I would like to seek your clarification regarding the packaging standard shown in the screenshot below.
As per the standard, when shipping PCBA from our factory to the customer end (outside the EPA area), is it mandatory to use a shielding bag, or is a normal ESD dissipative/antistatic Bubble bag acceptable which is having resistance <10^11 ohms & <100V static voltage ?
Please help to guide the exact ESD packaging requirement for PCBA during transportation from our factory to the customer’s site.
Greetings of the day from India to all the members on this forum.
Rahul Sir,
According to my opinion and knowledge;
During transportation outside an EPA it is out of one’s control as there shall not any possibility to shield them to provide Faraday cage protection to your PCBAs safety from external charges if they are just dissipative or antistatic ( low charging ).
Just dissipative or antistatic (low charging) bags or foam does protect your PCBAs but from inside only due to jerk or vibrations during transit but not from any external charges and thus a shielding or a conductive enclosures over that is preferred.
In case of a 3 layer static shielding bag, the outer layer and the inner layers are dissipative and the middle aluminum vaporization layer is conductive which acts as a shield to provide the Faraday cage protection.
When you use a conductive enclosure to keep the PCBAs covered in dissipative or antistatic (low charging) bags or foam in a way it acts as a shield indirectly because the external charges will get distributed across the total conductive area and it gets grounded while they are opened on a grounded surface.
Per ANSI ESD 541 table 1 outside EPA all three conditions are REQUIRED only
However, the intimate packing to the PCBAs in the conductive range is to be avoided to avoid CDM damage risk if the PCBAs are with any CDM sensitivity components or devices.
Thus; I feel you can make a tailoring statement per 6.3 and Annexure E.
I do not vouch for the conductive grid bag as an external cover . In my opinion it is an invitation to allow the external charges to penetrate inside from the open ( non grid portion)
Let us welcome our ESDA experts and other colleagues opinion as well .
As GH stated, you need the shielding property outside an EPA to provide the Faraday cage effect because you don’t know what amount of charge your ESDS items will be exposed to. You could determine if your “ESD dissipative/antistatic Bubble bag” has the discharge shielding property by doing the product qualification test from ANSI/ESD STM11.31. If your bag is less than the limits in ANSI/ESD S20.20 of < 20 nJ, you should be fine.
