Altium Designer Documentation

Arc (PCB)

Created: July 28, 2015 | Updated: June 16, 2017

The Arc Dialog.
The Arc Dialog.

Summary

This dialog allows the designer to specify the properties of an Arc object. An Arc is a primitive design object, used to create curved shapes on a single layer of a PCB. This could include: curved corners in the routing, a circular ring on the component overlay, or a curved edge on a keepout zone.

Access

The Arc dialog can be accessed prior to entering placement mode, from the PCB Editor – Defaults page of the Preferences dialog. This allows the default properties for the arc object to be changed, which will be applied when placing subsequent arcs.

During placement, the dialog can be accessed by pressing the Tab key.

While attributes can be modified during placement, bear in mind that these will become the default settings for further placement unless the Permanent option on the PCB Editor – Defaults page of the Preferences dialog is enabled. When this option is enabled, changes made will affect only the object being placed and subsequent objects placed during the same placement session.

After placement, the dialog can be accessed in the following ways:

  • Double-clicking on an Arc object.
  • Placing the cursor over an Arc, right-clicking and selecting the Properties command from the context menu.
  • Using the Edit » Change command and clicking once over the placed arc object.

Options/Controls

  • Radius - The radius of the Arc, measured from the center point, to the center of the Arc line.
  • Width - The width of Arc line.
  • Start Angle - The start angle of the Arc, measured from the X axis in the first quadrant (plane geometry).
  • End Angle - The end angle of the Arc.
  • Center X/Y - The X/Y location of the Arc center.

Properties

  • Layer - The layer that the Arc is placed on. Arcs can be placed on any layer other than the system layers.
  • Locked - Lock the object so that it cannot be edited graphically.
If attempting to graphically modify an object that has its Locked property enabled, a dialog will appear asking for confirmation to proceed with the edit. If the Protect Locked Objects option is enabled on the PCB Editor – General page of the Preferences dialog, and the Locked option for that design object is enabled as well, then that object cannot be selected or graphically edited. Double click on the locked object directly and disable the Locked property, or disable the Protect Locked Objects option, to graphically edit the object.
  • Net - If the Arc is a copper object, choose a Net for the Arc. All Nets in the current project will be listed in the drop-down list.
  • Keepout - Check this box to set the Arc object to act as a Keepout object. A Keepout object is displayed in the layer color, outlined in the Keepout color. A keepout object is used on a signal layer to create a layer-specific keepout. Layer-specific keepouts are not included during output generation.
  • Solder Mask Expansion - This field allows you to enable and control the expansion to be used with respect to the arc on the Solder Mask layer, to create the required opening in the mask. This opening can be larger (a positive expansion value) or smaller (a negative expansion value) than the arc itself. The following options are available:
    • No Mask - No opening in the solder mask.
    • Expansion value from rules - Choose this option to have the solder mask expansion for the arc follow the defined value in the applicable Solder Mask Expansion design rule.
    • Specify expansion value - Choose this option to override the applicable design rule and specify the solder mask expansion value for the arc.
  • Paste Mask Expansion - This field allows you to enable and control the expansion to be used with respect to the arc on the Paste Mask layer, to create the required opening in the mask. This opening can be larger (a positive expansion value) or smaller (a negative expansion value) than the arc itself. The following options are available:
    • No Mask - No opening in the paste mask.
    • Expansion value from rules - Choose this option to have the paste mask expansion for the arc follow the defined value in the applicable Paste Mask Expansion design rule.
    • Specify expansion value - Choose this option to override the applicable design rule and specify the paste mask expansion value for the arc.
Paste and Solder masks are shown in the negative, that is, when you see an object on one of those layers it is actually a hole or opening in that layer.

Quickly change the units of measurement currently used in the dialog between metric (mm) and imperial (mil) using the Ctrl+Q shortcut. This affects the dialog only and does not change the actual measurement unit employed for the board, as determined by the Measurement Unit setting in the Board Options dialog (Design » Board Options).

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