The PCB Auto Router is a feature of the CAD software that places traces automatically, often saving substantial time and effort. You can use the Auto Router to create your circuit initially or to modify a circuit at a later stage. For example, you might might place several footprints for a mini web server circuit, define nets and then run the Auto Router to create your circuit layout.
- Create nets if not already done.
- Click Tools | Route | Route All.
- Any connections the auto router fails to make will be displayed by unresolved Logical Connections lines (if enabled). Create those connections manually.
- Click Tools | Route | Router Settings.
The router settings dialog appears:
- Enter the desired parameters:
Nets to route
Number of nets to route. Click Change... to go to the edit nets dialog to choose nets to be routed.
Number of layers
Number of copper layers on which you want to auto-router to place traces - usually "Two sides".
Minimum distance between conductors and between conductors and other copper objects. Smaller values improve the chance of fully routing your board.
Width of new traces
Width of traces created during the routing process. Smaller values improve the chance of fully routing your board. This parameter will not affect existing traces.
Use individual trace width for each net
Check to make auto-router use trace widths assigned for each net individually. Click the "Edit widths..." button to go to theEdit nets dialog to specify the trace widths. For a net that doesn't have a trace width specified, the value "Width of new traces" will be used.
Number of passes
The number of times the auto router will try to route your board. Higher values improve the chance of fully routing your board but take longer to complete.
Similar to the snap grid, the routing grid specifies the distance between imaginary grid lines along which the auto router will place conductors. Lower values improve the chance of fully routing your board but creates a higher density of traces and takes longer to run. Higher values increase the chance to get an ugly layout with overcrowded traces, useless extra traces, etc.
Affects closeness to obstacles such as pads. Lower values usually improve the chance of fully routing your board but places traces closer to obstacles.
Trace bend Affects the number of bends. Lower values usually improve the chance of fully routing your board but increases the number of bends in traces. Layer change Affects the number of vias. Lower values usually improve the chance of fully routing your board but increases the number of vias.
45 deg trace
Affects the number of 45 deg trace segments. Lower values usually improve the chance of fully routing your board but increases the number of 45 degrees trace segments.
- Click OK.
- Create nets for the footprint if not already done.
- Click the footprint to select it.
- Click Tools | Route | Foute Footprint.
- Right click the logical connection or double click it.
- Choose "Auto route connection...".
- The Auto Router dialog appears.
- Enter the desired parameters.
- Click Route.
To "unroute", choose Edit | Undo.
When the autoroute mode is enabled Pad2Pad will automatically
reroute a footprint after it's moved with either the mouse or the
arrow keys. To turn the autoroute mode on/off please use the
"Route footprints automatically after moving" checkbox in
Tools | Route. To change the routing settings
choose Tools | Route | Router Settings.
The following video demonstrates how the autoroute mode works: