ABSTRACT
A typical electronic package consists of devices mounted on a substrate. The substrate, which provides mechanical support and acts as an electrical interconnect medium for the devices, consists of single or multiple layers of etched metallization separated by dielectric that acts as an insulator. Signal layers support signal interconnections, often with a given layer having traces in either the horizontal or vertical direction for ease of design and manufacture. In this chapter, the focus is on the estimation of the number of signal layers as a function of the magnitude and distribution of the signal circuitry on the substrate. It discusses the various factors that affect the number of signal layers. The chapter presents the density approach, where the equivalent integrated circuit count method, used for layer estimation in printed circuit boards, is described. It presents the connectivity approach which can be used for layer estimation in all substrates.
