Effect of Warpage Pattern of Printed Circuit Board on Solder Paste Volume in the Stencil Printing Process

Abstract

This study examines the influence of printed circuit board (PCB) warpage patterns on solder paste distribution during the stencil printing process (SPP). A multi-stage numerical model was developed and validated with experimental data, showing a deviation of less than 4%, to simulate the SPP with various warped PCB configurations. Various warpage patterns, including horizontal, vertical, spherical, and diagonal warpage, were analyzed along with key process parameters such as stopper load, squeegee load, and the positioning of clamping plates to identify the conditions that most significantly affect solder paste distribution. Results indicate that increasing the stopper load up to 170 N can reduce PCB warpage by approximately 60%, leading to a more even solder paste volume distribution. The squeegee load had minimal impact on gap reduction due to the constraints imposed by the side-clamping plates. Among the warpage patterns, diagonal warpage yielded the most uniform solder paste distribution, with up to 43% better consistency compared to horizontal warpage, which exhibited the greatest variation.