Ultra-thin, panel embedded packages in glass and laminate substrates with embedded copper heat-spreaders with near-zero thermal interface resistance are demonstrated for the first time. This unique package addresses the thermal dissipation requirements of 30W-100W power amplifiers by embedding the IC in the glass substrate and direct metallization with large copper heat spreaders. This package also demonstrates a solution to mitigate the stresses induced from copper-glass CTE mismatch using built-in stress buffers. Ultra-low loss dry film polymers used to embed the IC and serve as the RDL dielectrics result in low loss at GHz frequency bands.