Views: 12 Author: Hardy Ho Publish Time: 2016-05-18 Origin: Site
Conductive Silicone Rubber is a generic term referring to any rubberized material with conductive properties, such as glass silvering, silver-plated aluminum, silver., etc. These kind of conductive particle are well-dispersed in the silicone rubber. Conductive network forms when the neighboring conductive particles contact under pressure. It reduces or eliminates the EMI/RFI (electromagnetic interference and radio frequency interference) noise that is often associated with electronics.
Conductive Silicone Rubber Material Choice
When working with conductive Silicone rubber, it’s important to remember that galvanic compatibility will also have an effect on which wire type or filler should be used. Galvanic compatibility is the corrosion potential between the conductive material and the metal interface or mating surface. In some cases, one side of the material may be exposed to a different metal than the other; in this case, a conductive wire type or filler choice needs to be made where the difference in voltage potential between the dissimilar metals are as small as possible.
A widely popular form of conductive silicone rubber is conductive elastomer. Conductive elastomer can be die-cut to form a flat gasket but one of the large differences from other materials is that conductive elastomer can also be provided in a variety of different extruded profiles. Common profile configurations of conductive elastomers are: “D”, Round, “P”, Square, and Rectangular; these profiles can be extruded as a solid cross section or hollow depending on the compression required and height of the open aperture to be shielded. In conductive elastomer the base silicone rubber is usually comprised of compounds such as silicone, fluorosilicone, or EPDM (ethylene propylene diene monomer). The use of a specific rubber is based upon the properties unique to each and determined by the intended environment and application. For example, silicone is used for general weather sealing and high temperatures to 400 deg. F. Fluorosilicone is used for applications where exposure to jet fuel, gasoline, and alcohols are present. EPDM is used for applications where exposure to coolants, steam, phosphate ester.
After choosing a specific rubber suited for the intended environment, a conductive filler must be determined. Some of the most common conductive metal fillers used are silver aluminum, silver glass, silver copper, and nickel graphite.Determining the right filler is dependent on the level of shielding needed for a specific application, the more conductive the filler the higher the level of shielding achieved.
Conductive Silicone Rubber Principles
1. Conductive particles filled inside the conductive rubber reach a certain volume number, and contact one another, finally form electron continuous state. When strong electromagnetic wave in external electromagnetic field hits free electrons in conductive particles, forming an opposite electromagnetic field, internal and external electromagnetic field offset each other to weaken the effect of electromagnetic interference wave.
2. Another principle is energy transformation, in other word, law of conservation of energy. When electromagnetic wave hits free electrons, conductive particles generate heat in the process of electrons movement, which is electromagnetic interference wave - free electron movement kinetic energy - thermal energy, in order to weaken the electromagnetic interference.
Conductive Silicone Rubber Structure
Conductive Silicone rubber must be subject to certain compression force to good electrical conductivity, Therefore, the structure must be designed to ensure proper pressure. Optimal amount of compression plates is in height from 7 to 15% ; solid round , D -shaped highly compressed optimum amount of 12 to 30% ; tubular , P-shaped highly compressed form optimum amount of 20 to 60%.
Conductive Silicone Rubber Applications
Conductive rubber often refers to rubber material, whose volume resistance is within 10^9 ohms * cm. Conductive rubber can provide a good electrical conductivity (Inhibition of frequency 40 GHZ) with its good electromagnetic sealing and water vapor sealing ability. Its mass volume resistivity up to 0.004 ohms * cm, with good stability.
Conductive rubber is used in both military and commerce. Main function is to seal and electromagnetic shield. Products can adopt compression molding or extrusion molding. It is on chip or other cutting shape. Shielding performance is as high as 120 dB (10 GHz). Conductive rubber can be classified into eight general kinds as following,CONSIL-NC, CONSIL-V, CONSIL-A, CONSIL-N, CONSIL-C, SC-CONSIL, CONSIL-R, CONSIL-II.
It is also used in medical electrode. Volume resistance of conductive rubber is bigger compared with that of metal, based on volume resistance is proportional to the distance, the longer the distance, the greater the resistance. Conductive rubber has been widely used on the medical electrode. Electrode is thinner, generally below 1 mm, conductive rubber is completely electrified in this case.