A zone is a specific area of a PCB where specific electrical or mechanical rules and properties are required. Zones can be created for special technology regions or localized PCB materials and surfaces, requiring alternative rulesets. By defining zones in a multi-stackup PCB, you can optimize the design for electrical performance and manufacturability. This is particularly important in rigid-flex designs where different layer stackups are required in distinct parts of the design.
A nested stackup zone is useful when an area of the board requires special solder mask coating or specific plating requirements. The mask or plating materials can be specified in the zone stackup. With nested stackup zones, you can optimize the stackup for different areas of the board while ensuring that the design meets the required electrical and mechanical specifications.
Before the 22.1 QIR2 release, a zone can be nested within another. However, intersecting or overlapping zones are not supported in earlier releases. If a new zone overlaps or intersects an existing zone, the new zone is automatically trimmed to the boundary of the existing zone. Before this release, having any zone surrounded by another zone is not recommended.
Starting with the 22.1 QIR2 release, you can now define one zone inside another to ease the creation of rigid-flex designs that require complex stackups. For example, several zones can be rigid while others are flexible.
Zones can also be used to define constraint regions or placement rooms. Zone technology is also possible for alternate symbols or padstack placement associated with the zone. For further information, search the Cadence Help documentation for Technology Dependent Footprints (the tdf_editor command) and the ALT_SYMBOLS property. By default, the Allegro PCB Editor continues to support the alternate symbol methodology. The ALT_SYMBOLS property can be used with TDF to enable specific parts to override the mapping for a particular package type.
Using this latest release, you can create nested zones and edit zone boundaries even outside the Shape Edit application mode.
The steps for creation are as follows:
The steps for creation are as follows:
- To create the first zone, go to Setup > Zones > Create.
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- On the design canvas, create the first zone.
3. Now, place zone-2 in the zone-1 area by following step 1.
You can see that the nested zone is created successfully.
Editing the zone boundaries
Using this latest release, you can edit a zone boundary in the same way as you edit shape boundaries.
1. To edit the zone boundary, go to Shape > Edit Boundary.
Note: The Shape Edit application mode allows zone boundary editing as before.