1. Electrostatic Protection of Electronic Products
Charge accumulation on object surfaces, namely electrification, occurs due to contact separation between objects (such as friction, peeling, tearing and collision during handling) or electric field induction, resulting in diffusion, transfer and migration of charged particles inside or between objects.
Such electrification may attract fine dust particles with opposite charges in the air, reducing insulation performance, causing structural corrosion or damage to electrostatic-sensitive electronic components. Under suitable external conditions, accumulated charges will generate electrostatic discharge (ESD), resulting in local breakdown or damage to components. In severe cases, it may trigger fires and explosions. There have been reported explosion accidents caused by static electricity during maintenance of semiconductor integrated circuits on program-controlled switches.
Notably, structural damage and performance degradation of electronic components caused by static electricity are potential long-term hazards, often more harmful than fires and explosions. Such defects are difficult to detect, leading to random failures, and are easily confused with other failure causes.
With the widespread application of polymer materials, static phenomena in electronic products have become increasingly serious. Meanwhile, electronic components are becoming smaller and more compact, greatly increasing electrostatic risks. Microcircuit manufacturing overseas has widely adopted 0.8–1.0μm processing technology, while China has reached 2–3μm precision. Ultra-fine processing and miniature structures make products highly susceptible to static damage.
Electrostatic protection for electronic products features distinct characteristics:
- Ultra-fine and ultra-thin processing technologies and miniature structures make components far more sensitive to ESD than other industries. Even electrostatic discharge voltage below 20V can damage electronic components.
- Electrostatic-sensitive devices including discrete semiconductors, integrated circuits, thick and thin film circuits, resistors, capacitors and piezoelectric crystals act as the core of electronic equipment. Therefore, electrostatic protection covers almost all technical fields of electronic products, especially compact, high-frequency and high-density electronic devices.
- Electrostatic protection is a systematic project covering manufacturing, assembly, handling, inspection, testing, maintenance, packaging, transportation, storage and application. Working in a series linkage mode, any negligence in one link will cause overall protection failure. It is also closely related to operating environments (facilities, air humidity, floors, workbenches, equipment and tools) and personal protective gear (clothes, hats, shoes, gloves and wrist straps). Any oversight will compromise electrostatic protection effectiveness.
Corresponding systematic standards can be formulated according to the above characteristics. Comprehensive standardization is recommended to coordinate all relevant specifications from a systematic perspective, so that anti-static work in every link can be standardized and orderly managed.
The United States began electrostatic control for military electronic production in the 1970s, and issued official formal standards about 10 years later. The International Electrotechnical Commission (IEC) has released successive anti-static standards since the early 1980s. By comparison, China’s domestic anti-static standard system is still in the initial stage. Although basic foundations are in place, there remains a large gap in complete supporting standards and full-scale implementation.
2. Overview of IEC Anti-Static Standard Formulation
At least five IEC technical committees and subcommittees are engaged in electrostatic protection technologies, having formulated relevant standards and draft specifications. Their work is summarized as follows:
IEC/TC65 Industrial-Process Measurement and Control
In 1984, TC65 issued IEC 801-2 Electromagnetic Compatibility for Industrial Process Measurement and Control Equipment — Part 2: Electrostatic Discharge Requirements, which was equivalently adopted as Chinese national standard GB/T 13926.2-92. The standard was fully revised in April 1991, with the second edition currently in effect.
It specifies severity grades and test methods for ESD susceptibility testing of industrial measurement and control devices against discharges generated by human contact or nearby objects, to evaluate electrostatic tolerance of industrial instruments.
The first edition defined 4 severity grades corresponding to test voltages of 2kV, 4kV, 8kV and 15kV. The revised second edition expanded to 5 grades, providing separate voltage series for contact discharge and air discharge. Contact discharge voltages are 2kV, 4kV, 6kV, 8kV and X kV, while air discharge voltages include 2kV, 4kV, 8kV, 15kV and X kV.