Microelectronic die packages with leadframes, including leadframe-based interposer for stacked die packages, and associated systems and methods

A stacked system of microelectronic die packages, comprising:

• a first die package having a first lateral edge and first metal leads having first contact surfaces flush with the first lateral edge;
• a second die package having a second lateral edge and second metal leads having second contact surfaces flush with the second lateral edge and generally aligned with the first lateral contact surfaces;
• and
• external electrically conductive inter-package connectors, wherein individual inter-package connectors are connected to one of the first contact surfaces and a corresponding second contact surface, and wherein the connectors comprise individual metal solder lines that bridge a gap between the first and second packages.

A microelectronic device, comprising:

• a molded dielectric material having lateral-side, bottom-side, and top-side surfaces;
• a microelectronic die at least partially encapsulated within the dielectric material and spaced laterally apart from the lateral surface of the dielectric material;
• and
• individual metal leads electrically coupled with the die and having a wetting surface configured for attaching external inter-package solder lines, wherein the wetting surface includes an exposed metal portion that is flush with the lateral surface of the dielectric material and at least one of the top-side and bottom-side surfaces of the dielectric material.