Cyclic Bending Reliability of Silk Screen Printed Silver Traces on Plastic and Paper Substrates

Abstract

The effect of the substrate on the cyclic bending reliability of screen printed silver traces is studied in this paper. The silver screen printed test samples in this study were three different plastic films and three varieties of paper sheets. The specimens with line widths of 250, 500, 1000, and 2000 $\mu\mbox{m}$ were subjected to cyclic bending, and their electrical behavior was monitored with dc resistance measurements in situ . In this study, a 20% increase in resistance was defined as the failure criterion, and the reliability of each test population was assessed by a statistical Weibull analysis. The results showed that the reliability of the traces was highly dependent on the substrate thickness in all the studied materials. The traces on a 125- $\mu\mbox{m}$ -thick polyethylene terephthalate substrate were found to have the lowest characteristic lifetimes of about 1000 bending cycles, whereas the traces with the same geometry on polyethylene terephthalate with a thickness of 50 $\mu\mbox{m}$ endured hundreds of thousands of bending cycles. Similarly, decreasing the substrate thickness improved the reliability of the printed traces on paper substrates. This relationship was due to the reduced mechanical strain on the trace surface when using thinner substrates.