Certain small Surface Mount components, such as some SOD’s and SOTs for example, with terminal leads that can be in the form of either Gullwing or Outward flat ‘L’ depending on their dimensions.  

It’s important to distinguish between the two to assign the correct protrusion goals (toe, heel and side) to obtain the most reliable footprint mounting. 

This is how the PCBL Footprint Expert does it.

Gullwing terminals are generally for parts with relatively larger terminals and provide more heel fillet.

Gullwing goals should be applied when:

S min > D1 max

Or

(L max – L min) >= 0.50 mm

Outward Flat L terminals are generally for smaller parts and do not provide as much heel fillet.

Outward Flat L goals should be applied when:

S min <= D1 max

AND

(L max – L min)  <  0.50 mm

When a Gullwing change to Outward L occurs, this message will be displayed: