Rectangular Flat-Pack Lids Under External Pressure: Formulas for Screening and Design

Formulas are presented for the maximum tensile stresses in the lid seal and the maximum lid deflections of a rectangular flat-pack under external pressure. These formulas can facilitate (a) the proper design of the package so that it will retain its hermeticity under a given screening pressure and (b) the selection of a proper pressure to use in the hermeticity screening of an already designed package. Information is also given on the approximate equivalence of external pressure and centrifuge acceleration in regard to the seal stresses and lid deflections of a rectangular flat-pack.