An integrated circuit, IC, package assembly, comprising: - a die, - a first package substrate (112, 230), and - a second package substrate, - the first package substrate (112, 230) configured to route input/output (I/O) signals and ground between the die and the second package substrate, - the first package substrate having a - first side configured to receive the die and - a second side opposite the first side, - the first package substrate including: - a plurality of contacts (272, 274) disposed on the second side of the first package substrate; and - at least two ground vias (242, 244, 246; 252, 254, 256) of a same layer (292, 294, 296) of vias, and - signal vias (222, 232) of the same layer of vias (292, 294, 296), wherein an individual contact of the plurality of contacts is configured to form an individual solder joint with the second package substrate, wherein - the at least two ground vias form a cluster of ground vias (242, 244, 246; 252, 254, 256) electrically coupled with the individual contact, - the cluster of ground vias is surrounded by the signal vias of the same layer of vias, - the signal vias route input/output (I/O) signals through the first package substrate, and - the cluster of ground vias routes ground through the first package substrate, characterized in that the signal vias are configured in a hexagonal arrangement around the cluster of ground vias. - a die, - a first package substrate (112, 230), and - a second package substrate, - the first package substrate (112, 230) configured to route input/output (I/O) signals and ground between the die and the second package substrate, - the first package substrate having a - first side configured to receive the die and - a second side opposite the first side, - first side configured to receive the die and - a second side opposite the first side, - the first package substrate including: - a plurality of contacts (272, 274) disposed on the second side of the first package substrate; and - at least two ground vias (242, 244, 246; 252, 254, 256) of a same layer (292, 294, 296) of vias, and - signal vias (222, 232) of the same layer of vias (292, 294, 296), wherein an individual contact of the plurality of contacts is configured to form an individual solder joint with the second package substrate, wherein - the at least two ground vias form a cluster of ground vias (242, 244, 246; 252, 254, 256) electrically coupled with the individual contact, - the cluster of ground vias is surrounded by the signal vias of the same layer of vias, - the signal vias route input/output (I/O) signals through the first package substrate, and - the cluster of ground vias routes ground through the first package substrate, characterized in that the signal vias are configured in a hexagonal arrangement around the cluster of ground vias. - a plurality of contacts (272, 274) disposed on the second side of the first package substrate; and - at least two ground vias (242, 244, 246; 252, 254, 256) of a same layer (292, 294, 296) of vias, and - signal vias (222, 232) of the same layer of vias (292, 294, 296), wherein an individual contact of the plurality of contacts is configured to form an individual solder joint with the second package substrate, wherein - the at least two ground vias form a cluster of ground vias (242, 244, 246; 252, 254, 256) electrically coupled with the individual contact, - the cluster of ground vias is surrounded by the signal vias of the same layer of vias, - the signal vias route input/output (I/O) signals through the first package substrate, and - the cluster of ground vias routes ground through the first package substrate, characterized in that the signal vias are configured in a hexagonal arrangement around the cluster of ground vias.