ESD prevention techniques: Safeguarding sensitive electronics in workplace

ESD, characterized by the rapid exchange of electrostatic charge between objects of varying potentials, poses a significant threat to delicate electronic components, jeopardizing their functionality and reliability. In industrial environments, the consequences of ESD span from substantial financial losses due to product damage and rework to potential safety hazards.

As electronic devices become smaller and more complex, their susceptibility to ESD events increases, emphasizing the need for robust prevention measures. This article delves into the intricacies of ESD, explaining its underlying mechanisms and the diverse strategies deployed to safeguard sensitive electronics across various industries. As a reader, you will explore grounding techniques, material selection criteria, workstation design principles, and handling protocols. By the end, you will have a comprehensive grasp of tailored ESD control methodologies suited to their specific industrial contexts.

ESD prevention techniques

Electrostatic discharge (ESD) is a pervasive and costly issue in electronics manufacturing. Semiconductors carry stored charges that discharge upon contact with the human body or tools, often imperceptibly but damagingly. Handling PCBs with bare hands, placing synthetic materials near electronics, and rapid air movement can all cause ESD. Implementing ESD prevention methods during manufacturing and assembly is crucial to protecting circuits from this invisible threat. Daily activities can build up charges on your body, potentially harming sensitive components:

• Walking on carpet: 1,500 to 35,000 volts
• Walking on the untreated vinyl floor: 250 to 12,000 volts
• Working at a workbench: 700 to 6,000 volts
• Picking up a plastic bag from a workbench: 1,200 to 20,000 volts.

we will discuss some critical ESD control strategies as follows -

Grounding & bonding: Grounding and bonding play critical roles in electrical systems to ensure safety and functionality. They prevent electric shock, equipment damage, and fires. Grounding establishes a connection between circuits and the earth, redirecting current away from people and structures. It provides a low-resistance path for fault currents, triggering protective devices. This stable reference point reduces voltage fluctuations, protecting sensitive electronics. Grounding also manages electromagnetic and radio frequency interference, ensuring optimal performance. While bonding does not eliminate static charges, it establishes equipotential surfaces between the bonded objects, preventing potential differences that could lead to spark discharges. Key features includes:

Grounding

• It provides a low-impedance path for electrical currents to flow safely to Earth.
• Reduces risks of electrical shock, fire, and equipment damage.
• Mitigates electromagnetic interference (EMI) by creating a safe current return path.
• Implementation varies based on equipment type, location, and environment (e.g., grounding rods, plates, or wires).

Bonding

• Interconnects different equipment parts to maintain equipotential surfaces.
• Eliminates voltage differences that could cause EMI.
• Achieved through bonding wires or straps, depending on equipment and environment.

Personal grounding:

It serves as the first line of defense against static charges. This is important as humans primarily produce static electricity through Tribocharging. This can occur from simple actions, like walking across carpets to turning doorknobs.

It is essential to address ESD issues for worker safety and company profitability. Implementing approved ESD grounding requirements tailored to particular areas is vital. This involves first identifying the areas that require grounding. Personal Protective Equipment (PPE) is essential in diminishing ESD risks. Different key items includes:

• Anti-Static wrist straps: They are the primary means of grounding personnel, providing equipotential bonding in field service repairs. This device uses an ion neutralization mechanism that effectively neutralizes over 80% of static ions in the human body. When properly worn and connected to the ground or the equipotential bonding point, a wrist strap keeps the wearer at ground potential or the same potential as the object when a ground connection cannot prevent hazardous discharge between them and other grounded objects. Static charges are directed from the person to the ground, preventing accumulation. Typically, wrist straps include a current-limiting resistor integrated into the ground cord, which is necessary for personnel safety.
• ESD heel straps/ heel grounders: This durable shoe accessory fits all types of shoes, ensuring comfort and adjustability while being highly abrasion-resistant and providing complete static dissipation. Additionally, it comes with a 1 Meg Ohm safety resistor, ensuring a long life and preventing tearing.
• ESD safety shoes/slippers: Anti-static shoes are specialized footwear designed to prevent the accumulation and discharge of static electricity, protecting both the wearer and surrounding equipment. Equipped with conductive soles and laces, anti-static shoes ground the charge to prevent static charge accumulation and discharge.
• Anti-static ESD gloves: reduce static electricity accumulation on equipment or the body, minimizing the risk of electrostatic shock. Constructed with soft conductive materials and synthetic fibers(polyester, rayon, or spandex), these gloves conduct electricity or dissipate static electricity. Some ESD gloves even have carbon fibers or metal threads woven into the fabric to enhance their anti-static properties, providing protection for workers and products against the harmful effects of static electricity and ESD, such as damage to electronic components.
• ESD-safe clothes: ESD-safe clothing is engineered to prevent static charges from transferring from a person or their clothing into the surrounding area. Unlike regular clothing, which often insulates the body from electrical charges, ESD-safe garments are crafted from materials like cotton or polyester embedded with carbon fiber. These fibers create a Faraday Cage around the wearer's body, shielding and dissipating any charges that could otherwise damage devices sensitive to static electricity. Groundable static control garment systems are designed to ground the wearer through the ESD clothing, provided the fabric is conductive enough. Achieving this involves fitting a coil cord to the garment and touching the ground. For this system to function correctly, the ESD garment must have a resistance of less than 35 megohms from the wearer to the groundable point of the garment. All ESD-safe clothing must meet the standards for ESD clothing set by the IEC-61340-1-5 International Standard to protect the wearer and the surrounding environment from electrostatic discharge. To learn more about ESD-safe jackets, click here.

Proper use of PPE, functionality testing, and adherence to standard operating procedures (SOPs) for material handling, storage, and controlled environments are essential. Static-generating actions like touching hair, clothing, or paper should be avoided to prevent charge buildup and potential discharges.

Electrostatic Protected Area (EPA):

ESD-sensitive components and devices should only be unpacked, handled, or assembled within an EPA (Electrostatic Protected Area). An EPA offers optimal conditions for preventing ESD, with all materials being electrostatically dissipative and grounded to the same potential. This includes components, equipment, surfaces, and clothing within a designated area, ensuring targeted avoidance of electrostatic charges and potential differences. An EPA can range from a single workstation to an entire building, with all workstation rules applying uniformly. ESD poses a hidden threat in the electronics industry. It is essential to follow the three ESD fundamentals to control ESD in your workplace:

1. Ground all conductors, including people.
2. Remove unnecessary non-conductors (insulators).
3. Shield ESD-sensitive devices in transport outside an EPA.

An EPA can be distinguished into the central parts:

• EPA identifiers: To identify an EPA, use products such as floor marking tape and signs with clear messages, such as "Entering ESD Protected Area" or "Leaving ESD Protected Area." This alerts personnel and visitors when entering or exiting areas requiring special precautions like grounding via wrist straps, foot grounders, etc. Consistency in signage across the workplace floor avoids confusion. EPA identifiers include ESD floor marking tape and ESD marking/signs or levels.

Figure 1(a): ESD protective symbol, 1(b): ESD susceptibility symbol, 1(c): EPA identifiers (Source)

To learn more about ESD Labels and tape, click here

• Room-level control: Insulators cannot transfer charge carriers, preventing the establishment of an effective conductive path to ground potential or earth. We need to enhance the conductivity of the surrounding air to remove charges from insulators effectively. For instance, a balloon sticks to a wall at first due to a static charge but eventually fails as the charge dissipates into the somewhat conductive air. However, this process is slow. The more conductive the air is, the faster the charge will be neutralized. The two most commonly used methods to increase air conductivity are relative humidity and ionization. However, increasing humidity often introduces problems such as operator discomfort, metal oxidation, solderability issues, and high maintenance costs, making, air ionization the preferred method.
• Air ionizers are crucial for ESD protection as they neutralize electrostatic charges on insulators and isolated conductors. These devices generate positive and negative ions, which are dispersed throughout the workspace to counteract static charges on surfaces. Using emitter points to create an electric field, ionizers ionize air molecules, attracting opposite charges to eliminate static electricity buildup. In dry environments, where static buildup is more likely, ionizers are essential for maintaining ESD protection, especially when humidity levels are low. Pairing ionizers with appropriate grounding equipment, such as wrist straps and table mats, is necessary to ensure effective operation. Two principal ionization techniques exist Corona ionization, which electrically generates ions, and Alpha ionization, a non-electrical approach leveraging radioisotopic alpha particle emission.

Figure 2(a): Benchtop Ionizer (Source) Figure 2(b): Benchtop Ionizer (Source)

• EBP plug or bracket: Earthing is essential for dissipating electrostatic charges from ESD-sensitive components and work areas. At each workstation, earth bonding points connect ESD surfaces and personnel to a verified facility ground or grounding bus via bonding plugs or brackets. These points create a safe, accessible grounding point within the ESD-protected area (EPA) by interfacing with the equipment grounding conductor in the main outlets. Static charges on bonded EPA elements are shunted through the bonding point to earth ground. Proper EPA earthing is crucial when handling static-sensitive electronics. Bonding points enable straightforward, reliable personnel and surface grounding without requiring direct earth-ground access.
• ESD safe workbench: An ESD Workbench establishes a zero-potential ground between the floor, a worksurface, and a user. Conductive ESD-safe surfaces prevent defects and device failure by channeling, slowing down, and shielding electrically sensitive devices. The ideal work surface resistance for electronics manufacturing is above 106 ohms but below 109 ohms. Options like Neostat, which features a dual-layer rubber surface for safe grounding with a surface resistivity of 105 – 107 ohms, or Lamstat, with a surface resistivity of 106 – 108 ohms, offers a static dissipative plastic laminate surface suitable for soldering and chemical tasks. Modular add-ons and features, such as heat-resistant surfaces, provide an ideal fit and function for hand assembly lines. Typically, these benches include a central receptacle for connecting ground points from ESD floor mats, wrist straps, and other ESD accessories. The ESD workbenches have ESD dissipative surfaces, grounding features, and other ESD accessories. They also have adjustable height and ergonomics features like keyboard trays and monitor stands, integrated power outlets, and cable management systems, ensuring durability and easy maintenance for efficient and safe electronic assembly.

Figure 3: Sample of EPA workstation (Source)

To learn more about workstations, click here.

• ESD safe tools and instruments: ESD safe hand tools are specifically engineered to prevent static electricity buildup, effectively guarding against any potential electrostatic discharge. They play an essential role in industries where workers often interact with delicate electronic components, such as in electronics manufacturing, computer repair, and aerospace engineering. ESD-safe hand tools work on the basic principle of electrostatic conductive or dissipative materials. These tools are typically made of materials that do not generate an electrostatic charge when they come in contact with other materials. Furthermore, if these tools acquire a charge, the design allows the charge to dissipate slowly without creating a harmful ESD event.
• ESD mat: ESD mats, with a resistance range of 0.1 to 100 MΩ, prevent the buildup and discharge of static electricity, ensuring the safe handling of electronic components. The top layer is insulative, shielding the user from potential electrical shocks. The mats also feature a dissipative middle layer that disperses the static charge across the mat's surface, reducing the risk of a concentrated discharge. The conductive bottom layer of the mat serves as the primary pathway for directing static electricity away from the mat and into the ground. They safely discharge static charges from devices, protecting against sudden electrical surges. When used with wrist straps, the ESD mats provide comprehensive electrostatic protection by dissipating potentially destructive static charges and safeguarding sensitive electronic equipment and personnel from the harmful effects of electrostatic discharge events. To learn more about ESD mat technology in detail, click here. Here, we are offering MulticomPro’s ESD mats.
• ESD-safe shelves and carts: ESD-safe shelves and carts are designed with ESD considerations and are crafted from materials that dissipate static charges. To protect sensitive equipment. They feature antistatic casters, mats, adjustable shelves, component bins, and grounding chains, enhancing workplace safety and efficiency.

Figure 4: Antistatic storage cabinet (Source)

As a global distributor, we partnered with many suppliers and offer a wide range of products in Antistatic and ESD :

Conclusion

As technology evolves, so do the challenges. It is necessary to craft effective ESD prevention and adapt to emerging technologies. From robust grounding systems to cutting-edge ESD-safe materials and workstation designs, the toolbox of ESD control strategies continues to expand. Yet, the human factor remains pivotal, highlighting the significance of comprehensive ESD training and awareness initiatives for personnel handling sensitive electronics.

Collaborative efforts among researchers, manufacturers, and regulatory bodies are crucial to tackling emerging ESD threats, including those posed by advanced packaging technologies and automated handling systems. We can bolster the resilience of delicate electronics only through continuous refinement of our technologies, ensuring their secure and dependable operation in industrial settings worldwide.