A package on packaging structure provides for improved thermal conduction and mechanical strength by the introduction of a sold thermal coupler between the first and second packages. The first package has a first substrate and through vias through the first substrate. A first set of conductive elements is aligned with and coupled to the through vias of the first substrate. A solid thermal coupler is coupled to the first set of conductive elements and to a die of the second package. A second set of conductive elements is coupled to the die and a bottom substrate is coupled to the second set of conductive elements. The thermal coupler may be, e.g., an interposer, a heat spreader, or a thermal conductive layer.