Various aspects of the invention provide microelectronic component assemblies, memory modules, computer systems, and methods of assembling microelectronic component assemblies. In one particular implementation, a microelectronic component assembly includes a non-leaded first package, a second package, and a plurality of electrical junctions. The first package has a confronting surface that includes an exposed back surface of a microelectronic component and exposed contact surfaces. The second package has a confronting surface that includes an exposed back surface of a microelectronic component and exposed contact surfaces of a number of leads. Each of the junctions couples one of the contacts to the contact surface of one of the leads. The electrical junctions may also physically support the packages with their respective confronting surfaces juxtaposed with but spaced from one another, defining a peripherally open fluid passage and enhancing thermal performance.