The YIELDjet™ platform is the world’s first inkjet printing manufacturing equipment solution developed from the ground up for flexible and large-size OLEDs. With a novel architecture and breakthrough features, the solution addresses the technical challenges that previously prevented cost-effective mass production of flexible and large-size OLEDs. The challenges included inferior device lifetime, unacceptable particle levels, inconsistent reliability, and poor uptime performance.
The YIELDjet platform combines key technical innovations that work in concert to achieve what had previously been impossible—a system that could navigate the harsh terrain of OLED mass production. Listed below are the core innovations that would bring inkjet printing to the OLED production floor.
Trace amounts of oxygen and moisture, and large particles, can degrade OLED device performance and reduce yield. Processing in a clean, high-purity environment is a central requirement for OLED front plane manufacturing equipment.
The YIELDjet platform delivers a clean, high-purity environment by flowing nitrogen through the printer enclosure in combination with advanced particle control. Best practices from the semiconductor industry, along with intensive use of fluid flow simulation tools were applied to design the purged printer enclosure. This produced a printing platform that can achieve and maintain sub-1ppm levels of oxygen and moisture, meet particle requirements, and purge down to a process-ready state in 4-6 hours after a break to air. Consumables cost is minimized by recirculating the nitrogen in the system during production.
Uniform deposition of the printed layer is essential for uniform OLED displays. A key printing requirement to achieve this uniformity is the drop placement accuracy. Stage accuracy is an important component of drop placement accuracy. To achieve high stage accuracy that is scalable to all glass sizes, Kateeva pioneered the floating stage for inkjet printers. Here, the glass floats on a thin cushion of nitrogen which flows from a specially designed stationary stage. Pressure and vacuum are applied simultaneously to create frictionless motion of the glass at high accelerations while maintaining a high degree of accuracy. To further improve stage accuracy, fine position adjustments can be made in real time during a print scan.
Print non-uniformity can be caused by inherent variations in drop volume, speed, and angle across the nozzles in the print array. To address this challenge, the YIELDjet platform deploys ultra-fast print head monitoring technology and nozzle-mixing algorithms. A proprietary Remote Drop Inspection (RDI) system measures the drop volume, speed, and angle of every nozzle approximately 50X faster than conventional monitoring systems. The print heads are monitored continuously during glass loading and alignment, so it is not in the critical path of system throughput. Kateeva’s Smart Mixing™ software captures the ink drop data and calibrates the algorithms. The output is optimal drop pattern and nozzle mixing, which is then executed during printing. The final display is uniform and free of print mura.
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