Design for Cyclic Bending Reliability of Large PBGA Assembly Using Experimental and Numerical Methods

In this paper, four-point cyclic bend test was conducted for PBGA (plastic ball grid array) assembly with Sn-3.5Ag lead free solder joint. Bending fatigue life of solder joint was recorded by measuring resistance of the designed daisy-chain for solder joints. Failure analysis was performed using dye penetration and the critical solder joint location was observed. Then, comprehensive finite element modeling and simulation were conducted, including the effect of solder material constitutive model, triangular and sinusoidal loading profiles, constraint vs. contact boundary, on simulation result. The Anand constitutive model is one suitable solder material model used for cyclic bending modeling and simulation. The consistent simulation results were achieved for both loading profile of triangular and sinusoidal. Contact boundary application slightly overestimates the bending fatigue life compared to constraint boundary. Based on the developed bending simulation method, the design-for-bending reliability was conducted to improve the bending fatigue life of solder joint through designing the solder joint distribution layout.