Batch process fabrication of package-on-package microelectronic assemblies

A method of fabricating a microelectronic assembly, comprising:

• joining first and second subassemblies to form an assembly, the assembly comprising a first support element and a second support element, the first support element having an outwardly-facing first surface facing a first direction, and the second support element having an outwardly-facing first surface facing a second direction opposite from the first direction, the first support element having electrically conductive first elements at an inwardly-facing second surface thereof, and the second support element having electrically conductive second elements at an inwardly-facing second surface thereof, at least one microelectronic element being mounted overlying the second surface of one of the first and second support elements, a patterned layer of photo-imageable material overlying the second surface of one of the first or second support elements, the patterned layer having openings with cross-sectional dimensions which are constant or increase with height from the surface of the support element over which the patterned layer lies, and the assembly further comprising masses of bonding material extending from the first elements through the openings and electrically coupled with the second elements, the masses having cross-sectional dimensions defined by the cross-sectional dimensions of the openings;
• and
• flowing an encapsulant into a space between the first and second subassemblies to form an encapsulation contacting surfaces of at least portions of the masses.