Warpage Studies of Printed Circuit Boards with Shadow Moiré and Simulations

The demand for lightweight and high functionality devices is always a driving force in development of smaller, lighter and compact electronics circuit. Printed circuit board (PCB) is the most important structure that provides interconnection and supports the components; hence its flatness is always the main concern in SMT manufacturing. In order to ensure product reliability, the monitoring of thermally induced warpage of PCB during high temperature reflow is essential. PCB deformation occurs when there is mismatch of coefficients of thermal expansion between the materials. Thermally induced warpage in PCB can be obtained from the Shadow Moiré measurement, which is a non-contact full-field optical method integrated with a high temperature oven. In this study, a single-sided, small PCB (105 mm X 100 mm X 1.5 mm) and a large, multi-layer PCB (300 mm X 180 mm X 1.6 mm) are measured and analyzed. To reduce the temperature difference between the top and bottom of the PCBs, a heating profile is designed with the use of multiple thermocouples at various positions on the PCB. In addition, finite element analysis is carried out to determine the z-axis deformation of the PCBs. The finite-element simulation is setup to mimic the heating profile in the experiment. The results of simulation are compared to the experimental measurement.