ADVANCES IN CLEANING METAL AND GLASS SURFACES TO MICRON-LEVEL CLEANLINESS.

Abstract

A high-pressure 6. 9-MPa liquid spraying technique has been developed to remove small ( greater than 5 mu m) contaminant particles from large (100 m**2) surface areas. Chemically polished and etched 304 stainless-steel components are solvent sprayed to achieve cleanliness levels of less than 10 particle/cm**2 greater than 5 mu m diameter. The high-pressure and high-liquid-velocity cleaning technique can remove 99. 9% of greater than 5- mu m-diam particles in 5-10 s compared to only 20-60% greater than 5- mu m particles by ultrasonic cleaning in 2-10 min. High levels of particulate cleanliness are required for large solid-state laser systems where contaminants may migrate to optical surfaces and cause severe pitting. The pitted glass must be removed and periodically repolished to maintain acceptable beam quality. Special Class 100 clean room procedures and equipment have been developed to determine the degree of cleanliness of laser components and to maintain cleanliness during installation and operation. Development of these cleaning procedures resulted in greatly reduced failure rates for solid-state disk amplifiers. Although developed specifically for cleaning optical components, the basic technique should find wide application in any field requiring particulate-free surfaces.