A Lossy Electromagnetic Bandgap Structure for Mode Suppression in Chip Scale Packages

This paper introduces a novel concept for package mode suppression; a lossy electromagnetic bandgap (EBG) structure. It is comprised of an array of highly conductive metal vias connected to a patterned resistive film. These features may be formed inside the lid of a low temperature co-fired ceramic (LTCC) chip scale package (CSP) for broadband millimeter wave parasitic mode suppression. Full-wave simulations of an 8 mm square LTCC CSP are compared using two different lids; a simple metal lid versus an LTCC lid with an integrated lossy EBG structure. The package transitions are designed for 60 GHz operation, and a thru line is routed across the cavity floor and through an internal flip-chip die. End-to-end transmission coefficient and group delay are compared for the CSP with and without the lossy EBG structure. Simulated E field magnitude at sample points inside the package cavity are also compared for the two package lids. This new concept for cavity mode suppression is compatible with a low package height.