16mm Stroke Compact Planar Voice Coil Actuator for Wafer Transport Pick Heads

Flat-type linear voice-coil motor stator coils are lightweight, with fast response times and high frequency. They feature a short stroke and a compact design.The VCAP0020-0160-00A drives the vertical axis of wafer and carrier transport heads: the pick arm of an EFEM, the lift pin of a load lock, the Z axis of a sorter or the descend axis of an AOI handler. It offers 20 N peak force, 5.3 N continuous force at 25°C and a 16 mm stroke in a 59 × 50 × 22.5 mm body, powered at 27.6 V maximum with a 4.4 V/m/s back EMF constant. The 16 mm travel matches the working gap between a FOUP slot and a chuck, and the flat form factor fits between the arm plates of an existing transfer head.

A transport axis in a fab runs hundreds of thousands of cycles per month, always with the same motion: descend, contact, lift, retract. Pneumatic cylinders do this well but they arrive with an impact, and that impact is the main source of particle generation and of micro cracks in thin wafers. A voice coil replaces the end stop impact with a soft landing, because contact force is set by current and can be held at a few newtons for the last millimetre of travel. Cycle time does not suffer: acceleration is high and the axis settles without bounce, so the pick can start earlier than with a damped cylinder. Position feedback from an encoder also makes the descent profile programmable per product, so a fragile 50 micrometre wafer and a 775 micrometre wafer can share one head with different approach speeds. Since there is no air consumption, the head also runs quieter and cooler inside an already crowded EFEM enclosure, and there is no exhaust to disturb the laminar flow above the stage.

EFEM pick and place arms, load port and load lock lift axes, wafer sorters and frame handlers, FOUP and cassette openers, AOI and metrology handlers, and tray or magazine transfer axes in back end assembly lines.

Q: Does a soft landing slow down the transfer cycle?
A: No. The descent is fast until the last millimetre, then force limited, and the axis settles without the bounce a pneumatic cylinder produces, so the vacuum can be switched on earlier and the overall pick time is usually shorter.

Q: How is wafer breakage prevented?
A: Contact force is programmed per product and can be limited to a few newtons, and current feedback stops the descent if the force rises faster than expected, which is what happens when the arm meets a misaligned wafer.

Q: Can it be used inside a vacuum transfer chamber?
A: Yes, with the vacuum option: dry lubrication free construction, low outgassing cable and no trapped volumes. Vacuum rated units are quoted per chamber pressure requirement.

Q: Is air supply really not needed?
A: The axis is fully electric. Power and feedback cable only, which simplifies the cable chain in a moving arm and removes tubing that would otherwise generate particles as it flexes.

Q: What is the expected cable life on a continuously cycling arm?
A: The high flex lead wire is rated above ten million cycles. For higher counts, a rolling flex cable chain or a fixed cable with a service loop is recommended.

Actuator with high flex cable and mounting hardware. Vacuum version, encoder kit and matched drive modules are quoted on request.