ORNL Brings Photonic Curing to Market 

No matter how promising research breakthroughs in cancer research or clean energy may sound, we don't often hold our breath. The transition from academia to industry is where most technologies and medical treatments meet their end, which has led the Federal Laboratory Consortium for Technology Transfer to recognize laboratories that work to ensure that their work is seen through to the commercial marketplace.

Most recently, Oak Ridge National Laboratory (ORNL) was given the National FLC Excellence in Technology Transfer award for its pulse thermal processing (PTP) research and its collaboration with its private-sector counterpart, NovaCentrix.

The process in question is involved in the manufacturing of printed electronics by providing an alternative to traditional materials and processing tools (ovens, lasers) for electronics manufacturing. Then, glass or ceramic substrates are replaced by less expensive, more flexible materials such as polymers or paper for roll-to-roll processing. It also allows the target film to be heated in milliseconds without heating adjacent substrates.

NovaCentrix recently obtained the exclusive license for PTP and is integrating it into their existing line of photonic curing equipment called PulseForge systems.

The PulseForge 3300 toolset features ORNL's plasma arc lamp, which “is essentially lightning in a bottle,” explained Chad Duty of ORNL's PTP development team.

The lamp works by taking two electrodes, spacing them a foot apart, and passing an arc of electricity across that gap. The arc is contained in a quartz tube, and plasma is generated inside of an argon environment. What that does is generate radiant light possessing similar power density to that of a laser beam, only it's spread out over a very wide area.

The resulting heat rates that ORNL achieved are roughly 600,000 degrees Celcius per second, but the real advantage isn't so much in the temperature as it is in the area it can cover. Rather than passing a laser beam back and forth over a surface in need of heating, PTP can accomplish the same effect with a single 10-millisecond pulse, making it ideal for large surfaces.

Although ORNL and NovaCentrix have just stepped into the photonic curing spotlight, the technology actually got started with a company called Vortec Technologies out of Canada. Vortec had already been using the plasma arc lamp technology for silicon wafer processing, but understood that the technology could be used to additional ends, which is what led them to ORNL

Initially, ORNL researchers explored applications such as sintering and direct sheet fabrications, but they quickly realized that this only took advantage of the lamps' high intensity, disregarding the impressive speed at which it can turn completely on and off.

As a result, the PTP development team focused on applications such as flexible electronics, where the lamps' speed and intensity would allow it to rapidly heat one part of a circuit while leaving everything but the superficial surface undisturbed. So even in the case of a fairly thin material (like a millimeter of plastic used for a flexible circuit), the majority of that material would never see a significant temperature rise.

“With flexible circuitry, you have nanoparticle silver or copper-based ink that you can print at low temperatures just using your desktop Epson inkjet printer,” Duty explained. “You can print that out on paper or plastic and then flash the paper (even with printed circuitry on it) to melt metal right on top of the paper or plastic without harming the paper or plastic at all."

This is essential in applications such as thin-film solar cells, where the actual semiconductor deposited onto the millimeter-thick piece of plastic is only a micron or two thick. But in order for the semiconductor to achieve the correct crystalline structure, it must be heated to several hundred degrees Celcius—a temperature that plastic backing cannot withstand. With PTP, however, the semiconductor can be heated 700 degrees while the bulk of the substrate wouldn't see so much as a 25 degree temperature change.

In fact, Duty even remarked that if the plastic substrate were being held in someone's hand when the lamp was turned on, they wouldn't feel the temperature rise. When asked if this had been tested, he laughed and said no. “While it may be possible, it's not smart.”

Once this application had spent time in development, ORNL began working with NovaCentric on a conveyer belt-based system for PTP that can be adopted by electronics manufacturers. From there, the technology should play an even greater role in the manufacturing of flexible circuits used for LCDs, cell phones, keyboards, and even satellites.

Moving forward, the relationship between ORNL and NovaCentric should play an ongoing role in fine-tuning this technology for various commercial applications. For example if a solar cell manufacturer is looking to find the most effective way to use PTP in its production process, ORNL is prepared to work with them to refine the PTP system to meet their needs. From there NovaCentric would step in to manufacture the tools the company developed at Oak Ridge.

Whether other partnerships will collaborate to bridge these sorts of gaps in other fields has yet to be seen, but if ORNL's enthusiasm is any indicator, relationships such as these may be cropping with up more regularity in the future.