Dissipation factor Laminate

Grade 1—T1 Flex strength, MPa Water absorption, % Permittivity, 1 MHz Dissipation factor, 1 MHz Impact strength, J/m Dielectric breakdown parallel to laminations, kV... 

Laminate T °C GTE below ppm/°C Water uptake, MIL-P-13949F, mg Dielectric constant at IMH2 Dissipation factor at 1 MH2 Tensde strength, MPa " Modulus of elasticity, GPa Thermal conductivity, W/(m-K)... 

Chem. Descrip. Vinyl-toluene/butadiene emulsion copolymer Uses Film-former for solv.-based traffic paints, block fillers, paper coatings, adhesives, laminates, printing inks, hot melts, abrasion-resist, coatings, masonry and concrete paints, waterproof coatings Features Produces films with clarity, str., hardness and chem. resist. Properties Sol. in aromatic soivs., aliphatic blends, chlorinated HC, esters, ketones sp.gr. 1.026 dens. 8.56 Ib/gal ref. index 1.57 hardness (Sward) 20 (24 h) dissip. factor 0.0010 (100 Hz) dielec, const. 2.58 (100 Hz) vol. resist. 6.97 xIO ohm-cm Pliolite VTAC [Goodyear]... 

The major use of CE resins is in the electronic industry, including printed wiring circuit boards, thin cards, multichip module laminates and ship encapsulants. CE resins have replaced epoxy and bismaleimide resins to a great extent for such microelectronic application due to their comparatively lower moisture absorption and dielectric dissipation factor. 

Silicone laminates are useful from cryogenic temperatures to about 260°C. The dielectric properties of silicones are particularly useful. Both dissipation factor and dielectric constant are low at room temperature and remain relatively constant up to 150°C. Because of the presence of the silicon atom, silicone laminates have good arc- and track resistance. The physical properties of silicones are not greatly influenced by aging, but compared with laminates that are based on other resins, the flexural and tensile strengths of silicones are not unusually high. Silicone laminates are used in electronics, heaters, rocket components, slot wedges, ablation shields, coil forms, and terminal board. 

Grade X These laminates are used for mechanical applications and are affected by humidity. They are not usually used in electrical applications as an insulating material. The impact strength is low. Rolled tubes machine easily and have low dissipation factors. Rods are not available. 

The important feature of LC polyesters is a low coeffident of thermal expansion a < 1 x 10 grad that is comparable with the value for inorganic glasses (5 x 10 grad ) and significantly less in comparison with ordinary polymers (1 x 10 grad" ). These properties have led to the use of Vectra LC polymers in many electronic applications such as sockets, switches, bobbins, connectors, chip carriers, and sensors. Vectra LC polymers have replaced stainless steel in medical applications. The LC polyesters are particularly attractive for miaowave frequency electronics due to low relative dielectric constants, low dissipation factors, and the commerdal availability of laminates. 

Related to the dielectric constant is the dissipation factor (Df) or loss tangent. This is a measure of the percentage of the total transmitted power that will be lost as electrons dissipate into the laminate material. See Fig. 12.9 for a schematic representation of the test. 

Low and stable values of dissipation factor and permittivity under varying temperatures and also varying frequency became apparent when electronic applications for silicones were first developed over 30 years ago. Von Hippel measured very stable values of dielectric characteristics for silicone resin and silicone resin bonded glasscloth laminates at temperatures up to 200°C and at frequencies from 100 Hz to 100 MHz... 

High water absorption can result in pronounced reduction in the insulating resistance, dielectric breakdown, dissipation factor and mechanical strength. Water absorption is dependent upon the chemical nature of the polymer as well as upon the presence of voids, which is generally greater in composite materials such as laminates. In the... 

Test Methods for a-c Loss Characteristics and Permittivity (Dielectric Constant) of Solid Electrical Insulating Materials Test Method for Dissipation Factor and Permittivity Parallel with Laminations of Laminated Sheet and Plate Insulating Materials Test Methods for Relative Permittivity (Dielectric Constant) and Dissipation Factor of Polyethylene hy Liquid Displacement Procedure... 

Moisture. Like d-c resistance, both dielectric constant and dissipation factor are related to the presence of moisture. Unlike d-c resistance, a-c properties are sensitive to the presence of moisture even in the absence of a continuous low-resistance path. For example, moisture, absorbed in a filler at interfaces between different components or in laminations, can be detected by changes in dissipation factor and capacitance. Moisture may be detected a short distance below the surface. Thus, a-c measurements respond more quickly to the presence of moisture and detect moisture penetration before it can influence d-c resistance. 

Fig. 47. Effect of diying a 6.3-mm paper-phenolic resin laminate on dissipation factor, tan S (solid lines), and capacitance, C (broken lines), at 50 Hz. A, 4 h at 105°C B, 16 h at 105°C C, 96 h at 105°C and D, 192 h at 105°C before test. The laminate initially contained some residual water as pressed.

Fig. 48. Effect of voltage stress on dissipation factor of A, paper-phenolic resin, laminate at 23° after 1 wk at 90% rh and B, after 1 wk at 50% rh C, dry glass-cloth-silicone laminate.

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