OM-610-1002-1 Operator’s Manual Rev 37
PDS-2010 SECTION 5 OPERATION page 25
5.7 SEQUENCING COMPUTER
The sequencing computer is located on the electrical panel behind the front access panel. The ladder logic
program is installed at the factory and provides overall control of the system heating elements and alarm status
monitoring, based on inputs generated by other control system components. Changes in the factory-loaded
control program could affect machine safety and deposition quality; do not alter them.
Protracted Pump Down (Optional)
Some substrates continue to emit gas even after the system has been pumped down below the base pressure
setting. In this case, the operator may wish to extend the chamber evacuation time with a protracted pump
down. This can be achieved by lowering the set point (See Section 5.5.3).
The vaporizer temperature monitor is enabled immediately after the 10-second start-up delay of the
sequencing computer. A vaporizer temperature fault is identified when the vaporizer controller ALM light is
ON.
The chamber gauge temperature monitor is enabled after the chamber gauge has been within its deviation
limits (±10°C of set point) for at least 20 seconds after the PROCESS START/STOP pushbutton is depressed
(or after main power is turned on). After the chamber gauge monitor is enabled, any deviation from the gauge
tube heater set point, as indicated by the chamber gauge controller red ALM light, will initiate the fault
shutdown timer.
The furnace temperature monitor is enabled after the furnace has been within its deviation limits (±20°C of
set point) for at least 20 seconds after the PROCESS START/STOP is depressed (or after main power is
turned on). After the furnace monitor is enabled, any deviation from the furnace set point, as indicated by the
furnace controller red ALM light, will initiate the fault shutdown timer.
If the fault timer elapses after a temperature fault has been detected, a system shutdown will be executed. All
heater control outputs will be disabled and the fault alarm will sound.
In addition to temperature fault monitoring, the sequencing computer is provided with a process alarm that
indicates a possible pressure control problem during deposition.
The pressure control monitor observes the amount of time between any two-output requests by the vacuum
controller for vaporizer heat. If this time interval ever exceeds 10 minutes, it is a likely indication that the
chamber pressure has been somewhat above its set point for several minutes. This would indicate a vacuum
leak or a run-away vaporizer heating element.
Unlike the temperature fault monitors, the pressure control monitor will not initiate a fault shutdown sequence.
It merely provides the fault alarm that provides operator notification of the detected condition. The control
sequence is not affected.
Power Failure
The vacuum pump is equipped with an isolation valve that immediately seals the system upon power failure.
Once power has been restored and the PROCESS START/STOP button has been depressed until the green
light is lit, the computer will re-check the pre-coating conditions (following the same criteria as an automatic
coating cycle). When these conditions are again satisfactory, the coating process will resume.
NOTE: If the power interruption occurs during deposition then the vaporizer heaters will not be immediately
re-enabled upon power-up.
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