Printed Wiring Board Materials

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. 

Day, A. G. and Weller, M. G., Flammability testing of printed wiring board material and the effect of the conformal coating. Proceedings of Intemepcon Conference, Brighton, 1980. 

Ch oline in the form of choline base (hydroxide) is a strong organic base with a pH of approximately 14. This product can have industrial apphcations where it is important to replace inorganic bases with organic materials. Ch oline base is currently used in the formulation of photoresist stripping products for use in the printed wire board industry. Dilute aqueous solutions (5%) of ch oline base that have very low concentrations of metallic ions have been utilized for apphcations in the semiconductor industry. 

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. 

Electronic Materials. Applications of photopolymer technology to electronic products is probably one of the largest imaging categories in terms of sales and total number of patents and publications. A wide variety of products have been developed for the production of printed wiring boards (PWB) and the manufacture of integrated circuits (IC). 

Liquid encapsulation and potting compounds, e.g., for automotive parts Thermal and RT-curing adhesives, underfiller materials Composites, fiber-reinforced, e.g., for transportation or in printed wiring boards PCB build-up materials... 

The symposium and this book have enabled us to assemble the results of research by experts in polyimides and related materials, polymeric encapsulants, gels, and printed wiring board (PWB) substrates, with emphasis on the chemical aspects of these materials. 

Much of the newer technology is driven by the needs for low dielectric constant and controlled impedance, a low dielectric constant being an advantage of foamed materials. Clearly, dimensional stability is becoming increasingly important for printed wiring boards. 

Scanning acoustic microscopy (SAM) is an ideal nondestructive method for revealing internal flaws within materials or between material interfaces. SAM is extensively used in detecting voids, delamination, and other separations that can occur in adhesive-attached parts, especially after thermal cycling. SAM is particularly useful in the analysis or evaluation of many types of electronic parts, including ceramic and plastic-encapsulated ICs, plastic-encapsulated microcircuits (PEMs), hybrid micro-circuits, CSPs, PBGAs, and printed-wiring boards. 

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