The standard pad object can:
However, there is a huge variety of pad shapes needed for component footprints, and standard pads are not always enough. To create a different shape from those listed above, you must create a custom pad shape. Custom pad shapes are created by placing other design objects, such as arcs, fills, lines, or regions, to build up the copper shape required for the pad. A small pad is included within the shape to define the connection point in the pad, and if required, the drill hole location and size.
Any design object can be used to build up the required copper shapes needed for the pads. Choose the object to suit the shape required, for example the copper contact area for the switch shown below has been created from a series of track objects, surrounded by two arc objects.
For complex shapes, the Solid Region object is ideal as a polygonal object it can be used to create virtually any shape. The following footprint was created by first setting the grid to suit the zigzag requirements of the copper, and then placing one region object to give a single zigzag shape. This was then copied the required number of times to define the copper area of the capacitive slider footprint. Alternating surface mount and through-hole pads were added on alternating ends of each zigzag to define the connection points.
If the pad shape requires a shape defined at specific locations that do not fall onto a grid, it can be more efficient to define linear or point guides, and then place on these guides. The animation below shows a wedge-shaped pad being created by:
Another approach to defining an unusual pad shape is to first define a closed outline of the shape using lines and arcs, and then convert this outline to a Solid Region. The pads in the surface mount inductor footprint shown below were created using this approach.
The following steps were taken:
There are essentially two approaches for defining the solder and paste mask requirements for a custom pad:
Any primitive object can have a calculated Solder and/or Paste Mask, which can either be a user-specified amount or controlled by the rule system. This is achieved enabling the appropriate Mask Expansion settings in the Properties panel, as shown in the image below.
When the mask opening requirements are not simply an expansion or contraction of the copper shape, it will not be possible to use a calculated mask. In this case, place suitable design objects on the required Mask layer. Keep in mind that the Solder Mask is defined in the negative, that is, the placed objects define openings in the Solder Mask layer. The following image shows a printed button that has the solder mask opening defined by a manually placed full circle arc, placed on the Top Solder Mask layer.
Since the software is able to detect and resolve routing connections to any copper object, there are no specific limitations on how you route to a custom pad.
Custom pads are often created for components that have larger, unusually shaped pads. If these pads need to connect to a surrounding polygon, you should consider the polygon thermal connection spokes during the design of the custom pad. The software uses the small pads included in the custom pad shape as the polygon connection points. To ensure the small pads are connected by spokes, position them close to the edge of the custom shape so that the distance from the small pad edge to the edge of the custom shape is less than half the polygon connection spoke width. Place a small pad for each polygon connection point required.
* Footprints courtesy of Dennis Saputelli, Integrated Controls, Inc.