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Flexible glass has many applications including photovoltaics, organic light-emitting device (OLED) lighting, and displays. Its ability to be processed in a roll-to-roll facility enables high-throughput continuous manufacturing compared to conventional glass processing. For photovoltaic, OLED lighting, and display applications, transparent conductors are required with minimal optical reflection losses. Here, we demonstrate an anti-reflective coating (ARC) that incorporates a useful transparent conductor that is realizable on flexible substrates. This reduces the average reflectivity to less than 6% over the visible band from normal incidence to incident angles up to 60°. This ARC is designed by the average uniform algorithm method. The coating materials consist of a multilayer stack of an electrically functional conductive indium tin oxide with conductivity 2.95×10 Siemens/m (31 Ω/□), and AlSiO. The coatings showed modest changes in reflectivity and no delamination after 10,000 bending cycles. This demonstrates that effective conductive layers can be integrated into ARCs and can be realized on flexible glass substrates with proper design and process control.

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Flexible Hybrid Electronic (FHE) devices interface flexible sensors and circuits with conventional rigid electronic components. This work reports preliminary results for the reliability aspects of a project aimed at fabricating a Wearable Sensor Patch (WSP) to monitor ECG signals. The device was fabricated by interfacing flexible electroplated Cu circuit lines and an ECG sensor on a Kapton® polyimide (PI) substrate with rigid electronics connected using SnPb solder (reflow temperature: 204 °C), making it a FHE device. Phase I of this project faced reliability issues as Cu circuit lines were susceptible to failure due to cracking near the front-end signal conditioning chip. This issue needed to be resolved in Phase II of the project to produce a robust device fit to be used in real world applications. The effect of changes in Cu trace thickness (2 and 6 μm) and Kapton® PI thickness (2 and 5 mil) on device robustness was tested. Effect of the use of low reflow temperature SnBi solder (reflow temperature: 175 °C) on device reliability was also tested. Multiple devices fabricated using different configurations of Cu trace and Kapton® PI thicknesses and either SnPb or SnBi solder were bend tested to single out the most robust configuration. Improved solder pad design for Cu traces at solder joint sites was also tested. It was observed that only devices with 6 μm thick Cu traces, 2 mil thick Kapton® and SnBi solder had no defects as a result of thermal cycling during fabrication. They also performed best during bend testing. Some of the factors contributing to robustness of this configuration might be lower CTE mismatch due to lower solder reflow temperature as well as greater strength under bending due to increased thickness. Improved solder pad design for Cu traces also improved device robustness considerably.