The invention provides a semiconductor package assembly. The semiconductor package assembly includes a redistribution layer (RDL) structure die-attach surface and a bump-attach surface opposite the die-attach surface. A semiconductor die is mounted on the die-attach surface of the redistribution layer (RDL) structure. A first solder mask layer is disposed on the die-attach surface. The first solder mask layer surrounds the semiconductor die. An additional circuit structure is disposed on a portion of the first solder mask, surrounding the semiconductor die. The additional circuit structure includes a pad portion having a first width and a via portion has a second width that is less than the first width. The via portion passes through the first solder mask layer to be coupled the redistribution layer (RDL) structure.