Warpage characterization of a large size fan-out panel subjected to inhomogeneous heating by a digital fringe projection system

Abstract

Warpage is an essential issue of fan-out wafer/panel level packaging. Increasing size of wafers/panels poses new challenges to the warpage characterization system. In this work, a warpage measurement system based on digital fringe projection method is reported. It can cover 600 mm × 600 mm area with 4 × 4 camera array. Benchmark tests were carried out to evaluate the measurement error, which was found to be 0.053 %. The warpage evolution of a 515 mm × 510 mm panel with inhomogeneous heating was then studied by heating from room temperature to 90 °C. It was found that the warpage evolution of a large size panel can be very complex. Based on finite element modeling results, this can be attributed to temperature gradient, and several other factors, including mismatch of coefficient of thermal expansion, gravity, initial stress state and original layout design of the panel (such as size and count of chips, RDL design and chip position).