Facts
Pump induced pressure and flow pulsations generate hydraulic shocks due to discontinuous discharge of liquid. Hydraulic shocks through microporous membrane filters can increase particle release from the filters, which leads to wafer defectivity.

Test conditions
Pump induced flow pulsations of a diaphragm, bellows and Levitronix^® pump were compared for their effect on filter retention efficiency and particle hold up. Three different membrane filters were used. The retention efficiency is presented as the Log Reduction Value (LRV) at a particle size of 125 nm for each filter.

Results
Pressure pulsations have a negative effect on filter retention regardless of the filter used. The Levitronix^® pump, which provides the most stable flow, exhibited the highest retention values at each flow rate tested.

Retention efficiency as a function of pressure pulsation