Drop-impact Simulation Of PCB Assembly Using Finite Element Method

It is hard to solve drop/impact problems because of its strong nonlinear property. However, drop/impact problems happen frequently. FEM (Finite Element Method) technique is a proper method that can solve these problems efficiently.In this dissertation, the dynamic responses of PCB (Printed Circuit Board) assemblies during drop/impact process are dealt with by using FEA (Finite Element Analysis) software platform such as ANSYS and LS-DYNA. In practice, there are many limitations in drop/impact test. For example, it is difficult to mount sensors at critical locations so as to difficult to get dynamic stresses of solder joint or lead of components. These limitations can be dealt with by FEA. By using FEA, designers can quickly and conveniently characterize the drop/impact strength of PCB assemblies.At first, chapter 2 introduces two FEA software, i.e. ANSYS and LS-DYNA. Concretely, ANSYS is used as pre-processor, LS-DYNA as solution-processor, and ANSYS and LS-PRE/POST as post-processor. The modeling work is carried out by ANSYS and solved by LS-DYNA. Secondly, combined the powerful pre-process function of ANSYS with powerful nonlinear analysis capability of LS-DYNA, the drop simulations are performed. In order to verify the validity of LS-DYNA in solving drop/impact problems, a simple drop test is performed in chapter 3 and the impact pulse of testing is consistent with that of simulation. Results show the validity of LS-DYNA. The FEA modeling is generated by the combination of ANSYS with LS-DYNA. The effects of drop height, property of test-bed and property of curve generator to impact pulse are dealt with. The finite element simulation of impact pulse is achieved. It turns out to be a more convenient way to simulate standard impact pulse than testing. Furthermore, it is more convenient to characterize the performance of PCB assemblies or electronics products during drop/impact.By using simulation method of impact pulse, drop simulations of two types of PCB assemblies are performed. The effects of boundary condition of PCB, bend of PCB, the mount form and mount site of components, and material of solder joint to dynamic responses are dealt with. Concluded from the results of simulations, some useful advice that is helpful for designers to enhance the drop/impact strength of PCB assemblies during design stage is provided. Furthermore, this simulation method can be a referential method for designers to quickly characterize the performance of PCB assemblies.