Mike Mason, VP Technology at Powerlase, discusses advances and manufacturing benefits of Rapid Laser Patterning (RLP) in the production of Flat Panel Displays.
Since appearing on the market in the late 1990s, Flat Panel Displays (FPDs) televisions have become increasingly popular with consumer and business buyers. Initial uptake of the units was low, largely due to the high cost to the consumer. Ten years ago, a 42 inch FPD could cost in excess of £4000, making it a luxury purchase and often out of reach for the average household.
However, improvements in manufacturing efficiency combined with less expensive components and rising incomes have meant units have been widely adopted for both entertainment and businesses use. Even larger size displays are up to a third of the price they were three years ago.
There are two main types of FPD; plasma display panels (PDPs) and liquid crystal displays (LCDs). LCDs are more commonplace in the home due to their use for mobile phone and mobile device screens and televisions. PDPs represent a greater proportion of the large panel market (42 inches and above) and is the dominant technology for 50-inch plus screens. The cost benefits offered by PDP at large sizes has resulted in the technology becoming the choice for home cinema and public display use, while the home entertainment market is still hotly contested between PDP and LCD.
Manufacturers have achieved this cost reduction by continuously examining and improving the production methods of FPDs. The employment of new technologies and techniques has enabled manufacturing processes to be streamlined, thereby reducing costs.
One highly successful technique involves replacing traditional wet-etch lithography with laser-based systems for patterning thin films on glass display screens.
Saving Manufacturers Millions
Most significantly, the use of lasers in the patterning of glass removes the need to use toxic chemicals in the process. As well as being a great advantage in terms of making the process environmentally sound, this also provides two major cost benefits. Firstly, removing the chemicals from the process instantly reduces costs as the chemicals themselves no longer need to be purchased, which saves several million dollars per month for a production line. Secondly it saves the cost of safely disposing of them, which is also very high.
In addition, the clean room environment required for PDP manufacture is very expensive, and any reduction in the physical space required for unit production reduces the overall cost of production.
While the initial cost of using laser equipment is higher than traditional lithography, the savings provided by RLP very quickly negate the upfront expense.
In addition to this, the process of patterning with lasers has a yield greater than 99 per cent. This again compares favorably to the chemical counterpart, which achieves 80-85 per cent at best. When using the chemical-etch technique, between 15 and 20 per cent of screens are lost.
The manufacturing process is also streamlined with RLP. The glass patterning is reduced to a two-step process, the laser-processing and water rinsing stage. It therefore only requires two process steps, whereas wet-etch techniques require between six and ten steps to achieve the same result.
Rapid Laser Patterning – Best Practice
The unique nature of Q-switched diode-pumped solid state lasers (DPSSL) has played an innovative role in streamlining the process by the RLP of Transparent Conductive Oxides (TCOs) replacing the need for multi-stage production equipment.
Due to the continued drive by manufacturers for alternatives to lithography, RLP has been investigated for virtually all commercially available short pulse lasers (nanosecond or below) for processing ITO – ranging in wavelength from the Infrared (IR) to the Deep Ultraviolet (DUV).
Q-switched diode pumped solid-state lasers (DPSSL), with higher pulse energies, offer an answer to the successful introduction of RLP in the flat panel PDP market. These high pulse energies allow the use of beam delivery techniques more commonly associated with excimer lasers. The beam is homogenized, imaged onto a mask and re-imaged on to the substrate. The high pulse energies allow sufficient energy density to ablate large pixels (>1mm2) with a single pulse. Kilohertz repetition rates mean that thousands of pixels can be ablated per second – and by ‘stitching’ the pixels together large areas of active ITO electrode structure can be created very rapidly. To further improve throughput industrial systems, multiple lasers may be employed to achieve commercial throughputs that exceed those of conventional lithography.
The sustained cost advantage of RLP makes the technique extremely desirable for manufacturers. When coupled with the capacity for greener, cleaner technology, particularly in the current industrial and environmental climate, it not surprising some of the world’s leading PDP manufacturers are adopting this technology with great speed and success.
The commercial potential of RLP does not stop with the PDP market. This technique is also employed for a number of other FPD and thin film applications. Powerlase is now looking to deploy this technology in a number of other key industrial areas, such as solar cell and AMOLED manufacture, thereby helping to expand their markets and promote lasers for new industrial uses and processes worldwide.
By Mike Mason, VP Technology at Powerlase
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