Hello ESD Experts,
I would appreciate your guidance on whether ESD antistatic foam can be used for PCBA packaging purpose instead of antistatic bags.
Could you please share your opinion and recommendations on this point? I have reviewed the ESD standards but could not find any specific requirement or guidance regarding the use of antistatic foam for PCBA packaging.
Thank you in advance for your support.
Greetings of the day from India , to all the members on this forum 
A Good question Mr. Rahul 
Yes you are right that the ESD standards do not explicitly specify any requirement or guidance regarding the usage of ESD safe foams for PCBA packaging.
I am putting up my views a under and look forward for views and comments from our ESDA experts and other colleagues on the forum
1.First of all, the ESD safe foams are available in different types and widely used by many in the EPAs for different applications. I do not know which type of foam you are referring to, as the word Anti static basically applies for low static generators in ESD terminology as against the meaning in an English dictionary .
2.Secondly,in general the most important factor is that the ESD safe foams cannot be an equivalent to Faraday cage protection(shielding) bags which is an absolute requirement per both the standards when they are in transportation between the EPAs or to warehouse or outside.
3.ESD foams are available in static dissipative as well as in conductive range in PU-EPE-EVA type.
4.PU foams normally impregnated with dissipative or conductive additive during process and thus will be homogeneous in ESD safe properties .But, EPE & EVA ( I am referring to the ones mfd or processed in India and not the imported ) are normally externally coated with dissipative or conductive solvents and thus , they will not be volumetric ESD safe as per the requirement per ANSI ESD S541 table
5.Basically, any ESD-safe foam protects the PCBA against thermal shock and protect against charge generation on its surface but does not provide the Faraday cage shielding protection mentioned above which is available with metallised static shielding bags .
6.However, covering the PCBA first with a static shielding bag and mouth sealed (without any staples) and wrapping it with an ESD safe Conductive foam during transit would be good as it serves both ways to provide shielding and cushion against thermal shock .
7.Alternatively; the PCBA can be covered with a dissipative foam and put inside a conductive PP /molded sealed box ( with lids) which also serves both ways to provide shielding by the external conductive box and cushion against thermal shock by the dissipative foam. Here you can avoid the usage of bags.
8.Last but not the least ,a word of caution. Shielding bags are just 80-150 microns and are not supposed to be used for multiple applications as the sharp solder spikes/ sharp corners of the components on the PCBA directly in contact with the inner layer of the bags as well frequent folding of the bags may lead to hair line pin holes or cracks on the middle metallized layer of the static shielding bag which will make its shielding property null & void. *
* Industrial practice for verification of ESD packaging topic exchange of views in the forum and Andy Sir’s posting may please be referred to on the Static shielding bags.
Look forward to others views as well
Thank you
This is actually a more complex problem with many solutions. While discharge shielding can be measured in a shielding bag or a moisture barrier bag, there are many packaging constructs that will provide discharge shielding. Often they cannot be measured directly.
First, the principle of dischage shielding is much diffrent from EMI or RF shielding. In therory, dischage shielding is to prevent a person in an uncontrolled enviroment to damage a device if they touched the package. What is needed to mitigate the discharge energy in this case.
Simple answer, place the device in a high resistance material in intimate contact with a low resistance material around that. One example that can be used is totes or boxes that provide an air gap that have a dissipitive or conductive material around that. That is why conductive boxes, either cardboard or plastic can work as long as they measure less than 1x10E11. The air gap is being used as a very high resistance barrier.
In this example with the foam, the foam must be dissipitive and in intimate contact with the device. In this case, the thickness of the foam and the resistance should dissipate the charge before a damaging event can occure. Of course this needs to be verified with an experiment.
One suggesting is to take a functional device and place it in the package. Submit the package to ESD discharges as high as can be done, and then see if the device is damaged. Keep all the documentation on how the experiment was conducted for proof of packaging test. If the device does not get damaged, then the packaing should be fine.
One additional item, the foam needs to be qualifed at 12% RH as it will go in an uncontrolled enviroment. The experiment should be done in a very high humidity. This sounds counterintuitive but the foam worst case is low humdity but the discharge test worst case is at high humidity.
Once again, Greetings of the day from India , to all the members on this forum
Thank you JK Sir for your detailed information.
True that your last para on PQ test and 12% Rh is a crucial and very important factor which I missed to touch in my post.
Thank you again with regards
Thank you so much JK Sir & Vijay Sir for your valuable response and guidance on the packaging foam.
Thank you Rahul Sir
If the exchange of ideas can help the industry that is very good . 