In a new paradigm being created by several of today’s newest technologies, better products don’t necessarily cost more to make, and high speed doesn’t have to mean sacrificed quality. Hybrid technologies like the new gyrotron beam system* break this cycle and apply a new set of rules to old, frustrating problems. With this new technology, production numbers and product performance expected by new millennium standards become plausible.
Though originally developed in Russia in the 1980s, the millimetric wavelength, high frequency, microwave-beam technology of the gyrotron beam elicits distinctly Western images of futuristic manufacturing plants, where thousands of units are perfectly produced each day at unheard-of speeds. Ultra-rapid, selective heating with exceptionally high heat density are standard for the space-age beam, which is light-years apart from conventional methods used for annealing, coating and joining everything from glass and ceramics to semiconductors.
A New Way of HeatingManufacturing processes today demand a lot of material capabilities with enhancements such as composite formulations, complex shapes, multilayer processes and ever-increasing production speeds. The gyrotron beam meets these needs by selectively heating one material while leaving others cool, focusing its energy only where needed, and heating one layer of material through a surrounding layer, enabling manufacturers to make the most of advanced product formulations. The technology combines the focusing ability of a beam (like lasers or e-beams) with the volumetric heating capabilities of microwave, providing fast, efficient thermal treatment of almost any material except metal.
In all heating processes, heat density is fundamental to efficiency and uniform processing. The gyrotron emits a beam with an exceptionally high power density that can be focused, spread over a surface, directed, or even split—all with superior heat density where it’s focused and no heat where it’s not. Its millimetric wavelength ensures that the energy is used in heating the material being processed, not the space around it, thereby creating efficiencies of 60-80%. Because of its ability to achieve volumetric, uniform heating at virtually any temperature, sensitive processes such as annealing ceramics, bending glass and processing semiconductors become elementary and lay the groundwork for the creation of new products with unique properties.
A Millimetric Microwave BeamThe gyrotron is essentially a 5-ft-long, 125-lb metal tube that generates a microwave beam from a few KWt to 100 KWt (dozens of times higher than the usual industrial microwave). The beam is directed with metal mirror optics to effect specialized heating of specific materials or finished parts (see Figure 1). Custom protective work chambers offer all of the required shielding and can be configured for large and small products for both conveyor-type and non-continuous operations. The unique optical capabilities of the gyrotron beam processes create a beam that can be split to process materials from several sides simultaneously or to provide heat treatment for several production lines at once. The system uses material characteristics for differential energy absorption, as well as beam focusing and manipulation, to reach the desired effects.
Because of its small footprint and rapid installation time, the gyrotron can be added to an existing production line fairly readily for heating items as diverse as dinnerware and sanitaryware, electronic components, automotive windshields and semiconductor wafers.
Processing CeramicsBecause the system can easily reach temperatures of 2000∞C and higher, one of the best candidates for the gyrotron beam is ceramics. Compared to using conventional heat sources, including industrial microwaves (2.45 GHz), the gyrotron reduces energy usage and processing time by 3-20 times, depending on the process. Unique product features are also a common result. In sintering, for example, the system provides accelerated densification rates and high microstructure uniformity throughout the part.
Because of the beam’s ability to heat materials differentially, a real boon for ceramic applications using the gyrotron technology would be in joining dissimilar materials with different melting points, such as metal to ceramic parts within a single assembly. Applying electrically conductive films to glass and ceramics is another example. High-performance ceramic bonding, where superior joint strength is needed, is also feasible, as brazes can be used with melting points higher than the permissible temperature of the ceramic materials being joined. Applications include high-volume firing of advanced and traditional ceramics and refractories, as well as processes like sanitaryware repair. Brazing of metals to ceramics for advanced engine development is an automotive application that can clearly benefit by the ultra-rapid, volumetric and selective heating of this process.
Coatings are also a clear benefactor of the gyrotron beam’s selective heating capability. The system can apply virtually any coating on any substrate, regardless of preconceived temperature constraints. In the case of ceramic coatings, a self-regulating “avalanche process” occurs, where each micro-layer of a coating changes from absorbing the gyrotron’s energy, to reflecting it as it is heated, and then to melting, at which point the heating stops, and the next layer is allowed to repeat the process. The resulting coating is exceptionally strong with a wide transition zone.
Processing GlassGlass easily absorbs infrared energy, creating temperature differences between the interior and the external surfaces of the glass sheet, which can cause cracking. For this reason, the heating ramp rate of the sheet must be kept low.
The gyrotron beam creates uniform temperature distribution inside the glass, allowing a high heating ramp rate to be maintained for virtually any thermal treatment process. This capability reduces process time by up to 10 times. Heat shaping automotive and architectural glass, both pressed and gravity bent, take on new possibilities in complex geometries. Coated, laminated and tempered glass can be heated and shaped in new ways, and soldering and welding can be performed on tempered glass without significant loss of heat strength characteristics. In many cases, expensive tunnel furnaces can be eliminated or dramatically shortened by implementing the gyrotron beam technology as a stand-alone or assistant heater.
A system is currently being prototyped for tempering thin glass (2 mm and thinner) without optical distortion, initiating advances in weight reduction of automotive and construction glass. This will also open opportunities for replacing numerous plastics with thin tempered glass—a new glass market. Advantages of gyrotron glass processing include new designs for windshields and side lites by firing coatings without heating the entire glass sheet; the possibility of producing complex shaped automotive glass by local over-heating of bending areas and follow-up heating during bending; the production of new window types by joining glass sheets without loss of flatness; and thermal processing of coated glass without coating damage; as well as decreases in process times (very often from hours to seconds) and reductions in cost (often by many times). New glass products made with the gyrotron technology are expected to be on the market within the next several months.
Processing SemiconductorsExtensive work is underway in using the gyrotron beam in semiconductor manufacturing as a next-generation rapid thermal processing (RTP) tool. Amorphized and non-amorphized wafers are being annealed/activated with the ultra-rapid thermal processing ability of the gyrotron beam. The system allows semiconductor materials to be processed with a sharp front slope, ultra-high power density and simultaneous cooling, ensuring a sharp backslide slope to the pulse profile. As a result, ultra-shallow junctions and high concentrations of active carriers are achieved. Current test results in this application fall well beyond the XJ curve (the standard indicator) and exceed the semiconductor industry roadmap parameters for the year 2005. Ultra-fast heating rates; high, uniform power density over large surfaces; ease of integration into production; and easy maintenance/high reliability make the technology of particular interest in this field.
A 21st Century ToolThe gyrotron beam offers a range of capabilities that have not previously been available in thermal processing. Using this new tool, glass can be bent, shaped and welded; high performance ceramic coatings can be easily and quickly applied to both metal and ceramics; and semiconductor crystals can be annealed. The technology is super-fast in nature—beyond infrared or e-beam methods—and it is selective. Heating of ceramics, glass and other materials can take place rapidly in a single site, significantly reducing a furnace’s size. Virtually any type of coating can be applied to almost any substrate, without heating the substrate. Additionally, the technology delivers volumetric uniform heating capability for material thicknesses ranging from dozens of microns to dozens of inches.
The benefits of the gyrotron beam can be applied in diverse processing environments to increase throughput and speed, enhance product quality, and reduce energy consumption and operating costs. With this new technology, the impossible can become viable in leading-edge product design.
For More InformationFor more information about the new gyrotron beam technology, contact Vlad Sklyar or Lian Sawires at Gyrotron Technology, Inc., 2014 Ford Rd., Unit 11, Bristol, PA 19007; (215) 826-8415; fax (215) 826-8416; e-mail Gyrotron@worldnet.att.net; or visit http://www.gyrotrontech.com.
*The gyrotron beam technology was developed and is supplied by Gyrotron Technology, Inc. (GTI), Bristol, Pa.