Wiring Board Material Properties

The electrical properties of polymers are important in many applications [1]. The most widespread electrical application of polymers is the insulation of cables. In recent years, high-performance polymers have become important in the electronics industry as encapsulants for electronic components, as interlayer dielectrics, and as printed wiring board materials. The dielectric constant (or permittivity) and the dissipation factor (or power factor or electrical loss tangent) tan 8, which are dimensionless quantities, are the key electrical properties. 

Silicon—Ca.rbon Thermoset. The Sycar resins of Hercules are sihcon—carbon thermosets cured through the hydrosilation of sihcon hydride and sihcon vinyl groups with a trace amount of platinum catalyst. The material is a fast-cure system (<15 min at 180°C) and shows low moisture absorption that outperforms conventional thermosets such as polyimides and epoxies. Furthermore, the Sycar material provides excellent mechanical and physical properties used in printed wiring board (PWB) laminates and encapsulants such as flow coatable or glob-top coating of chip-on-board type apphcations. 

JL olymers are increasingly being used in a wide variety of applications in electronics and photonics, most of which use polymers in their traditional role as engineering materials (e.g., circuit boards, molded products, wire and cable insulation, encapsulants, and adhesives). In addition, many other unique applications require material properties that only polymers can provide. Examples include resist materials for the lithographic fabrication of integrated circuits (1C) and polymers for optical recording. These types of applications may be considered passive in the sense that the polymer does not play an active role in the operation of the device or circuit. Rather, it serves some other function such as mechanical support, electrical insulation, or in the case of resists, some intermediate function in the fabrication of the device. 

Saytex CP-2000 is widely used for printed wiring boards laminates made from FR4 epoxies. It is reacted into the epoxy, so that there is no potential for leaching out of the resin. The FR meets the German Dioxin Rule. It is environmentally acceptable, thermally stable at high temperatures and does not disrupt resin properties when soldered. It can be used as an additive in ABS and also as a raw material in brominated epoxy oligomers in ABS and high impact polystyrene (HIPS). 

UL746 A B C D E Underwriters Laboratories. Pol5mieric materials Short term property evaluations Long term property evaluations Use in electrical equipment evaluations Fabricated parts Industrial laminates, filament wound tubing, vulcanised fibre, and materials used in printed wiring boards... 

In addition to providing circuit interconnection, a multilayer printed wiring board (ML-PWB) provides the electrical and mechanical platform for the system. This means that the electrical and thermal properties of the ML-PWB material are very important for the proper functioning of the system. Among the properties of importance are dielectric constant, Du (also known as Er) dielectric loss, Df (or tan 8) glass transition temperature, Tg time to delamination,Txxx thermal decomposition temperature.Ta coefficient of thermal expansion, CTE and moisture absorption. The following sections discuss the importance of these properties to an ML-PWB snbstrate. 

Electro-insulation materials. The retention of dielectric properties in a high-temperature environment, coupled with good corrosion resistance in contact with certain reactive chemicals, suggests excellent possibilities of polybenzimidazole use in electrical insulation and other dielectric applications at high operating temperatures and/or in aggressive chemical environments. Typical applications, hence, can be foimd in special cable and wire insulation, in the manufacture of circuit boards and radomes for supersonic aircraft, as battery and electrolytic cell separators, and as fuel cell frame structural materials. Some recent publications in the patent and technical report literature may serve to illustrate such applications. 

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