Advancements in Inductive Inline Metrology for High-Yield, High-Throughput R2R Processing Systems

Presented by Michael Hofmann, SURAGUS GmbH

In high-speed web coating processes, cost per square meter is one of the defining factors for successful commercialization of flexible materials. Due to the demand for high-throughput, high-yield and low coating cost requirements, equipment manufacturers design innovative systems and processes that significantly improve the quality and productivity of functional coatings. These defining factors have opened new avenues for the mass production of battery electrodes and current collectors, fuel cell components MEA/GDL, smart films, flexible electronics, rollable displays etc., by roll-to-roll (R2R) coating on polymers, thin glass (UTG), metallic foils, and textiles. With increasing complexities in device architectures and manufacturing processes, the application of reliable inline characterization techniques is of tremendous importance for process monitoring and quality control to have a higher system uptime and abundant data.

The performance of the innovative functional coatings is ultimately determined by the quality of electrically conductive layers among other properties. A host of inline parameters viz., sheet resistance, resistivity/conductivity, metal layer thickness, anisotropy, emissivity, weight, residual moisture, drying status etc can be measured in real-time with high sensitivity and repeatability by non-contact, non-destructive eddy current technology. Due to its high sensitivity to conductivity, permeability, and permittivity, high-frequency eddy current technology registers a signal shift from a recipe variation of transparent electrodes (e.g., ITO, AgNW, CNT), pastes and inks (e.g., Ag, Cu) and active materials (e.g., LiCoO, NMC).

With advanced process integration and automation capabilities, the inline sensors can be introduced into both existing and new production lines for PVD, CVD, electroplating, printing, spraying, slot-die coating, curtain, etc. This report demonstrates the wide-range of possibilities for early-stage monitoring in R2R manufacturing processes. Recent innovation in eddy current sensors for slurry monitoring, hot environments, narrow spaces and in-vacuum traverse are included in this paper to explain the capabilities for material testing and characterization.