Fuse element, fuse device, and protection device

A fuse device comprising:

• an insulating substrate;
• a first electrode and a second electrode provided on a front surface of the insulating substrate;
• a fuse element;
• a heat-generating element provided on the front surface or a rear surface of the insulating substrate;
• an insulating material covering the heat-generating element;
• a heat-generating element lead-out electrode electrically connected with the fuse element and disposed to face the heat-generating element;
• and
• a cover member provided on the insulating substrate and covering the fuse element;
• wherein,
• the fuse element comprises a flat plate-shaped blowout section with no through-hole disposed between the first electrode and the second electrode, wherein a length of a width of the flat plate-shaped blowout section has a length greater than 100% and equal to or less than 200% of a length of a width of each of joining portions joining the first electrode and the second electrode to the flat plate-shaped blowout section;
• the fuse element is composed of a low melting-point metal layer and a high melting-point metal layer laminated on both surfaces of the low melting-point metal layer;
• a side surface of the fuse element which is joined to the first electrode and a side surface of the fuse element which is joined to the second electrode are coated with the high melting-point metal layer;
• side surfaces of the fuse element in a direction connecting the first electrode and the second electrode are not coated with the high melting-point metal layer, wherein the low melting-point metal layer is exposed on the side surfaces of the fuse element in the direction connecting the first electrode and the second electrode;
• the fuse element is connected to the first electrode and the second electrode via solder;
• leakage of the low melting-point metal layer from the side surface to a junction of the fuse element and the first electrode and to a junction of the fuse element and the second electrode does not occur;
• inflow of the solder to the low melting-point metal layer does not occur;
• the heat-generating element and the heat-generating element lead-out electrode are electrically connected;
• and
• the low melting-point metal layer and the solder provided between the fuse element and the first electrode is not in direct physical contact and the low melting point metal layer and the solder provided between the fuse element and the second electrode is not in direct physical contact.