diff --git a/modules/library-conventions/pages/packages.adoc b/modules/library-conventions/pages/packages.adoc index f9a28362..8be471b4 100644 --- a/modules/library-conventions/pages/packages.adoc +++ b/modules/library-conventions/pages/packages.adoc @@ -84,10 +84,20 @@ The following conventions apply to package names: == Pads -* *Always add all pads of packages*, even those which are not always connected. - For example, the package "TO220" has a metal tab, so you should define it as - a pad, no matter if it's often not connected (and even not connectable when - mounted vertically). +* *Each lead of the package should be represented by a separate package pad*, + even if there are internal connections (e.g. multiple GND leads) or + unconnected leads (e.g. the often unused metal tab of a TO220). Exceptions: +// Note: There's no strong reasoning behind these exceptions. If they +// turn out to be a problem in practice, they might need to be removed. +** Multiple mechanical leads which have a package-internal connection (e.g. + tabs of the metal housing of an USB connector) should be represented by + a single package pad (and all footprint pads connected to it). +** Leads for pure mechanical purpose without any internal connection at all + (e.g. split solder tabs of a plastic connector) shouldn't be added as + package pads (the corresponding footprint pads can be left unconnected). + If in doubt or if connected to a metal cover of significant size (possibly + having a shielding function), treat them like normal, electrically relevant + leads. * *Use pad names according {ipc7351-pdf}[IPC-7351]* (if applicable). For packages which are not covered by IPC-7351: ** If the function of a pad is absolutely clear, choose its abbreviated