The role of surface roughness on the electrical behavior of flexible and stretchable screen-printed silver ink on Kapton substrate

Changes in the morphology and profile of the printed electronic traces affect the radio frequency (RF) performance, especially when compared to the simulated designs, which are primarily rectangular and smooth. The shape and morphology of the printed traces depend on the printing system, a combination of ink and substrate properties, and the printed technology used for fabrication. This paper investigates the significance of printing parameters like roughness, height, width, and profile shape on the RF performance of screen-printed traces statistically. This paper also derives a model based on actual profile shape and roughness measurements from incorporating these effects into the simulations. From the statistical study, we found that the role of surface roughness becomes more significant as the frequency increases. Thus, modeling surface roughness in flexible hybrid electronics simulations is fundamental for accurate results. Different simulated profile shapes also showed their effect on the RF performance, when combined with roughness, showed better correlation with experimental data. Our proposed model combines the modified Morgan and Hammerstad equation with the compound conductor model. Our proposed model uniquely integrates the modified Morgan and Hammerstad equation with the compound conductor model, leveraging a comprehensive approach focused on the quality and uniformity of printed electronics trace. This integration is aimed at constructing a model that is firmly grounded in actual roughness data, resulting in a solution that is both straightforward to implement and exceptionally accurate in its outcomes. The model agreed well with experimental measurement data over 7 GHz-40 GHz with a root-mean-square error average of 5.7%.