User Guide

These rules make sense if, for example, you consider that it might be
possible, within the Design Rules, to route two tracks between two pins
of a component, but that an inappropriate relationship between the two
gridscouldpreventthis(seediagram).
RoutingGrid
The Autorouter grid has to be set in the AUTO command setup menu
(Routing Grid). This is not the same as the currently used grid in the
Layout Editor window that you have selected with the GRID command.
Bear in mind that for the routing grid the time demand increases expo
-
nentially with the resolution. Therefore select as large a grid as possible.
The main question for most boards is how many tracks are to be placed
between the pins of an IC. To answer this question, the selected Design
Rules (i.e. the minimum spacing between tracks and pads or other
tracks)mustofcoursealsobeconsidered.
Theresultis:
The two grids must be selected so that component’s pads are located on the
routinggrid.
Trackpatternswithdifferentplacementgrids
There are of course exceptions, such as with SMDs to which the oppo
-
site may apply, namely that a position outside of the routing grid leads
to the best results. In any event the choice of grid should be carefully
consideredinthelightoftheDesignRulesandthepadspacing.
Theexampleabovemayclarifythesituation:
For the component on the left, the pads are placed on the routing grid.
Two tracks can be routed between two pads. The pads of the component
in the middle are not on the routing grid, and therefore only one track
canberoutedbetweenthem.
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TheAutorouter