Thermal Technology Develops Commercial EFG Crystal Grower

Sept. 14, 2009
Date Announced: 14 Sep 2009 Thermal Technology announces the successful testing of the first commercially available edge-defined, film-fed growth (EFG) crystal grower with the capacity to grow sapphire crystals up to 12 inches wide, 20 inches long and 0.6 inches thick (300 mm x 500 mm x 15 mm). The first sapphire test plate grown was over 15 mm thick throughout, eight inches wide and 16 inches long with no visible bubbles in the useable area. There were no cracks, grain boundaries or twins. Thermal Technology will ship its first EFG sapphire crystal grower to the customer in September. The EFG process was invented in the United States over 40 years ago for the production of sapphire filaments. Since then it has been used to produce a wide variety of shaped sapphire parts including plates, tubes, rods and ribbons. It uses a molybdenum die or shaping unit to define the cross sectional shape of the part being grown.“We are very excited about this system,” says Matt Mede, president and CEO of Thermal Technology. “The market is requiring larger crystals, and up until now large sapphire crystal producers had to build their own machines.”Equipment for growing smaller EFG sapphire crystals is commercially available in the Ukraine.Sapphire (aluminum oxide) has a unique combination of physical and chemical properties including hardness, transparency over a wide range of wavelengths from infrared to ultraviolet and a high dielectric strength; it is chemically inert and has a high melting point. This makes it ideal for a wide variety of applications including supermarket scanner windows, pads for orthodontics, substrates for GaN blue LEDs and silicon devices, wear surfaces, cutting edges, IR windows, and transparent armor – the application requiring large plates such as the one shown here.In order to meet the customer’s acceptance criteria, Thermal Technology was required to develop a crystal growth process demonstrating the successful operation of the machine. Using a hot zone and die assembly as well as control software provided by Dr. Frank J. Bruni, a crystal growth consultant also based in Santa Rosa, Thermal Technology was able to grow the first slab after just a few operational tests. “This was a challenging project,” Dr. Bruni said, “given the very high temperatures (over 2,000 C) and the large volume of sapphire that had to be melted. Of particular difficulty was achieving a uniform temperature across the surface of such a large die. The crystal is separated from the die by a thin layer of molten sapphire. One side of that layer, the crystal interface, must be at the freezing point of sapphire while the other side must be slightly higher to maintain the flow of liquid by capillary action. Getting the temperature field that uniform over a large surface area is not easy.”Thermal Technology designs and manufactures crystal growing systems and high temperature vacuum furnaces for laboratory and production use. The furnaces accommodate metals, ceramics, glass, nanopowders, and emerging materials. Thermal Technology’s manufacturing and corporate offices are located in Santa Rosa, California. They also have sales offices in Illinois, New Hampshire, Germany and China.

Patty Mede, Marketing Coordinator 707-571-1911

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