Tuesday, August 21, 2012

Is my core conductive garment suitable for use in electronics manufacture?

We are looking for a new ESD garment/jacket. The recent garment we tested reduces in Rp-p with washing, but passed the charge decay test. The supplier stated that this fabric is woven with a core conductive fibre, so therefore the charge decay is the valid test (referring to BS EN 1149-3). BS EN 61340-5-1:2007 only specifies that the garment should pass Rp-p < 1x1012 ohms. So if the garment passes the charge decay test but fails the resistance test where do we stand?

 EN1149-3 is a standard for evaluating garments for use in flammable atmosphere areas, not electronics manufacture. The evaluation criteria are quite different.

The only test currently recognised by 61340-5-1 is the point to point resistance test for which it gives requirements. If it fails the test, it fails the test.

If you want to accept garments on a different basis than this test, and still comply with 61340-5-1, then you would need to devise some  sort of technical evaluation of the garment performance to convince yourself it does the job you intend it to do. You should then document your technical evaluation, including your qualification test methods and results, as a tailoring exercise in the ESD Program Plan. You should of course also instigate a program of suitable compliance verification tests in your Compliance Verification Plan.

Core conductive fabrics often fail the resistance test by the nature of their construction. Whilst that does not necessarily mean they are unsuitable for use in electronics manufacture, it does mean we have no agreed method of demonstrating whether they are suitable or not.

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