【国外标准】 Standard Practice for Sampling for Particulate Contamination by Tape Lift

3.1 The tape lift provides a rapid and simple technique for removing particles from a surface and determining their number and size distribution.3.2 By using statistically determined sample size and locations, an estimate of the surface cleanliness level of large areas can be made. The user shall define the sampling plan.3.3 The sampling plan shall consider the importance of surface geometry and surface orientation to gas flow, gravity, obstructions, and previous history of hardware. These factors influence particle fallout and entrapment of particles on the surface. The geometry of joints, recessed areas, fasteners, and the correspondence of particle-count data to area can be maintained.3.4 The selection of tape and the verification of its effect on the cleanliness of the hardware is very important. The tape adhesive should have sufficient cohesion to avoid transfer of the adhesive to the surface under test. The impact of adhesive transfer should be evaluated by laboratory testing before using the tape on the hardware. Since potential for adhesive transfer exists, cleaning to remove any adhesive might be required. In addition, the tape should have low outgassing characteristics, and as a minimum, it should meet the requirements of less than 1.0 % total mass loss (TML) and 0.1 % collected volatile condensable materials (CVCM), as measured by Test Method E595.3.5 Care should be exercised in deciding which surfaces should be tested by this practice. The tape can remove marginally adhering paint and coatings. Optical surfaces should not be tested until verification has been made that the surface coating will not be damaged. The minimum effectiveness of particle removal from smooth surfaces and angles down to 90° for all practice methods is 90 % for particles larger than 5 μm. Rough surface finishes result in low removal efficiencies. Surface finishes up to approximately 3.20 μm (125 μin.) have been tested and found to give satisfactory results.3.6 This practice has been tested only on surfaces at room temperature. Evaluation of temperature effects must be conducted prior to using the test on surfaces other than room temperature.3.7 Only personnel experienced in microscopic particle-counting techniques should be used to count and size the particles.1.1 This practice covers procedures for sampling surfaces to determine the presence of particulate contamination, 5 μm and larger. The practice consists of the application of a pressure-sensitive tape to the surface followed by the removal of particulate contamination with the removal of the tape. The tape with the adhering particles is then mounted on counting slides. Counting and measuring of particles is done by standard techniques.1.2 This practice describes the materials and equipment required to perform sampling of surfaces for particle counting and sizing.1.3 The criteria for acceptance or rejection of a part for conformance to surface cleanliness level requirements shall be determined by the user and are not included in this practice.1.4 This practice is for use on surfaces that are not damaged by the application of adhesive tape. The use of this practice on any surface of any material not previously tested, or for which the susceptibility to damage is unknown, is not recommended. In general, metals, metal plating, and oxide coatings will not be damaged. Application to painted, vapor deposited, and optical coatings should be evaluated before implementing this test.1.5 This practice provides three methods to evaluate tape lift tests, as follows:Practice Sections   A—This method uses light transmitted through the tape and tape adhesive to detect particles that adhere to it. 4 to 6 B—This method uses light transmitted through the tape adhesive after bonding to a base microscope slide, dissolving the tape backing, and a cover slide. The particles are embedded in the adhesive, and air bubbles are eliminated with acrylic mounting media. 7 to 9 C—This method uses light reflected off the tape adhesive to detect particles that adhere to it. 10 to 121.6 Units—The values stated in SI units are to be regarded as standard. The values given in parentheses after SI units are provided for information only and are not considered standard.1.7 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.1.8 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.