Solder on slot connections in package on package structures. An apparatus includes a substrate having a front side surface and a back side surface; a first passivation layer disposed over at least one of the front side and back side surfaces; at least one via opening formed in the first passivation layer; a conductor layer disposed over the first passivation layer, coupled to the at least one via and forming a conductive trace on the surface of the first passivation layer; a second passivation layer formed over the conductor layer; and at least one slot opening formed in the second passivation layer and exposing a portion of the conductive trace for receiving a solder connector. In additional embodiments the substrate may be a semiconductor wafer. Methods for forming the structures are disclosed.