Investigating the Significance of Surface Roughness for Screen-printed Silver ink on Kapton Substrate

Minor changes between the designed Flexible hybrid electronic (FHE) devices and the actual realized printed devices are very crucial for the development and maturity of this technology. The quality of printed electronics depends on mechanical and chemical factors such as ink properties and the printing technique [1], [2]. Fluctuations in the quality of printed electronic devices, such as thickness, width, waviness, and surface roughness, affect their radio frequency (RF) performance [2]. In this paper, we investigate statistically, using design of experiments (DoE) techniques, the significance of surface roughness of screen-printed silver ink traces on the RF performance. Ninety-six microstrip lines were printed; we measured the average thickness, average width, average roughness, and average waviness, for all the samples. Also, we measured the S-parameters for all the samples; then, we extracted Insertion-loss at four different frequencies. We performed simple statistical analysis and checked independence and normality assumptions for our data. We considered the thickness, width, roughness, and waviness to be our independent variables. We performed regression analysis and best subsets regression four times each time we consider the insertion-loss as the dependent variable. We were able to conclude that surface roughness becomes more significant as the frequency increases for screen-printed FHEs.