Operation and Maintenance Manual Model 7AA Wafer Grinder
7 - 22 Version 1.2 - April 18, 1996
WHEEL WEAR COMPENSATION
Wheel wear compensation is critical to maximizing machine
performance, particularly when dual grind cycles are required.
As mentioned previously the Spindle Pretravel and Dynamic
Offset data are used to calibrate the coarse and finish wheel
positions during machine initialization.
The thickness measurement feedback compensation is used to
maintain final grind thickness during a grind cycle. However,
during production the grinding wheels will accumulate wheel
wear. The rate of wheel wear is a function of many process
variables including amount of stock removal per wheel, feed
rates, coolant flow, wafer product diameter, and grinding wheel
bond specification. Since no measurement is available for
determining each wheel position as wheel wear accumulates
the wheel wear compensation is critical for accurately predicting
this information. Incorrect wheel wear compensation may result
in poor grind finish, increased wafer stress, poor thickness
control and reduced wheel life. The effects of wheel wear
compensation vary with the amount of grinding performed
between machine initializations.
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