Editing Place and route (section)

==Printed circuit board==
The design of a printed circuit board comes after the creation of a [[Circuit diagram|schematic]] and generation of a [[netlist]]. The generated netlist is then read into a layout tool and associated with the footprints of the devices from a library. Placing and routing the devices can now start.<ref name="Layout_book">{{Cite book|author=J. Lienig, J. Scheible|title=Fundamentals of Layout Design for Electronic Circuits|url=https://link.springer.com/book/10.1007/978-3-030-39284-0|page=26-27|chapter=Chap. 1.3.3: Physical Design of Printed Circuit Boards|publisher=Springer|date=2020|doi=10.1007/978-3-030-39284-0 |isbn=978-3-030-39284-0|s2cid=215840278 }}</ref>

Placing and routing is generally done in two steps.  [[Placement (EDA)|Placing]] the components comes first, then [[Routing (EDA)|routing]] the connections between the components.  The placement of components is not absolute during the routing phase, as it may still be changed by moving and rotating, especially with designs using more complex components such as FPGAs or microprocessors.  Their large number of [[signal (electrical engineering)|signal]]s, and their [[signal integrity]] needs may require optimization of the placement.<ref name="PCDandF">{{cite web |url = http://pcdandf.com/cms/content/view/4345/95/ |title = FPGA/PCB Co-Design Increases Fabrication Yields |access-date = 2008-07-24 |publisher=Printed Circuit Design and Fabrication}}</ref>

The resulting design is then output in RS-274X [[Gerber format]] to load in the [[Computer-aided_manufacturing|computer-aided manufacturing (CAM)]] system of the manufacturer. In contrast to an IC layout, where the entire finished layout is stored in one graphics file, different files and formats are needed for PCB manufacture. The fabrication data consists of a set of Gerber files, a drill file, and a pick-and-place file containing the location and alignment of the devices generated for automated placement of the devices in the assembly process.<ref name="Layout_book" />