A contact spring for placement in a gap between an electrical substrate opposite a lid (electrically conductive heat spreader) of an electronic device comprises a spring that both conducts heat from the substrate to the lid and electrically connects the substrate and lid. The spring comprises a flat single element configured as a plurality of polygons, providing contact points, the spring substantially lying in a plane and extending substantially in a straight line, or a spiral. The spring in an electronic device such as a flip chip ball grid array having this lid and an electrical substrate with EMI emitters: (1) provides low impedance electrical connection between the electronic circuit and lid; (2) grounds the lid to the electronic circuit; (3) minimizes EMI in the electronic circuit; (4) conducts heat from the electronic circuit to the lid; or any one or combination of the foregoing features (1)-(4).