Friday, September 21, 2012

When components in non-ESD packaging are assembled with ESDS in an EPA used in the

  Users of electrononic components do not want static-generating materials in their EPAs, but  suppliers of non-ESDS often use non-ESD packaging. Is there any packaging guidance for non-ESDS?

Users of ESD susceptible components will not want to bring ordinary packaging materials into an EPA workstation where ESDS are handled. There are no requirements in the standards for suppliers of non-ESDS components to supply their product in non static generating packaging. So, many will use ordinary plastics in their packaging which could compromise ESD safety and compliance if brought onto an EPA workstation. It is for the user to decide how to handle this, e.g. by removing non-compliant packaging before bringing the component into the EPA workstation.

This is one reason why the modern standards say that non-essential insulators must not be present on a workstation where ESDS are handled, rather than in the EPA in general. Some people write their ESD control program to allow items in non-ESD packaging to a bench conveniently placed near the one where they handle ESDS, but not near enough to cause ESD risk from the plastic packaging. The packaging can then be removed from the component on a workstation where ESDS are NOT handled and the component transferred to the workstation where they are assembled with ESDS. This approach relies on a high level of understanding by operators to prevent stray packaging arriving on the workstation where ESDS are handled and other ESD risks.

Others write their ESD program to prohibit non-essential insulators from the EPA, and repackage the non-ESDS into ESD packaging before they are brought into the EPA.

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.