An electronic board comprises a plane printed circuit, a thermal drain and an expandable locking means positioned along one edge of the printed circuit comprising a part for transmission of movement and a part mobile in translation along an axis including a component perpendicular to the printed circuit. The part mobile in translation has at least one recess opening onto a face of the expandable locking means perpendicular to the printed circuit. The locking means is designed to rigidly fix the board in a chassis and to press the thermal drain against a face of the chassis. The printed circuit comprises a region which enters into the recess or recesses of the expandable locking means.