App Note: Fluid Dispensing Using Pressure Control
In silicon wafer polishing systems (and often in biotech processes), head pressure in a liquid chamber is used to deliver fluid from the chamber into the application. To ensure accurate delivery, the headspace pressure must be incredibly precise.
Nitrogen, vented to atmosphere through an exhaust valve, is the most common process gas in these applications. A PCD-Series Pressure Controller can monitor and tightly control the nitrogen head pressure on the liquid chamber, allowing it to precisely dispense fluid via an activated solenoid or needle valve.
As the fluid level decreases, the Alicat will increase the amount of nitrogen flowing into the chamber to ensure the headspace pressure remains constant, or changes as desired. With a 1 msec processing time, very precise pressure changes can be applied to the system, while maintaining stability as high as 1 part in 10,000 (0.01% of full scale).