I. Principles of ESD Generation

 

The principle of ESD (Electrostatic Discharge) is that charge accumulates on the surface of an object due to processes such as friction, contact, and separation. When the charge accumulates to a certain level, an electric field is formed on the object's surface. If the charge on the object's surface is suddenly released during this process, an electrostatic discharge phenomenon occurs.

 

ESD usually occurs between two objects, one with a higher charge density and the other with a lower charge density. When these two objects come into contact or close proximity, charge is transferred from the object with the higher charge density to the object with the lower charge density, releasing a large amount of energy instantaneously.

 

ESD can cause serious damage to sensitive components such as electronic devices and semiconductor devices, including short circuits, chip burnout, and damage to circuit boards.

 

II. ESD Protection Measures

 

To prevent ESD damage to electronic products, the following measures are usually taken:

 

1. Grounding: Connect equipment, workbenches, etc., to ground to release electrostatic charges.

 

2. Use of anti-static materials: Use anti-static work clothes, gloves, shoes, and other personal protective equipment, as well as anti-static packaging materials and trays.

 

3. Control of environmental humidity: Increasing environmental humidity can reduce the generation of static electricity.

 

4. Static elimination equipment: Use ionizers, static elimination bars, and other equipment to neutralize electrostatic charges in the work area.

 

5. Personnel training: Ensure that operators understand ESD-related knowledge and operating procedures and correctly implement anti-static measures.

 

III. ESD Control Items for Regular Testing

 

To ensure the long-term effectiveness of ESD protection measures, the following items need to be tested regularly:

 

1. Grounding system: The integrity and effectiveness of the grounding system are crucial for releasing electrostatic charges. Regularly test the grounding resistance to ensure good grounding connections and that the resistance value meets the specified requirements.

2. Static elimination equipment: The performance of static elimination equipment such as ionizers and static elimination bars may change over time and with use. Regularly test their elimination capabilities to ensure they are working properly.

3. Personal protective equipment: The conductive properties of personal protective equipment such as anti-static work clothes, gloves, and shoes may wear out or fail. Regularly test the resistance value of these items to ensure they meet anti-static requirements. 4. Work Surfaces and Equipment Surfaces: Work surfaces and equipment surfaces should have good conductive properties. Surface resistance should be tested regularly to ensure that static electricity can be effectively dissipated.

5. Packaging Materials: The conductive properties of anti-static packaging materials also need to be tested regularly to prevent static electricity from causing damage during packaging and transportation.

6. Environmental Humidity: Controlling environmental humidity is one of the important measures to reduce the generation of static electricity. Environmental humidity should be tested regularly and kept within a suitable range.

7. Electrostatic Testing Instruments: Instruments used for detecting static electricity, such as electrostatic voltmeters and surface resistance testers, also need to be calibrated and tested regularly to ensure their accuracy.

8. Employee Training Effectiveness: Regularly assess employees' understanding of ESD knowledge and operating procedures to ensure they can correctly implement anti-static measures.

9. Audits and Inspections: Conduct regular ESD management audits and inspections to ensure that various control measures are effectively implemented and to identify and resolve potential problems in a timely manner.

 

Regular testing of these items can help identify potential problems in the ESD control system and take appropriate corrective actions to ensure that ESD risks are effectively controlled, improving product quality and reliability. The testing frequency should be determined based on the specific production environment, product characteristics, and relevant standards. At the same time, establish a record and reporting system to track and analyze test results and continuously improve ESD control work.

 

IV. ESD Testing Methods and Relevant Standards:

 

ESD testing items and methods include the following:

 

1. Grounding Resistance Testing: Use a grounding resistance tester to measure the resistance value of the grounding system. Standards usually require the grounding resistance to be less than 1 ohm.

 

2. Surface Resistance Testing: Use a surface resistance tester to measure the surface resistance of work surfaces, equipment surfaces, packaging materials, etc. For work surfaces and equipment surfaces, standards usually require the surface resistance to be between 10^6 and 10^9 ohms; for anti-static packaging materials, the surface resistance is usually required to be between 10^3 and 10^12 ohms.

3. Human Body Comprehensive Resistance Testing: Use a human body comprehensive resistance tester to measure the comprehensive resistance of personnel wearing anti-static work clothes, gloves, and shoes. Standards usually require the human body comprehensive resistance to be between 10^6 and 10^9 ohms. 4. Ionizer Fan Testing: Use an ionizer fan tester to measure parameters such as the balance, discharge time, and residual voltage of the ionizer fan. Standard parameters for ionizer fans may vary depending on the model and application.

5. Electrostatic Voltage Detection: Use an electrostatic voltmeter to measure the electrostatic voltage on the surface of objects or in the environment. Standards typically specify the upper limit of electrostatic voltage in specific areas or during specific processes.

6. Humidity Detection: Use a hygrometer to measure environmental humidity. Controlling humidity within the 40-60% relative humidity range can reduce the generation of static electricity.

 

V. ESD Standards and Specifications:

 

- ANSI/ESD S20.20-2014: This is a widely used ESD standard covering ESD control procedures, materials, equipment, and personnel training.

- IEC 61340-5-1: This is an ESD standard published by the International Electrotechnical Commission, including regulations on ESD control methods and testing requirements.

- JESD 625-A: This is a standard published by the Electrostatic Discharge Association of America, focusing on ESD control procedures and auditing.

 

When performing ESD testing, select appropriate testing instruments and perform measurements correctly according to the instrument's operating instructions. Regularly calibrate the testing instruments to ensure their accuracy. In addition, refer to relevant industry standards and internal company regulations to ensure that the test results meet the requirements.