Small cutouts like those in the pads you are describing are usually 
restricted to slots or cutouts with a radius at each end or corner. This is 
because they are usually created using spinning drill or router bits. There 
are many ways to specify slots unfortunately none are as simple and 
automatic as assigning a hole size to a pad. Slots usually require some 
sort of special instructions and dimensioning- the fabrication drawing is 
an ideal place for such.

Because of the extra work involved for the designer and the extra cost of 
the fab, its common to simply use a round hole with a tight tolerance just 
large enough to encompass the tab or pin. If you must specify a slot there 
are several favorite ways to do this.

My preferred method is to omit all holes from the slot pads and manually 
spec the requirements on the fabrication drawing. This way, I don't need to 
worry about unwanted internal plane clearances and unwanted round thermal 
reliefs showing up in the Gerbers. Another method is to use a single hole 
to mark the center of the slot and spec the slot dimensions on a drawing. 
Yet another way is to use a hole to mark the center of the radius at each 
end of the slot.

Also very important... you will need to manually create clearances for the 
slots on all unconnected internal plane layers and don't forget to specify 
plated or non-plated for the slot. If you do use holes to mark the center 
or endpoints of the slot, its best to make these holes direct connected to 
the plane and manually create thermal reliefs if necessary, otherwise the 
resulting Gerbers will have thermals that don't match the shape of the slot.

Hope this helps.

Mark Koitmaa, C.I.D.
TechServ Printed Circuit Design Services
Tel: 408-369-7950
Fax: 408-369-7952
http://www.techservinc.com


At 10:23 AM 2/27/2002, you wrote:
>How do I specify a pad with a rectangular or square cutout? I'm using a
>switch and a stereo phone jack that require rectangular and square mounting
>holes respectively.
>
>Sean James
>PCB Designer
>Telecast Fiber Systems
>102 Grove Street
>Worcester, MA 01603
>TEL 508-754-4858 x33
>FAX 413-541-6170

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