Actually, the thing we call Static electricity is an imbalance. It’s an imbalance in the amounts of positive and negative charges found within the surface of an object. Only the imbalance between opposite charges is important, and their motion or “static-ness” is irrelevant. For example, the imbalance can flow along as an electric current, yet it loses none of its familiar “static electrical” properties. While it is flowing the charge still crackles, glows, and attracts dust and lint. But how can we have “static” electricity that flows? Motionless motion? Simple. “Static electricity” is all about the charge-imbalance, and it has nothing to do with charges at rest. “Static electricity” was misnamed.
“Static Electricity” is not un-moving, it really means “High-voltage Electricity.”
Static electricity is simply high voltage. High voltage has all the characteristics of “static electricity.” And when grade-school textbooks are trying to teach about “static,” they are really trying to explain pure voltage: voltage without current.
Commonly, electrostatic charges are created by the contact and separation of two materials. This process is called “triboelectric charging”, which involves the transfer of electrons between two materials. Once charges are created and remain on a material, they become electrostatic charges. The imbalance of charges produces an electric field between material bodies. Meanwhile, the built-up electric field can result in the transfer of charges due to the electrical potential difference. This phenomenon is known as electrostatic discharge (ESD).
One of the most common causes of electrostatic damage is the direct transfer of electrostatic charge from the human body to a device. The sudden release of charges into the device can produce extremely high voltage or current at the device that can result in irreversible transformation and destruction of the device.
ESD sensitivity classification and measurement
The highest voltage level that a device can survive is called “ESD withstand voltage (Vw)”, which can be used to classify the ESD sensitivity of the device. The ESD sensitivity classification for a device tested by HBM is shown below, which gives an indication of the level of ESD protection required.
ESD sensitivity classification for HBM test
Class ESD withstand voltage, Vw
0 0 ~ 250 V
1A 250 ~ 500 V
1B 500 ~ 1000 V
1C 1000 ~ 2000 V
2 2000 ~ 4000 V
3A 4000 ~ 8000 V
3B > 8000 V