Dissipation factor temperature

Polytetrafluoroethylene transitions occur at specific combinations of temperature and mechanical or electrical vibrations. Transitions, sometimes called dielectric relaxations, can cause wide fluctuations in the dissipation factor. 

The dissipation factor (the ratio of the energy dissipated to the energy stored per cycle) is affected by the frequency, temperature, crystallinity, and void content of the fabricated stmcture. At certain temperatures and frequencies, the crystalline and amorphous regions become resonant. Because of the molecular vibrations, appHed electrical energy is lost by internal friction within the polymer which results in an increase in the dissipation factor. The dissipation factor peaks for these resins correspond to well-defined transitions, but the magnitude of the variation is minor as compared to other polymers. The low temperature transition at —97° C causes the only meaningful dissipation factor peak. The dissipation factor has a maximum of 10 —10 Hz at RT at high crystallinity (93%) the peak at 10 —10 Hz is absent. 

Fig. 10. Power factor at 1 MHz vs temperature for some commercial glasses. Courtesy of Corning Inc. The power factor is the ratio of the power ia watts dissipated ia a material to the product of the effective siausoidal voltage and current ia volt-amperes. When the dissipation factor is less than 0.1, the power...

BiaxiaHy orieated PPS film is transpareat and nearly colorless. It has low permeability to water vapor, carbon dioxide, and oxygen. PPS film has a low coefficient of hygroscopic expansion and a low dissipation factor, making it a candidate material for information storage devices and for thin-film capacitors. Chemical and thermal stability of PPS film derives from inherent resia properties. PPS films exposed to tolueae or chloroform for 8 weeks retaia 75% of theh original streagth. The UL temperature iadex rating of PPS film is 160°C for mechanical appHcatioas and 180°C for electrical appHcations. Table 9 summarizes the properties of PPS film. 

Electrical Properties. Polysulfones offer excellent electrical insulative capabiUties and other electrical properties as can be seen from the data in Table 7. The resins exhibit low dielectric constants and dissipation factors even in the GH2 (microwave) frequency range. This performance is retained over a wide temperature range and has permitted appHcations such as printed wiring board substrates, electronic connectors, lighting sockets, business machine components, and automotive fuse housings, to name a few. The desirable electrical properties along with the inherent flame retardancy of polysulfones make these polymers prime candidates in many high temperature electrical and electronic appHcations. 

T and are the glass-transition temperatures in K of the homopolymers and are the weight fractions of the comonomers (49). Because the glass-transition temperature is directly related to many other material properties, changes in T by copolymerization cause changes in other properties too. Polymer properties that depend on the glass-transition temperature include physical state, rate of thermal expansion, thermal properties, torsional modulus, refractive index, dissipation factor, brittle impact resistance, flow and heat distortion properties, and minimum film-forming temperature of polymer latex... 

Electrical and Mechanical Properties. Electrical properties include dielectric strength, dielectric constant, dissipation factor, and volume resistivity these properties can change with temperature and absorbed water. 

The electneal properties of PTFE are dominated by its extremely tow dielectric constant (2.1) This value is invanant over a broad range ot temperatures (- 40 to 250 °C) and frequencies (5 Hzto 10 GHz). Smularly, PTFE has an unusually low dissipation factor, which is also quite mdependent of temperature and frequency fhis behavior results from the high degree of dipolar symmetry of the perfluonnated and unbranched chains The dielectnc strength, resistivity, and arc resistance are very high... 

The dissipation factor of capacitors at high frequencies is determined by the series resistance. For low frequencies there may be losses caused by leakage currents as well as by slow components in the polarizability, especially of high e ceramics and polymer dielectrics. The dissipation factor of the SIKO at room temperature is below 10-4. At 200 °C it is still very low (2X10-4). 

Material response is typically studied using either direct (constant) applied voltage (DC) or alternating applied voltage (AC). The AC response as a function of frequency is characteristic of a material. In the future, such electric spectra may be used as a product identification tool, much like IR spectroscopy. Factors such as current strength, duration of measurement, specimen shape, temperature, and applied pressure affect the electric responses of materials. The response may be delayed because of a number of factors including the interaction between polymer chains, the presence within the chain of specific molecular groupings, and effects related to interactions in the specific atoms themselves. A number of properties, such as relaxation time, power loss, dissipation factor, and power factor are measures of this lag. The movement of dipoles (related to the dipole polarization (P) within a polymer can be divided into two types an orientation polarization (P ) and a dislocation or induced polarization. 

There have been isolated QSPR studies of a number of other polymer properties. These include the dielectric constant [144], the dielectric dissipation factor (tan 8) [168], the solubility parameter [169], the molar thermal decomposition function [170], the vitrification temperature of polyarylene oxides [171], and quantities relating to molecularly imprinted polymers [172, 173]. The interested reader is referred to the literature for further information. 

Figure 5. Dissipation factor D at 1 MHz vs. time at a specified temperature for a 1-ftm thick polyimide film.

Relative to microelectronic applications, the out-of-plane dielectric constant for BPDA-PFMB films measmed after aging at 50% relative humidity for 48 h at 23°C was between 2.8 and 2.9 (0.1 kHz to 1 MHz) (ASTM D-150-81These values are considerably lower than that of commercial polyimides such as PMDA-ODA (pyromellitic dianhydride, PMDA) (s = 3.5 at 1 kHz and 3.3 at 10 MHz). The dielectric constant and tan 8 (dissipation factor) were temperature- and frequency-dependent. The dielectric constant, which was independent of temperature until near 210°C increased above this point until a frequency-dependent maximum was reached at about 290°C. The dissipation factor, which was also independent of temperatme below 200°C, underwent a rapid increase with no maximum between 200 and 400°C owing to ion conductivity. The temperatme at which this increase occurred increased as the frequency increased. The films also... 

Also as discussed earlier, a difficulty can arise when a material being irradiated possesses a dissipation factor that increases with temperature. A microwave-driven thermal runaway can result unless the temperature is carefully monitored and the power controlled. On the other hand, solvents show a general decrease in dielectric constant with temperature. Efficiency of microwave absorption diminishes with temperature rise and can lead to poor matching of the microwave load, particularly as the fluid approaches the supercritical state. Solvents and reaction temperatures should be selected with these considerations in mind, as excess input microwave energy can lead to arcing. 

Alternative polymers that have certain advantages over polyimides have also been introduced they include poly(phenylquinoxaline), poly(phenylquinoline), and poly(benzocyclobutenes) (PBCBs) (93,116). The PBCBs have a low curing temperature (250 °C), low dielectric constant (2.6), low dissipation factor (0.0045), and low moisture absorption (0.3%) The development of specialty polymers for packaging and high-density interconnections will continue to be an active area of research as polymer manufacturers focus on the needs of the microelectronic industry. 

The dielectric constant remains at 2.04 over a wide range of temperature and frequencies (from 100 Hz to 1 GHz). The dissipation factor at low frequencies (from 10 Hz to 10 kHz) decreases with increasing frequency and decreasing temperature. In the range from 10 kHz to 1 MHz, temperature and frequency have little effect while above 1 MHz the dissipation factor increases with the frequency.55... 

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