SMTA International Conference Proceedings


Authors: Ousama Najjar, Ph.D
Company: Arlon, Inc.
Date Published: 9/22/2002   Conference: SMTA International

Abstract: Paradoxically, the controversy over as well as the interest in and demand for non-halogenated prepregs and copper clad laminates have grown over the last few years. Several factors have contributed to the quest for these materials, including consumer environmental concerns and proposed environmental legislation. Brominated epoxy laminates based on bisphenol-A have been the workhorse of the PWB industry. Such resin technology imparts many desired physical and chemical properties, including UL 94-V0-flammability compliance.

A number of strategies have been considered in Europe and the Far East in order to replace the current technology based on halogen-containing epoxy1-3. A variety of materials known for their fire-extinguishing ability such as organic phosphorus and nitrogen-containing derivatives, and inorganic fillers such as aluminum and magnesium hydroxides have been investigated, yet not fully explored. Unfortunately many of the efforts so far have led to materials with performance inferior to FR-4 systems.

Properties such as thermal and mechanical performance, electrical properties or flammability have been compromised in many of these approaches. We explored two routes to solve the problem, an additive approach and a fully reactive resin system approach. It was determined that the fully reactive system was the better protocol as superior laminate properties were achieved.

Halogen and antimony-free prepregs and laminates based on phosphorus and nitrogen-containing epoxy, and compounds with inherently non-flammable molecular structures were fabricated. The epoxy resin was modified to meet performance requirements, including Tg >150 °C and UL 94 V0 flammability. The varnish was coated on an aramid substrate and relatively high peel strength values were achieved compared to conventional epoxy aramid materials. The laminate properties are discussed.

In particular the present work was aimed at the development of an environmentally friendly Thermount® RT© nonwoven aramid based product for use in applications requiring laser microvia formation and HDI systems such as mobile telephone handsets and other consumer electronic products. The laminate flatness, excellent registration and CTE control make this material ideal for HDI applications.

Key words: green, halogen-free, epoxy, flammability.

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