Relative humidity affects material’s resistance properties. I’m thinking about if it would be more practical, if ESD packaging standard would determine RH ranges in addition to resistance ranges for material classification. For example: “the material is dissipative when Rs or Rv is between 10E04 and 10E11 ohm, measured at 9% < RH < 15%”.
What is your opinion?
Hi and welcome to the forum. You are quite right about humidity and resistance.
For packaging materials and almost all of the material testing such as worksurfaces, the ESD Association standards calls for testing at 12% Rh +/- 3% and a temperature of 23C +/- 3C. This would be the product qualification of these materials.
If you find a data sheet that claims a resistance range quoting one of the ESD Association standards and if they followed the standard then the resistance is done at a very low RH. The round robin testing done in the past has shown that testing at 12% is a worst case condition and that is where the resistance should be reported.
For packaging materials in particular, the lowest RH is where the material needs to be tested. Packaging material can be located anywhere so the worst case condition must be reported.
If you have any other questions or would like more clarification, please add to the forum.
John K
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A potential supply of low charging (pink) bags in India has been requested, by our factory there. The only issue is that the testing was only carried out at 50% humidity. The datasheet quotes conformity to both ESD S20.20 and 61340-5-1, but not which version. Testing under condition 12 ± 3 % RH and 23 °C ± 2 °C seems very rare in India for packaging material. Mechanical items would be shipped in these bags to the UK.
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Hello Susan and welcome to the forum,
No matter which version of ANS/ESD S20.20 or IEC 61340-5-1, packaging materials are suppose to be tested at 12% Rh and 23C. However, in this case, if the parts are only mechanical, ANSI/ESD S20.20 or IEC 61340-5-1 does not apply. The requirement for packaging only applies to ESDS items.
There may be other reasons that a customer requests packaging like this as the parts in the package may enter the EPA. While there might not me any testing in India at the required environment, there are other world wide companies that do provide that data.
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Thank you John. These mechanical items will be present in both India and UK EPA’s.
Susan,
Here is where the process could help. If the packaging material is removed prior to entering the EPA, then the packaging for mechanical parts could be anything. Or if there was a way to remove the packaging material without being in close proximity to ESDS items, then it could be anything.
It would be a good idea to check the mechanical part to see if removing the packaging material charged the part before it gets installed in the assembly.
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