Cohesive Modeling of Solder Interconnect Failure in Board Level Drop Test

Numerical approach using finite element method has been extensively used to access reliability of electronic components subjected to board level drop test and system level drop test for portable electronic products. Dynamic crack growth and separation of solder material from its pad interface are known failure modes for lead-free solder interconnect. The constitutive behavior of this phenomenon can be naturally described using traction-separation relationship. In this study, the cohesive constitutive relation and the creation of new free crack surfaces for crack propagation are demonstrated using Needleman´s model and Abaqus cohesive elements. Comparisons of modeling technique and limitations between two approaches and the procedure to extract traction-separation parameters from experimental data are discussed. The material constitutive behavior of solder material was obtained from high strain rate testing on the order up to 6.43/sec. Board level drop simulation is conducted with incorporated cohesive surfaces for failure prediction. The prediction of failure is in accord with experimental observation