I have a scenario where incoming reels from suppliers are handled directly by the reel (Non moisture sensitive, Level 1). the reel is placed and handled with ESD grounded personnel as well as ESD carts (with ESD wheels). For the proper identification of this activity, we have some paper sheets that are printed and stick with a rubber band to the reel. This rubber band and paper sheets are regular (non-ESD) - Let’s assume they are required items in the process for identification purposes.
After the rubber band stick the paper to the reel, they place the reel facing up (and the paper facing the mat) … or sometimes they place the paper facing up and the reel touching the mat (With the paper facing up).
When checking with a Voltage meter, the voltage variates from -20 to +36 Volts for both scenarios.
Questions:
How to address these scenarios in my ESD program?
I have thought in these 2 options:
a. As part of my insulator program, these 2 insulators are checked every X time, based on the initial check and risk, and keep those records as evidence, for each item (rubber band and paper separated).
b. Adding a risk assessment to my program where I check those items every X time, based on the initial check and risk, and keep those records (these is different from a. option because this one address the configuration and use of those 2 insulators together and not as individual items)
Could you give me some guidance.
I have other scenarios like these and would like to have a more robust plan to control them.
Thank you!
I would evaluate the carrier tape on the reel to see if that was an ESD safe package. This can be done using the two point probe or some other resistance measurement. If the carrier tape is an ESD safe package, then anything around the reel would not matter as the carrier tape is providing the protection.
If not, use the limits in ANSI/ESD S20.20 of less than 125 v on the insulator would meet the requirements.
Additional question: For a case in which a pink bag (low charging property) that has a resistivity between 110e9 and 110e13, that is placed on top of an unprotected board, is this approach right?: I’m saying is an insulator based on the resistivity, and It has to measure less than 125V… Am I correct?
If an unprotected board is placed on anything, it is now considered a worksurface and the requirements for a worksurface applies. In ANSI/ESD S20.20 the resistance point to ground of a worksurface is less than 1x10E9 ohms. An pink bag that is described would not meet those requirements.
In this specific example, I don’t see this as a threat. To work on the PCB the bag and its content must be removed. I would take many measurements to ensure that there is little or no risk. I would measue this combination in a low humidity enviroment if one exsists.
In addition to Johns guidance above, I would also caution you to the fact that because of how the pink poly articles are manufactured there may be a danger of off gassing of the material and contaminating your product. Also, overtime and use the chemical composition of the pink additive of the material may wear away leaving only the poly underneath with could be a large charge source.
In my industry (aerospace and defense), we generally do not allow pink poly type items in our processes.