Cushioned Shielding Bags

In a previous post we learnt how to select the correct ESD bag for your application, we want to focus on the next step: how to correctly use your ESD bag. We’ll use shielding bags as an example as they are the most commonly used ESD bags. However, the below can be applied to all types of ESD bags.

There are a few “dos and do-nots” you should keep in mind to ensure you get the most from your ESD bags. Nothing is worse than investing in all the right equipment and then using it incorrectly rendering all your efforts void. So, on that note, we have comprised a list of 5 tips for you on how to most efficiently use your shielding bags.

5 Tips On Efficient Use of Shielding Bags With ESD Sensitive Items:

1. Enclose Your ESD Sensitive Item with a Shielding Bag

Shielding bags should be large enough to enclose the entire product within. The shielding bag should be closed with a label or tape. Alternatively, you can use a zipper-style shielding bag. Following this advice ensures a continuous Faraday Cage is created which provides electrostatic shielding. This is the only way to ensure ESD sensitive devices placed inside the shielding bag are protected. If you are unfamiliar with the term “Faraday Cage”, scroll to the bottom of this page – we’ve included a more detailed explanation at the end of the post.

 

Enclose_Shielding_Bags
Enclose your ESD sensitive item

 

Please do not staple your shielding bag. The staple punctures the shielding layers and will provide a conductive path from the outside of the shielding bag to the inside. Charges outside the shielding bag could potentially charge or discharge to ESD sensitive components inside the shielding bag.

If you’re unsure as to what the correct size is for your application, catch-up on this post which will provide all the required information.

2. Remove Charges from Shielding Bags

When receiving an ESD sensitive device enclosed in a shielding bag, make sure you place the closed shielding bag on an ESD worksurface before removing the product. This will eliminate any charge that might have accumulated on the surface of the shielding bag.

 

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Remove charges

 

 3. Do Not Overuse Shielding Bags

Re-using shielding bags is acceptable as long as there is no damage to the shielding layer. Shielding bags with holes, tears or excessive wrinkles should be discarded.

 

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Don’t overuse shielding bags


 4. Shielding Bags Are Not A Working Surface

Do not use a shielding bag as an ESD worksurface. Although a shielding bag is safe to use around ESD susceptible products, it is not intended to be a worksurface for product. When working on ESD sensitive devices, do so using ESD worksurfaces that are grounded correctly.

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Don’t use shielding bags as your ESD worksurface

 5. A Shielding Bag Is Not A “Potholder” Or “Glove”

Do not use a shielding bag as an “ESD potholder” or “ESD glove”. This type of use offers no ESD protection to the product.

If you need to handle ESD sensitive devices, make sure you are properly grounded using wrist straps or heel grounders.

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Shielding bags are no “ESD glove” or “ESD potholder”

Some of you may have read through this post and have stumbled across the term “Faraday Cage” as you have not come across it before. We’ve also mentioned it before when talking about storing and transporting ESD sensitive items. However, we’ve never actually explained what a Faraday Cage is – so let’s rectify that!

What Is A “Faraday Cage” Or “Faraday Shield”?

A Faraday Cage or Faraday shield is an enclosure formed by conducting material or by a mesh of conductive material. Such an enclosure blocks external static and non-static electric fields. Faraday Cages are named after the English scientist Michael Faraday, who invented them in 1836.

What Is An Example of Faraday Cage Effect?

An impressive demonstration of the Faraday Cage effect is that of an aircraft being struck by lightning. This happens frequently but does not harm the plane or passengers. The metal body of the aircraft protects the interior. For the same reason, a car may be a safe place during a thunderstorm.

 

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Lightning striking an airplane

 

How Is A Faraday Cage Effect Used In ESD Protection?

In ESD Protection, the Faraday Cage effect causes charges to be conducted around the outside surface of the conductor. Since similar charges repel, charges will rest on the exterior and ESD sensitive items on the inside will be ‘safe’.

Examples of ESD control products that provide a Faraday Cage or shielding include Metal-In and Metal-Out Shielding bags.

When Is ESD Shielding Packaging Used?

ESD shielding packaging is to be used particularly when transporting or storing ESD sensitive items outside an ESD Protected Area.

ESD Packaging Standards For Outside An EPA

Per Packaging Standard ANSI/ESD S541 clause 6.2 Outside an EPA “Transportation of sensitive products outside of an EPA shall require packaging that provides:

  • Low charge generation.
  • Dissipative or conductive materials for intimate contact.
  • A structure that provides electrostatic discharge shielding.

Additional ESD Definitions

Other helpful ESD related definitions from the ESD Association Glossary ESD ADV1.0 include:

Faraday Cage“A conductive enclosure that attenuates a stationary electrostatic field.
Electrostatic discharge (ESD) shield: “A barrier or enclosure that limits the passage of current and attenuates an electromagnetic field resulting from an electrostatic discharge.
Electrostatic shield: “A barrier or enclosure that limits the penetration of an electrostatic field.

So, hopefully we’ve clarified a few things today when it comes to the “shielding” property by explaining the phenomenon of the “Faraday Cage”. Don’t forget to implement our tips when it comes to using your ESD bags!

 

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:

  1. What do you intend to put inside the ESD bag? ESD sensitive items? Non-ESD sensitive items?
  2. Is moisture an issue you need to consider?
  3. Do you need your ESD bags to be self-sealable? Or will you be using ESD tape/labels to close your bags?
  4. Are the items inside your ESD bag sensitive to physical damage?
  5. Are the items you’re storing in your ESD bag particularly sharp which could potentially damage the material?
  6. 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:

  1. 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
  2. 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
  3. 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
  4. 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
  5. 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
  6. 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.

In our last post, we talked about the ESD protective packaging requirements for ESD sensitive items and provided you with 6 steps to choose the correct type of packaging. We thought today we could go in a little bit more detail and introduce you to some types of packaging and how to use them. If you read our recent post on Tips to Fight ESD, you will remember how important it is to protect your ESD sensitive items when leaving an EPA. Yet, too often we see customers who have the perfect EPA, but when it comes to transporting and storing their precious components, it’s all falling apart.

Packaging required for transporting and storing ESD sensitive items
During storage and transportation outside of an EPA, it is recommended that ESD sensitive components and assemblies are enclosed in packaging that possesses the ESD control property of shielding. See our last post for more details.

Remember:

  • In ‘shielding’ we utilize the fact that electrostatic charges and discharges take the path of least resistance.
  • The charge will be either positive or negative; otherwise the charge will balance out and there will be no charge.
  • Charges repel so electrostatic charges will reside on the outer surface.

The Faraday Cage effect
A Faraday Cage effect can protect ESD sensitive items in a shielding bag or other container with a shielding layer. To complete the enclosure, make sure to place lids on boxes or containers and close shielding bags.

Cover must be in place to create Faraday Cage and shield contents.

Types of shielding packaging
The below list gives a few examples of what types of shielding packaging is available on the market. This list is by no means complete; there are many different options out there – just make sure the specifications state “shielding” properties.

  • Metal-In Shielding Bags
    ESD bags which protect ESD sensitive items. The ESD shielding limits energy penetration from electrostatic charges and discharge. They offer good see-through clarity. Available with and without zipper.

    Example of a Metal-In Shielding Bag – Click here for more information
  • Metal-Out Shielding Bags
    Integral antistatic and low tribocharging bags which will not electrostatically charge contents during movement. Bags have an aluminium metal outer layer of laminated film. Available with and without zipper.

    Example of a Metal-Out Shielding Bag – Click here for more information
  • Moisture Barrier Bags
    Offer ESD and moisture protection and can be used to pack SMD reels or trays.

    Example of a Moisture Barrier Bag – Click here for more information
  • Cushioned Shielding Bags
    These bags combine the “Faraday Cage” and mechanical protection. They shield about twice as well as normal shielding bags of equivalent size.

    Example of a Cushioned Shielding Bag – Click here for more information

Additional options for storing ESD sensitive items
Do you have the following in place?

  • ESD flooring
  • Grounded personnel (using foot grounders)
  • Grounded racking

IF (and this is a BIG IF) the above requirements are fulfilled, you can use conductive bags or containers to store your ESD sensitive items. Conductive materials have a low electrical resistance so electrons flow easily across the surface. Charges will go to ground if bags or containers are handled by a grounded operator or are stored on a grounded surface.

Conductive materials come in many different shapes and forms:

Conductive Black Bags
Tough and puncture resistant bags which are made of linear polyethylene with carbon added. The bags are heat sealable.

Example of a Conductive Black Film – Click here for more information
  • Rigid Conductive Boxes
    Provide good ESD and mechanical protection. Boxes are supplied with or without high density foam for insertion of component leads or low density foam which acts as a cushioning material.
  • PCB Containers
    Are flat based and can be stacked. They are made of injection moulded conductive polypropylene.

Again, there are many more options available on the market so make sure you do your research.

Note: we do not recommend using conductive packaging to transport ESD sensitive devices. Also, pink antistatic and pink antistatic bubble bags are not suited for storing or transporting ESD sensitive components.

Final thoughts
Packaging with holes, tears or gaps should not be used as the contents may be able to extend outside the enclosure and lose their shielding as well as mechanical protection.

Also, do not staple ESD bags shut. The metal staple provides a conductive path from the outside of the ESD bag to the inside. The use of a metal staple would undermine the effectiveness of the ESD bag making a conductive path for charges outside the bag to charge or discharge to ESD sensitive components inside the bag. To close an ESD bag, it is recommended to heat seal or use ESD tape or labels after the opening of the bag has been folded over. Alternatively, you can use ESD bags with a zipper.