The extent to which electronic components are damaged by static electricity varies depending on their type. Even a static voltage as low as 100 V can result in damage. In recent years, with the increasing integration of electronic components, the threshold electrostatic voltage required to cause damage has continuously decreased.
The human body typically generates electrostatic voltages ranging from 2 to 4 kV, usually due to minor movements or friction with insulating materials. Consequently, if the electrostatic potential carried by individuals comes into contact with integrated circuits (ICs), nearly all ICs may be damaged. This risk exists in any working environment lacking appropriate electrostatic discharge (ESD) protection measures. The damage caused by static electricity to ICs is not limited to the manufacturing stage but also extends to assembly, transportation, and handling processes.
To address these issues, the following ESD protection measures are recommended:
1. ESD protection at the operational site: Electrostatic-sensitive devices must be handled exclusively within designated anti-static work areas.
2. Personnel ESD protection: Operators should wear anti-static garments, gloves, footwear, headwear, and wrist straps.
3. ESD protection during storage and transportation: Electrostatic-sensitive devices must not be stored or transported in a charged state.
To achieve effective ESD control, the primary objective is to reduce the voltage of charged objects to within the safety limits specified by design requirements. This implies minimizing charge (Q) and resistance (R), while maximizing static capacitance (C), as described by the following equations:
V = I × R
Q = C × V
where V denotes voltage, Q charge quantity, I current, C static capacitance, and R resistance.
It should be noted that resistance values should not be arbitrarily reduced. Particularly in large-scale anti-static areas, safety considerations such as controlled leakage paths must be addressed when selecting materials.
Implementation of ESD protection measures includes the inspection and setup of IC handling environments. The primary goal of these measures is to maintain the workplace—including personnel—at an equipotential level. Specific practices include:
1. Connecting a 1-megohm resistor in series with a grounding point and wearing an anti-static wrist strap during operations.
2. Grounding test equipment, tools, soldering irons, and other instruments.
3. Installing and grounding anti-static mats on workbench surfaces.
4. Requiring operators to wear anti-static clothing and footwear.
5. Installing anti-static flooring or conductive rubber mats on the ground.
6. Ensuring that ICs remain at the same potential during packaging and transportation.
Testing frequency and precautions for ESD performance:
Anti-static rubber mats (table and floor), work shoes, garments, and containers should be inspected at least once per month. Anti-static wrist straps, ionizing air guns, fans, and measuring instruments should undergo daily checks. During testing, environmental factors such as temperature and humidity must be taken into account.
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