RATING OF FINE MEMBRANE FILTERS USED IN THE SEMICONDUCTOR INDUSTRY.

Membrane filters are used extensively in the semiconductor industry to remove particles and bacteria from a wide range of process fluids, including water, gases, and solvents. Users of these filters are faced with selecting from various types, rated by their suppliers as 0. 2 mu m and finer. Questions are frequently raised as to how these filters are rated and whether the efficiencies of identically rated filters are equal. A description is given of the methods used for rating filters in these sizes. The methods used to derive the specific rating of a filter should be considered in filter selection. However, this alone will not necessarily assure the user of a reliable and consistent product. The microbial challenge test remains the most sensitive for validating the whole filter cartridge. However, since this is a destructive test, it can be performed on only a proportion of the cartridges. Therefore, this test must be closely correlated to the nondestructive forward-flow integrity test, performed on 100% of all electronics-grade cartridges, starting with the filter medium and ending with the finished cartridge.