Test & measurement
VAD Instrument has selected Renishaw’s UHV optical encoders for its motion platforms.
semiconductor wafer inspection, wafer bonding, photolithography and thin film deposition. Motion platforms are an integral part of
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these complex procedures and must be compatible with a vacuum environment. Renishaw’s TONiC UHV optical encoders
are specially designed for use in high and ultra- high vacuum enclosures and meet the strict requirements of FPD and semiconductor process equipment. VAD Instrument, based in South Korea, manufactures a wide range of precision motion platforms for semiconductor, FPD and electronics applications. VAD selected Renishaw’s TONiC UHV
encoder and RLE fibre optic laser encoder for its latest range of vacuum compatible platforms, which deliver improved motion control performance.
CHAllenges To generate a high-quality vacuum, or ultra- high vacuum (UHV), the air is first removed from an enclosed space (vacuum chamber) by means of a series of pumps. Many modern precision industrial processes
are carried out in a vacuum environment in order to minimise the impact of airborne contaminants. Vacuum-compatible motion platforms consist of bearings, guide rails, leadscrews and motors that have been specially designed. The dissipation of motor heat is often problematic in a vacuum and may be strictly regulated by cooling systems. One precondition for vacuum-compatible components is that outgassing, as measured by residual gas analysis (RGA), is negligible. Optical encoder components, such as the
readhead and scale, that are installed inside a vacuum chamber have several features including high temperature resistance (>100°C) to endure the bake-out procedures required for UHV. These include high cleanliness to eliminate surface fingerprints, oils and lubricants; air vents to ensure full venting of air spaces within the readhead; cable with PTFE insulation and silverplated copper braiding; and laser inscription rather than labels to remove adhesives. For the end-user, careful design of in-vacuum
equipment enables reductions in pumping times, better process control and higher throughput.
Optical encoders for motion platforms
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solUtIon VAD designs and builds customised precision motion platforms and process equipment for use in a vacuum environment. Its motion control products use Renishaw’s TONiC encoder systems with scales specified
February 2021 Instrumentation Monthly
acuum technology is used in many high- precision manufacturing processes. Typical applications include
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