A support substrate has a mounting face and a connection face opposite to the mounting face. An electronic chip is mounted to the mounting face and a matrix of connectors is mounted to the connection face. The support substrate includes an interconnection structure formed by a pair of conductive interconnection tracks that electrically connect the electronic chip to the matrix of connectors and circulate differential signals. The two interconnection tracks of the pair of conductive interconnection tracks extend facing each other at different depths of the support substrate. An isolation structure in the support substrate laterally isolates the pair of conductive interconnection tracks. Isolation plates above and below the pair of conductive interconnection tracks provide further isolation.