A surface mount fuse and fuse element thereof are disclosed. The fuse element has a lead-free flat fuse, a flux layer, and a porous metal layer. The porous metal layer is bonded on one surface of the lead-free flat fuse through the flux layer. A part of the flux layer penetrates into the porous metal layer through capillary action, so the flux fills the pores of the first porous metal layer to distribute on the lead-free flat fuse evenly. When overcurrent occurs in the current loop and high temperature occurs, the flux layer helps the porous metal layer and the lead-free flat fuse to melt effectively, thereby interrupting the current loop in time.

A fuse element includes a low-melting-point metal plate, a first high-melting-point metal layer, and a second high-melting-point metal layer. The low-melting-point metal plate has a first main surface, a second main surface, a first side surface, and a second side surface. The first main surface and the second main surface face each other. The first side surface and the second side surface face each other and each connect the first main surface and second main surface. The first high-melting-point metal layer is disposed on the first main surface and second main surface. The second high-melting-point metal layer is disposed on the first side surface and second side surface. The fuse element has a cut-out portion in which at least a portion of the second high-melting-point metal layer is cut out.

A protective element includes: an insulating substrate; a heating element provided on a front surface side of the insulating substrate; an insulating layer covering the heating element; an intermediate electrode provided on the insulating layer; a fuse element mounted on the intermediate electrode; a cap member covering the front surface of the insulating substrate; and a flux. The cap member includes at least one protrusion that retains the flux and is provided facing the intermediate electrode. At least one end portion of the intermediate electrode extends beyond the fuse element. The at least one protrusion is provided at a position facing the fuse element which is mounted on the intermediate electrode and at a position facing the at least one end portion of the intermediate electrode at which the fuse element is not mounted, and retains the flux on the fuse element and at the end portion.