IBIS spec 5.1里有介绍 " e) m: t! [. e& j' a3 n
Section 7 describes the package model format of IBIS % j- F9 ?) N9 M2 m9 r3 qVersion 2.1 and a subsequent extension. Package models can be formatted within .ibs files or can 9 e: {7 G' ~/ D# f
be formatted (along with the Section file header keywords) as .pkg files.