The purpose of the experiment was to indicate which element of the production process of flexible Printed Circuit Board is optimum in terms of the reliability of final products. According to the Taguchi method in the experiment five factors, two levels each, were chosen for the subsequent analysis. These include: the number of conductive layers, the thickness of the laminate layer, type of the laminate, the diameter of the plated holes, the current density in the galvanic bath. The reliability of the PCBs in produced variations was verified using the Interconnect Stress Test environmental test. The qualitatively best variant of the board construction was indicated using the signal-to-noise ratio and analysis of variance method for each factor. The factors that turned out to be the most important in terms of reliability are the number of conductive layers and the current density in the galvanic bath. The optimal variant of the board construction is two conductive layers, on a polyimide laminate, where laminate layer is 100 μm thick, hole diameter equal to 0.4 mm and current density of 2 A/dm2 in the galvanic bath. Therefore the plated experiment indicated factors needed to obtain a high-quality product with a low failure rate.