Methods of forming package on package assemblies with reduced z height and structures formed thereby

A method of forming a microelectronic package structure comprising:

• forming an opening in a central portion of a first package substrate, wherein a first section of the first package substrate is adjacent a second section of the first package substrate;
• placing a plurality of stacked die between the first section and the second section of the first package substrate, wherein a second side opposite a first side of a first die of the plurality of stacked die, a second side opposite a first side of the first section and a second side opposite a first side of the second section are substantially coplanar;
• wirebonding each of the individual die of the plurality of stacked die to at least one of the first section or the second section;
• and
• forming a molding compound on the first section of the first package substrate, the second section of the first package substrate, and on the plurality of stacked die.

A microelectronic system, comprising:

• a board;
• a microelectronic package assembly attached to the board, wherein the microelectronic package comprises:
• a first package, wherein the first package includes a first substrate section and a second substrate section;
• a plurality of stacked die disposed between the first substrate section and the second substrate section, wherein a surface of a first die of the plurality of stacked die is coplanar with a surface of the first section and with a surface of the second section;
• and
• a second package physical and electrically coupled to the first package.