pcb-rnd knowledge pool

Abstract: Layers can be added to a design with the layers section of the preferences menu. If the layer is created with the "negative drawing" option selected, any drawn features will be subtracted from the layer. This is particularly useful for soldermask openings or copper features.

  Users may at times require windowing of the soldermask layer to expose a copper track.

The layer preferences dialog provides a visual stack up of the layers in a design. The user can right click on a layer to add an additional layer, and in the layer creation dialog window the user is given the opportunity to nominate the new layer as one in which "drawing with subtraction" is used.

Layer groups with multiple layers in them are called composite , regardless of the layers being positive or negative. If a layer group's first layer is a negative layer, an implicit all-board positive fill is automatically applied before the first layer.

With this type of layer, any drawn feature is subtracted from other features. This allows complex windowing of existing features on any layer type.

Note: subtraction is not available on copper layers.