Do you ever wonder why, when viewing pictures or videos of people working at an electronics manufacturing facility, they’re all wearing what look like lab coats? They don’t appear to be working with food, pharmaceuticals, or chemicals, so what gives? Those are electrostatic discharge (ESD) smocks, and they are designed to prevent the buildup and release of static electricity. They’re just one of many ways electronics contract manufacturers ensure they can build a high-quality reliable assembly that will not fail once in the field. You will rarely see, feel, or hear ESD. It can happen anywhere at any time. ESD events cause the electronics industry billions of dollars every year in component replacement costs, field repairs, and customer service.
What is ESD? Electrostatic discharge refers to the sudden and momentary flow of electric current between two differently charged objects when they come close together or when the dielectric between them breaks down, often creating a visible spark. A common example of ESD is the shock you receive after walking across a carpeted floor and touching a metal door handle. That small shock you feel may not seem like much to you, but it can cause significant damage to electrical components, compromising their integrity.
The two primary types of damage incurred by ESD are referred to as latent failure and catastrophic failure. When a component passes testing but later fails during use by the customer for no apparent reason, that is considered latent failure. This leads to poor quality products and dissatisfied customers at best. Worst case scenario, as with medical devices or aerospace technologies, the failure would have severe consequences, such as life or death. Catastrophic failure happens when a component is exposed to ESD, and the device circuitry is immediately permanently damaged. Luckily, such failures may be caught during testing and the manufacturer may be able to diagnose the issue and replace the part prior to shipping the completed assembly to the customer.
So how can electronics manufacturers prevent ESD? For starters, manufacturing facilities should have a Quality Management System in place that governs the policy and procedures in place to prevent ESD. The policy should include designating an Electrostatic Discharge Protected Area (EPA) marked by signage that warns you before you enter or leave the area. In an EPA, all materials are kept at the same electric potential, all conductive and dissipative materials are grounded, and workers are grounded. All these measures prevent a charge build-up on ESD-sensitive components.
In any electronics manufacturing facility, the use of dissipative materials and grounding is critical. Within the EPA, the floors are covered with ESD flooring which resembles carpet tiles and/or linoleum. Conductive elements such as carbon and graphite that are distributed throughout the flooring material give ESD floors electrical conductivity, creating an electrical pathway from the walking surface to ground. Some ESD floors prevent charge generation as well. All work surfaces should be covered with anti-static table mats, which collect static and then discharge it through a grounding port. Items that are sensitive to static can be placed on these mats.
Operators working within the EPA wear specialized gear which helps neutralize static discharge created as they move about. ESD jackets (those smocks!) contain a grid of conductive fibers embedded throughout the garment that serve to shield sensitive electrical devices from static charges the operator may generate while moving about. Using the properties of both conductive and dissipative materials, they allow for the controlled dissipation of static charge. (ESD Coat Chronicles: The Fabric of Safety, 2024) ESD wrist straps consist of a wristband and ground cord that provides an electrical connection of a person’s skin to ground, allowing the electricity to flow safely away from any sensitive components. ESD heel straps, worn on top of an operator’s shoe, work in the same way, but allow the operator to walk around freely, as they don’t require them to be strapped to a ground port.
When handling electronic components and assemblies, it is imperative that operators use special packaging. When moving assemblies throughout the production process, ESD boxes, or specialized conductive totes or bins serve to protect the assemblies. In addition, when shipping electrical components, placing them inside anti-static bags and wrapping them in static dissipative bubble wrap will help to ensure the parts can arrive safely and in good condition.
While an electrostatic discharge event may not seem like a big deal in the moment, that small spark of energy can be detrimental to electronics. If it’s not detected prior to that assembly entering the field, the product’s inevitable failure can lead to a wide range of consequences including customer dissatisfaction, costly repairs, and even life or death scenarios. The best strategy for an electronics manufacturer to avoid such consequences is prevention. Having a non-negotiable ESD policy in place that requires proper training, awareness, and a fully controlled environment complete with equipment and tools to prevent ESD is key. So, the next time you’re perusing a potential electronics manufacturing partner’s website and wonder why they make such poor fashion choices for their uniform requirements, just know that those smocks! are just one facet of what’s likely a meticulously executed plan designed to ensure your product lives up to your quality standards.
