INFICON STC-2000A Thin Film Deposition Controller Operating Manual - Manual (Page 276)

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STC-2000A DEPOSITION CONTROLLER
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SECTION 8.XX page 276 of 292
SECTION 8.3 FAQs
Question: Why, when exiting a deposit mode (system shutter closing), does the thickness reading fluctuate
greatly?
Answer: There are several possible causes for this phenomenon. First, if the system shutter closing causes
any electrical noise in the system and the instrument is not grounded properly, thickness fluctuations may
be experienced. There is a #6-32 threaded ground stud near the AC power connector on the back panel of
the STC-2000A. This stud should be used to make an electrical connection between the STC-2000A and
system ground, which should be earth ground as well. This connection should be made with a 16 AWG (or
larger) gauge stranded copper wire. Second, a loose cable connection may cause these fluctuations simply
from the mechanical vibrations of the system. Check all cable connections to be sure that they are tight.
The most likely culprit is the in-vacuum cable (silver braided sheathing) between the feedthrough and
sensor head.
Question: When entering deposit and the system shutter opens, why, does the substrate sensor indicate a
negative rate?
Answer: This will typically occur in,but is not limited to, a resistive source system that has not been baked
out adequately, possibly just pumped down from atmosphere. What causes this is water vapor that has
condensed on the surface of the crystal. When the system shutter is opened, the heat from the resistive
source causes the water to evaporate from the crystal sensor surface. This evaporation translates to the
STC-2000A as a negative rate since the loading on the crystal is decreasing momentarily, rather than
increasing (as it would in a deposition).
SECTION 8.4 System Battery and Memory Considerations
The STC-2000A system board contains a 3V Lithium backup battery. This battery maintains the
contents of the real time and date memory while the STC-2000A is turned off. Under normal
circumstances the battery has an average life of 4+ years.
SHOCK HAZARD
Replacement of the battery toward the end of its life should be performed to eliminate memory
loss problems due to battery failure. The battery should be replaced with the same type, 3V Lithium,
Rayovac BR1225, Sycon Part Number 360-001.
Replacing the Battery: observe precautions described at the start of this section
The battery is held in a 12mm horizontal 'coin slot' holder on the main CPU board.
WARNING There are potentially lethal voltages present within the STC-2000A control unit
with a line cord or an INPUT/OUTPUT cable attached. Service should be attempted by qualified personnel
only. Disconnect all cables and power cord when removing, installing, or servicing any component of the
STC-2000A instrument.
Remove the bottom cover of the unit, the battery is located on the PCB having the 9 pin D-sub that
provides the RS232 connection as indicated on the rear panel. This PCB is labed 502-196. Remove the old
battery and replace it with the new one. Place a label on the inside of the unit case, near the battery,
specifying when it was replaced to facilitate future maintenance.
Re-Entering Time and Date Parameters
The Non-Volatile memory will still be intact but the time and date information may not be correct.
Re-enter and verify this information before putting the unit back into service (See section 3.14).