Carbon Ink

Using carbon ink in place of Hard gold is an option that offers lower costs and high robustness. Using carbon ink reduces material costs by replacing gold with carbon, and reduces process costs by “replacing the electrolytic bath with a simple screen-printing process.” And regarding Robustness, tests have shown that a typical carbon ink is hard enough to withstand >1 million pushbutton operations (keypad) or 100 insertion operations ... (edge connector) without showing wear or increased resistance.”  However, it has been noted that “carbon inks must have good viscosity stability for warmer climates and require good printing properties to give even coverage over the copper pads.” Another disadvantage is that the cured carbon ink must be able to withstand process steps including “solvent cleaning and soldering without loss of adhesion and conductivity.”