Electrostatic Management in Cleanroom Environments
Electrostatic management in cleanroom environments has become necessary to control
electrostatic attraction and bonding of particulate to product surfaces, damage from
electrostatic discharge(ESD), malfunction of delicate instrumentation by electro
magnetic interference(EMI), and contamination by microbial bioburden. Many industries now require the
documentation and certification of an electrostatic management system to ESDA S20.20-2007.
The most common components in a complete ESD control program are personnel gowning, ionizers, temperature and humidity control, and flooring. It is impossible for any one of the above
components to individually control static electricity.
- Cleanroom Air Handling Systems
control temperature and relative humidity which will directly affect static discharge, if relative humidity is less than 30%, the incidence of static discharge is increased. Therefore, it is advised to control relative
humidity in the cleanroom as a part of the complete ESD program. Steady-state DC ion emitters can be duct mounted to generate a well balanced flow of ionized air particles.
Which neutralizes any stray electrostatic buildup in the air handling duct system.
- Electrostatic Precipitator Type Filtration Systems
based on the principle of two stage electrostatic air filtration. Fine sub-micron suspended particles are electrostatically charged using high-voltage electric field, which
then get attracted and precipitated on opposite charged electrode plates. Cost of the additional electrical components is partially offset by the increase in filtration performance
(either higher flow at the same pressure drop and filtration efficiency or lower pressure drop at the same flow and efficiency, as compared to mechanical filtration of the same size)
this is a highly cost effective way to achieve a higher level of bio burden control.
Benefits in cleanroom HVAC systems that include:
- Improvement in particle count
- Reduction in bioburden inside the cleanroom
- Power saving in air handling systems
- Reduction in downtime for filter maintenance
- Reduction in cooling coil maintenance
- Enhanced HEPA filter lifespan
- Zero replacement cost of pre-filters
- Electrostatic Dissipating Protective Flooring Systems are formulated to provide insulated protection for cleanroom
In work areas, unchecked static electricity can pass from personnel to equipment thereby creating potential damage to digital products and circuitry. ESD control flooring products
absorb static electricity, thereby safeguarding equipment. Products should meet ESDA S20.20-2007, ANSI/ESD STM7.1 Floor Materials, and ANSI/ESD S6.1-Grounding, standards. Grounding,
testing and certification of the flooring system should be completed by licensed electricians and certification companies.
- Cleanroom Ionization Systems Air ionization complements and completes any program that intends to eliminate all electrostatic charge sources.
In many areas, such as cleanrooms and mini environments, air ionization is the only practical method of static control. A typical room ionization system can remove 1,000 volts in
less than 1 minute. Research has shown that room ionization typically reduces particle counts by 50% to 90%. Room ionization can increase equipment uptime and decrease tool repair
costs up to 50%.
Personnel Gowning garments, shoes, point to point grounding systems should meet ESD DSTM 2.1 – 2009. ESD garments can be worn in a variety of industries which include pharmaceutical,
biotechnical, biological and good processing. Designed for cleanrooms up to and including Class 10 (ISO 4), where bacterial filtration, static charges, particulate and fluid resistance needs to be controlled.
Cleanroom electrostatic control cannot be implemented by utilizing only one of the above systems. It requires a multi prong
approach and the use of all systems to effectively control electrostatic discharge. Management must implement a
electrostatic control program to include personnel training, auditing, and certification of
electrostatic control devices. Cost savings by implementing a electrostatic control program can then be
measured against the cost of the entire system implementation.