The YIELDjet™ FLEX system is the display industry’s first inkjet solution engineered specifically for OLED Thin Film Encapsulation (TFE) mass production. TFE is a critical enabling process for flexible OLED. Before the YIELDjet FLEX system, there were no practical mass-production solutions capable of satisfying customers’ cost and quality requirements.
The system offers superb control over every ink drop, and generates near-zero material waste. Yields are dramatically higher than alternative deposition approaches, and cost of ownership, vastly lower, making the system the most cost-effective TFE solution for high-volume OLED production.
Encapsulation is required to protect OLED devices from oxygen and moisture. For flexible OLED, conventional glass encapsulation had to be replaced with TFE, which includes an organic layer. The imperatives for organic layer deposition in mass production were stringent, and included: an oxygen and moisture-free processing environment; excellent film uniformity; ultra-low particles; the ability to neutralize incoming particles; high productivity, and easy maintenance. Inkjet printing was a promising candidate. But could it make the transition from the lab to the production floor?
Conventional evaporators and competing inkjet printers have been unable to overcome the TFE organic layer deposition challenges. Issues such as particle contamination, high non-uniformity, and onerous maintenance requirements have prevented these technologies from achieving the high yield/low cost imperatives required for mass production. In contrast, the YIELDjet FLEX system, which is based on the YIELDjet platform, overcomes the challenges by deploying a host of enabling innovations such as nitrogen integration, floating stage, ultra-fast drop monitoring, and SmartMixing™ software. Today, the system is the tool of choice for TFE mass production, delivering millions of flexible OLED products every year with “near-zero” yield loss.
Device features and particles from upstream processes can create defects and degrade the barrier properties of the TFE, which reduces yield. The organic layer must cover up these particles/device features and planarize the top surface, which dramatically improves the barrier properties. The optimized process of the YIELDjet FLEX system, which deposits liquid ink, has demonstrated excellent planarization behavior and enhanced TFE barrier properties.
A highly uniform TFE organic film is required to ensure a uniform appearance of the final display (called a “mura-free” display). The YIELDjet FLEX system eliminates print mura by combining an ultra-fast Remote Drop Inspection (RDI) system with SmartMixing™ printing software (which is optimized for TFE). An advanced motion control system ensures that the optimized drop pattern is printed accurately. In addition, the system is engineered for maximum manufacturing flexibility. Edge profiles are tunable for bezel engineering, and almost any display shape can be printed by simply changing a graphical input file. These capabilities have all been proven in mass production.
One of the biggest advantages of the YIELDjet FLEX system is its proven track record in mass production. In the past several years, the systems have consistently produced millions of OLED panels with “near-zero” defect rates, and outstanding uptime. Also, Kateeva’s experience bringing advanced inkjet printing into mass production helps reduce time-to-market.
Furthermore, the extremely low defect rate of the YIELDjet FLEX system delivers tangible value to customers, as yield is one of the most important factors affecting the profitability of an OLED mass-production line. We estimate, for example, that a 1% annual yield loss in a typical ½ Gen 6 mobile OLED display line would produce a $20M loss in scrapped displays. With Kateeva’s tool, the loss from scrap is negligible, making it the lowest risk choice for display manufacturers. Competing inkjet printing systems are unproven in mass production, and would inevitably take much longer to achieve these high yields.
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