COMPUTER AIDED DESIGN OF PRINTED CIRCUIT BOARDS

CADPCB is a software package developed for automatic design of printed circuit boards. The system builds layout automatically, using the connection list specified by the user. However, in order to be more flexible and comply with the userʹs specific requirements, it can also be used interactively. CADPCB consists of two main parts of placing and routing. The former places the components of different sizes on the board and consists of two phases. In the first phase, initial placement, the program automatically locates each component in the computed locations of the plane, using pair linking method. In the next phase, modification and refinement, the user can interact with the program, change the allocated locations of any desired component and rerun the program for replacement of those remaining. In the latter, which also consists of two phases, routing is performed. In its first phase, the paths between a pair of pins are calculated. The calculations are based on minimum spanning tree and a slightly improved version of modified Lee algorithm. In the second phase, a graphic editor helps the user to interactively add paths not drawn in the first phase or change the already drawn paths to suit more his requirements. Here, different layers of the complete layout can be displayed on the graphic display unit. CADPCB is installed on a PDP 11/45 minicomputer, with graphics and plotter facilities, is capable of preparing camera-ready layouts of the two layers and can be installed on other computer systems with similar capabilities.