Arbitary SMD and DRC frustration

I have created a footprint for a SON-6 package, quite small. The datasheet calls for oblong pads 0.28mm wide by 0.75mm long and one end being completely rounded (i.e, r=0.14). I used a polygon with wire width 0 to achieve this as the embedded help file appears to say DRC does not check wire width of polygons used for arbitary pads. However, DRC is throwing up a width error for these smd pads. If I thicken the wire width to fit in with my DRC settings I can't create the smd shape I need. Is this a bug in the software or a bug with the way I'm trying to work? Any feedback other than 'just use rectangular smd pads' is welcome.

Thanks, William

0 Richard_H over 12 years ago

Hi William,

could you please send me the library you created. So I could check what the problem is there.
Please send it to: support@cadsoft.de

Regards,
Richard
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0 Former Member over 12 years ago in reply to Richard_H

Hi Richard,

I sent the library file this morning, did you have a chance to look at it yet?

Thanks

William
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0 Richard_H over 12 years ago in reply to Former Member

Hi William,

you have to draw the polygons in a reasonable wire width. If you take 0 as width, there will be additional constraints for the production process. Gerber data usually doesn't accept 0 width data. This is also written in the manual:

8.14 Arbitrary Pad Shapes
[.........]
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.
[........]

I am currently discussing with our development team whether we can change
this for the future.....

Regards,
Richard
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0 Former Member over 12 years ago in reply to Richard_H

Thanks for confirming Richard. So it seems the polygon smd pad function isn't yet up to the job for very small packages - even if I declare a polygon line width of 0.01mm that makes a significant error difference to the area and spacing for my SON-6 footprint. I guess if I just approve the errors for now and verify the gerber output, that is the only option for me today.
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