ESD simulator or ESD generator or ESD gun

Introduction: 

ESD (Electrostatic discharge) is a phenomenon of sudden and momentary flow of electric current (i.e., sudden discharge of charges) between two electrically charged objects at different potentials. The build-up of static electricity between two objects is caused by the event tribocharging or electrostatic induction. ESD occurs as a visible spark (sometimes invisible) when bringing the two differently-charged objects very close together/touch or when the dielectric breakdown occurs between them.

ESD event occurs when a human touches a sensitive electronic device/component or when a conductive metal tool is touched between the objects at different potentials. The other causes of ESD events in the electronics field are the handling of printed circuit boards or troubleshooting electronic devices without using an electrostatic wrist strap, and rapid movement of air near electronic equipment. 

An ESD event occurs with peak impulse current in the Ampere range having rise time in the range of Ps (pico-second) to the nanoseconds. For example, ESD event due to a human may have rise times ranging from approximately 200 ps to greater than 10 ns with peak impulse currents from a few amperes to greater than 30A. A person may/may not feel the discharge, but that is sufficient to damage sensitive electronic components. Hence, it is necessary to test the electronics products against ESD is a must.

 What is an ESD simulator or ESD generator?

ESD simulator is used to simulate/generate the ESD pulses as per all international EMC standards such as IEC/EN 61000 4-2 to test the immunity of the electrical and electronic equipment against ESD. i.e., an ESD generator generates ESD pulses to simulate the Human Body Model (HBM), Machine Model (MM), and Charged-Device Model (CDM). The ESD simulators can discharge voltage up to KV (Kilovolt) range for conducting both air discharge and contact discharge tests as per EMC standards.

How ESD pulse is generated? or how does an ESD simulator work?

A simplified circuit of an ESD simulator is shown below. Let discuss the HBM model.

         Simplified circuit of the ESD simulator

As per IEC standard, the charging resistor Rc value is 50 to 100 M ohms, the total value of energy-storage capacitor CS and distributed capacitance cd is CS + Cd = 150 pF± 10%. The capacitor Cs represents the electrostatic capacitance of the human body. The discharge resistor Rd represents the resistance of the human skin (330 Ohms ± 10%). Initially, the capacitor (CS + Cd) is charged to a certain value through the charging resistor Rc by closing the switch (S1). During charging, the discharging switch (S2) is in an open state. After charging, the switch (S1) is opened, and now the switch (S2) is closed, now the capacitor (CS + Cd) starts to discharge, which results in electrostatic discharge on the EUT occurs.

Key features of ESD simulator:

• Test voltage up to kV range for air and contact discharge
• LCD touch screen
• Changeable R/C networks
• Automatic polarity switching
• Compliant with a huge range of OEM and international standards
• Active log
• Temperature and humidity monitoring

Specification details of the ESD simulator:

Discharge voltage: Represents the minimum and maximum amplitude range of the discharge voltage that can be provided by the ESD simulator in both air and contact discharge mode. It is in the range of V to KV.

Discharge network/pulse network: Represents the discharge network capacitor and resistor values of the ESD generator. It may be 100 to 200 pF,1500 Ohms /150 pF, 30 ohms/ 150 to 300 pF,330 to 2000 Ohms/ 150 to 5000 pF , 0.5 to 5000 Ohms.

EMC standard: Represents the ESD test standards to which the ESD simulator comply.

Polarity: Represents the Polarity of the ESD voltage from the ESD simulator. The ESD generator has the capability to generate burst voltage in Positive/negative/alternating polarity.

Current Rise time: Represents the impulse current rise time of ESD event in ns (nanosecond). It is the time taken by the current from 10 % to reach 90% of the peak value.

Holding time: It represents the time period prior to the air discharge, during this period; the decrease of the discharge electrode voltage due to current leakage will not be greater than 10 %. Usually, the holding of the ESD simulator is 5 seconds.  

Repetition Frequency: Represents the number of ESD pulse/pulses per second.

Discharge repetition CD: Represents the time gap range provided by the ESD simulator for the repetitive contact discharges. It is represented in second.

Dimensions: Represents the dimension of the ESD simulator in L X W X H mm.

Weight: Represents the weight of the ESD simulator in Kg.

Operating temperature: Represents the safe operating temperature limit of the ESD simulator in °F (°C).

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