Interconnecting Substrates Opportunities for the innovative structuring of high resolution circuit tracks, as well as drilling a large number of small vias is gaining immense popularity. A number of companies are developing HDI boards for portable products. The Japanese first introduced HDI substrates in products such as mobile phones, camcorders, car navigation systems, PC cards and notebook computers. North American and European mobile phone makers then promoted the use of HDI substrates in their products with a close eye on workstation and network systems. The extreme requirements for chip-pad count and density, derived from the projected silicon technology revolution, have become primary challenges to continued package development and have profoundly influenced substrate technologies.
Applications are workstations, network systems and many telecommunications products.
Microvia Technologies Prohibitive costs and a limited number of ceramic substrates have led to a conversion to organic substrates to perform circuit functions beyond simple interconnection wiring and impedance control. Both the NEMI and SIA roadmaps suggest that all interconnections consist of organic materials, because FR-4 type material is still the least expensive way to make even multilayer PWBs. This combination of the two lands is what helps make HDI structures such a useful development for interconnecting area-array packages. Photo-imageable Materials Available technologies for microvia HDI formation in the dielectric layers include, laser ablation, photovia techniques, plasma etching, and the less popular vias and circuitry formed by conductive inks. It is the most mature technology with products that demonstrate proven reliability.