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Glass Slurry AutomationMillions of Dispenses, No Downtime

Pump Provides Precise Dispensing for Glass Slurry Automation Process

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-300 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 5mL 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 nearly 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 an 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 5 mL 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-300 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.

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