Fatigue behaviour of inkjet-printed silver interconnects on silica-coated mesoporous flexible PET substrate

Abstract

Inkjet-printed silver conductive patterns are used in many flexible electronics applications ranging from health care, inventory management to aviation. Understanding of the electrical behavior of these printed patterns under different mechanical stresses and environment conditions is important for their real-life application use. The present work addresses a special system, silver interconnects on silica-coated porous polyethylene terephthalate (PET) substrate. The combination of the porosity, roughness, and a sintering temperature limited by the low glass transition temperature (Tg) of the PET leads to unique behaviors that may easily be misinterpreted. Thus, while the interconnect resistance does increase during stretching and decrease with unloading the resistance at zero load was lower after a given cycle than before it, and it continues to drop for quite a while in consecutive cycles. This effect was stronger for higher strain amplitudes, but it could be reduced or eliminated by preceding low temperature annealing. Humidity exposure and thermal cycling also led to major drops in resistance, albeit for different reasons, but both led to faster fatigue in subsequent mechanical deformation. Accounting for these behaviors in the assessment of life under realistic use conditions requires a mechanistic understanding.