By Donald J. Davis, business unit leader of KDI Technical Services, Kent Displays, Inc.

Cleanroom-based roll-to-roll (R2R) manufacturing is a critical enabler for defect-free, scalable production of flexible electronics. This article highlights the importance of cleanroom environments in mitigating contamination risks, influencing equipment design and enhancing in-line inspection and process control. It explores how cleanroom-compatible systems support high-yield manufacturing for new applications. Despite added complexity and cost, cleanroom R2R unlocks premium markets and improves reliability. For converters, cleanroom R2R isn’t optional; it’s a strategic imperative for entering advanced electronics markets and future-proofing operations.

As flexible electronics continue to reshape industries – from medical diagnostics to consumer displays – the pressure to deliver defect-free, scalable products has never been greater. While roll-to-roll (R2R) manufacturing is widely recognized for its throughput and efficiency, one critical enabler often goes underappreciated: the cleanroom.

Cleanroom-based R2R manufacturing isn’t just a niche; it’s a necessity for high-yield production in contamination-sensitive applications [1]. This article explores why cleanroom environments are essential, how they influence equipment design and process control and what opportunities they unlock for converters entering advanced electronics markets.

Why cleanrooms matter in roll-to-roll

Flexible electronics rely on ultra-thin substrates, functional coatings and precise layer alignment. These features make them highly susceptible to airborne particles, static discharge and humidity fluctuations. A single micron-sized contaminant can cause device failure, reduce yield or compromise long-term reliability.

Cleanrooms mitigate these risks as specialized facilities controlling airborne particulate levels, temperature and humidity. Cleanrooms use advanced air filtration, such as high-efficiency particulate air (HEPA) filters above the work surface, to flush out particulates and maintain a clean environment. Airflow through HEPA filters comes from advanced HVAC systems that provide precise temperature, humidity and pressure control. Specialized building materials are used for floors, walls and ceilings that are smooth and non-shedding and easy to clean. Cleanrooms also have strict protocols for personnel who wear specialized garments and footwear to minimize contamination from skin and clothing.

ISO 14644 standards [2] define the allowable particle counts per cubic meter of air as shown in Figure 1. Note that all concentrations are cumulative, e.g. for ISO Class 5, the 10,200 particles shown at 0.3μm include all particles. ISO Class 7 or better often is required for electronics-grade converting. For converters, this means adapting not just the process, but the entire environment their roll-to-roll asset is located in.

Equipment design for cleanroom converting

Operating in a cleanroom demands more than installing HEPA filters. Converting equipment must be designed with contamination control in mind:

• Material selection: Stainless steel, anodized aluminum and anti-static polymers reduce particle shedding and electrostatic buildup.
• Enclosure strategies: Modular covers and laminar flow hoods isolate critical zones, like coating heads and web paths (see Figure 2).
• Web-handling adaptations: Precision tension control, edge guidance and non-contact rollers minimize mechanical stress and particle generation.

These design choices aren’t just about compliance; they’re about performance. Cleanroom-compatible equipment enables tighter tolerances, smoother runs and fewer defects.

In-line inspection and process control

In cleanroom R2R setups, inspection isn’t an afterthought – it’s integral. In-line metrology systems [4] monitor coating thickness, registration and surface defects in real time. Optical sensors, machine vision and spectral analysis tools feed data into feedback loops that adjust process parameters on the fly. Figure 3 shows the workflow for the optical inspection [5] of coated films where a line-scan camera is used to detect a coating defect, a classifier identifies the defect, the visualizer shows the defects on roll maps and finally roll grading is performed.

This proactive approach reduces scrap, improves first-pass yield and supports traceability. For converters, it means fewer surprises and more predictable output, especially critical when scaling to high-volume production.

Applications driving cleanroom roll-to-roll adoption

Kent Displays has been using cleanroom R2R for manufacturing flexible liquid crystal displays and other devices for over 15 years, as shown in Figure 4. Others use cleanroom R2R processes for medical devices and printed electronics. Cleanroom R2R is gaining traction across sectors that demand both precision and cleanliness:

• OLED and microLED displays: Require defect-free layers and tight registration.
• Flexible batteries and supercapacitors: Sensitive to moisture and particle contamination.
• Biosensors and diagnostic strips: Must meet medical-grade sterility and reliability standards.

In each case, cleanroom R2R enables scalable production without compromising quality. It’s not just about meeting specs – it’s about unlocking new markets.

Challenges and opportunities

Cleanroom operations come with added complexity: higher capital costs, stricter protocols and specialized training. But the payoff is substantial. Converters that invest in cleanroom R2R gain access to premium markets, reduce rework and position themselves as strategic partners in high-tech supply chains.

Emerging trends, such as AI-driven inspection, predictive maintenance systems and digital twins, are making cleanroom R2R more accessible than ever. For converters willing to adapt, the opportunity is clear.

Conclusion

Cleanroom roll-to-roll manufacturing is more than a technical upgrade; it’s a strategic advantage. As flexible electronics evolve, so must the environments and processes that produce them. By embracing cleanroom principles, converters can deliver higher yields, enter new markets and future-proof their operations.

The hidden engine behind high-yield flexible electronics isn’t just the R2R line – it’s the room around it. 

References

1. Montbach, E., & Davis, D. (2018). Roll-to-roll manufacturing of flexible displays. In J. Greener, G. Pearson, & M. Cakmak (Eds.), Flexible Display Technology (Chapter 10). Wiley. https://doi.org/10.1002/9781119163824.ch10
2. ISO 14644-1:12015(E), pg 5
3. New Era Converting website. https://neweraconverting.com/equipment/laminators-embossers-and-calenders/cleanroom-equipment, accessed 10/6/2025
4. Young, John. “Inline Inspection Systems for Web Converting” Converting Quarterly, Spring 2023
5. Dr. Schenk https://www.drschenk.com/publications/web-inspection.html

Donald J. Davis has 35 years of experience in advanced manufacturing, including liquid crystal displays, military laser systems, MEMS and nano-embossed plastic films. He is the business unit leader for KDI Technical Services, a division within Kent Displays, Inc., that focuses on cleanroom-based contract manufacturing. Under Davis’ leadership over the past 17 years, KDI has implemented three roll-to-roll manufacturing lines for flexible liquid crystal displays for the manufacture of the Boogie Board® electronic writing tablet and other devices. He also leads technical development for KDI – aligning the company with partners in digital manufacturing and helping secure grant funding for key research initiatives. Prior to joining KDI, he held technical positions at Avery Dennison and Hana Technologies. Don is the 2015 recipient of the Visionary Manufacturing Leadership Award and has spoken at conferences such as FLEX, Association for Roll-to-Roll Converters Business Summit, ESTECH, LOPEC and Prinse’22. He can be reached at email: ddavis@kentdisplays.com, www.kentdisplays.com, www.SwitchVue.com.