Hello, experts：
Regarding the STM4.1 standard, there are several issues that require technical support from experts:
The low and medium humidity storage specified in 6.5.2 and 6.5.3 define a storage time of at least 72 hours after installation. Can I assume that these samples should be stored for at least 48 hours without being installed on shelves or turnover vehicles.
If the shelves are approved according to section 8.0, currently we do not have such a large low humidity box to accommodate such a large shelf for low and medium humidity storage. Can we approve the anti-static mats on each layer of the shelves or refer to the working surface in section 7.0 for approval testing.
Looking forward to the experts’ response, thank you!
Frank,
It sounds like you want to do product qualification for a mobile workbench at your facility. You could approve your mats separately if you plan to ground them with something like a wire before work is done, but if you plan to use the ground path through the mat, cart and ESD floor, you should test the entire mobile workbench.
I suggest you consider the provision in ANSI/ESD S20.20 which says, “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.” Depending where you are located, you may be able to do this testing this winter in the northern hemisphere at your facility. If not, you could do the testing now and then again when you are in a condition of the facility’s lowest humidity. This would avoid needing a large test chamber to do the testing.
You also asked about the pre-conditioning of samples. If you mount the mat on a workbench, then it would require 72 hours. If not, the pre-conditioning is 48 hours. If you do the testing in your facility, I recommend making sure the mobile workbench is assembled and sitting in the facility for the 2-3 days prior to testing.