Strasbaugh Mechanical Maintenance Procedures
Version 1.2 - April 18, 1996 7 - 21
As with Spindle Pretravel the test for determining Dynamic
Offset should only be performed before any error or wheel wear
compensation has been applied. A dual grind cycle is required
for dynamic offset measurement with all parameters set for the
actual production dual grind cycle. Once the Spindle Pretravel
has been accurately adjusted a dual grind cycle should be used
to grind two wafers. Measure the error for each wafer and
compare it to the programmed thickness. Determine the grind
error using the formula
grind error = programmed thickness - actual
thickness
If the grind error is positive increase the Dynamic Offset value
by the error; if negative decrease the value. Using multiple
wafers for the test will produce an average for more stable
results. Multiple wafer measurements should not vary by more
than 5 microns. If larger differences result then feed rates may
be excessive for the grind wheels and/or wafer product.
After modifying dynamic offset data the machine must be
reinitialized. Dynamic offset compensation is only implemented
during machine initialization.
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