Last time, we discussed the storage requirements of ESD sensitive items. Today we want to focus on the overall selection process for ESD bags: from choosing the correct type of material all the way through to determining the right size for your application. Sounds complicated? Honestly – it’s not and once you have the right tools (you’re welcome!), you’ll be an expert in no time. So, let’s go!
Choose the correct material for your ESD bag
Before you get started, you need to be clear about the purpose of your ESD bag and the environment it’s being used in. Make sure you have the answers to the following questions:
- What do you intend to put inside the ESD bag? ESD sensitive items? Non-ESD sensitive items?
- Is moisture an issue you need to consider?
- Do you need your ESD bags to be self-sealable? Or will you be using ESD tape/labels to close your bags?
- Are the items inside your ESD bag sensitive to physical damage?
- Are the items you’re storing in your ESD bag particularly sharp which could potentially damage the material?
- Will the ESD bags (and obviously the items inside) be stored on a grounded shelf inside an EPA or are they being transported outside of an EPA, as well?
Once you have answers to ALL of the above questions, you can move on to the below selection chart and choose the right material for your application.
| ESD sensitive items | Moisture protection | Self-sealable | Physical protection | Inside/ Outside EPA |
|
| Metal-In | x | x | Both | ||
| Metal-Out | x | x | Both | ||
| MBB – High Barrier | x | x | x | Both | |
| MBB – Low Barrier | x | x | x | Both | |
| Bubble Shielding | x | x | Both | ||
| Conductive Black | Only if used on a grounded surface | Inside only if used with ESD sensitive items |
A few more details on the different types of materials listed in the above chart:
- Metal-In Shielding Bags
ESD bags which protect ESD sensitive items. The ESD shielding limits energy penetration from electrostatic charges and discharge. The dissipative outer layer dampens any discharge and therefore reduces damaging electrostatic events. They offer good see-through clarity. Available with and without dissipative zipper.
Metal-In Shielding Bag – more information - Metal-Out Shielding Bags
Integral antistatic and low tribocharging bags which will not electrostatically charge contents during movement. Bags have a protective coated aluminum metal outer layer of laminated film; this promotes a more rapid discharge of static fields creating the event which the metal layer then attenuates. If RF field sensitivity is an issue, metal-out bags may be unsuitable. The rapid discharge to the highly conductive outer layer can create a higher radiated field which in return can cause issues for objects inside or near the bag. Available with and without dissipative zipper.
Metal-Out Shielding Bag – more information - Moisture Barrier Bags (MBB) – Low Barrier
Offers ESD and moisture protection and can be used to pack SMD reels or trays. Available with and without dissipative zipper (except Dri-Shield® 2700).
Low Barrier Moisture Barrier (MBB) Bag – more information - Moisture Barrier Bags (MBB) – High Barrier
Offer ESD and moisture protection and are ideal for applications where high moisture protection or conformance to IPC/JEDEC J-STD-033 is required. Available with and without dissipative zipper (except Dri-Shield® 3000).
High Barrier Moisture Barrier (MBB) Bag – more information - Cushioned Bags
These bags combine the “Faraday Cage” and mechanical protection. They shield about twice as well as normal shielding bags of equivalent size. Bubble cushion layer provides heavy-duty protection that absorbs impact and prevents product damage.
Cushioned Bag – more information - Conductive Black Bags
Black conductive film is made of virgin low density materials with black conductive compound to achieve high toughness and strength. This is commonly used for material handling, shipping and storage.
Conductive Black Bag – more information
Calculating the correct size for your ESD bag
Once you have selected the correct type of material, it’s time to choose the right size for your ESD bag. There are different ways to determine this based on the type of material you use:
Shielding and Black Conductive Bags:
A. Bag Width = Item’s Thickness + Item’s Width + 25mm
B. Bag Length = Item’s Thickness + Item’s Length + 50mm
Moisture Barrier Bags (MBB):
A. Bag Width = Item’s Thickness + Item’s Width + 25mm
B. Bag Length = Item’s Thickness + Item’s Length + 76mm
Cushioned Bags:
A. Bag Width = Item’s Thickness + Item’s Width + 76mm
B. Bag Length = Item’s Thickness + Item’s Length + 76mm
Bonus Tip: Measuring a bag
It might seem obvious to some of you but given that we do get these types of queries on a regular basis, we thought this would be a good opportunity to include. Imagine you already have ESD bags that you use in your company. Someone has just taken the last one off the shelf and you need to order some more. How do you know what size ESD bag you have in front of you so you can place a new purchase order? No worries – we have the answer:
A. The width is measured from inside seam to inside seam. This is also your opening.
B. The length is measured from the top of the opening to the bottom of the bag.
Bonus Tip 2: Remember your ESDS items
Outside an ESD protected area, the objective of ESD protective packaging is to prevent a direct electrostatic discharge to the ESD sensitive item contained within and allow for dissipation of charge from the exterior surface. In addition, the packaging should minimize charging of the ESD sensitive item in response to an external electrostatic field and triboelectrification. If the user does not know the sensitivity of the items being used, we would always recommend static shielding packaging to be on the safe side.
