Reliability Analysis of Laminated Oxide/Metal/Oxide Flexible Conductors Through Cyclic Bending After Accelerated Weathering

The effect of weathering caused materials deterioration on the cyclic bending reliability of laminated oxide/metal/oxide (OMO) flexible conductors is investigated. The OMO samples in this study were commercially available and with a sheet resistance value of 16 ohms per square. Replicated samples of three populations were aged by accelerated weathering with the conditions of UVA 0.77 W/(m
²
.nm) at 75°C for 6 days (d), 9 d, and 15 d, respectively. Subsequently the OMO samples were subjected to cyclic bending and meanwhile their resistance values were recorded through real-time measurements. The data of each weathered population was assessed through Weibull analysis. In the statistical Weibull analysis, a 250% increase in resistance was adopted as the criterion of electrical failure. The results indicate that the bending reliability of the OMO flexible conductors highly relies on the substrate integrity after weathering. The unaged samples were found to have the highest characteristic lifetime of about 48,000 bending cycles. However, the characteristic lifetime significantly decreased as the weathering time increased. Moreover, increasing the weathering time raised the shape parameters of the weathered populations. This behavior was due to the degradation of polymeric substrate after weathering of UVA irradiation at elevated temperature. The weathering caused substrate embrittlement enlarged the mechanical stress in the OMO coatings, leading to surface cracking when under bending.