Electrostatic Discharge (ESD)

Electrostatic Discharge (ESD – Electrostatic Discharge) is the sudden and uncontrolled transfer of electric charge between two objects with different electrical potentials. This phenomenon typically occurs as a result of physical processes such as triboelectric charging (charging by friction), induction (charge separation due to a nearby electric field), and corona discharge (ionization of insulating materials like air due to high electric field intensity).

When charged objects rapidly approach or come into contact, the potential difference discharges rapidly in the form of an arc (spark).

For example, a person walking on a carpet under conditions of 10% relative humidity can generate potentials up to 35,000 volts. Voltages above 3,500 V can cause a painful sensation, while those exceeding 8,000 V can produce visible arcs.

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The formation of static electricity is classified into two main types:

• Volumetric Static Electricity: Occurs within the internal structure of a material.
• Surface Static Electricity: Occurs on the outer surface of a material and is the source of the majority of industrial problems.

The primary causes of charging are:

• Friction (triboelectric effect): For example, walking on a wool carpet.
• Contact and Separation: The separation of two materials after contact.
• Induction: Being near a strong electric field.

This charging generates a voltage (V) depending on the material’s capacitance (C) and the amount of accumulated charge (Q).

ESD causes serious damage especially in microelectronic circuits. For instance, CMOS integrated circuits can be damaged by exposure to as little as 250 V of ESD. In manufacturing environments, 30–50% of product failures are attributed to ESD. ESD events in the 5 V–100 V range can also cause permanent damage to microchips.

In the electronics manufacturing industry, annual losses due to defective product returns amount to approximately $4.5 billion USD.

A single damaged chip may result in a $5 loss; if mounted on a circuit board, the loss rises to $50; at the system level, it can reach $500; and if the faulty product reaches the field, repair costs can escalate to $5,000.

ESD occurs more readily in cold and low-humidity regions. For example, personnel in areas such as Alaska and Alberta wearing thermal protective clothing accumulate higher electrostatic charges. A person walking on polyethylene flooring in low humidity can become charged up to 12,000 V, while walking on handmade carpets can generate up to 35,000 V.

Measures taken against ESD include:

• Grounding Systems: Copper plate-type grounders increase surface area to enhance grounding effectiveness. Structures with high conductivity and low spreading resistance are preferred. Electrical charges are safely conducted to ground through grounding systems.
• Antistatic Clothing: ESD-protective garments are typically made from a blend of cotton and conductive fibers (e.g., aluminum-coated). Their fabric topology is designed to prevent both charge accumulation and sudden discharge. Conventional topologies include homogeneous surfaces, conductive coatings, unidirectional conductive structures, and grid patterns.
• Workstations: Antistatic tables, carpets, and wrist straps made from conductive materials prevent static charge buildup in place of insulating surfaces. These setups ensure the safe handling of ESD-sensitive components during R&D processes.
• Environmental Humidity Control: Maintaining relative humidity between 40% and 60% significantly reduces static charge accumulation. As humidity increases, the amount of accumulated charge decreases.

Aircraft in flight become subject to triboelectric charging through contact with ice crystals, rain, sand, and exhaust gases. External atmospheric fields also contribute to charge accumulation. These charges discharge via:

• Corona discharge
• Electrical streaming
• Arcing

High-voltage charges can cause electromagnetic interference in radio and navigation systems. To mitigate this, static discharge wicks installed on aircraft allow controlled dissipation of charges into the atmosphere. In modern aircraft, where composite fuselage materials with low conductivity are increasingly used, conductive mesh structures are incorporated to safely distribute lightning current through the structure.