Microwave packaging uses signal vias and interposers, such as metal lead frame interposers. For example, the microwave circuit die includes signal vias that electrically connect the top side and the bottom side of the die. Microwave signal circuitry on the die have signal paths that are electrically connected to the top side of the signal vias. The microwave signal circuitry typically may have an operating frequency of 300 MHz or faster. The bottom side of the signal vias are electrically connected to corresponding areas on the top side of the interposer. The bottom side of the die may also include a ground plane, with ground vias that electrically connect the top side of the die to the ground plane.