The zero slack feature in Ansys Icepak alleviates some restrictions encountered when using non-conformal assemblies. Zero slack non-conformal assemblies not only reduce mesh count but also allow the user to mesh specific objects separately. In this model, the zero slack capability allowed you to mesh the package object separately.
Nonetheless, there are certain limitations of zero slack non-conformal assemblies that you must keep in mind:
Surfaces of objects that are coplanar with a zero slack non-conformal interface cannot participate in radiation.
Zero slack assembly interfaces cannot touch 2D objects, such as fans, openings, grilles, conducting thin plates, and so on.
Zero slack assembly interfaces cannot touch the sides of blocks with individual side specifications.
Always check that objects coplanar with a zero slack interface are correctly meshed.