Bearings Minimise Friction and Wear

Bearings Minimise Friction and Wear Applied Materials chose a customised Type X 4-point contact bearing for the gripper arm on its Quantum X ion implant machine for the processing of silicon wafers Without sacrificing bearing accuracy, Kaydon Reali-Slim bearings can be optimised to minimise friction, outgassing, contamination and wear. Applied Materials UK in Horsham chose these bearings for a gripper arm assembly on its Quantum X ion implant machine for the processing of silicon wafers.This is a single-wafer, high-current implanter using fixed beam technology. Ion implantation is a process where electrically charged atoms are fired into the silicon wafer material to change the electrical properties of the material.It can be applied at various points of the wafer process.The gripper assembly is responsible for loading the wafer into the implant chamber and the role of the Kaydon bearings is to support the rotation of the gripper.RA Rodriguez is the UK factory representative for Kaydon. The bearing selected was a customised Type X 4-point contact bearing that accepts radial, thrust and moment loading.It was supplied with a flanged outer race for fixing to the gripper arm plate. AISI 440C stainless steel races and balls were a must as the application called for contaminant-free, no-lube operation.This material choice ensures minimum surface degradation and particulate formation.To accommodate the low-torque operation under vacuum the bearing was also specified with PTFE cage. 'The gripper arm assembly and therefore the bearings needed to operate in a high vacuum environment'.'They also had to be electrically conductive', explained Applied Materials Senior Design Engineer, Bert Webber.'Another important characteristic for this application was compact design'. The single four-point contact Reali-Slim effectively replaced the need for Applied Materials to specify two bearings, making the design more compact and simplifying the mounting.In addition to the obvious cost savings this arrangement also created space for easy installation and maintenance, as well as reducing weight. The ability of this Type X bearing to carry three types of loading simultaneously is thanks to the gothic arch geometry of the inner and outer races.It was also supplied with internal diametral pre-load to ensure zero free-play.This is accomplished by using balls that are larger than the space provided in the raceways.The balls and raceways therefore have some elastic deformation in the absence of an external load.