A package includes a pad chip having contact pads, a spring chip having micro-springs in contact with the contact pads to form interconnects, the area in which the micro-springs contact the contact pads forming an interconnect area, an assembly material between the pad chip and the spring chip arranged to form a gap between the pad chip and the spring chip, and an underfill material in a portion of the gap to form a mold from the pad chip and the spring chip. A package includes a pad chip having contact pads, a spring chip having micro-springs in contact with the contact pads to form interconnects, the area in which the micro-springs contact the contact pads forming an interconnect area, an assembly material between the pad chip and the spring chip arranged to form a gap between the pad chip and the spring chip, an underfill material in the gap to form a mold from the pad chip and the spring chip, and at least one wall between the underfill material and the interconnect area. A method of assembling a package includes aligning a pad chip with a spring chip to form at least one interconnect in an interconnect area, adhering the pad chip to the spring chip so that there is a gap between the pad chip and the spring chip, dispensing underfill material into the gap to seal the interconnect area from an environment external to the package, and curing the underfill material to form a solid mold.