7AF Software Version 6.05.0 Features
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It is likely that additional decimal digits of this variable will be used for additional flags in the future. When that
happens this safety feature will use the one’s digit of the machine variable.
New Flag For Spinning the Wafer Dry
Since version 5.07, Machine Variables 42 and 44 have given times for the wafer to remain spinning on the chuck
after grinding has finished and the bridge has moved away. Spinning helps to dry the wafer. However it has
been observed that water is thrown into the 7AF and, occasionally, onto finished wafers in the receive cassettes.
There is now a flag added to these variables to allow raising the grind seal during this spin dry so that the water
is caught.
Dry time has always been limited to 60 seconds. You may now add 100 to this dry time to signal that you want
the grind seal to be raised. Thus, the value 145 requests 45 seconds of spin with the seal raised, while 30
requests 30 seconds of spin with the seal remaining lowered. The only allowed ranges of values are 0-60 and
100-160.
Time Delay For Work Chuck Conditioning Arms
It is possible for an operator to make bad choices when moving the conditioning arms during Machine
Maintenance. As an example, suppose the arm is in the Over and Up position, above the work chuck. If the
operator presses Park, then waits for the arm to park away from the chuck, and then presses Down, everything is
fine. But if he presses Park and then immediately presses Down, the arm will crash onto the chuck. Software
will now detect and prevent this, but it needs some help in the form of a delay between button presses to allow
the Opto-22 inputs and outputs to stabilize.
Machine Variable 17, formerly called Work Chuck TopFlush 0=No, now called Work Chuck Machine Maint
will provide this time delay. The ones digit still controls the TopFlush as it has done before. The tens digit
provides the new time delay for the conditioning arms, ranging from 0-9 seconds. If the operator makes a
conditioning arm request he will not be permitted to make another one for this many seconds. To operate
without any delay, and without protection against too-quick presses, just leave the tens digit as zero.
Coarse and Fine Wheel Following Errors
It has occasionally been reported that the coarse and/or fine wheel can spin slowly when not in use. Since the
software is constantly examining the status of the various axes of motion, this can produce an error message
called a Following Error. The error complains that the wheel is not where it is supposed to be, i.e., at rest.
However it does not really matter that the wheels are spinning. Two changes are now being made to ignore
useless messages about grind wheel Following Errors.
The 1000’s digit of Machine Variable 19, Special Options, will now cause grind wheel Following Errors to be
ignored whenever the grind wheel is not being used. In other words, if the wheel is supposed to be at rest, but is
spinning, there will be no message. (Five digits of variable 19 are now in use for five different purposes.)
Machine Variable 49, called RPM for Following Error, will cause grind wheel Following Errors to be ignored
at low-speed, whether or not the wheel is being used. If a value is placed into this variable, any Following Error
will be ignored as long as the wheel is spinning at a speed lower than (or equal to) this value.
Other Changes
a. Operator messages no longer conceal fault messages. The box with the operator message has been moved.
b. Changing Machine Variables 25, 35 for Coarse and Fine Wheel Wear Limits no longer forces home and
reference.
c. A situation in which the pre-aligner tries forever to align a wafer, never issuing a fault message, has been
fixed. Three tries are now made to align. If they all fail, there will be an alarm unless you have set the flag in
Machine Variable 19, Special Options, that pretends the wafer is aligned
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