What Is a Conductive Rubber Sheet?
A conductive rubber sheet is a sheet or mat made of rubber compounded with a special material that conducts electricity.
Silicon rubber is made from a compound containing silicon, which is an insulator and does not conduct electricity easily. Therefore, conductive rubber sheets are made by compounding a large amount of conductors into synthetic or natural rubber, such as silicon rubber, which has insulating properties, to give conductivity to silicon rubber, which does not conduct electricity.
Furthermore, by changing the rubber material, it is possible to add features such as weather resistance, heat resistance, and chemical resistance. Therefore, selecting conductive rubber that is made of suitable materials for the intended use can provide higher conductivity effects.
Uses of Conductive Rubber Sheets
Conductive rubber sheets are used in laboratories and factory lines that handle ESD-sensitive electronic components, as well as in areas where static electricity generated by friction is required to prevent electrically charged ignition and equipment malfunction. Specifically, they are often used to prevent ESD breakdown at sites where explosives are handled, flooring materials in operating rooms, and manufacturing and evaluation facilities for semiconductors and electronic components.
In addition, they are used to eliminate static electricity generated by friction when lifting and lowering tanks of gas or oil. Conductive rubber sheets, in sheet or mat form, can be used in a variety of situations. Since they can inhibit the adhesion of dust caused by static electricity, they are used not only for workbenches and clean room flooring but also for preventing shock accidents in factories by preventing the human body from being electrified.
Principle of Conductive Rubber Sheets
The principle of conductive rubber sheet is that conductive rubber sheet can be given conductivity by blending conductive materials such as metallic powder or carbon black called filler with rubber, which is an insulator. With ordinary rubber sheets, it takes some time for the electrification force to diminish, but with conductive rubber sheets, the electrification current or static electricity flows into the rubber sheet side instantly upon touch, preventing the human body or certain parts of the body from being electrified.
By increasing the content of the conductive component, it is possible to have the characteristic of instantaneous release of the charged charge, but care must be taken because the elasticity and extensibility inherent to rubber are lost. The volume resistivity, an indicator of the characteristics, is around 1.0×10²Ω-cm, and some sheets can be connected to a ground wire to release the charged charge.
Types of Conductive Rubber Sheets
Among rubber sheets, the following three types of sheets are often used for conductive rubber sheets. The most common colors are black and green, but some manufacturers offer other colors as well.
1. CR Sheet
Also called chloroprene sheet, it has excellent heat resistance and oil resistance.
2. NBR Sheet
Also called nitrile rubber sheet, this material has excellent oil resistance.
3. NR Sheet
A natural rubber material that has excellent abrasion resistance, elasticity and weather resistance.
Other Information on Conductive Rubber Sheets
1. Conductive Rubber Sheet Compatible With Grounding Kit
Many conductive rubber sheets for work tables and floor mats that handle electronic components for which ESD protection is important are compatible with special grounding kits. In such cases, a ground wire is usually clipped to a corner of the sheet with a packing to connect it to a power outlet, and a resistor of several milliohms is sometimes molded into the sheet.
2. Conductive Rubber Sheet for Switch Contacts
In addition to its use as an anti-static and electromagnetic sheet, conductive rubber used in conductive rubber sheets is also widely used as remote control switch contacts in minute sheet sizes. This conductive rubber may cease to function as a switch contact point due to age-related deterioration or contamination.
In such cases, the emergency treatment method often used is to remove dirt or to reinforce the deteriorated and broken rubber with aluminum foil or conductive tape. However, this method leaves concerns about aging resistance. There are also commercially available conductive rubber sheets for remote control contacts, which can be used for this purpose.