The silicon PCB

In its simplest form, a silicon hybrid is essentially a miniaturised PCB built on a silicon wafer, and like any other PCB it is made up of layers of metal tracks separated by a suitable dielectric. However, unlike a conventional PCB, a silicon hybrid is manufactured using IC fabrication techniques. The author discusses the Research Initiative in Silicon Hybrids (RISH). Developing silicon hybrids as a viable interconnection technology requires the successful solution of a wide range of problems. There is the obvious issue of developing reliable manufacturing techniques, but silicon hybrids also create their own special demands on chip-to-substrate connection technology, packaging, substrate and IC testing, and computer-aided-design (CAD) software. All these different aspects of silicon-hybrid development are being covered by the RISH project with a view to providing the collaborating companies with a `tool-box´ of processes from which the appropriate tool can be selected for a given application