High interconnection density-current trends

Describes some trends in high interconnection density media, including fine-feature printed circuit boards (for fine-pitch surface mounted devices and for Multi-Chip Modules using unpackaged ICs-Chip-on-Board) and silicon motherboards, comparing the benefits and the limitations of the different options. Examples are given showing improvements in the desired attributes and means of overcoming problems. This trend towards high density is evident in all market sectors from consumer products to mainframe computers. GEC-Marconi Research Centre has been actively working in this field, solving the problems of interconnect in the 1990s and beyond. Their objective is to be both evolutionary and revolutionary, providing implementation of technology into product at the earliest opportunity. One example is a double-eurocard board reduced to a Chip On Board format 72 mm square. Also, the quantity of decoupling capacitors and terminating resistors has been greatly reduced due to the short runs between components. This example is a microprocessor module manufactured using PCB techniques having 80 μm (0.003") tracks and 150 μm (0.006") plated through holes (PTH), realised in eight layers