High-frequency dielectric radio

High-Frequency Dielectric (Radio Frequency) Heating... 

RF (radio frequency) welding Utilizes specific bands of radio frequency waves which are directed through specially constructed tooling to form localized melting/joining of certain dielectric thermoplastic materials. Can be used to form hermetic seals. Also known as high frequency or dielectric welding. 

Use The oxide ferrites in rectifiers on memory and record tapes, for permanent magnets, semiconductors, insulating materials, dielectrics, high-frequency components, and various related uses in radio, television, radar, computers, and automatic control systems. 

Radio-frequency welding (dielectric welding, high-frequency welding) n. 

The dielectric loss factor (loss factor) of a material is the product of the dielectric constant and the tangent of the dielectric loss angle for a material. This is a measure of how easily the material will heat up in a high-frequency field such as a radio frequency or microwave frequency oven. 

A low dissipation factor is important for plastic insulators in high-frequency applications such as radar equipment and microwave parts smaller values mean better dielectric materials with less dielectric heating. A high dissipation factor is important for polymers that are to be heated in a radio frequency or microwave oven for welding, drying, etc. 

Figure 3 shows the real part e and the imaginary part e"oi the complex dielectric constant e= e - je of conducting polymer composites in dependence on frequency. The permittivity measurements show resonance polarization of the composite materials (Fig. 3). The resonance frequency is around 1.5 GHz. This could be explained with polarization and conductivity losses of carbon black particles in the polymer matrix. The measurements show low relative permittivity almost in the whole range of frequencies. The composites possess high values of e, e"dead high tannin the radio frequency range, at 1.5 GHz indicating that the composites could be utilized as EMI shielding material at this frequency range. Figure 4 shows the loss factor tanj = e"ie versus frequency for selected composites.

A common cause of RF contact burns is from the metal electrode jigs of dielectric heating and plastics welding apparatus, operating at radio frequencies. Unless the output is pulsed there is unlikely to be a shock risk, but an accidental hand contact, for example, will draw out an arc when the hand is removed and a high frequency burn will result. The burning is a function of the arc energy, and for low power apparatus only a minor burn is likely. More powerful equipment, above about 1 kW, can inflict more serious burns. 

---