Dielectric breakdown strength

Water as an impurity accelerates the oxidation rate. Figure 4 compares growth curves for Si02 under dry and steam conditions. Halogens can also be introduced to the oxidation process, thereby reducing sodium ion contamination. This improves dielectric breakdown strength, and reduces interface trap density (15). 

The dielectric breakdown strength in vitreous siUca depends on its impurity content, its surface texture, and the concentration of stmctural defects, such as cord and bubbles. Good quaUty glasses have room temperature breakdown strength in the range of 200—400 kV/cm. 

Ferroelectrics. Ferroelectrics, materials that display a spontaneous polarization ia the abseace of an appHed electric field, also display pyroelectric and piezoelectric behavior. The distinguishing characteristic of ferroelectrics, however, is that the spontaneous polarization must be re-orientable with the appHcation of an electric field of a magnitude lower than the dielectric breakdown strength of the material. 

Static charge generation causes an ignition hazard only if the accumulated charges create an electric field that is sufficient to produce an electrical discharge in a flammable atmosphere. In most processes, this means that the electric field intensity at some location must reach the dielectric breakdown strength of air (nominally 3 x 106 V/m). The objective of static control measures is to ensure that electric field intensities cannot reach this value. 

Banford et al. studied the radiation effects on electrical properties of low-density polyethylene (LDPE) at 5 K with the use of a 60Co gamma source and a thermal nuclear reactor [86]. They reported that both the electrical conductivity and the dielectric breakdown strength of LDPE at 5 K were not significantly affected by radiation absorbed doses up to 10s Gy, but an erratic pulse activity under high applied fields was observed in the sample irradiated at 106 Gy. 

Polynapthalenes are in general, rigid rodlike low molecular weight aromatic polymers and are insoluble in most common solvents. Thin films of polynapthalene deposited by CVD are microcrystalline as deposited, and show a low dielectric constant (e = 2.4), with high dielectric breakdown strength (3 MV/cm), along with excellent thermal stability (dissociation temperature 570°C). CVD studies have so far been done primarily in view of their low dielectric constants, for use as intermetallic dielectrics in ULSI interconnect applications. 

The electrical properties of interest for ceramics include conductivity, resistivity, dielectric breakdown strength, dielectric constant, loss factor, and electromechanical coupling. Most ceramics do not have high electrical conductivity, and thus ceramics have found application as electrical insulators for many years. The electrical insulating capability of some ceramics is also retained under high electric field this is referred to as high dielectric breakdown strength... 

Until recently, little attention has been given to the dielectric breakdown strength of lead azide values reported in the literature vary from 20 to 300 kV/cm. Past studies were primarily directed to the dependence of the dielectric strength on such factors as sample thickness, density, temperature, etc. Little attention was given to the type or shape of electrode, the electrode material, or the degree of contact between sample and electrodes. Thus the measured dielectric strength was determined by the conditions of the measurement, which were usually different for each investigation. 

The third problem associated with water based varnishes is poor electrical insulation properties of the laminate after moisture conditioning. This problem is probably the most critical problem because insulation failures of the laminate can lead to electrical failure of the finished printed circuit board. This property is measured by conditioning the finished laminate in a high moisture environment and then testing the dielectric breakdown strength. ED24574 has excellent insulation resistance. This was achieved by a proprietary resin composition. 

Dielectric Breakdown Measurements. The dielectric breakdown strength was measured on the freely standing BCB-2 films as described above. The breakdown strength was 2.5 x 10 v/cm for 22 mm thick films. This value is -50% of the breakdown strength measured for 1.5 mm polyimide films on Si (8). However, the breakdown strength does not vary proportionally to the film thickness. The breakdown strength was also measured for 1.7 mm BCB-2 films deposited on a Si substrate. The value obtained from this measurement was 4.0 x 106 v/cm. The latter value was much closer to breakdown strengths observed in polyimide films of comparable thickness. 

The dielectric breakdown strength of the BCB films was observed to be close to that reported for polyimide films of comparable thickness. The value of 4 x 10 V/cm appears to be acceptable for use in multilevel interconnection structures. 

Minimizing dielectric thickness is an alternative to increasing the capacitance of these hlms snbject to the constraint of acceptable leakage currents, effective insulation of the gate, and snfficient dielectric breakdown strength. 

Tables 3.70 through 3.72 summarize the effect of one-year South Florida outdoor exposure on the electrical and mechanical properties of FEP. Little change has occurred in the dielectric breakdown strength, dielectric constant, and dissipation factor of FEP due to exposure. Tensile strength and break elongation measurements are essentially unchanged. The only decline is in the MIT flex life (ASTM D2176) of the one-year sample, which could be due to measurement error. The reason for a decrease in flex life could be the MIT method that has a high degree of uncertainty. Certainly, the other mechanical properties do not support the measured decline in the flex life.

These five factors are difficult to measure and control routinely due to a need for special equipment and procedures. A number of indirect properties have been defined to measure the impact of the five parameters. They include specific gravity, tensile strength, break elongation, dielectric breakdown strength, and heat of fusion. These properties are measured by relatively simple and quick methods. 

Dielectric breakdown strength is a function of microporosity but not molecular weight or crystallinity. The number and size of the microvoids affect the dielectric strength. Table 10.11 shows the relationship of dielectric breakdown strength to microporosity. 

Electrically speaking, the ultrathin BLMs and biomembranes possess very large capacitance ( 1 /rF cm ) and dielectric breakdown strength (> 200 kV/cm). These, along with other unique attributes, are listed in Table 3. 

A number of approaches have been explored for increasing the dielectric constant of elastomers for DEs. The most common approach involves the addition of high dielectric constant filler materials to an elastomer host. Silicone is of particular interest for this type of approach as it possesses good actuation properties to begin with, is readily available in gel form, and has a low dielectric constant. Results thus far do not appear particularly promising increases in dielectric constant have been met with concomitant increases in dielectric loss and reductions in dielectric breakdown strength [184—186]. It has also been shown that the elastic modulus is affected by the addition of filler [187]. 

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