Atmospheric Pre-aligner Manual
4000-0015 Rev 1
48
If the sensor does not trigger the signal during a set time, the firmware sets
Bit # 7 of the STAT response to indicate an error, usually that no wafer is
present.
The recommended pressure values to the fitting are required in order to
validate the warranty.
This diagnostic tests the vacuum valve(s) and vacuum sensor(s) attached
to the pre-aligner:
• The vacuum to the wafer chuck is controlled by Vacuum Valve #1 and
sensed by the Vacuum Sensor. On the PRE-200 pre-aligners, the
sensor is visible through the end cover near the CCDs.
• The vacuum to the pins is controlled by Vacuum Valve #2 but does not
have a vacuum sensor.
When you toggle the switches, the valve and sensor have opposite
indicators. That is, when the vacuum valve is on, the sensor is off, and
so on.
• With Vacuum Valve #1 in the Off state (valve open) and an
appropriate vacuum source connected to the Pre-aligner, repeatedly
place and remove a wafer on the Wafer Chuck and watch Vacuum
Sensor #1.
Turn the vacuum valve off (open the valve) by using number key 1 for
valve one and then pressing the 2 key for the second valve. Place and
remove a wafer on the chuck. The vacuum valve should indicate On and
Off respectively. If it does not, verify that the correct vacuum pressure is
present at the fitting.
#1 #2
Vac Sensor On/Off On/Off
Vac Valve On/Off On/Off
Press ‘1’ or ‘2’
(Vacuum Sensors)
(Vacuum Valves)
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