Costs of Electrostatic charge and discharge
In ordinary circumstances, Electrostatic charge and discharge are little more than an annoyance. However, in an increasingly technological age, the familiar static shock can be costly or dangerous. As electronic devices became faster and smaller, their sensitivity to ESD increased. Today, ESD impacts productivity and product reliability in virtually every aspect of today’s electronics environment.
1) Product contamination
Charged surfaces can attract and hold contaminants, making removal from the environment difficult. When attracted to the surface of a silicon wafer or a device's electrical circuitry, these particulates can cause random wafer defects and reduce product yields.
2) Catastrophic product failure
When electronic device is exposed to an ESD event, it may no longer function. The ESD event may have caused a metal melt, junction breakdown, or oxide failure. The device's circuitry is permanently damaged causing the device fail. Such failures usually can be detected when the device is tested before shipment. If the ESD event occurs after test, the damage will go undetected until the device fails in operation
3) Latent product defect - possibly causing large hidden costs
A latent defect, on the other hand, is more difficult to identify. A device that is exposed to an ESD event may be partially degraded, yet continue to perform its intended function. However, the operating life of the device may be reduced dramatically. A product or system incorporating devices with latent defects may experience premature failure after the user places them in service. Such failures are usually costly to repair and in some applications may create personnel hazards.
Latent defects are extremely difficult to prove or detect using current technology, especially after the device is assembled into a finished product.
4) Malfunction of electronics equipment
Electrostatic discharge also may upset the normal operation of an electronic system, causing equipment malfunction or failure
Control Methods of ESD
1) Grounding
A primary means of protecting of ESD susceptible (ESDS) items is to provide a ground path to bring them to the same electrical potential. All conductors in the environment, including personnel, must be bonded or electrically connected and attached to a known ground or contrived ground, creating an equipotential balance between all items and personnel. Electrostatic protection can be maintained at a potential above a "zero" voltage ground reference as long as all items in the system are at the same potential. It is important to note that non-conductors in an Electrostatic Protected Area (EPA) cannot lose their electrostatic charge by attachment to ground.
2) Using conductive and dissipative static control paint and metal for non conductive objects
3) Ionization
Air ionization can neutralize the static charge on objects by charging the molecules of the gases of the surrounding air. Whatever static charge is present on objects in the work environment will be 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 clean rooms where chemical sprays and some static dissipative materials are not usable.

There are several different technological methods for air ionization, but any method cannot be the best for every different circumstances. By fully understanding the application needs of those methods’, you can choose the most appropriate one according to your own circumstances.

-AC Ionizers
AC system uses the same emitter which emits positive and negative ions by turns very fast and continuously. The probability of ion reunion is high. Thus, strong air flow is needed to minimize the reunion.

-AC high frequency Ionizer
AC high frequency system uses corona emission method. Compared to the AC system, it has more stable ion balance and excellent performance at short distance ESD elimination

-Steady-state DC Ionizer
SS DC system uses different emitters for positive and negative ions each. The probability of ion reunion is lower than that in AC ionizer and thus, the lower level of air flow is needed. Each emitters should be located close enough not to make ion hot spots.
Pulsed DC Ionizer
Pulsed DC system uses different ion emitters for positive and negative ions each and each emitter becomes On/Off by turns. The On/Off cycle time can be controlled according to the air flow.

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