Understanding ESD: Models, Classes, and Protection

This article delves into the world of Electrostatic Discharge (ESD), covering ESD classes, models, protection mechanisms, the Human Body Model, and manufacturers of ESD test equipment.

When two surfaces in contact are separated, electron movement can occur, creating an imbalance. This results in one surface with a positive charge and the other with a negative charge.

Examples of ESD include lightning and the zap you feel from a doorknob. Generally, ESD is the transfer of electrostatic charge between bodies (or surfaces) at different electrostatic potentials.

The following table illustrates scenarios where significant charges are frequently generated. While people often discharge static electricity, about 3000 volts are needed to feel it. However, ESD that’s imperceptible to humans can easily damage electronic components. Voltages of 100 volts or less can be harmful, and smaller components are more sensitive. Such damage is often invisible to the naked eye.

Table 1: Typical Voltage Levels of Charges Generated

Just as we’ve adopted methods to control germs in medicine, we need to implement various ESD protection devices and methods to control Electrostatic Discharge. The following table details ESD classes with sensitivity levels and the electronic components affected by them.

ESD Classes

The following table lists various ESD classes, including class 0, class 1, class 2, and class 3A.

Table 2: ESD Classes

Principle Sources of ESD in ICs

Common ESD sources include:

• A person walking on synthetic flooring accumulating up to 20,000 volts, which is discharged upon touching a grounded object.
• Equipment accumulating static charge due to improper grounding, discharging through ICs when placed on test sockets.
• ICs themselves becoming charged during transport and when contacting charged objects.

ESD Human Body Model, Machine Model, Charge Device Model

Different ESD models exist, including the Human Body Model, the Machine Model, and the Charge Device Model.

ESD Human Body Model

Figure 2 illustrates the ESD of a human body, referred to as the ESD Human Body Model. The peak current is approximately 1.3A, with a rise time between 10 to 30 ns.

ESD Machine Model

Figure 3 depicts the ESD of a machine, known as the Machine Model (MM). The peak current is about 3.7A, the rise time is 15 to 30 ns, and the bandwidth is about 12 MHz.

ESD Charge Device Model

Figure 4 illustrates the ESD of a charged device, called the Charge Device Model (CDM). The peak current is about 10A, with a rise time of about 1 ns.

ESD Protection Mechanism

Common ESD protection mechanisms include:

• ESD protection circuits (as mentioned for different models).
• Current limiting characteristics of n-well resistors.
• Avalanche multiplication in pn-junctions.
• Avalanche breakdown of nMOS.
• Thermal breakdown of nMOS.

ESD Protection Devices

Here’s a list of ESD protection devices:

• n-well Resistors
• Gate-Grounded nMOS Transistors (GGNMOS)
• Gate-Coupled nMOS Transistors (GCNMOS)
• Silicon Controlled Rectifiers (SCR)
• Medium Voltage Triggered SCR

ESD Test Equipment Manufacturers

The following is a list of ESD test equipment manufacturers:

• Advanced Test Equipment Corp. (https://www.atecorp.com/) {ESD Gun, ESD Simulator}
• Thermo Fisher Scientific Inc. (https://www.thermoscientific.com/) {ESD Tester}
• TREK, INC (https://www.trekinc.com/) {ESD Audit Equipment, ESD Test Equipment}
• HV TECHNOLOGIES, Inc. (https://www.hvtechnologies.com/)
• United Static Control Products (https://www.ultrastatinc.com/)
• ESD testers and Meters (https://www.esdmeters.com/)
• Botron Company Inc. (https://www.botron.com/) {ESD table mat, floor mat, equipments, wrist straps, gloves, chairs etc.}

Test and Measurement Equipments

• Test and Measurement Equipments
• BER Testing equipments
• Agilent T & M Solutions
• Anritsu T & M Solutions
• Rohde & Schwarz T & M solutions
• Wireless channel emulator
• Vector signal generator
• Vector signal analyzer
• Power Analyzer Equipments
• Protocol Analyzer