Analysis of warpage and reliability of very thin profile fine pitch ball grid array

Abstract

With the evolution of advanced integrated circuit (IC) packaging technology, the use of experiments to identify package performance and life expectation will take a significant amount of time and cost to finish the job. To reduce the cost of research and testing, predictive analyses of reliability and performance using simulation tools have become a feasible approach for the IC assembly industry. Therefore, this study utilized Moldex3D molding simulation software to analyze very thin profile fine pitch ball grid array (VFBGA) packages and established a numerical analysis procedure from the molding and curing process, the post-mold cure (PMC) process, to a thermal cycling test (TCT) to predict the amount of package warpage during processing and reliability after TCT.The results showed that the warpage trends of both experiments and simulations during the same temperature ramping process were similar. In the thermal cycling analysis, potential failure locations were found to be at the copper pillars and redistribution layer (RDL), where the maximum Von Mises stress occurred at the lowest temperature (−65 °C). The fatigue life model, Coffin–Manson model, was used to calculate the potential fatigue life at the two locations, resulting in 1689 cycles (copper pillars) and 9706 cycles (RDL L1).

Keywords

• Advanced IC packaging
• Residual stress
• Redistribution layer
• Pressure–volume–temperature–cure equations
• Viscoelasticity
• Reliability