A semiconductor chip (102) assembled on a substrate (101). The substrate has a first surface (101a) including conductive traces (110), which have a first length (111) and a first width (112), the first width being uniform along the first length, and further a pitch (114) to respective adjacent traces. The semiconductor chip has a second surface (102a) including contact pads (121); the second surface faces the first surface spaced apart by a gap (130). A conductive pillar (140) contacts each contact pad; the pillar includes a metal core (141) and a solder body (142), which connects the core to the respective trace across the gap. The pillar core (141) has an oblong cross section of a second width (151) and a second length (152) greater than the second width. Trace pitch (141) is equal to or smaller than twice the second width (151). The trace pitch is equal to or smaller than the second length (152).