AF32 Glass, IR Optics
Feb 2008SCHOTT North America Inc.Request Info
Volume Zerodur ProductionELMSFORD, N.Y., Feb. 1, 2008 -- Schott introduced AF32 glass designed for optoelectronics applications, and an expanded line of advanced optics to include infrared (IR) materials available in both zinc sulfide (ZnS) and IR chalcogenide glasses, at SPIE Photonics West 2008.
The company also exhibited a hexagonal piece of Zerodur and announced expanded capabilities for its volume production. A glass ceramic, Zerodur offers zero thermal expansion in LCD lithography to manufacture cell phone displays, computer monitors and TVs, as well as in large-format mirror substrates for telescopes.
The new IR material is available in large sizes and custom shapes, and as windows, domes or lens blanks. Potential applications include night-vision devices, temperature analysis tools and equipment inspection systems.
A Schott employee demonstrates a new testing device that measures the stress birefringence of optical material. (Photo: Schott)
Schott offers two grades of zinc sulfide (ZnS) material: regular (FLIR)-grade and multispectral (clear)-grade. FLIR-grade ZnS is a polycrystalline optical material with high performance in fracture strength and hardness. Often used in the 8 to 12-µm range, FLIR grade ZnS is resistant to rain and particle corrosion, making it suitable for defense applications. Clear-grade ZnS is produced by treating ZnS after growth with a hot isostatic process that eliminates the material’s microscopic voids and defects. The hot isostatic process also produces a clear material. Clear-grade ZnS is used in applications across the visible to infrared region, typically from 0.45 to 12µm.
Schott offers five different Infrared chalcogenide glass (IG) variations. These IG glasses have excellent transmission and a low thermal change in the refractive index which enable optical designers to use IG glass to design color-corrected optical systems without thermal defocusing. Optimized for pairing with other IR materials in optical designs, the IG line is available as custom-cut blanks, generated lens blanks and moldings for customer fabrication.
AF 32 is an aluminoborosilicate glass that is alkali-free in synthesis. This property helps ensure that a camera module’s delicate CMOS image sensors are not degraded when packaged using the wafer-level chip scale packaging (WLCSP) process. Easy to cut and dice, the AF 32 material helps manufactures achieve a high yield during the final dicing process for the optical assembly.
“We think the AF 32 is the ideal packaging material for image sensor packaging, WLO and MEMS (microelectromechanical systems) applications,” said Oliver Jackl, general manager sales. "The camera phone and CMOS image sensor markets are aggressively seeking ways to decrease the size of their modules, and our AF 32 glass will help the industry achieve this goal. Its performance surpasses that of AF 45, which has been used by companies like Tessera Technologies Inc., a provider of miniaturization technologies for the electronics industry, for its Shellcase wafer-level packaging solutions for image sensors.”
WLCSP is increasingly being used for packaging camera modules. Schott said manufacturers are using its alkali-free AF 45 for these packages’ back glasses and the cover glasses. "With a coefficient of thermal expansion close to silicon, high luminous transmittance and good cosmetic properties, AF 45 provides manufacturers with a glass suitable for traditional 8-in. WLCSP processes," Schott said. "In addition, the use of a down-draw process to manufacture AF 45 means manufacturers can obtain the glass at various thicknesses."
The company also said it has increased its capabilities to manufacture Zerodur, and that initial deliveries for new extremely large telescopes could take place in 2009. The Thirty-Meter Telescope (TMT) -- a collaboration of Caltech, University of California and the Association of Canadian Universities for Research in Astronomy -- is expected to have a mirror diameter of approximately 30 meters comprised of about 500 mirror segments. In addition, the European Southern Observatory (ESO) is planning the European Extremely Large Telescope (E-ELT), which will use a mirror with a diameter of 42 meters comprise of more than 900 hexagonal segments. Other major projects are planned in China, Japan and the US.
“Zerodur is absolutely predestined for use in the large telescopes that are currently being planned all over the world,” said Westerhoff. “This glass ceramic offers extremely low thermal expansion, yet high chemical stability. Zerodur can also be produced in high, reproducible quality in large volumes and is easy to process, polish and coat. We are particularly proud of our CNC-processed, lightweight honeycomb-structured mirror substrates that result in a weight reduction of more than 80 percent."
Zerodur was developed for astronomy applications in 1968, one year before the first moon landing. It has been used for optical elements in space probes, as well as in projects like the Very Large Telescope from the intergovernmental European Organization for Astronomical Research in the Southern Hemisphere. SCHOTT supplied four eight-meter mirror substrates for that project.
Because of its zero thermal expansion, Zerodur is also used to make calibrated measurement standards for precision measurement technology. Other products include precision components for microlithography and ring laser gyroscopes. Prisms and mirrors that often weigh tons are also needed in LCD lithography in order to manufacture the displays for cell phones, monitors and flat-screen televisions.
Zerodur glass ceramic is used in LCD lithography to manufacture cell phone displays, computer monitors and televisions. At the SPIE Photonics West 2008 exhibition, Schott exhibited a hexagonal piece of Zerodur similar to those being used in large astronomy projects.
For more information, visit: www.us.schott.com
Schott North America Inc.
555 Taxter Rd.
Elmsford, N.Y. 10523
Phone: (914) 831-2200
Fax: (914) 831-2201