Thermomechanical modeling and evaluation of the impacts of BGA warpage on low-cycle solder fatigue

Given the complex, 3D nature of electronic component geometries, high package assembly temperatures, and the large difference in thermomechanical properties between silicon dies, organic substrates, and package lids or molding compounds, commercial electronic components typically exhibit significant warpage behaviors over temperature. Warpage measurements are presented for various ball grid array (BGA) packages. For these components, warpage behaviors include simple convex or concave in addition to more complex shapes, with zero-warpage temperatures ranging from 180°C to room temperature to sub-room temperature. Results of finite-element-based thermal fatigue analyses for various idealized and increasingly realistic cases demonstrate that package warpage has a larger effect on BGA fatigue than in-plane CTE mismatch between the package and underlying printed circuit board (PCB). While the choice of zero-warpage reference temperature is observed to affect subsequent fatigue life predictions, the magnitude of this effect over a wide range of reference temperature values is less than plus-or-minus 2 percent.