Transporter cars

Good Morning
Can you help me? I have a question about shipping carts for ESD sensitive components.
In the plant we do not have an ESD floor in all areas and all PCB components are transported in dissipative containers, magazines with protective coating, trays and shielded bags from one area to another within the plant.

Do all carts need to be grounded with drag chains if we don’t have an ESD floor?
Is it necessary to document these verifications?
Can this requirement be waived?


This question has been raised a few times. Let’s take a look at it from an ANSI/ESD S20.20 perspective.

As I understand what you are saying, you use cards to transport ESD sensitive items from one EPA to another but through a non EPA (areas without ESD compliant floors). But you also state, that you use packaging solutions (trays, shielding bags) when you do that. The packaging that you used in the facility does not have to be the same as when it leave the facility. I would conclude from your description that you are transporting ESD sensitive devices in ESD protective packaging while transporting thought a non EPA.

If this is the case, only the way you package the ESD sensitive device needs to be documented when making this movement. The requirement does not have to be waived as it is compliant with the standard.

This would be similar in storing ESD sensitive devices in a warehouse where packaging is used for protection.

If you have any additional question, please feel free to ask.

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Greetings, thank you for your timely response.

I have a doubt regarding the transport carts, according to what has been said, if all my PCBs are transported in dissipative materials within the safe area without an ESD floor, it is necessary to continue verifying the transport carts with a resistance < 1.0 x 109 ohms as required in Table 3 of ANSI/ESD 20.20?

Thank you, your answers will be very useful

If you are protecting the product using proper packaging, than there is no requirement for the cart to have any ESD compliancy. As such, when you roll the cart off of your grounded floor you are no longer dissipating any built up of static charge through the cart to ground.

That said, I would verify your packaging to insure it is in fact compliant for transporting ESD sensitive items outside of an EPA. A dissipative bag will not be sufficient as it relies on a ground to dissipate any accumulated charge. A static shielded bag will protect the item from any outside static charge, which is where I believe you need to be.

Hope this helps

Again, this really depends on the process. A dissipative bag might work within a facility while transporting on a cart. A simple tray may provide enough protection.

What needs to be evaluated is not the cart by itself, but how is the process defined. If the cart is grounded during the load and unload of the ESDS items, this provides protection. What is important now is the transport itself.
If the cart is not grounding while transport, what happens. The cart and content may charge. Is this a problem? If nobody touches the product during transport the cart, ESDS items and anything else on the cart may charge. However, everything on the cart should be at the same potential and a discharge should not happen.
When the cart is grounded again, charges will equalize with ground and the ESDS items will be able to be handled again.
What is important is how you define the process and what actually happens during the transport.

Is this what you should do? I don’t know as it is your process and you need to evaluate it. Can this be compliant to ANSI/ESD S20.20. Yes.

Thanks for the support, your comments are very helpful.
best regards