Size Does Matter

摘要

One issue faced by many PCB designers at the start of a new project is the issue of predicting the size (area and layer count) of a design. Often, a designer may waste time trying to place and route a design on a PCB that is too small, or increase manufacturing time by using a board that is too large. Remember the PCB designs of 20 years ago? Components were all through-hole devices, while most logic was contained in 14-pin DIPs and vias were centered on 100-mil grids. With the limited autorouting tools available, many PCB tool vendors utilized via masters that could define and populate all legal via sites in the board. Routing would then involve selecting from any of the unas-signed vias to change layers. This was a reasonable and straightforward way to predict board size and layer count when working with such a rigid physical geometry, based on the component count alone.