Multilayer package substrate with stress buffer

A semiconductor package includes a multilayer package substrate including a top layer including a top dielectric layer and a top metal layer providing a top portion of pins on top filled vias, and a bottom layer including a bottom dielectric layer and a bottom metal layer on bottom filled vias that provide externally accessible bottom side contact pads. The top dielectric layer together with the bottom dielectric layer providing electrical isolation between the pins. And integrated circuit (IC) die that comprises a substrate having a semiconductor surface including circuitry, with nodes connected to bond pads with bonding features on the bond pads. An electrically conductive material interconnect provides a connection between the top side contact pads and the bonding features. At least a first pin includes at least one bump stress reduction structure that includes a local physical dimension change of at least 10% in at least one dimension.