Modeling of hermetic transitions for microwave packages

Abstract

Two numerical techniques, the finite difference in time domain (FDTD) and the finite element method (FEM) in frequency domain, are employed to characterize microstrip hermetic transition geometries in an effort to investigate high-frequency effects. Measurements performed on these transitions compare favorably with theory. Two different types of transitions have been analyzed from 10 to 25 GHz and have been found to be limited in performance by higher return loss as frequency increases. It is shown that microstripthrough-CPW hermetic transitions in the shielded environment may suffer from parasitic waveguide modes which, however, can be eliminated with the use of vias at appropriate locations. The hermetic wall on top of the CPW section shows a relatively small (I 2 dB) effect on the original circuit performance. Similarly, the hermetic bead transition shows good performance at a lower frequency region while it degrades as frequency increases. This indicates the need for very careful characterization of transitions intended for use in microwave and millimeter-wave applications.

An X-band small outline leaded plastic package for MMIC applications

“…It solves a solution space by the finite element method (FEM) algorithm. The FEM algorithm has been used previously to judge package electrical performance [11].…”

“…In this case (9) and the argument is the same as (10) The capacitance per unit length for due to the finite thickness of the conductors is the parallel plate formula (11) and with dielectric present, . In Fig.…”