An assembly comprising: a circuit board, a connector on the circuit board and comprising a plurality of leads connected to the circuit board and made of an electrical conductive material; and a flat cable extending straight in a direction and having a front end that is insertable and connectable to the connector, the flat cable comprising: a plurality of conductors made of an electrical conductive material, and extending straight along a lengthwise direction of the flat cable, spaced apart a predetermined distance in a widthwise direction of the flat cable; and a cable body made of an insulating material, and extending straight along the lengthwise direction of the flat cable, wherein the conductors are mounted on at least one surface, the cable body includes a cable insert part at an end to be inserted into the connector, and the cable insert part includes a plurality of protruding portions protruding out from one end of the conductor at two ends in the widthwise direction of the cable insert part; wherein the protruding portions are configured to protrude out from one end of the conductor as much as a predetermined gap so that the gap is formed between an extension line from one end of the conductor and an extension line from one end of the protruding portions; characterized in that the protruding portion is formed with a protrusion height that is higher than a height of a lead connected to the circuit board having the external connector; and the cable insert part further includes a reinforcing portion provided on at least part of surface of the protruding portion and configured to reinforce stiffness of the protruding portion. a circuit board, a connector on the circuit board and comprising a plurality of leads connected to the circuit board and made of an electrical conductive material; and a flat cable extending straight in a direction and having a front end that is insertable and connectable to the connector, the flat cable comprising: a plurality of conductors made of an electrical conductive material, and extending straight along a lengthwise direction of the flat cable, spaced apart a predetermined distance in a widthwise direction of the flat cable; and a cable body made of an insulating material, and extending straight along the lengthwise direction of the flat cable, wherein the conductors are mounted on at least one surface, the cable body includes a cable insert part at an end to be inserted into the connector, and the cable insert part includes a plurality of protruding portions protruding out from one end of the conductor at two ends in the widthwise direction of the cable insert part; a plurality of conductors made of an electrical conductive material, and extending straight along a lengthwise direction of the flat cable, spaced apart a predetermined distance in a widthwise direction of the flat cable; and a cable body made of an insulating material, and extending straight along the lengthwise direction of the flat cable, wherein the conductors are mounted on at least one surface, the cable body includes a cable insert part at an end to be inserted into the connector, and the cable insert part includes a plurality of protruding portions protruding out from one end of the conductor at two ends in the widthwise direction of the cable insert part; wherein the protruding portions are configured to protrude out from one end of the conductor as much as a predetermined gap so that the gap is formed between an extension line from one end of the conductor and an extension line from one end of the protruding portions; characterized in that the protruding portion is formed with a protrusion height that is higher than a height of a lead connected to the circuit board having the external connector; and the cable insert part further includes a reinforcing portion provided on at least part of surface of the protruding portion and configured to reinforce stiffness of the protruding portion.