Wear reliability and failure mechanism of inkjet-printed conductors on paperboard substrate

In this research, we conducted a wear test on inkjet-printed silver conductors using different loads and counter materials (two paperboards, brushed steel sheet, and sandpaper) with similar surface roughness values. The conductor’s reliability was characterized by resistance measurement, the failures and tested counter materials were analyzed using an optical microscope, profilometer, scanning electron microscope, and energy dispersive spectrometer. It was found that the counter material has a dominant impact on a conductor’s reliability and failure mechanism compared with load. The conductors were exceptionally reliable but subject to adhesive wear when tested by paperboards. They were also highly reliable when tested by brushed steel sheet although the silver became severely detached, and the conductivity was lost suddenly when a major scratch was caused by two-body and three-body abrasive wear mechanisms. Sandpaper rubbing caused the most severe silver detachment and quick loss of conductivity, as a large amount of small-size (5–15 µm) silicon carbide particles with sharp edges and corners caused a dense cutting effect via two-body abrasive wear (by cutting) mechanism. Additionally, the failures in almost all samples occurred in the areas in contact with the counter edges, suggesting that failure was accelerated by the edge effect. This study proves that inkjet-printed electronics on the investigated paperboard is exceptionally durable when rubbed by paperboards and steel sheets, and thus provides a reliable solution to intelligent packaging. To promote intelligent packaging, more paperboards, as well as approaches for reducing the edge effect can be investigated.