Aspects of electronic packaging for mainframe applications are reviewed. A new generation of microwiring boards has been introduced, based on Cu/polymer layers on a polyimide base or metal/polymer layers on a multilayer ceramic or silicon base for high-end technologies. Advanced multilayer printed circuit boards will fulfil the requirements for low-end applications for the late 90s. In order to satisfy the desired reduction in line delay by packaging components on both sides of large-size wiring substrates, wiring technology is being challenged by miniaturized line structures and increased wiring density. High circuit integration, associated with revolutionary developments in device technology, reduction in chip-feature size, and a packaging technology based on multichip modules, has led to a significant increase in power dissipation and related flux. >