Characterization of Bending, Crease, Aging, and Immersion Effects on Flexible Screen-Printed Silver Traces

Printed flexible electronics have been a great interest in the electronics industry in recent years since this technology can be used to replace existing rigid printed circuit boards and open new application domains. Several used cases for flexible substrates involve mechanical bending and creasing as well as exposure to liquids. Hence, there is a need for the characterization of the reliability of the silver races on flexible substrates under such conditions. In response, ASTM standard tests were used to quantify the effects of repeated bending and creasing on the resistance change in commercially used silver inks screen printed onto the flexible substrates. Three distinct ink/substrate combinations were investigated in terms of bending and crease testing up to 10 000 cycles. Traces with and without dielectric encapsulant were exposed to the water immersion and the simulated sweat tests for up to 2500 h of exposure. The effects of mechanical stress and liquid exposure on the surface morphology and oxidation species were analyzed and corroborated with the electrical results.