THERMO-MECHANICAL SIMULATION AND OPTIMIZATION ANALYSIS FOR WARPAGE-INDUCED PBGA SOLDER JOINT FAILURES

摘要

In SMT assembly process, the thermal warpage becomesrnone of the root causes of solder joint reliability failures forrnPBGA. The accurate prediction for warpage of PBGA andrnPCB is an important and challenging task of numericalrnsimulation of PBGA solder joint defect. In this paper, thernnumerical analysis of warpage in PBGA and PCBA isrncarried out in consideration of the residual stressesrnproduced during SMT reflow process. The analysisrnmethodology using a viscoelastic based material model isrnadopted to account the time and temperature dependentrnbehavior of an epoxy molding compound. In order to get arnseries of material constant for Generalized MaxwellrnViscoelastic Model, DMA (Dynamic MechanicalrnAnalyzer) tests for mold compound material sample isrnperformed to generate viscoelastic material relaxationrnfunction through curve fitting. The experimental researchrnon thermo warpage at different temperature for bothrnPBGA and assembled PCBA is carried out by using thernShadow Morie method. The experimental data isrncompared with the simulation results as verification forrnFEA modeling. It is found that the predictions are inrnagreement with experimental data, especially inrnqualitative analysis. Optimization analysis is alsornperformed to study the effect of PBGA material properties,rnmolding curing temperature and SMT process parametersrnon warpage and solder joint failures.