Warpage characterization of panel Fan-out (P-FO) package

Panel Fan-out (P-FO) packaging technology is known as a new generation FO technology because of high throughout and low cost superiority comparing to first-generation Fan-out Wafer Level Package/Packaging (FO-WLP). However, the process induced warpage is one critical issue needed to be solved. In this paper, the P-FO packages were assembled on a carrier in size of 370 × 470 mm like a panel, and the focus is how to reduce the warpage of FO panel in several major processes, such as lamination, photolithography and ball placement (BP) process through numerical simulation and experimental study. The FO panel encapsulated by lamination film has a large warpage of 9 mm after lamination film post-curing and 4 mm after full reconstruction process completion respectively, which is primarily attributed to the Coefficient of Thermal Expansion (CTE) mismatch of constituent materials. An effort on material selection for CTE mismatch purpose was applied to reduce the panel warpage to the extent of 3 mm and 1 mm, after lamination film post-curing and full reconstruction process respectively. Besides, the CTE effect of dielectric layer and metal trace on panel warpage before ball placing is found to be more than 1 mm. An approach of reducing carrier size is further proposed to control the warpage within 1 mm for BP process.