that:(1)The vibration of SAC305 solder joints is reliable.The performance is higher than the vibration reliability of 63Sn37Pb solder joints.(2)By imposing a fixed restraint in the center of the printed board assembly,the fatigue life of the solder joints can be improved.The more central fixed restraints,the higher the fatigue life of the solder joints.