If two parallel electrodes with a length of L and a distance of d are placed on a solid material plane, the surface resistance Rs of the material between the two electrodes is proportional to d and inversely proportional to L, and can be expressed as follows:

Calculation formula for surface resistivity

The proportion coefficient ρ s in the equation is called surface resistivity, which is related to the surface properties of the material and varies greatly with factors such as the temperature and relative humidity of the surrounding gas medium. The unit is expressed in Ω (ohms).

When d=L, the value of surface resistance Rs is equal to the surface resistivity ρ s

How to distinguish between conductors, insulators, semiconductors, or anti-static materials

How can anti-static boards achieve static discharge?

Can anti-static organic glass/PC/PVC be processed by laser?

What is the main difference between organic glass casting board and extrusion board?

What are the main differences between the three materials of anti-static organic glass/PC/PVC board?

What is the main difference between anti-static plastic board and ordinary board?

How long can the anti-static effect of the anti-static board be maintained?

What is the anti-static index of an anti-static board?

How is UL94 formulated for fire rating?

UL94 flammability level is the most widely used plastic material flammability standard. It is used to evaluate the ability of materials to extinguish after being ignited. There are multiple evaluation methods based on combustion speed, combustion time, anti dripping ability, and whether the droplets are burning. Each tested material can obtain many values based on color or thickness. When selecting a material for a certain product, its UL rating should meet the thickness requirements of the plastic part wall. The UL rating should be reported together with the thickness value, and reporting only the UL rating without thickness is not enough.

The flame retardant rating of plastics increases gradually from HB, V-2, V-1 to V-0:

HB: The lowest flame retardant rating in UL94 standard. Require a combustion rate of less than 40 millimeters per minute for samples 3 to 13 millimeters thick; Samples less than 3 millimeters thick have a combustion rate of less than 70 millimeters per minute; Or turn off before the 100mm mark.

V-2: After conducting two 10 second combustion tests on the sample, the flame extinguishes within 30 seconds. Burning materials can fall off.

V-1: After conducting two 10 second combustion tests on the sample, the flame extinguishes within 30 seconds. No combustibles should fall.

V-0: After two 10 second combustion tests on the sample, the flame extinguishes within 10 seconds. No combustibles should fall.

Anti static boards can have both surface and overall anti-static properties. Surface anti-static boards are coated using coating technology to form a thin, micrometer sized hard film on the surface of organic glass (PMMA), PVC, PC, and other boards. The anti-static layer can only be removed by mechanical processing, and wiping with chemical solvents such as alcohol has no effect. This process perfectly retains the inherent transparent and beautiful characteristics of plastic boards, while also having anti-static functions. Transparent anti-static plastic boards can only be manufactured using this process.

The overall anti-static material is generally made by adding conductive materials such as carbon black or metal powder to plastic raw materials. The color is generally black or yellow, opaque, and used for fixtures and fixtures. It is not suitable for use as dust-free room partitions and equipment covers. The anti-static index of the overall anti-static material is not only surface resistance, but also volume resistance.

When an electric field is generated by the charge on a charged body, and the electric field strength exceeds the insulation breakdown strength of the surrounding medium, the medium near the surface of the charged body ionizes, causing the transfer of electrostatic charges, thereby causing the charge on the charged body to tend to decrease or disappear. At this time, electrostatic discharge (ESD), which means "electrostatic discharge", will occur.

The harm caused by ESD to electronic products is mainly manifested as damage, and breakdown is one type of damage. The typical forms of ESD failure in electronic components include 1) thermal secondary breakdown, 2) metallization melting, 3) bulk breakdown, 4) dielectric breakdown, 5) gas arc discharge, and 6) surface breakdown. The failure of the first three is related to energy, while the failure of the last three is related to voltage.

The particularity of ESD: Firstly, the generation and accumulation of static electricity require certain conditions and processes, so unprotected products may not necessarily be damaged by ESD, and there is a certain degree of randomness; The second reason is that in most cases, the energy of ESD is relatively small, so those who are injured by ESD are not immediately scrapped. Some only show an increase in leakage, unstable operation, and even do not show obvious performance during factory testing. If problems are found later, it is easy to attribute them to poor materials or poor design without self reflection. Therefore, people often do not realize the harm of ESD and have a mentality of taking chances.

Devices that are prone to damage due to ESD during daily operations, storage, transmission, testing, and other processes are called electrostatic sensitive devices, abbreviated as SSDs.