Documentation

Styles and Spacings and Rules By Area

8 min read

Overview

Each design has a set of styles, spacings and rules in their technology giving the track/via styles, spacings and rules to be used for different nets in the design. You can also set up a different set of spacings, routing styles and rules to be used within specific named areas of the board.

These are useful for defining areas around BGA components for example, where tracks and vias can be smaller and closer together in order to route out from the BGA pads. It is also useful for dividing the board into functional areas where different track/via sizes, spacings and rules are required for some nets.

Shortcuts

Menu: Setup

Default Keys: T

Command: Technology

Locating this option

Available from: Setup menu > Technology option > Spacing Rules tab

Using Area Based Styles, Spacings and Rules

Use the following steps to set up your design for area based styles, spacings and rules.

  1. Add the Area

    Add an area to the board on the layer where the different styles, spacings, and rules are required. This area can be in a footprint or in the PCB design or Profile. Name the area to make it possible to refer to it when later defining the styles, spacings, and rules.

    Use the Properties dialog to edit the area and check the Override Within Area box. This enables this area to be used when using a default track style for a new track, or by Design Rule Check when checking spacings and rules. Make sure the area is not marked as a Keep Out area.

    If the area is in a footprint, its name will be kept when the component is added to a design. For example, if you set an area around a Ball Grid Array footprint and name it “BGA”, all components using this footprint in the design will have an area called “BGA”. This makes it easier when setting up styles, spacings and rules for the area by name. The design now contains duplicate area names, but they are made unique when used in the Find Bar by adding the component name to the end of the area name, for example “BGA(U2)“.

  2. Defining the rules

    Several of the technology rules can be made specific to a given area. This is achieved by adding your area name as a condition. You can use wildcard characters to match a group of areas. (So BGA* would match all areas named BGA followed by any string).

    In general, rules are applied in the order they are defined (i.e. from the top of the list in the Technology dialog), with the first matching rule applying. You should therefore place more specific rules higher up the list. So you could define a rule specific to a given net, in a given area, on a specific layer. Then define a more general rule for the net, then a final catch all rule.

  3. Setting Spacing Rules for the Area

    This is done by using the Spacing Rules in the Technology dialog to set up Match Pair spacings for the area.

    In the Match Pair Rule page use the New button to define the new area based rule.

    You will now find that the options for Design Rule Check, Online DRC, Measure Tool and most of the interactive operations will use these spacings when checking two items that are within the named areas.

    Area based Match Pair spacings can also be defined on specific layers, so a through board area, may have different spacings for specific layers.

  4. Setting the Default Routing Styles for the Area

    The default styles for tracks and vias are associated with nets using the Net Styles technology rules. These rules can be specific to an area by adding the area name as a condition, again using wildcard characters to specify a group of areas.

    Different net style rules can be used to achieve the following:

    • Use wildcard characters to reduce the number of rules required.
    • Define different default track styles for the Bottom of the board and for Inner layers.
    • Define different default via styles to be used for each layer span.
    • Define different default track and via styles to be used within specific named areas.

In the net Styles dialog use the New button to define the area based styles entry. You will be presented with the Net Styles dialog to setup the default styles and the conditions for them to be used. Add the name of the Net or Net Class for which the default styles will apply, using wildcards to specify groups of Nets.

You will now find that the interactive operations that add tracks or vias will use these default styles when the items are within the named areas. For example, changing layer or layer span will change the track style as long as the default was being used.

Area based Net Styles can also be used to define default routing styles for a single specific inner layer of the board. You can set the For Tracks on Side box to specify default track styles for the Top, Bottom or All Inner layers of the board. This functionality can be enhanced by adding a named area around the entire board on a specific inner layer, and by including the layer name in the net styles entry.

Interactive Routing

With area based styles defined, adding or editing an existing track that is using the default track style for its net will check each time you add a corner to see if the style needs to be changed due to crossing an override area border. This is further enhanced when Online DRC is enabled, as the track will then stop at the edge of the styles override area, thus forcing the next corner to be added on the edge so that the style change can be on the area boundary. Click once to add a corner on the area edge and carry on the other side of the area with the different style. This allows you to easily route out of a BGA area using thin tracks running closer to each other, and then click on the area boundary to swap to using thicker tracks and a larger spacing on the other side. There are Options which determine how the track style change should take place.

The area based track style changes only happen when adding or editing a track, and not when moving track segments. If you move track segments into one of these areas and want them to take the different style defined for the area, use the Use Default Track/Via Style option described below. Conversely, if a track has been added that changed styles by crossing an area and you did not want it to, select the track and use Change Style to set it back to the required width.

When adding a Differential Pair track in paired mode, the track will not stop at area boundaries, or have their style changed when adding a corner. If you do need to achieve a style change when entering an override area, stop short of the area edge and use the Start Mirroring Paired Track option to separate the two tracks. These tracks will now stop at the area edge and change style after adding a corner on the area boundary. Join the tracks back together on the other side of the area edge to carry of adding paired tracks with the new width.

Forcing a Track to Use the Default Style

If you have existing areas already containing routing that you are overriding styles for, or you change the area based styles after completing some routing, you can change the existing tracks and vias to use the new default styles by using the Via Style option. Frame select the area and its contents and use the Use Default Track/Via Style option from shortcut menu to reset the styles. If a track goes across an area boundary it will be split so that the two halves can have different styles.

Autorouting

At this point in time the Autorouter will not obey area based rules or styles, so routing in these areas should be completed using manual routing methods first and locked before using the Autorouter to complete the remaining nets of the design.

Areas | Area Properties | Match Pair Rule | Design Rule Check | Net Styles | Spacing Rules | Via Style | Using Net Styles

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