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Modified by Admin on Sep 13, 2017

A large part of the time spent designing a board is for interactive routing. Helping to make this phase more efficient, Altium Designer 14.3 combines automatic rule switching with intelligent track segment creation. By defining Room-based routing width design rules, tracks can automatically neck and expand as a room is entered or exited.

Automatically Necking the Routing

You can configure Altium Designer so that the routing automatically necks when it enters or exits a placement room, if that room has been used to scope a routing Width Constraint design rule. The following animations demonstrate routing out of, and into a BGA that sits within a placement room.

Width rules are obeyed, and track segments are intelligently sized as the room boundary is crossed.

Defining a Room-based Routing Rule

A room-based routing rule requires a placement room to be defined first. A placement room is also design rule. While you can create the rule and then define the room from the design rule dialog it can be more efficient to do it the other way around, interactively create the room and Altium Designer creates the design rule for you.

Creating the Room Rule

The Design » Rooms submenu has a number of room definition commands.

Rooms are a useful feature for controlling where components are placed, and also for controlling what rules are applied within that area of the board.

A room created around selected components will result in the following:

A Component Class of the selected components is created. Review the class (Design » Classes) and update the Component Class Name as you require.
A Placement Room Definition design rule is created. The rule is scoped to target the Component Class created in step 1, if you changed the Component Class name then the rule scope (Full Query) must be updated to match.
The Placement Room Definition design rule is also automatically named. Update the name as required and take note of the name, because the room will be referenced in other design rules by its Name.
If required, resize the room. To do this, click once to select it, then click and hold on a vertex to move a corner or an edge. After clicking on a vertex to move it, you can also press Shift to perform a symmetrical resize.

In this example the rule has been scoped to target a specific BGA footprint ('BGA50P18X18-180'), rather than a component class.

A Placement Room Definition design rule is normally scoped to target one or more components. In this situation, where it is ultimately being used to control the routing within the area defined by the room, you do not actually have to scope it to target specific components. For example, the scope of the rule (Full Query) could be set to All, and the routing would still behave as required. The advantage of scoping it to target the component(s) within it, is that if the component(s) need to be moved, then the Design » Rooms » Move Room command can be used to move the room and the components together.

Creating the Room-based Routing Rule

Once the room has been defined, the routing width rule can then be defined. The image below show an example of a Routing Width rule that is scoped to instruct Altium Designer to set the routing width to 0.075mm whenever the routing touches the room named Room_BGA. In Altium Designer 14.3 the interactive routing engine was enhanced to automatically terminate the current track segment and start a new segment at the room boundary, to satisfy a rule such as this.

A Routing Width design rule scoped to set the width of all nets to 0.075mm within the room Room_BGA. Note that this rule appears first in the tree, indicating that it is the highest priority routing width rule.