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Two common approaches to cleanliness assessment are the extractive and nonextractive methods. Extractive techniques remove ionic soils from samples and measure conlamination levels on samples on a weight-per-area basis, either in total or by specific species. Extractive tests assess the effectiveness of processes in avoiding or removing ionic surface residues from printed wiring boards (PWBs), printed wiring assemblies (PWAs) or components. Nonextractive techniques are electrical tests of samples, PWBs or PWAs under specific environmental conditions. They evaluate the effect of any soils on the ability of tested parts to function in either typical or "worst case" environments.
Two Extractive Techniques
1) The solvent extract conductivity (SEC) test and the resistance of solvent extract (ROSE) test are methods familiar to most assembly shops. IPC test methods and acceptance/rejection criteria are often used in product and process specifications. The SEC and ROSE techniques do not identify the species of contaminate, only the amount of ionic material removed from the PWA by exposure to an isopropyl alcohol/deionized water solution.
The temperature of the SEC or ROSE...