Parametric study of warpage of PWB assemblies and PWB assembly warpage minimization by component layout optimization

Out-of-plane displacement (warpage) has been a major concern for board-level electronic packaging. Warpage occurred during surface-mount assembly processes and normal operation causes many failures such as misregistration, delamination, die cracks, solder fatigue, and solder opening. Warpage results from a combination of material, geometry, and process effects. In the case of printed wiring board assembly (PWBA), component layout plays a crucial role. Many material, geometry, and process related parameters contribute to PWBA warpage. In this paper, a systematic design of experiments (DOE) is conducted so that the modeling results incorporate all relevant individual and interacting parametric effects, and so that the subsequent data analysis is computationally efficient. Subsequently, the parameters are optimized within practical range to achieve the minimum warpage. Component layout effect on PWBA warpage is also investigated. It is assumed that the materials and dimensions of the printed wiring board (PWB) as well as the components are fixed. The objective is to identify component layouts on the PWB so that it suffers minimal warpage. Evolutionary structural optimization (ESO) is used where the design domain is meshed to fine finite elements and materials at element locations are removed or grown iteratively according to a preset criterion. In conclusion, PWBA warpage can be minimized by carefully levering material, geometry, and process parameters, as well as component layout design.