On the ARPA sponsored High Density Microwave Packaging (HDMP) program, a team composed of Texas Instruments (TI), Martin Marietta, and General Electric (GE) is developing a packaging system to support tile conformal phased arrays. Significant volume and weight reductions are projected relative to today's microwave module technology. The team's approach utilizes a stacked module configuration, with a surface contact vertical interconnect between module layers. The module layers are built on a metal matrix composite AlSiC substrate with silicon and MMIC devices mounted face-up in substrate wells. Chip-to-chip interconnect is provided by an enhanced version of Martin Marietta's Microwave High Density Interconnect (MHDI) process. Stacked module assemblies are surface mounted on an RF/DC manifold on the back of the conformal array surface. Incremental technology demonstrations are planned as part of the program, culminating in a 96-element brassboard array demonstration.<<ETX>>