Solder Mask Expansion

Rule category: Mask

Rule classification: Unary


The shape that is created on the solder mask layer at each pad and via site is the pad or via shape expanded or contracted radially by the amount specified by this rule.


Default constraints for the Solder Mask Expansion rule.

  • Expansion – the value applied to the initial pad/via shape to obtain the final shape on the solder mask layer. Enter a positive value to expand the initial pad/via shape; enter a negative value to contract it.

How Duplicate Rule Contentions are Resolved

All rules are resolved by the priority setting. The system goes through the rules from highest to lowest priority and picks the first one whose scope matches the object(s) being checked.

Rule Application

During output generation.


  1. Partial and complete tenting of pads and vias can be achieved by defining the appropriate value for the Expansion constraint:
    1. To partially tent a pad/via, covering the land area only – set the Expansion to a negative value that will close the mask right up to the pad/via hole.
    2. To completely tent a pad/via, covering the land and hole – set the Expansion to a negative value equal to or greater than the pad/via radius.
    3. To tent all pads/vias on a single layer - set the appropriate Expansion value and ensure that the scope of the rule targets all pads/vias on the required layer.
    4. To completely tent all pads/vias in a design in which varying pad/via sizes are defined - set the Expansion to a negative value equal to or greater than the largest pad/via radius.
  2. Solder mask expansion can be defined for pads and vias on an individual basis in the associated properties dialog. Options are available to follow the expansion defined in the applicable design rule or to override the rule and apply a specified expansion directly to the individual pad or via in question. Options are also available to force complete tenting of the pad/via on the top and/or bottom.


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