Found this text written by Richard Hammerl at **broken link removed**
The typical way to draw an arbitrary pads shape is:
- Place a PAD or SMD
- Use POLYGON to draw the final pad shape
- For a SMD typically in Layer Top
- For a PAD you have to draw the final shape in all the layers you plan
to use (Top, Bottom, Inner layers...)
The PAD/SMDs center must be inside the polygon's area. Otherwise
that polygon is not recognized as a part to the pad. Use a reasonable
wire width for the polygon, which fulfils the Design Rules.
- The alternative to POLYGON is WIRE
Start the wire in the origin of the PAD/SMD. You have to draw this
area in any signal layer you plan to use. Please use a reasonable wire
width, which fits to the Design Rules.
- Check the solder stop mask
Mask data will be generated for the PAD/SMD area only. Display
layers 29, tStop and 30, bStop. If you want to have the area not
covered by solder stop lacquer, draw it manually in the appropriate
layer(s).
- Check the cream frame (solder paste mask)
Display layers 31, tCream and 32, bCream for this. As we agreed upon
defining packages always on the top side of a board, the layer we have
to check is 31, tCream. Mask data will be generated automatically for
the SMD area only. If this is not what you would like to have, simply
draw the mask manually. Keep in mind that it is possible to switch off
automatic generation of mask data in the SMD properties (Cream
on/off).