A design of experiments study on solder volume for flexible circuit board

This study investigates the factors influencing solder paste volume in the production of flexible printed circuit boards (PCBs) using Design of Experiments (DOE) techniques. The objective is to reduce defects stemming from insufficient solder paste volume, which currently results in significant production losses. The research focuses on three critical parameters, including squeegee speed, squeegee pressure, and stencil thickness, which are key variables affecting solder volume during the stencil printing process in Surface Mount Technology (SMT). A two-stage experimental approach was applied. First, a Completely Randomized Design (CRD) was used to individually assess the effects of each factor while the other parameters are constant. This allowed for a preliminary understanding of how each parameters impacts solder volume. Subsequently, a two-level factorial design (2k factorial) was employed to analyze both main and interaction effects of the identified factors. The experimental results revealed that all three factors, which are squeegee speed, pressure, and stencil thickness, significantly influence solder paste volume. An optimal combination of process parameters was further determined using Response Surface Methodology (RSM). The results indicate that adjusting squeegee speed, pressure, and stencil thickness within optimal ranges reduces defectsand ensures solder volume remains within the specification range of 90%–110% per unit.