Tailoring Statement of Product Qualification environment

Technical Questions
#1

Dear ESD experts,

For qualification of item only use within the factory, the ANSI/ESD S20.20 state that we shall test under the annual lowest RH% of the factories (if not to follow standard test method conditioning).

How ever in our factories, the Rh% is control in the range of 40%-60% (typical above 47%).

Is it acceptable if we declare a tailoring statement to accept the product qualification to be conducted under ambient RH% (any within the range of 40%-60%) as follow:

Tailoring Statement: Product qualification for items used within facility shall be conducted at Relative humidity (RH) range 40%-60% instead of Annual minimum RH for items are used within EPA.
ANSI/ESD S20.20
Requirement Affected: Item 7.3 Product Qualification Plan “Organizations with facilities where the annual minimum relative humidity (RH) is above the environmental conditioning levels identified within the product qualification test method for each ESD control item can use this minimum value to qualify each item used within that facility”.
Technical Rationale for Deviation:
Our factory maintains a controlled RH environment of 40%-60% per Site Facilities Infrastructure & Environment Process. Historical data demonstrates that this RH range effectively supports ESD control for all qualified items. The facility’s annual minimum RH does not drop below 40%, ensuring no conditions occur that would compromise ESD control effectiveness.
Testing under this RH range accurately represents the operational environment within the EPA and aligns with product qualification requirements. This ensures compliance with ANSI/ESD S20.20 while optimizing test conditions for facility-specific environmental factors.

Thank you in advance for your advices.

#2

Tailoring should include some sort of technical reason for the excludsion. In this case, while I see a technical section, I don’t think this would be acceptable. In this case, if the tailoring statement is accepted, technically you can qualify an ESD control item at 60% Rh and consider it done. While you do define the enviroment, an item at 60% may change at 40%. That is an assumption. In this case, you would need to prove that the 60% case does not change at 40% in order for the technical justification to be complete.
That would mean you would need to test some items at 40% to see if they change. In that case, all items should be tested at 40%.
If you facility is not at the lowest level, then a plan can be adopted that measurements are taken for qualificaiton until the lowest level is achived. In other words, take the intial measurments and it is at 55% today. In a couple of months, while monitoring the enviroment, there is a period when it goes to 45% Rh. Update the data at that point. Continue to do that until the lowest Rh is achived. That will be the data for qualificaiton.

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