dynamic/static contamination test

Asoe,

The systems you are describing are Resistivity of Solvent Extract (ROSE) Testers. These systems are available using one of two technologies, Static or Dynamic.

Both systems use a calibrated test solution comprised of IPA and DI water. The test solution extracts contamination from an assembly. In order to determine the assembly�s contamination, one must first know the exact cleanliness (resistivity) of the test solution.

Before an assembly is inserted into the test solution, the test solution must be �cleaned up�, removing prior contamination from the assembly. This �clean-up� process is accomplished by directing the test solution through ion-exchange resins until the solution is at a known and acceptable level of purity.

On a static-based system, the test solution is filtered and �cleaned-up� then the assembly is inserted into it. Contamination is extracted from the assembly and measured in the test solution. As the contamination is extracted from the assembly, the test solution becomes dirtier. At the end of the test, a comparison is made between the beginning cleanliness of the test solution and the ending cleanliness of the test solution. The difference is what was extracted from the assembly.

A dynamic-based cleanliness tester works off of a similar principle. The test solution is �cleaned-up� prior to the insertion of an assembly. The difference is what happens during the test. On a dynamic-based system, the test solution is filtered and �cleaned-up (re-deionized) during the test. The theory behind dynamic technology is that cleaner (higher resistivity) test solution is better at extracting contamination compared to dirtier solution. If a solution is dirty, the contrast between clean and dirty is lowered as is its ability to detect contamination. The cleaner a test solution stays during a test, the more sensitive the test.

Years ago, the US Navy (under the auspices of the EMPF) conducted a study entitled �An In depth Look at Ionic Contamination Testing� (cited by Dave F). This study compared static and dynamic testing technologies and is a worthwhile (albeit long) read. It is available at EMPF (see link on prior posting).

I hope this helps!

Mike Konrad Aqueous Technologies www.aqueoustech.com 909.944.7771 ext 29

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