High density interconnect (HDI) packaging for microwave and millimeter wave circuits

High density interconnect packaging can be achieved by several different strategies. One is the use of conventional thick film metallization with several layers on a single substrate. Several substrates are electrically connected together using blindmate vertical interconnects that form a 3-D package. High temperature cofired ceramics (HTCC), such as alumina and aluminum nitride (ALN), use this strategy. Thin film metallization on multiple layers of polyimide will also accomplish similar interconnect densities on a single substrate material with no need for vertical interconnects to adjoining substrates. Laminates composed of Duroid, E-glass. or thermoplastic materials can also be pressed together to form a single high density interconnect substrate. These materials also have sufficiently small loss tangents enabling their use into the millimeter range. This paper discusses the manufacturability, design tradeoffs. performance, and costs of all three technologies. More detailed results will be presented for the high density interconnect using multilayer AlN at X-band; these results will be compared with microwave and millimeter wave packages that are currently in development using laminates or polyimides.