The Effect of Torsional Bending on Reliability and Lifetime of Printed Silver Conductors

Abstract

Capability of high speed and low-cost manufacturing makes the printing techniques very promising approach for largearea flexible electronics mass manufacturing. Due to fast and intensive technology development, the lack of knowledge about the reliability and lifetime of printed electronics is obvious, requiring further investigation. Especially, the effect of torsional bending on lifetime is mostly unexplored field of reliability testing. In this study, a torsional bending test of parallel printed silver conductors (0.3 mm, 0.5 mm pitch) on polymer substrate (Polyethylene terephthalate, 125 m thickness) were conducted and analyzed. According to the experimental results, torsional bending causes wear-out type failures in conductors and the length-to-width (LTW) ratio of the sample's substrate was observed to have a significant impact on reliability. If the LTW ratio is smaller than 3, the lifetime of printed conductor seems to collapse, and samples lasted for approximately only 17 bending cycles on average. Lifetime was improved by increasing the LTW ratio and samples withstood over hundreds of cycles with LTW ratio of higher than 15. However, the distance of a conductor from the edge of the substrate was not observed to have any significant influence on the reliability under torsional bending.

Advances in design and manufacture of stretchable electronics

“…This was considered in a study on the impact of torsional bending on PET supporting R2R screen-printed silver tracks. 71) Samples were twisted by 180°both clockwise and counterclockwise, while measuring four-point resistance and investigating heat patterns with thermography. The tests revealed that length to width ratio of the substrate drastically influenced the sample reliability, where samples with a length to width ratio below three experienced greater magnitude of stress.…”

Finite element analysis of stress distribution in soft sensors under torsional loading

“…During practical applications these sensors operate under intermittent or cyclic mechanical deformations such as bending, stretching, twisting and a combination of these. The sensor response changes with induced stresses during these mechanical movements, and often device failure occurs after repeated stress cycles [17][18][19]. Therefore, greater attention is needed to predict the response of flexible systems under various mechanical deformations [19][20][21].…”

“…Whilst few attempts have been made in this regard, most of the previous studies have focused only on the analysis of mechanical stress distribution and its effect on device performance under tensile and compressive bending and stretching conditions [13,19,[22][23][24][25][26]. Whilst these encouraging works mark a step in the right direction, a very few of them have aimed to understand the stress evolution under twisting (torsional) loading [17,18,27].…”