With electronic components getting smaller and more sensitive, it’s important to make sure they are protected from ESD events like static discharge. Per ANSI/ESD S20.20, “Protective packaging is required to store, transport, and protect ESDS electronic items during all phases of production.” Per the new 2018 requirements for ANSI/ESD S541, the shielding requirement was changed that remaining discharge for the bags should be less than 20 nanojules.
One of the more common used bags is a low charging Pink Poly bag. These bags are made from a tinted polyethylene material with an antistatic coating that can wear away. This turns the bag insulative over time, making it noncompliant to ANSI/ESD S541 recommendations. They also lack discharge shielding protection which makes components within the bag susceptible to ESD event damage. Metallized Shielding bags are constructed from a metalized polyester film and a low charging polyethylene laminate. This provides the bags with a shielding layer that creates a Faraday cage protecting the ESD sensitive components within the bag from possible ESD event damage. The low charging inner layer and outer layer of the bag prevent tribocharging from occurring, minimizing the build up of ESD charges when handling components.
Watch this video on Pink Poly vs Static Shielding Bag Testing and learn why Metallized Static Shielding Bags are the best packaging solution offering full protection against ESD events.
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.
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.
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.
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.
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.
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.
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!
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.
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.
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.
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.
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.
Additional options for storing ESD sensitive items Do you have the following in place?
Grounded personnel (using foot grounders)
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.
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.
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.
If your company has an ESD Control Program per ANSI/ESD S20.20 in place, you need to define ESD protective packaging for ESD sensitive items (ESDs).
“The Organization shall prepare an ESD Control Program Plan that addresses each of the requirements of the Program. Those requirements include: – Training – Product Qualification – Compliance Verification – Grounding / Equipotential Bonding Systems – Personnel Grounding – ESD Protected Area (EPA) Requirements – Packaging Systems – Marking” [ANSI/ESD S20.20 clause 7.1 ESD Control Program Plan]
But where do you start? Don’t panic – we’re here to help and we’ll be following the guidelines set-out in the ESD Standard.
Definition and Purpose of ESD Protective Packaging ESD Protective Packaging covers any materials coming into direct contact with ESD sensitive devices during handling, shipping and storage. You don’t need to worry about secondary or exterior packaging unless it’s used for ESD protection purposes.
“Packaging for ESD sensitive items is commonly derived by modifying existing packaging to prevent the packaging itself from causing static damage. The packaging generally retains physical and environmental protective qualities. ESD protective packaging has been modified further to prevent other sources of static electricity from damaging a packaged item.“ [ANSI/ESD S541 Foreword]
The fundamentals of ESD control include grounding all conductors in the EPA. ESD packaging will have special material composition to lower the resistance so that when grounded, electrostatic charges will be removed to ground thus protecting your ESD sensitive devices inside.
“Transportation of electrostatic sensitive devices requires packaging that provides protection from electrostatic hazards in the transportation or storage system. In the case of an EPA designed with continuous grounding of all conductors and dissipative items (including personnel), packaging may not be necessary.” [ANSI/ESD S541 clause 6. Packaging Application Requirements]
Example of ESD Packaging
Packaging is to be determined for all material movements inside and outside of the ESD Protected Area (EPA). Best practice is to define the required packaging or material handling item on the product’s bill of materials. Remember: the ESD packaging is just as important as a component part.
Customer contract packaging can take precedence, but otherwise “the organization shall define ESD protective packaging requirements, both inside and outside the EPA per ANSI/ESD S541 or in accordance with the contract, purchase order, drawing or other documentation necessary to meet customer requirements.” [ANSI/ESD S20.20 clause 8.4 Packaging]
Choosing your ESD Protective Packaging Numerous factors need to be taken into consideration when choosing your ESD protective packaging including the “environment and device sensitivity.” [ANSI/ESD S541 Annex A.1 Environment and Device Sensitivity]
It is best recommended to follow these 6 steps:
Understand the product sensitivity You can gather information about the ESD sensitivity of an item by either measuring it in-house, contacting the manufacturer of the product or by analyzing published ESD sensitivity data.
Determine the distribution environment for the packaged product Knowing the environment in which the product is shipped and how it will be handled is extremely important. Humidity and temperature are the main factors to consider when it comes to choosing the right type of packaging for your ESD sensitive items. If items are susceptible to moisture, a barrier material should be chosen to prevent excessive humidity exposure. On the other hand, condensation may occur inside the packaging if temperatures vary around the dew point of the established interior conditions. In those instances, desiccant should be put inside of the package or the air should be removed from the package before shipment.
A Moisture Barrier Bag – click here for more information
Determine the type of packaging system that is best suited for the intended application The first step is to choose low charging or static dissipative materials when in contact with ESD sensitive devices. Many companies also require the packaging to protect the contents from a direct discharge or exposure to electric fields. In addition to these requirements, there are further questions that need to be asked:
Returnable or reusable packaging?
Disposable or one-time only packaging?
Aesthetic requirements for packaging?
Select and test packaging materials Test methods are explained in ANSI/ESD S541 and will classify packaging materials as conductive, static dissipative or insulative.
Design a packaging systemOnce the ESD sensitivity and distribution environment have been evaluated and available materials have been selected, the design of the packaging system can begin. Per the ANSI/ESD S541, the following general rules apply:
Inside an EPA: “Packaging used within an EPA (that satisfies the minimum requirements of ANSI/ESD S20.20) shall be:
Low charge generation.
Dissipative or conductive materials for intimate contact.Items sensitive to < 100 volts human body model may need additional protection depending on application and program plan requirements.” [ANSI/ESD S541 clause 6.1 Inside an EPA]
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.”
[ANSI/ESD S541 clause 6.2 Outside an EPA]
Example of ESD Packaging
In addition to these guidelines, there may be additional factors that should be considered, e.g.:
Cost/value relationship: The cost of the packaging compared to the total value of the contents is important. Some companies choose less expensive packaging for less valuable parts.
Test the final packaging design for effectiveness It is highly recommended to subject packages to the type of hazards that can be expected during shipments. These tests can, for example, involve the following:
High voltage discharges to the exterior of the packaging
Simulated over the road vibration
Final thoughts on ESD Protective Packaging Now that you have an understanding of the factors to consider when choosing your ESD Protective Packaging, you’re ready to implement the above guidelines. ESD packaging comes in all sorts of shapes and forms so bear in mind to not just look at bags when deciding what type of packaging to choose.
Also, remember that ESD packaging should be marked. We’ll cover the specifics in a later post.