The invention concerns an assembly comprising a piezoelectric resonator (14) and a case (10), the case including a base part (11), on which the resonator is mounted, a wall (12) extending from said base part so as to surround at least partially said resonator, and a cover fixed to said wall in such a way as to close said case. The base part includes a main portion (17) and at least two conductive vias (16a, 16b). The conductive vias electrically connect The piezoelectric resonator to an outside circuit through the base part, and each of the conductive vias is surrounded by a insulating lining (18) so as to insulate the vias from the main portion (17). The main portion (17) of the base part (11) is divided into two parts by an insulating partition (21) in such a way that the two conductive vias are on different sides of the partition.