Electrical properties printed wiring substrate

The major disadvantage of phenolics is low insulation resistance. Phenolics generally exhibit greater water absorption and sensitivity of the electrical properties to humid environments than epoxy resins, although only the so-called low-loss grades are used for printed wiring substrates. For these reasons, the use of phenolics in laminate fabrication has been restricted to the lower cost paper-based reinforcements. 

The most widely used plastic materials in the printed wiring industry are epoxy resins based on bisphenol A. Epoxy-glass fabric laminates account for approximately 80% of the consumption of printed wiring substrates in the USA. In particular, laminates with specifications equal to or better than NEMA grade GIO or FR4, which combine very good dimensional stability with excellent electrical properties, are suitable for the fabrication of high density wiring that is required for computers and telecommunications equipment. 

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. 

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