We are currently using ESD dissipative containers to store and transport in process PCBA’s. The containers are stored on grounded shelving. During transport from one location to another we either use either a plastic cart or move the containers by hand. We do not have any floor grounding in our facility. Are there any concerns with static building up in either the cart or the person and transferring through the dissipative container to damage the circuit boards?
Hello joshsvoboda and welcome to the forum.
Great question… I would refer you to S20.20 section 8.3.1 on insulators. This section has a great discussion on non-essential and process essential insulators and the requirements for mitigation.
For your particular question, while it is best to exclude any insulators (plastic carts included) from an epa. Hopefully your technicians are well trained to remember not to place your PCBA’s unprotected on the carts. It sounds as if you all have a sound handling process with the proper handling containers. That being said. Your plastic cart will generate a charge when moved, we just don’t know how much. so I would recommend you take some field measurements and then make a decision based on your measurement results if your process can handle the results you get.
Removal of the plastic carts would give you a better safety margin and reduce the possibility of damage to your product due to mis-handling.
Josh,
I agree with Matt. Another thing to consider is if the dissipative containers prevent anyone from touching the ESDS items while in transit. If so, it may not matter if they charge up while moving from one place to another. As long as the dissipative containers are grounded before anyone handles the ESDS items after transit, the ESDS items should also be grounded and safe for handling by a grounded person.
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Are your individual PCBs in metalized shielding bags? Is there a lid on your static dissipative container? Are you aware of S541 requirements?
We are using Protective Pak dissipative carboard containers with the pcb assemblies separated by the dissipative dividers into individual slots. The containers would only be using during transport from one EPA grounded shelf to another EPA grounded shelf. The containers are open on the top no lid or shielded bags. I am not aware of S541 is there a copy to reference?
My typical response to many of these situations is, “It depends”. With what you descirbe, the loading and unloading of the PCBs are done when the container is on a grounded worksurface could work. The process would have to ensure that PCBs are not handled during the transportation process. This could be checked by observation and what is done in the training or procedures for your factility.
The process here is loading in a controlled enviroment, transport in a “controlled” but not EPA to a controlled enviroment where the PCB would be unloaded. The dissipative container can be considered ESD protective packaging in this case.