Effect of substrates surface condition on the morphology of silver patterns formed by inkjet printing

Preheating is considered to be an effective method to improve the resolution of inkjet printing conductive tracks. However, although preheating can accelerate the evaporation of the droplets, it also changes the surface condition of substrate, which affects the spreading behaviour of the droplets. In this study, four types of commonly used substrates are employed to investigate the effect of preheating on inkjet printed silver patterns. The result shows that coffee stain effect becomes more obvious as the substrate temperature increases. Optimal preheat temperature exists for each substrate, which is >;80°C for glass, 30-40°C for polyimide, 60-70°C for FR4 and 50-60°C for hydrophobic paper. Mathematic model has been established to discuss the factors in this process. During the track printing stage, overlap rate was also studied to achieve continuous and homogenous tracks.