ESD (Electrostatic Discharge) refers to the instantaneous current release caused by the sudden imbalance of potential difference between charged objects. In the field of electronics, ESD is one of the main causes of device damage.
The recognition of electrostatic hazards began with the warning of major accidents.
In 1967, the USS Forrestal exploded due to the failure of the missile shielding connector, causing static ignition, resulting in an explosion and causing losses of US$134 million and 134 casualties; in 1969, three supertankers in the Netherlands, Norway and the United Kingdom exploded due to static electricity during tank washing. These events forced the global industry to face up to ESD risks. Early protection relied on passive components such as resistors and capacitors to disperse charges. The technical means were simple and concentrated in the military and aerospace fields. China established the Electrostatic Professional Committee in 1981, marking the beginning of systematic research.
With the popularization of integrated circuits, protection technology has entered a period of rapid iteration. In the 1980s, TVS (transient voltage suppressor) diodes became mainstream, using reverse breakdown characteristics to discharge static electricity. However, after the CMOS process replaced TTL, the reduction in device size led to a decrease in robustness, which gave rise to active protection structures such as GGNMOS (gate grounded NMOS) and GDPMOS, and Soft Tie technology adapted to high-frequency circuits by reducing parasitic capacitance. In the early 21st century, high-efficiency devices such as SCR (silicon-controlled rectifier) and LVTSCR (low-voltage trigger SCR) were commercialized, and the response speed and clamping capability were significantly improved. The concept of system-level protection has become mature. For example, the Rail-Based strategy manages the risks of multi-voltage domain chips through dedicated discharge paths, and the Stack structure solves the protection needs of high-voltage ports. The improvement of international standards (such as the IEC 61340 series) and the Chinese national standard (GB/T 20158) has further standardized the design process.
In recent years, the miniaturization of chips has highlighted the risk of CDM (charged device discharge) failure. The protection unit has been integrated into the chip, combined with layout optimization to reduce parasitic effects. Diversification of application scenarios promotes technology customization: automotive electronics require high-temperature resistant devices, the Internet of Things relies on low parasitic capacitance SCR, and 5G communications use high dielectric constant materials to reduce signal interference. Smart sensing materials such as flexible electronic skin even integrate ESD protection with pressure and temperature sensing, and expand to the wearable field. Modern ESD protection has formed a full-chain system of "materials-devices-systems-environment".
The core concept of ESD electrostatic protection design: blocking and dredging
"Blocking" and "dredging" are essentially a dual strategy of blocking electrostatic intrusion through physical isolation and directional discharge of charge through low-impedance paths, forming a systematic control of electrostatic discharge energy. This concept stems from a deep understanding of the characteristics of electrostatics-the electrostatic voltage can be as high as tens of thousands of volts, but the amount of electricity is extremely small (microcoulomb level), and the discharge time is extremely short (nanosecond level).
"Blocking" is to avoid electrostatic discharge through insulation treatment, while "draining" is to design the path for static electricity to enter the large pool. The core of "blocking" is to block the path for static electricity to invade sensitive circuits. By increasing the distance between the shell and the internal circuit through structural design, for example, increasing the distance from the shell gap to the PCB to ≥4mm, the 8kV static energy can be naturally decayed to zero in the air. For metal decorative parts or interfaces, etc., which are easy to discharge, use insulating coatings and sealants to fill the gaps, or add metal shielding covers to block air breakdown (the breakdown distance of 8kV air discharge is about 6mm). The non-conductive shell forms a shielding layer by spraying EMI conductive paint, which guides the static charge to the shell grounding and suppresses EMI interference.
The core of "draining" is to provide a safe and efficient low-impedance discharge path for static electricity and guide it into the "earth pool" (such as the PCB ground plane). Due to the small amount of static electricity, it is necessary to expand the charge capacity through multi-layer PCB design (≥4 layers) and a complete copper-clad ground plane; double-sided boards require interlaced power/ground grids (grid size ≤13mm). The design of the discharge path follows three principles: stay away from sensitive circuits, release to a large pool as soon as possible, and increase resistance in easily damaged paths. The voltage of static electricity is very high but the amount of electricity is small. When designing, the number of layers and area of the PCB must be considered to expand the capacity of the "pool".
The key to ESD design is to effectively manage static electricity and ensure equipment safety. In short, ESD protection is like water management: "blocking" is a shield, using an insulating barrier to resist high voltages of tens of thousands of volts; "draining" is a channel, using a low-resistance path to remove nano-coulomb charges. Both are indispensable. Only by collaborative design at the structural, circuit, and material levels can the "microscopic world" of electronic equipment be protected from instantaneous static electricity shocks.
Common ESD protection products in the electronics field:
ESD Grounding Clip: An ESD grounding clip is a tool used to directly ground devices susceptible to discharge events. When properly grounded in this way, the risk of ESD (electrostatic discharge) damage is greatly reduced.
Anti-static wrist straps (often called ESD wrist straps): work essentially the same way as static grounding clips, except they connect the user to ground instead of the electrical device being handled.
Sticky Roller: Also known as sticky roller or anti-static sticky roller, it is widely used in ESD control and clean room environment.
Anti-static bags: Used to store electronic products that are susceptible to static electricity. When you buy a motherboard, graphics card, or any device that contains a printed circuit board, it will usually be packed in an anti-static bag.
ESD shoes: The terms ESD safety shoes and anti-static shoes may often be used interchangeably, but technically have slightly different definitions. Both help to minimize static buildup caused by the wearer moving around by quickly conducting any potential charge to ground.
ESD Mat: Static control grounding mat. Usually made of ESD safe rubber or similar material.
ESD Gloves: Anti-static gloves for electronics, often called electrostatic discharge safety gloves, are required to be worn in almost all cleanrooms and static controlled environments. They make handling items and components such as PCBs, motherboards and backplanes safer without the risk of sudden static discharge to sensitive components.
