The invention provides a semiconductor package assembly. The semiconductor package assembly includes a redistribution layer (RDL) structure having a first surface and a second surface opposite to the first substrate. The RDL structure includes a redistribution layer (RDL) contact pad arranged close to the second surface. A passivation layer is disposed on the RDL contact pad. The passivation layer has an opening corresponding to the RDL contact pad such that the RDL contact pad is exposed to the opening. A first distance between a first position of the opening and a central point of the opening is different from a second distance between a second position of the opening and the central point of the opening in a plan view.