PCB Design Blogs

In standard PCB designs, various masks and surface finishes require verification of proper clearances and coverage. The rigid-flex designs not only have the same mask and surface finish requirements but also have additional geometries, such as bend areas and stiffeners. These geometries, present on different layers, require verification of special clearances or overlaps of materials and spacing between these layers. The inter-layer checks provide spacing checks between objects of one layer and those on another layer. These checks usually defined for rigid-flex designs can also be used in standard single or multilayer designs.

To create inter-layer checks, you need to select two subclasses and then set the following for the rule: Type, Value, DRC label, and the DRC layer display. You can view the effects of these rules in the Allegro Layout Editors. In the Spacing domain, the Spacing workbook in the Inter Layer drop-down provides a matrix to select subclasses, types of constraints, and their values for defining inter-layer spacing checks.

You can also manage the layer pairs in the Layer Pair Management pane. The pane consists of two columns on the top and a matrix with check boxes for creating or deleting layer pairs below them. The left column, labeled as Layer 1 lets you select a subclass for the first layer from the list of eligible subclasses, and the right column, labeled as Layer 2 lets you select the subclass for the second layer as also the intersection. Row and column filters are available with the columns to search subclasses and subclass types.

Defining Constraints for Inter-Layer Checks

To create a constraint between two subclasses, enable the check box where the two subclasses intersect in the matrix. Hover over the check box to highlight the row and column headers and to display a tooltip showing the layer pair name.

On enabling the check box, a new row is added at the top of the constraint table.

Set the values for Type, Value, DRC label, and then select the Enabled check box to enable the rule. Similarly, you can add and edit multiple rules according to the need of your design.

To delete a rule, deselect the check box in the selection matrix or click X in the Delete column of the constraint table for that row.

To learn in detail about this feature, watch the Creating Inter Layer Checks available in the Constraint Manager from within the Allegro PCB Editor video on the Cadence Support portal. Click the video link now or visit Cadence Support and search for this video under Video Library.

I hope that this video will help you in creating inter-layer checks available in constraint manager more easily and effectively from within the Allegro Layout Editors.

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