Strasbaugh Mechanical Maintenance Procedures
Version 1.2 - April 18, 1996 7 - 13
As mentioned in the preceding section the chuck vacuum and
grind hood door can be controlled manually using the [+/-] and [.]
keys, respectively. The vacuum is required to secure a dressing
disk for wheel dressing. The door must be lowered to prevent
coolant water from escaping while grinding. Both are toggle
functions, that is, they turn on and off successively each time the
key is pressed. Both will turn off upon hitting the [R] key.
PROCEDURE
The work chuck surface must be clean and flat for grinding. Chuck
grinding is required to true the chuck surface to the machine after
installation. During production any foreign particles suspended in
the chuck surface will cause stress fractures in the wafer.
The chuck should be ground with the coarse wheel. To grind the
chuck use the manual jog mode to move the work chuck to the
wafer chuck position for the coarse wheel and jog the coarse wheel
to a position approximately 200 microns above the chuck surface.
(If the machine has been initialized the operator need only observe
the position coordinates on the CRT display for jog positioning.)
press the [.] key to lower the grind door. With both spindles in
position press the [6] key to start both spindles rotating and the
coolant flow. Press and hold the [E] key to feed the wheel into the
chuck. For dressing operations typical removal depth is
approximately 200-400 microns; for truing a new chuck removing
500-700 microns should provide complete coverage.
Once the desired removal depth is reached release the [E] key and
allow the wheel to dwell for 10-30 seconds. Press the [B] key to
raise the spindle above the ground chuck surface approximately
200 microns. Press the [5] key to stop the spindle rotation and jog
the grind spindle to its upper limit. Raise the grind door and jog the
work chuck to its home position.
The machine must be reinitialized after chuck grinding.
The parallelism of ground wafers is dependent on the flatness of
the chuck. Chuck flatness is achieved by proper alignment
between the grind and work spindles. After grinding the chuck it is
recommended that the chuck flatness be checked to verify that
wafer parallelism is within tolerance. (see next section.)
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