Electrostatic discharge (ESD) is the sudden flow of electricity between two electrically charged objects caused by contact, an electrical short, or dielectric breakdown. ESD can cause severe damage to electronic components, leading to failure or degradation of performance. A clean room is a controlled environment with a low level of pollutants such as dust, airborne microbes, aerosol particles, and chemical vapours to prevent electrostatic discharge that could damage sensitive components. This blog provides a comprehensive guide to understanding the technical specifications, essential components, and various options for creating an ESD clean room.
Clean Room Classification
Clean rooms are classified by the number of particles per cubic meter at a specified particle size. The most common standards are ISO 14644-1, which defines clean room classifications from ISO 1 to ISO 9 based on the maximum allowable particle count, and Federal Standard 209E, where Class 1 is the cleanest and Class 100,000 is the least clean. For an ESD clean room, the typical classifications range from ISO 3 to ISO 8, depending on the industry requirements.
Clean Room Sections
The flooring in an ESD clean room is critical for dissipating static electricity. The two main options are conductive flooring, with a resistance range of 2.5 x 10^4 to 1.0 x 10^6 ohms, which quickly dissipates static charges, and static-dissipative flooring, with a resistance range of 1.0 x 10^6 to 1.0 x 10^9 ohms, which provides a slower, controlled dissipation of static electricity. Vinyl flooring is a common choice for ESD clean rooms due to its durability and ease of cleaning. It is available in conductive and static-dissipative varieties. However, it can be susceptible to wear and tear in high-traffic areas. Epoxy flooring is another option, known for its extreme durability and resistance to chemicals. It can be formulated for ESD control, though it can be expensive and requires professional installation. Rubber flooring offers comfort underfoot, good ESD properties, and slip resistance but may not be as durable as vinyl or epoxy.
Workstations in an ESD clean room must be designed to control and eliminate static electricity. Key components include ESD mats and benchtops made from static-dissipative materials with a surface resistance of 1.0 x 10^6 to 1.0 x 10^9 ohms, grounding systems to prevent static build-up, and ESD chairs made from conductive or static-dissipative materials with grounding capabilities. Grounding systems, which include grounding cords, wrist straps, and common point ground systems, ensure that any static charge is safely dissipated to ground.
Personnel in ESD clean rooms must wear special garments to prevent static charge build-up. These include ESD coats made from conductive or dissipative fabric, ESD footwear including shoes and heel straps that are grounded, and ESD gloves to prevent static charge from hands.
Maintaining clean air is crucial in an ESD clean room. High-Efficiency Particulate Air (HEPA) filters capture particles as small as 0.3 microns with 99.97% efficiency, and Ultra-Low Penetration Air (ULPA) filters capture particles as small as 0.12 microns with 99.999% efficiency. HVAC systems are designed to control temperature, humidity, and air pressure, which are critical for preventing ESD events.
Ionizers neutralize static charges in the air and on surfaces. There are two main types: AC ionizers, which use alternating current to create a balanced ion field, and DC ionizers, which use direct current for a more stable ion output. Overhead ionizers, mounted on ceilings or walls, neutralize static charges in the air. Benchtop ionizers, placed on workstations, neutralize static charges on surfaces and components.
Regular monitoring and testing are essential to ensure effective ESD control. This includes surface resistance meters to measure the resistance of surfaces, wrist strap testers to ensure that personnel grounding devices are functioning correctly, and field meters to measure electrostatic fields in the clean room.
Implementation and Maintenance
Creating an ESD clean room requires careful planning and design. Key considerations include determining the size and layout based on the type and volume of work, choosing materials that meet both clean room and ESD requirements, and planning the workflow to minimize contamination and static charge generation. Proper installation is crucial for the effectiveness of an ESD clean room. This includes ensuring that the flooring is properly grounded and meets ESD standards, installing HVAC and filtration systems to provide clean, temperature-controlled air, and equipping workstations with ESD mats, grounding systems, and ionizers.
Regular maintenance and monitoring are essential to ensure the continued effectiveness of the ESD clean room. This includes regularly testing surfaces, grounding systems, and ionizers to ensure they are functioning correctly, scheduling maintenance for HVAC systems, filters, and other critical components, and providing ongoing training for personnel to reinforce the importance of ESD control and clean room protocols.
EIA specializes in providing comprehensive ESD cleanroom solutions tailored specifically for the PCB manufacturing industry. Our expertise ensures that your clean room environment meets the highest standards for both particulate and electrostatic control, protecting your sensitive electronic components from potential damage and ensuring optimal performance. EIA’s commitment to quality extends to our robust monitoring and testing protocols, ensuring that all ESD control measures are functioning correctly and consistently.