NextFlex’s collaboration with Advanced Functional Fabrics of America (AFFOA) and Pennsylvania Fabric Discovery Center (PaFDC) in the realm of integration of Flexible Hybrid Electronics (FHE) into fabrics and garments has highlighted the need for a thin, conformal, and scalable FHE encapsulation solution, as compared with NextFlex’s current silicone overmold encapsulation process. NextFlex began experimenting with lamination approaches to meet these needs. The effort began as a makeshift solution for an early wearables demonstrator and has recently blossomed into a standardized, repeatable, and durable toolset. Setting itself apart from traditional lamination processes is the newfound ability to accommodate demanding 3D device & electrical geometric complexities and demanding end-use performance and durability requirements.
The process starts after populating components onto an additively manufactured conductor layer atop a flexible polymer substrate. A moisture-cure silicone conformal coating is applied to provide mechanical compliance around the surface mount technology (SMT) components. Sheets of a laminate film composed of a thermoplastic polyurethane and a hot-melt adhesive are pre-cut to create keep-out regions in the final encapsulation. After the conformal coat cures, the pre-cut laminates are placed around the devices. The device & material stack is placed into custom silicone cushions, then is heated and compressed for bonding of the hot-melt material to the substrate and SMT components. The creative use of custom, device-specific silicone cushions ensure firm but evenly distributed pressure across the system during production while maintaining material registration during thermal expansion and gas outflow. The process has allowed for second-to-minute scale processing versus hour scale processing time for thermally cured silicone devices.
The process enables the use of keep-outs for end-use connectorization, various sensors, embroidery, and fabric-friendly mechanical anchor points when completed. The process boasts a much lower processing time, cost-to-scale ratio, contamination risk, and barrier to entry in terms of facilities, capital, and specialized knowledge compared to existing in-house overmolding processes. Being a newly developed capability, improvements in chemical durability and material optimization still need to be undertaken. NextFlex aims to improve the versatility, processability, and environmental requirements to benefit projects and member knowledge. Improved encapsulation manufacturing methods will enhance the FHE ecosystem. In this presentation, NextFlex will share details and lessons learned regarding the process and materials.
