Strasbaugh nTellect (Model 7AF) Wafer Grinder
4 - 4 Version 1.2 - June 2004
SPINDLE ASSEMBLIES
COARSE/FINE SPINDLES
Identical except for the type of diamond wheel installed, the coarse and fine spindles
grind the wafers on the left and right work chucks. Each is an air bearing spindle (for
details, see below) mounted vertically and passing through a casting mounted to the
vertical rails. The vertical rails are lubricated by the automatic lubricator; frictionless
vertical movement is provided by the linear bearings.
The drive assembly is a recirculating ball lead screw support, with the ball screw
driving the spindle up and down. Within the coupling between the ball screw and the
assembly that moves the spindle up and down, a load cell is installed to measure the
spindle weight. The information from the load cell is used to determine the amount of
down force applied to the wafer.
The spindle drive system consists of a pulley system with a toothed belt drive
connecting the lead screw to the reducer of the brushless DC servo motor. This
arrangement converts motor drive into vertical linear motion, moving the spindle
assembly up or down.
The ball screw assembly is attached to the spindle, and a counterbalance assembly
mounted to the same spindle adjusts the amount of spindle weight seen by the wafer.
The counterbalance assembly also has a load cell to read the counterbalance required.
Hard stops and proximity sensors defer possible runaway motion.
Within the spindle assemblies are mechanisms for adjustment of side to side and front
to rear positioning, with dial indicators installed at the factory to aid in adjustment.
The diamond wheels mount to the air bearings on backing plates; the type of wheel
installed gives the spindle its identity as either coarse or fine.
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