footprint=package_name should exist somewhere in the symbol and
be made invisible. This attribute is used by lepton-netlist and primarily
for the PCB package.
Attach this attribute just like the device (device attribute) attribute. This is a free standing or floating attribute.
package_name is the pcb footprint or package type like
DIP14 or DIP40. Although this attribute in principle is
pcb package dependent, gEDA/gaf conventions exist to make this
attribute as portable as possible, allowing for easy collaboration and
sharing between users.
Footprint naming conventions.
If the symbol does not have a footprint, then the value of
footprint= should be set to none. If the footprint must
be overridden in a schematic, then the value of footprint=
should be set to none. If the footprint is not known, then the
value of footprint= should be set to unknown.