The Difference Between Anti-Static, Static Dissipative, and Conductive ESD Bags
The manufacturing, transportation, and delivery of electronic circuit boards, flat-panels, motherboards, hard drives, microchips, and more requires use of ESD-safe, static controlled bags. Problematically, the confusion of terminology between anti-static, static-shielding, and static dissipative bags creates a risk of errant voltage, improper handling, and compromised electronic devices.
Are Anti-Static Bags ESD-Safe? What Are they Made Of?
Standard plastic bags, commonly made of polyethylene, fail to protect ESD-sensitive devices from the flow of electrically charged objects caused by contact, and electrical short, or dielectric breakdown. ESD is not only a silent killer in high-tech electronics manufacturing and production, but also during hobbyist projects or small-batch electronics repair. Static electricity control during packaging, transportation, handling, and repair is essential for compliance with EMI/EMC testing standards and compliance with ANSI/ESD S.20.20. The handling and transportation of ESD sensitive items requires protection from both triboelectric build ups caused by contact with personnel or other surfaces, but also when transporting devices between ESD compliant areas and non-compliant areas.
What’s the Difference Between an Anti-Static Bag and A Static Shielding Bag?
Anti-static bags prevent triboelectric charge build up but do not shield components inside the bag from electrostatic discharge. Anti-static bags sustain safe component handling only in EPAs (ESD protected areas). Static shielding bags provide a full encompassing ESD protection mechanism for components within the bag, and in both EPA and non EPA areas.
What’s The Definition of Anti-Static? Are Pink or Blue Bags ESD Safe?
The definition of anti-static only means that a material will not generate triboelectric charges when in contact with fabric, hair, plastic packaging, or other insulators. Generally, anti-static bags rely on an ESD coating which mitigates tribocharging, and reduces the likeliness of electric potential that leads to ESD events. Electronic devices, IC components, and other ESD-sensitive devices are not safe from ESD events when stored, handled, or transported outside an ESD safe environment inside an anti-static bag. Again, pink or blue anti-static bags are only ESD safe for components inside of an EPA (ESD protected areas). Only static shielded ESD bags provide protection for transportation outside of an ESD safe area or for shipment. ESD sensitive components should never be shipped in pink or blue anti-static bags!
Is an Anti-Static Bag the Same as a Static Dissipative Bag?
No. Static dissipative ESD bags provide static dissipative materials that slowly drain charge. In ESD area, these bags provide safe transport of papers or documents without transferring any charges from a non-ESD safe area. Clear static dissipative bags are not safe for components, as a component may absorb an ESD shock without the protection of a faraday cage. Hence, only non-ESD sensitive products render safe use with static dissipative bags. Specifications should be noted clearly when purchasing clear ESD bags; a truly static dissipative bag will produce the surface resistance noted below.
Static dissipative materials have a surface resistance greater than 10 kilohms but less than 100 gigohms when tested according to ANSI/ESD STM11.11 or a volume resistivity greater than 1.0 × 105 ohm-cm but less than or equal to 1.0 × 1012 ohm-cm when tested according to the methods of ANSI/ESD STM11.12. ESDA.org
What Are Anti-Static Bags Made Of?
Standard pink, blue, and sometimes clear anti-static bags are made of polyethylene with an outer layer of ESD material. Sometimes, these bags can also be black when trace amounts of carbon are deposited during the manufacturing process. Pink or clear anti-static bags are only safe for use in an EPA (ESD protected area). Transferring a component from an EPA area to a non-EPA area inside of a pink, blue or clear anti-static bag is not safe.
Are Static Dissipative Bags Conductive?
No. static dissipative bags are not conductive, but instead have a surface resistance of more than 1 x 10 5 ohms/sq but less than 1 x10 11 ohms/sq. The precise resistance of a static dissipative layer inhibits charges from transferring to nearby components by a controlled bleeding of the charge, but the layer does not offer protection for a charge that reaches the bag from a charged item, tool, or a person. Safe ESD packaging for commercial applications is defined by ESD/ANSI S20.20 which you can learn more about here, including links to free PDF documents from ESDA.org.
What Are ESD Conductive Bags and What Are They Made Of?
Conductive bags, also known as static shielding bags, or metalized shielding bags feature polyethylene terephthalate (PET), which is the most common material used for the manufacturing of conductive ESD bags. Metalized film layers and conductive function shield contents from static charges via the Faraday cage effect. A dielectric layer of plastic film, polyester, and a conductive metal aluminum layer, protects ESD sensitive devices from shocks generated from the user, the surface, or other surrounding materials. Conductive ESD bags provide safe transit from an EPA area to a non EPA area.
Types of Metalized Shielding Bags
Static shielding bags feature either a metal-in or metal-out construction.
Metalized shielded bags feature either a metal-in or metal-out design. The buried metal design is common for the packaging of ESD sensitive (ESDS) components. Metal-out shielding bags also protect against static induced damage. The benefits of metal-in construction is usually a factor of cost and durability. A metal layer closer to the outside surface results in a lower resistant reading than the metal-in ESD bags, which can be important in some applications.
“Metal-out shielding bags have a highly conductive outer layer which promotes a more rapid discharge in static fields thereby creating the event which the metal layer must then attempt to attenuate. Metal-in shielding bags have a dissipative outer layer which inherently dampens the discharge thereby lessening very damaging electrostatic events. The shielding capabilities of the actual metal layer is a function of its conductivity not its position in the bag.” – ESD Journal
Discharge shielding is provided by materials that have a surface resistance equal to or less than 1 kilohm when tested according to ANSI/ESD STM11.11 or a volume resistivity of equal to or less than 1 × 10 ohm-cm when tested according to the methods of ANSI/ESD STM11.12. In addition, effective shielding may be provided by packaging materials that provide a sufficiently large air gap between the package and the ESDS contents. – ESDA.org
Packing and Handling Requirements for ANSI/ESD Compliance
Core Requirements for ESD/ANSI TR20.20 Packaging and Materials:
- The main ESD function of these packaging and materials handling products is to limit the possible impact of ESD from triboelectric charge generation, direct discharge, and in some cases electrostatic fields.
- A second requirement is that the material can be grounded so that the resistance range must be conductive or dissipative. A third property required outside the EPA is to provide protection from direct electrostatic discharges that is discharge shielding. –
- A third property required outside the EPA is to provide protection from direct electrostatic discharges that is discharge shielding. ESDA.org
ANSI/ESD STM11.31 measures provides a method of evaluation for the energy transferred from the package to the interior.
The ability of some packages to provide discharge shielding may be evaluated using ANSI/ESD STM11.31 which measures the energy transferred to the package interior. A material’s low charging properties are not necessarily predicted by its resistance or resistivity.
Find a Metal-in or Metal-Out Conductive Static Shielding Bag Supplier
Here are some direct links to pricing and products for ESD packaging.