Materials Issues in Electronic Systems

The materials of electronic systems can be summarized in terms of relatively few basic elements and compounds. The chips are silicon with aluminum metallization and silicon dioxide or silicon nitride dielectric. A glass is used for passivation. The chips are packaged in epoxy molding compounds which are filled with silica powder. Electrical connections are made via gold wires from chip bonding pads to lead frames constructed of copper or an alloy of iron and nickel. The packaged chips are attached by solder to printed circuit boards that are composed of epoxy-glass (or sometimes polyimide) substrates that support copper interconnection patterns. In some cases alumina substrates are employed with refractory metals. Connection to other boards are made through connectors composed of molded plastic (diallyl) phthalate, polyphenylene sulfide, etc.) with beryllium copper contact fingers, and cables with copper conductors insulated with extruded plastic.