When RSM
Electron Power Inc., manufacturer of high
reliability hermetic semiconductor and
microelectronic components, decided to
automate the slurry dispensing process on
their diode manufacturing line, they chose
the QV CeramPump® valveless piston pump and
V-200 Controller from Fluid Metering, Inc.
RSM's line of Sensitron products is designed
for use in industries that require high
reliability components. These components are
typically used for aerospace, military,
medical, and high reliability industrial
applications. During the diode manufacturing
process, the QV CeramPump® metering pump
dispenses a hermetic coating of 5u glass
slurry individually to each diode as it
moves down a conveyor system. The hermetic
design ensures high reliability in
applications having temperature extremes,
high altitude, high frequency, and severe
environmental conditions.
Dr. Yunji L. Corcoran, vice president and
general manager at RSM, explains that RSM
chose the QV because accuracy and
consistency in the amount of slurry
dispensed from diode to diode is extremely
important since many of the operations to
follow will be performed in lots as batch
processes. When processing in lots or
batches, correction to compensate for
individual component variation is not
possible.
Therefore it is important that processes
performed individually yield components with
properties near identical with one another.
Consistency in dispensing can be measured in
monitoring both the accuracy and precision
of the dispenses.
Accuracy is a comparison of the average
value of dispensed amounts to the desired or
target value. Precision is the range or
degree of variation from dispense to
dispense and will affect component
variation. The QV system is both accurate
and precise, capable of providing a 1%
dispense accuracy with a 0.5% precision.
Along with the V-300 controller, the system
replaced a manual dispensing method and
produced cost savings by reducing the number
of components requiring rework due to
inconsistent slurry coatings. What makes QV
CeramPump® technology so unique is its
valveless piston design. One moving part, a
special rotating and reciprocating ceramic
piston, accomplishes all fluid control
functions of the pump without valves.
The reciprocating action performs the
pumping function, while the simultaneous
rotation of the piston alternately aligns a
flat on the piston with the inlet and
discharge ports of the pump. The flat
creates a fluid path between the ports and
the pump chamber, effectively functioning
like a valve. At no time during the pumping
cycle are the inlet and discharge ports
interconnected, thereby eliminating the need
for check valves.
The fluid dispensed during RSM's diode
coating process is a proprietary 5u glass
slurry. In addition to having only one moving
part, the CeramPump® has internal components
made of sapphire-hard ceramics, providing
excellent wear resistance against the
abrasive glass slurry. Tom Merck, facility
manager at RSM, estimates that the QV
CeramPump® delivers 200,000 dispenses per
week and will operate for about three years
or approximately 32 million dispenses before
internal components show enough wear to
require replacement.
The QV dispense volume is easily adjusted,
without tools, while running or while at
rest by using a convenient flow control
knob. A dial indicator gives a direct
reading for ultra-fine flow adjustments in
dispense volume settings enabling changing
from one dispense volume to another with
little or no downtime. Dispense speed is
controlled by the V-200 Stroke Rate
Controller, and is adjustable either
manually in 0.1% increments or
electronically via a 4-20 mA input common
for most process controls.
It is useful in controlling production
speed, as well as for fast priming. With
virtually only millionths of an inch
clearance, the interface between the
precision ceramic piston and mating liner
form a fluid seal capable of maintaining
pumping pressures up to 100 psig. The QV
pump can also self prime up to 15-ft.
vertical lift dry, 30-ft. wet. |
|
Fluid
Metering's QV CeramPump and V-300
Controller dispenses a hermetic
coating of 5u glass slurry to each
diode. |
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