What is Air Ionization and How Does it Work?
Air ionization neutralizes static charge on insulated and isolated objects by producing a balanced source of positively and negatively charged ions. Whatever static charge is present on objects in the work environment will be reduced and neutralized by attracting opposite polarity charges from the air. Because it uses only the air that is already present in the work environment, air ionization may be employed even in cleanrooms where chemical sprays and some static dissipative materials are not usable.
Necessary non-conductors (i.e. process-required insulators) in the environment cannot lose their electrostatic charge by attachment to the ground. Ionization systems provide neutralization of charge on these necessary non-conductive items (circuit board materials and some device package are examples of necessary non-conductive items). Assessment of the ESD hazard created by electrostatic charge on the necessary non-conductors in the workplace is required to ensure that appropriate actions are implemented, commensurate with risk to ESDS items. See the Full to ESDS Items.
What is an ion?
An ion is an atom that has a positive or negative charge. When an atom or molecule has an equal number of protons and electrons, it is balanced or neutral. If an electron is lost the atom becomes positively charged. If an electron is gained, it becomes negatively charged.
Air is a mixture of gases including nitrogen, oxygen, carbon dioxide, water vapor and other trace gases, any one or more of which can be ionized. When any one or more of these gas molecules gains or loses an electron, it becomes charged and thus called air ions.
An air ionizer is a device that uses high voltage to ionize or electrically charge air molecules. Air ionizers are used in many different applications from purifying the air of particulates, contaminants, and allergens to controlling electrostatic discharge (ESD) in work environments.
How Do Air Ionizers Create Ions?
There are two methods air ionizers work. The first is alpha ionization, which uses a nuclear source such as polonium 210. The polonium 210 particles collide with the air, transferring electrons, causing the neutral air molecules to become negative ions. Since the polonium loses electrons, it becomes a positive ion. Alpha ionizers are beneficial because they create an equal number of positive and negative ions.
The second method is called corona ionization, which uses an electrical current to create bipolar ionized air. The ionizer applies a high-voltage electrical current composed of a flow of negatively charged electrons, to a metal prong or needle. Electrostatic repulsion causes the electrons to detach from the prong or needle, attaching themselves to the molecules or nitrogen and oxygen in the air, forming negative ions, which are attracted to the static charge in the work environment thus neutralizing it. These ions also attract certain types of molecules in the work environment like dust and other air particulates. These particulates cluster around the ion, weighing it down and forcing it to fall to the ground, cleaning the air.
Corona ionization can further be divided into AC and DC. AC or alternating current ionization uses one emitter to produce both positive and negative ions. This type of ionization is mainly used to protect components during assembly. DC or direct current uses separate positive and negative power supplies that run simultaneously to create bipolar ions. DC ionizers are more efficient at producing ions and use lower operating currents, making them a better fit for cleanroom applications.
Use of Ionizers for Non-Essential Insulators
All non-essential insulators such as coffee cups, food wrappers, and personal items shall be removed from the EPA. The ESD program shall include a plan for handling process-required insulators in order to mitigate field-induced CDM damage. If the field measured on the process required insulator is greater than 2000 volts/inch and the process required insulator is less than 30 cm (12″) from the ESDS item, steps shall be taken to either:
- Separate the required insulator from the ESDS item by a distance of greater than 30 cm (12″)
- Use ionization or other charge mitigating techniques to neutralize the charge.
How Are Air Ionizers Used?
Air ionizers are the best option for any environment working with materials like quartz, glass, plastic, and ceramic are inherently charge generating because these materials are insulators, this charge cannot be easily removed by grounding. However, air ionization should only be one part of controlling ESD in work environments.
Ionizing bars provide rapid neutralization of static charges to prevent electrostatic attraction of particles (ESA) and electrostatic discharge (ESD) in applications such as cleanrooms and workstations. This Simco powered IONforce bar produces positive and negative ions that rapidly neutralize any potentially destructive charges in the work area.
The XC2 has shown to be specifically useful for larger areas, offering under 12 second discharge times at 6 foot workbench distance from the face of the blower. The weight-saving design allows the Aerostat XC2 to be mounted above the work surface, which is especially effective for flat panel display module assembly.
Overhead Cleanroom Ionizers
The Model 5810i is certified for use in ISO Class 4 cleanrooms (Fed. Std. 209(e) Class 10). The ionizer can operate with external sensors to maintain precise balance (better than ±1V) by altering ion output and adapting to environment changes. With the reliability of steady-state DC, the established method for eliminating the effects of ESD and ESD-induced electromagnetic interference (EMI) in high-tech facilities, the Model 5810i delivers maximum ion output where and when you need it.
Cleanroom Benchtop Ionizers
Simco-Ion’s ISO Class 5 Self-balancing blower with FMS Interface is an efficient and small blower for controlling static discharge in hard-to-reach areas.