Several basic concepts of static control technology
We generally think that static control is a very mature and accurate technology, but the description of this technical language is not very accurate in application. For example, we sometimes say that resistivity actually refers to resistance, and when it actually represents the resistance range of a certain material, it uses a common vocabulary like "conductivity."
Therefore, in order to correctly implement static control technology, in a certain sense, it must first be able to accurately describe the content that needs to be expressed in the communication process, and effective communication must start with a clear definition and correct use of terminology. Below we introduce some of the basic concepts used in static control technology.
1. Resistance and Resistivity: This is the two most critical concepts in electrostatic control technology. They are often confused, not only used to represent materials, but also to describe test methods for evaluating materials.
2. Body resistance coefficient: refers to the ratio of the DC voltage drop per unit thickness of a material to the current passing through a unit area. The bulk resistivity is one of the basic parameters of a material and its electrical conductivity is expressed in ohms/cm.
3. Surface resistivity: This parameter is used for a film material of a certain thickness, which is defined as the ratio of the DC voltage drop per unit length on the surface to the current flowing through the unit width. It refers to the resistance between the two opposite sides of the square, as long as the area is much larger than the film thickness, the resistance is independent of the size of the square. The unit of surface resistivity is ohms.
4. Resistivity: on the other hand, it indicates that different shapes (area and length) and resistivity of the material hinder the current, which is the same
It indicates the surface appearance of the material or the circuit connectivity between the surface and the ground and the discharge capacity of the object in ohms.
5. Surface resistance: According to EOS/ESD S11.11 “Measurement of bulk resistance of electrostatic discharge planar materials”, bulk resistance refers to the ratio of DC voltage to current passing between the two ends of the material, and its unit is also ohm.
6. Insulation material: refers to a material with a surface resistivity of 1×1011 Ω/cm or more. There is substantially no current flowing on the surface or inside of the insulating material, and its resistance is large and it is difficult to ground. The static charge in this material will remain on it for a long time.
7. Conductive material: refers to a material whose surface resistivity is less than 1 × 105 ohms or whose volume resistivity is less than 1 × 104 ohms / cm. This material has a low electrical resistance, and electrons flow very easily on its surface and inside, flowing to any other conductor or earth that is in contact.
8. Antistatic property: Generally refers to the property of the material to suppress friction and electrification. The antistatic properties of a material are not necessarily related to its electrical resistance or electrical resistivity.
9. Discharge material: refers to a material having a surface resistivity greater than or equal to 1 x 105 and less than 1 x 1012 ohms, or a bulk resistivity greater than or equal to 1 x 104 and less than 1 x 1011 ohm/cm.
10. Electrostatic shielding material: The material with a surface resistivity of less than 1×104 ohm per millimeter thickness of the electric layer or a material with a bulk resistance of less than 1.0×103 ohm/cm. The Faraday protective cover made of this material can prevent static sensitive components. Affected by static electricity.