Typically, ESD currents take low impedance paths to the ground to balance potentials.
An ESD wrist strap is commonly used to ground the user working on circuits.
Other electrostatic discharge prevention methods include the use of antistatic bags and sprays.
If you have ever rubbed a ruler against woolen cloth or hair and felt static, you might have observed an example of static electricity. This static electricity gets discharged when it comes in contact with a conductor. And, if you have ever experienced a slight shock when touching a metal object, that shock was most likely due to electrostatic discharge.
Electrostatic discharge affects not only humans, but also electronic devices. Sensitive electronic circuits can be damaged by electrostatic discharge, which is why electrostatic discharge prevention methods are so critical. These methods can be used to prevent problematic electrostatic discharge from harming sensitive circuits. In this article, we will explore what causes electrostatic discharge as well as a few ways to prevent it.
What Causes Electrostatic Discharge?
Irrespective of the material classifications based on electrical conductivity, all materials are sources of electrostatic discharge (ESD). Materials store either positive charges or negative charges. Human skin and animal fur accumulate positive charges, whereas plastics and other synthetic materials store negative charges.
Any material storing charge depends on its capacity, and it is more like a capacitor action. In the case of the human body, it is analogous to a 250pF capacitor capable of storing charges up to 25000V.
The Effects of Electrostatic Discharge on Electronics
Electrostatic discharge causes current to flow in objects. Usually, ESD currents take low impedance paths to the ground to balance potentials. It may take the metal body of the device to travel or any other path to reach the ground. Repeated electrostatic discharge and current flow subsequently disrupt the operation of a device. When a device is repeatedly subjected to electrostatic discharge, the internal components cross threshold values frequently, degrade over time, and finally, break down.
Fortunately, electrostatic discharge prevention methods exist to prevent devices from breaking down due to this discharge.
Electrostatic Discharge Prevention Methods
Unfortunately, electrostatic discharge is everywhere, and in the electronics manufacturing sector, it is costly to deal with. Electronics, especially semiconductors, carry stored charges. When these stored charges come in contact with the human body or tools, electrostatic discharge occurs. This discharge may be imperceptible by humans, but is damaging nonetheless.
Troubleshooting or working on printed circuits boards with bare hands, placing synthetic materials close to electronic devices, and rapid air movements around the electronic equipment are all sources of electrostatic discharge. When manufacturing and assembling electronics, using electrostatic discharge prevention methods can prevent this harmful discharge from damaging circuits.
Here are three commonly used electrostatic discharge prevention methods: grounding, antistatic bags, and antistatic sprays.
For personnel working on printed circuit boards, grounding is the best way to get rid of ESD. Providing a ground makes the lowest impedance path for the ESD current flow. An ESD wrist strap is commonly used to ground the user working on the circuits. Grounding mats or antistatic mats are also used to place the electrostatic-sensitive equipment to reduce the risk of ESD. Grounding the workbench is another prevention method.
Antistatic bags are used to protect electrostatic-sensitive electrical and electronic components. These packaging materials prevent static electricity interactions. Usually, antistatic bags are made of polyethylene terephthalate and come in semi-reflective or clear forms. These bags come in a variety of sizes and colors and are widely used to pack hard drives, motherboards, sound cards, graphic cards, etc.
To prevent the clinging of charges onto a material, antistatic sprays can be used. When this liquid is sprayed, it prevents the accumulation of charges, thus eliminating electrostatic electricity. Antistatic sprays are used on equipment that is moving at rapid speeds or on surfaces with high static charges, which are difficult to harness or block.
Electrostatic discharge prevention methods are effective in eliminating the ill effects of static electricity. Another solution is to incorporate ESD protection circuitry as an auxiliary circuit in main circuit boards to reduce electrostatic discharge problems. Cadence software offers ESD analysis tools that help with electrostatic discharge prevention in massive electronic systems.