JP6423384B2 - Protective element - Google Patents

Description

  The present invention relates to a fuse element for a protective element made of a composite metal material, and a protective element for an electric / electronic device using the fuse element.

  In recent years, with the rapid spread of small electronic devices such as mobile devices, small and thin protective elements mounted on a protection circuit for a power supply to be mounted are used. For example, a surface protection component (SMD) chip protection element is preferably used for the protection circuit of the secondary battery pack. These chip protection elements detect excessive heat generated by the overcurrent of the protected device, or respond to abnormal overheating of the ambient temperature, forcibly actuate the fuse by heating the built-in heater etc. under specified conditions. There are non-recoverable protection elements that interrupt the circuit. In order to protect the safety of the device, the protection element heats the resistance element by a signal current when an abnormality occurring in the device is detected, and the heat generation blows a fuse element (also called a fuse element) made of a soluble alloy. The circuit can be shut off by cutting the fuse element by overcurrent or the circuit can be cut off.

  The fuse element applied to such a protection element is, for example, as described in Patent Document 1, a lead element of a lead-free metal composite material, which is used when the protection element is surface-mounted on an external circuit board. It consists of an easily meltable low melting point metal material that can be melted at a soldering operation temperature, and a hardly fusible metal structure material that can be dissolved in a liquid phase low melting point metal material. There is a fuse element characterized in that a low-melting-point metal material that has been made into a liquid phase by a soldering operation is supported and held by a solid-phase metal structure material until the soldering operation is completed. The low melting point metal material and the metal structure material of the fuse element are fixed to each other, and the low melting point metal material that has become liquid phase by the heat of the soldering operation is not melted for a certain period of time with the solid phase metal structure material at the operation temperature. In this way, the fuse element is devised so that the fuse element can be joined to the electrode pattern of the protective element with a low-melting-point metal material in a liquid phase while adhering to and supporting by using interfacial tension. At least during the soldering operation, the shape of the fuse element is maintained to prevent the fuse element from malfunctioning at the soldering operation temperature. When this protective element is mounted on a protected device, the metal structure material of the fuse element is diffused or dissolved in the low-melting-point metal material, which is the medium, due to the heat of soldering. Or disappears easily by heating the heater of the built-in resistance heating element, and can be operated without interfering with fusing thereafter.

  Conventionally, the fusible alloy constituting the fuse element of the protection element described above has an exposed surface of a metal structural material made of Ag, Cu or an Ag alloy, Cu alloy on one side, and thus is susceptible to sulfur corrosion due to weakness to sulfur gas. In extreme cases, the fuse element may break during storage and transportation due to a small amount of outgassing from the packing material, or corrosion products such as silver or copper sulfide may extend between the electrode patterns of the protective element and connect to adjacent patterns. There was a problem that it was easy to short-circuit.

  The electrical resistance value of the protective element that functions to cut off the current of the power line is preferably as small as possible because there is less loss of electrical energy. In that respect, it is very convenient to have a low electric resistance material Ag, Cu or an Ag alloy, or a Cu alloy metal structure material in the fuse element. However, since metal structure materials such as Ag material and Cu material have a relatively high melting temperature and are not meltable at the operating temperature of the protective element, when they are not sufficiently melted or diffused into the low melting point metal material and remain in a thick film In addition, conventional fuse elements may require extra time for fusing or may cause fusing failure in extreme cases, and metal structures cannot be provided thick enough to reduce electrical resistance. It was. In addition, with the progress of miniaturization and thinning of protective element fuse elements and electrode substrates, when using thinner fuse elements, the metal structure material cannot be thickened, so the metal structure material has a low melting point in the liquid phase. When the fuse element is excessively diffused or dissolved in the metal material and thinned, and the fuse element is joined to the electrode pattern, the fuse element may be deformed, or the surface of the metal structure may be undulated. There was a drawback that would worsen. For this reason, when the fuse element is covered and covered with a cap-shaped lid in a later process, if the fuse element is significantly deformed, the lid cannot be mounted horizontally or may be displaced from the predetermined mounting position. This hinders the mounting work of the lid and causes assembly failure.

Japanese Patent Laying-Open No. 2015-079608

  Accordingly, an object of the present invention is proposed to solve the above-mentioned problems, and prevents the sulfidation corrosion of the fuse element of the protective element, and is a metal structure composed of Ag material, Cu material, or the like. An object of the present invention is to provide a fuse element that can increase the thickness of the material and reduce the fusing time, and to provide a protection element using the fuse element. In addition, a fuse element that is further adapted to the reduction in size and thickness of the protective element is realized.

  According to the present invention, an intermediate structure material made of a solid metal that easily diffuses or dissolves in a metal, a covering material made of a soluble metal on at least one surface of the intermediate structure material, and further soluble on the other surface of the intermediate structure material The intermediate structure material has a first melting temperature that exceeds the bonding operation temperature, the covering material has a second melting temperature that is lower than the intermediate structure material, A fuse element is provided in which the material melts at the joining operating temperature and has a third melting temperature that is less than or equal to the second melting temperature. The melting temperatures of the intermediate structural material, the covering material, and the bonding material are in the order of the first melting temperature> the second melting temperature> the third melting temperature in the order of higher temperatures.

  According to another aspect of the present invention, a protection element using the fuse element is provided. The protective element according to the present invention is a preparatory step of preparing the fuse element and an insulating substrate having a pattern electrode, a bonding flux applying step of applying a bonding flux to the insulating substrate, an insulating substrate coated with the bonding flux, or a pattern of the fuse element A mounting process in which an electrode and a bonding material are brought into contact with each other and placed on an insulating substrate, and an insulating substrate on which a fuse element is placed is melted at a bonding operation temperature of 183 ° C. or higher and lower than 400 ° C. A fusing flux applying process for applying a fusing flux for operation to the joined fuse element, and a packaging process for covering the fuse element on the insulating substrate coated with the fusing flux with a cap-like lid and packaging. . The fuse element according to the present invention is joined to a pattern electrode provided on the surface of an insulating substrate and used as a fuse element of a protection element. This fuse element is placed on an insulating substrate by bringing the bonding material of the fuse element to which a bonding flux has been applied in advance and the pattern electrode of the insulating substrate into contact with each other, and the patterning electrode is melted at the above-described bonding operation temperature. Are joined together. At that time, the molten bonding material bonds the fuse element and the pattern electrode. Since the intermediate structural material is kept solid at the bonding operation temperature, it is fixed to the pattern electrode by the liquid phase bonding material while partially diffusing or dissolving in the covering material and the bonding material while maintaining the shape of the fuse element. . Thereafter, a fusing flux is applied to the fuse element, and the top is covered with a cap-shaped lid and packaged to form a protective element. Thereafter, the protection element is mounted on a protection circuit such as a secondary battery, and is soldered at a maximum temperature of about 183 ° C. or more and 300 ° C. or less. With this soldering heat, the intermediate structure material of the fuse element built in the protective element is diffused or melted again into the coating material and bonding material, but it is mounted with the fuse element shape maintained without malfunction. it can.

  The protection element according to the present invention includes an insulating substrate, a plurality of pattern electrodes provided on the surface of the insulating substrate, and a fuse element electrically connected to the pattern electrode, and the fuse element is easily diffused or dissolved in metal. An intermediate structure material further comprising an intermediate structure material made of a solid metal, a covering material made of a soluble metal on at least one surface of the intermediate structure material, and a bonding material made of a soluble metal on the other surface of the intermediate structure material The material has a first melting temperature that exceeds the joining operation temperature, the covering material has a second melting temperature that is lower than the intermediate structural material, the joining material melts at the joining operation temperature, and A protective element having a third melting temperature equal to or lower than the second melting temperature is provided. This protective element may be provided with a resistance heating element on its insulating substrate as required.

  Since the fuse element of the present invention covers at least the upper and lower surfaces of an intermediate structural material made of Ag, Cu or an alloy thereof with a coating material and a bonding material that are difficult to sulfidize, discoloration and sulfidation corrosion of the fuse element can be prevented. In addition, since the upper and lower sides of the intermediate structural material are sandwiched between the erodible bonding material and the diffusion medium coating material, even if the metal structural material remains as a thick film, it promotes melt diffusion from both sides of the intermediate structural material And can be surely melted. Therefore, since the film thickness of the intermediate structure material of the fuse element can be made thicker than before, it contributes to lowering the electrical resistance of the protection element. The intermediate structural material is sandwiched between different coating materials and bonding materials, and the melting temperature of the coating material is set to be equal to or higher than the melting temperature of the bonding material. Since it melts into the pattern electrode of the insulating substrate and then the coating material melts, it prevents the fuse element plate from wavy or curled at the joining temperature of the bonding material even if the fuse element is thinned. This can contribute to further downsizing and thinning of the protective element. If this covering material is melted at the operating temperature of the fuse element, it does not necessarily have to be melted in the joining operation. If a coating material that does not melt in the joining operation is used, the fuse element plate surface is further difficult to deform.

  The fuse element of the present invention is placed on the insulating substrate by contacting the insulating substrate to which the bonding flux has been applied in advance or the pattern electrode of the fuse element and the bonding material, and melting the bonding material at the above-described bonding operation temperature. Bonded to the pattern electrode at once. The molten joining material joins the fuse element itself and the pattern electrode. Since the intermediate structural material maintains a solid state at the bonding operation temperature in the bonding process, the intermediate structure material melts or diffuses into the bonding material that is melted while maintaining the plate shape of the fuse element and the covering material that is the diffusion medium, while the liquid phase is in the liquid phase. It is fixed to the pattern electrode by the bonding material and melts at a predetermined operating temperature.

A fuse element 10 according to the present invention is represented, and the fuse element 10 is made of a three-layer composite metal material in which a covering material is laminated on an upper surface of an intermediate structural material and a bonding material is laminated on a lower surface. The perspective view which decomposed | disassembled the component member of the protection element which concerns on this invention is shown. It is the protection element 20 of Example 2 of this invention, (a) shows the top view which cut | disconnected the cap-shaped cover body along the dd line | wire of (b), (b) is D- of (a). A sectional view along line D is shown, and (c) shows a bottom view thereof. It is the protection element 30 of Example 3 of this invention, (a) shows the top view which cut | disconnected the cap-shaped cover body along the dd line | wire of (b), (b) is D- of (a). A sectional view along line D is shown, and (c) shows a bottom view thereof. It is the protection element 40 of Example 4 of this invention, (a) shows the top view which cut | disconnected the cap-shaped cover body along the dd line | wire of (b), (b) is D- of (a). A sectional view along line D is shown, and (c) shows a bottom view thereof.

  As shown in FIG. 1, a fuse element 10 according to the present invention includes an intermediate structural member 11 made of a solid metal that easily diffuses or dissolves in a metal, and a covering material 12 made of a soluble metal on at least one side of the intermediate structural member 11. And a joining material 13 made of a fusible metal on the other surface of the intermediate structural material 11, the intermediate structural material 11 has a first melting temperature exceeding the joining operation temperature, and the covering material 12 is The second melting temperature is lower than that of the intermediate structural material 11, and the bonding material 13 is melted at the bonding operation temperature and has a third melting temperature lower than the second melting temperature. To do.

  The intermediate structural material 11 of the fuse element 10 is made of a metal material that easily diffuses or dissolves into the solid phase or liquid phase of the covering material 12 and the bonding material 13 at the bonding operation temperature. At least during the bonding operation, the fuse element 10 It functions as a structural material that supports and holds the shape so as not to melt. The covering material 12 of the fuse element 10 covers the exposed surface of the intermediate structural material 11 and shields it from corrosive gas and moisture, and the fuse element 10 is blown together with the intermediate structural material 11 at a temperature lower than the second melting temperature. It functions as a structural material that holds it, and at a temperature equal to or higher than the second melting temperature, it has a function of forming a liquid phase and eroding the intermediate structural material 11 to make the fuse element 10 operable. As long as the covering material 12 can be melted at a predetermined fusing temperature of the fuse element 10, it does not necessarily have to be melted in the joining operation. The bonding material 13 of the fuse element 10 functions as a brazing material or a solder material for bonding the fuse element 10 to the pattern electrode provided on the insulating substrate of the protection element, and at the temperature equal to or higher than the third melting temperature 11. Has a function of allowing the fuse element 10 to operate. The bonding material 13 is melted at the predetermined fusing temperature of the fuse element 10 as well as being melted during the bonding operation.

  As the intermediate structural member 11, a diffusible solute metal capable of maintaining a solid at a joining operation temperature of 183 ° C. or higher and lower than 400 ° C., for example, Ag, Cu, or an alloy containing 50% by mass or more thereof can be suitably used. The covering material 12 provided on one surface of the intermediate structural material 11 is, for example, Sn or Sn alloy (for example, Sn—Ag alloy, Sn—Bi alloy, Sn—Cu alloy, Sn—Zn alloy, Sn—Sb alloy, etc. ) Is preferred. Furthermore, the bonding material 13 provided on the other surface of the intermediate structural material 11 is, for example, a Sn—Ag alloy, a Sn—Bi alloy, a Sn—Cu alloy, a Sn—Zn alloy, a Sn—Sb alloy, a Sn—Ag—Bi alloy. , Sn-Ag-Cu alloy, Sn-Ag-In alloy, Sn-Zn-Al alloy, Sn-Zn-Bi alloy, Zn-Al alloy, or Au, Ni, Ge, Ga, Mg, P Added alloys can be used. The means for providing the covering material 12 and the bonding material 13 on the surface of the intermediate structural material 11 is not particularly limited as long as the covering material 12 and the bonding material 13 can be fixed to the intermediate structural material 11. For example, the covering material 12 and the bonding material 13 can be fixed to the surface of the intermediate structural material 11 by means such as cladding, plating, melt coating, pressure bonding, and adhesion with a fusible resin such as rosin. In addition, the fuse element according to the present invention may be a composite metal material in which a bonding flux is previously incorporated in the laminated interface of the bonding material 12.

  The protection element according to the present invention is manufactured using the fuse element 10 described above. As long as the protective element of FIGS. 2 to 5 can be manufactured, the manufacturing method is not limited to a specific method. For example, a preparation step of preparing the fuse element 10 and an insulating substrate having a pattern electrode, a bonding flux applying step of applying a bonding flux to the fuse element or the insulating substrate, a pattern electrode of the insulating substrate to which the bonding flux is applied, and the fuse element A mounting step in which the bonding material is placed in contact with each other and placed on the insulating substrate, and the insulating substrate on which the fuse element is placed is melted at a bonding work temperature of 183 ° C. or more and less than 400 ° C. to collectively join the pattern electrodes. It is assembled by a bonding process, a fusing flux application process for applying an operating fusing flux to the joined fuse elements, and a packaging process for covering the fuse element on the insulating substrate coated with the fusing flux with a cap-shaped lid and packaging. . For example, the fuse element 10 to which the bonding flux is applied in advance is placed on the insulating substrate 21 with the bonding material 13 and the pattern electrode 22 of the insulating substrate in contact with each other, and the maximum temperature is a temperature of 183 ° C. or higher and lower than 400 ° C. The bonding material 13 is melted through a reflow furnace set in a profile, thereby being collectively bonded to the pattern electrode 22. The bonding material 13 melted at this time is interdiffused into the intermediate structure material 11 and the pattern electrode 22 to bond the intermediate structure material 11 and the pattern electrode 22 together. Since the intermediate structural member 11 maintains a solid at the reflow temperature, the intermediate structural member 11 is bonded to the pattern electrode 22 while maintaining its shape. Thereafter, a fusing flux for operation is applied to the joined fuse element 10, and the fuse element 10 on the insulating substrate is covered with a cap-like lid 25 and packaged to form a protective element.

  As the heating means applied to the above-described bonding process, any method and apparatus may be used as long as the fuse elements placed on the insulating substrate can be collectively heated to the working temperature. For example, heating using a high-temperature batch furnace, heating using a hot plate, heating using a reflow furnace, and the like can be suitably used. In addition, the bonding flux application process applies the bonding flux in advance for the purpose of activating the bonding surface by removing the oxide film on the surface of the metal material of the pattern electrode and the fuse element under the heating of the bonding process. As long as the metal surface of the fuse element can be activated, other activation means can be used instead, and the bonding flux application step can be omitted or replaced. For example, when a reflow furnace using an activated gas such as a hydrogen reduction furnace or a formic acid reduction furnace is used, the bonding flux application step may be omitted. Also, when the bonding flux is built in the laminated surface of the fuse element in advance, the bonding flux application process may be omitted.

  The protection element according to the present invention is a protection element using the fuse element. As shown in FIG. 2, the insulating substrate 21, a plurality of pattern electrodes 22 provided on the surface of the insulating substrate 21, and the pattern electrodes 22 and a cap-like lid 25 covering the top of the fuse element 10, and the fuse element 10 includes an intermediate structural member 11 made of a solid metal that easily diffuses or dissolves in metal, The intermediate structural member 11 is provided with a covering material 12 made of a soluble metal on at least one surface and a bonding material 13 made of a soluble metal on the other surface of the intermediate structural member 11, and the intermediate structural member 11 has a bonding work temperature. The covering material 12 has a second melting temperature lower than that of the intermediate structural material 11, and the bonding material 13 has a bonding work temperature. In it melted, and characterized by having a third melting temperature below the second melting temperature.

  The insulating substrate of the protection element of the present invention is made of a heat-resistant insulating substrate, for example, a glass epoxy substrate, a BT (Bismaleimide Triazine) substrate, a Teflon (registered trademark) substrate, a ceramic substrate, a glass substrate, etc., on one side of the insulating substrate. A resistance heating element may be provided as necessary. This resistance heating element is provided with an insulating coating as required. The cap-shaped lid is only required to cover the insulating substrate and the upper part of the fuse element and hold a desired cavity space, and is not limited in shape and material. For example, the cap-shaped lid includes a dome-shaped resin film material. Plastic materials, ceramic materials, etc. can be suitably used.

  The fuse element 10 of the present invention is bonded to the protective element by bringing the bonding material 13 and the pattern electrode provided on the insulating substrate of the protective element into contact with each other to melt the bonding material at a predetermined bonding operation temperature. The protective element of the present invention is then soldered and mounted again at an arbitrary temperature on a circuit such as an electric device. During this time, a diffusion layer in which the respective metal materials are diffused or dissolved is formed at the interface between the intermediate structural material 11 of the fuse element and the covering material 12 or the bonding material 13. Does not affect the fusing operation.

  As shown in FIG. 1, the fuse element 10 according to the first embodiment of the present invention includes an intermediate structural member 11 made of Ag having a thickness of 5 μm and a first melting temperature of 962 ° C., and an upper surface of the intermediate structural member 11. A coating material 12 having a second melting temperature of 232 ° C. made of Sn having a thickness of 3 μm and a third melting temperature made of an Sn-3Ag-0.5Cu alloy having a thickness of 87 μm are further formed on the lower surface of the intermediate structural material 11. It is comprised with the composite material which provided the joining material 13 of 219 degreeC by electroplating.

  The protection element according to the present invention is a protection element using the fuse element 10 of the first embodiment. As shown in FIG. 2, the fuse element 10 is composed of the fuse element 10 previously applied with a bonding flux (not shown). The bonding material 13 and the pattern electrode 22 of the insulating substrate 21 are placed in contact with each other and placed on the insulating substrate 21, and the temperature profile is peaked at a preheating temperature of 180 to 190 ° C. for a residence time of 45 seconds and a residence time of 225 ° C. or higher for 30 seconds. After the joining material 13 is melted through a reflow furnace set at a temperature of 235 ° C. and joined together to the pattern electrode 22, a fusing flux is applied to the joined fuse element 10, and the fuse element on the insulating substrate is made of a heat-resistant plastic. Covered with a lid 25, the cap-shaped lid 25 and the insulating substrate 21 are fixed with an epoxy resin. As a protective element.

  As shown in FIG. 3, the protection element 30 of Example 2 according to the present invention includes an insulating substrate 21 made of alumina / ceramic, and a plurality of Ag alloy pattern electrodes 22 provided on the upper and lower surfaces of the insulating substrate 21, A fuse element 10 electrically connected to the pattern electrode 22 on the upper surface of the insulating substrate 21 and a cap-shaped lid 25 made of a liquid crystal polymer covering the upper portion of the fuse element 10 and fixed to the insulating substrate 21 are provided. The intermediate structural member 11 having a first melting temperature of 962 ° C. made of Ag having a thickness of 5 μm, and the covering member 12 having a second melting temperature of 232 ° C. made of Sn having a thickness of 3 μm on the upper surface of the intermediate structural member 11. And a composite metal material provided with a bonding material 13 having a third melting temperature of 219 ° C. made of an Sn-3Ag-0.5Cu alloy having a thickness of 87 μm on the lower surface of the intermediate structural material 11. Becomes, are bonded to the pattern electrode 22 by melting the bonding material 13. The pattern electrode 22 has a half through hole 23 of Ag alloy that electrically connects the pattern electrodes 22 on the upper and lower surfaces of the substrate.

  The protection element 30 according to the third embodiment of the present invention is a protection element using the fuse element 10 according to the first embodiment. As shown in FIG. 4, an insulating substrate 31 made of alumina / ceramic and the insulating substrate 31 A plurality of Ag alloy pattern electrodes 32 provided on the upper and lower surfaces, a resistance heating element 34 electrically connected to the pattern electrodes 32 and provided on the lower surface of the insulating substrate 31, and an electric connection to the pattern electrodes 32 on the upper surface of the insulating substrate 31 The fuse element 10 and a cap-shaped lid 35 made of a liquid crystal polymer that covers the upper portion of the fuse element 10 and is fixed to the insulating substrate 31. The fuse element 10 is a first melt made of Ag having a thickness of 5 μm. An intermediate structural member 11 having a temperature of 962 ° C., and a covering member 12 having a second melting temperature of 232 ° C. made of Sn having a thickness of 3 μm on the upper surface of the intermediate structural member 11; Further, the intermediate structure material 11 is made of a composite metal material provided with a bonding material 13 having a third melting temperature of 219 ° C. made of an Sn-3Ag-0.5Cu alloy having a thickness of 87 μm. It is melted and joined to the pattern electrode 32. The pattern electrode 32 has a half through hole 33 of Ag alloy that electrically connects the pattern electrodes 32 on the upper and lower surfaces of the substrate. Although not shown, the surface of the resistance heating element 34 is subjected to glass overglazing.

  The protection element 40 according to the fourth embodiment of the present invention is a protection element obtained by modifying the protection element 30. As shown in FIG. 5, an insulating substrate 41 made of alumina / ceramic, a plurality of Ag alloy pattern electrodes 42 provided on the upper and lower surfaces of the insulating substrate 41, and the upper surface of the insulating substrate 41 electrically connected to the pattern electrode 42. A resistance heating element 44 provided on the insulating substrate 41; a fuse element 10 that is in contact with the resistance heating element 44 and electrically connected to the pattern electrode 42 on the upper surface of the insulating substrate 41; The fuse element 10 includes an intermediate structural member 11 having a first melting temperature of 962 ° C. made of Ag having a thickness of 5 μm, and a thickness of 3 μm on the upper surface of the intermediate structural member 11. From the Sn-3Ag-0.5Cu alloy having a thickness of 87 μm on the lower surface of the intermediate material 11 and the covering material 12 having a second melting temperature of 232 ° C. made of Sn That the third melting temperature is a composite metal material provided with the bonding material 13 of 219 ° C., it is bonded to the pattern electrode 42 by melting the bonding material 13. The pattern electrode 42 has a half through hole 43 of Ag alloy that electrically connects the pattern electrodes 42 on the upper and lower surfaces of the substrate. Although not shown, the surface of the resistance heating element 44 of Example 4 is glass overglazed.

  In the protective elements of Examples 2 to 4, the wiring means for electrically connecting the pattern electrodes on the upper and lower surfaces of the insulating substrate is replaced with conductor through holes penetrating the substrate instead of the half through holes 23, 33 and 43. The surface wiring may be changed to a planar electrode pattern.

  The fuse element of the present invention can be incorporated and mounted in a protective element by whole heating and melting such as reflow. Furthermore, the protection element of the present invention using this fuse element is soldered and mounted on an electric circuit board by reflow soldering together with other surface mount components, and can be used for a protection device for a secondary battery such as a battery pack.

10 ... fuse element,
11: Intermediate structural material,
12 ... covering material,
13: bonding material,
20, 30, 40 ... protection element,
21, 31, 41 ... insulating substrate,
22, 32, 42 ... pattern electrodes,
23, 33, 43 ... Half through hole,
34, 44... Resistance heating element,
25, 35, 45... Lid.

Claims (9)

An intermediate structure material made of a solid metal that easily diffuses or dissolves in a metal, a covering material made of a soluble metal on at least one side of the intermediate structure material, and a joint made of a soluble metal on the other surface of the intermediate structure material The intermediate structure material is made of Ag, Cu or an alloy containing 50 mass% or more of these, and has a first melting temperature exceeding a joining operation temperature, and the covering material is more than the intermediate structure material. A fuse element having a second melting temperature having a low melting temperature, the bonding material being melted at the bonding operation temperature and having a third melting temperature equal to or lower than the second melting temperature. . The fuse element according to claim 1, wherein the covering material is made of Sn or an Sn alloy. The bonding material is Sn—Ag alloy, Sn—Bi alloy, Sn—Cu alloy, Sn—Zn alloy, Sn—Sb alloy, Sn—Ag—Bi alloy, Sn—Ag—Cu alloy, Sn—Ag—In alloy. , Sn—Zn—Al alloy, Sn—Zn—Bi alloy, Zn—Al alloy or at least one metal material selected from the group of alloys obtained by further adding Au, Ni, Ge, Ga, Mg, P to the alloy The fuse element according to claim 1 or 2 , wherein the fuse element is used. The fuse element according to any one of claims 1 to 3 , wherein the joining operation temperature is 183 ° C or higher and lower than 400 ° C. An insulating substrate; a plurality of pattern electrodes provided on a surface of the insulating substrate; a fuse element electrically connected to the pattern electrode; and a lid that covers an upper portion of the fuse element, wherein the fuse element includes Ag, An intermediate structure material made of Cu or an alloy containing 50% by mass or more of these, a covering material made of a soluble metal on at least one surface of the intermediate structure material, and a soluble metal on the other surface of the intermediate structure material The intermediate structure material has a first melting temperature that exceeds a bonding operation temperature, the covering material has a second melting temperature lower than the intermediate structure material, The bonding material is melted at the bonding work temperature and has a third melting temperature equal to or lower than the second melting temperature. The protection element according to claim 5 , wherein the insulating substrate further includes a resistance heating element. The protection element according to claim 6 or 7 , wherein the covering material is made of Sn or an Sn alloy. The bonding material is Sn—Ag alloy, Sn—Bi alloy, Sn—Cu alloy, Sn—Zn alloy, Sn—Sb alloy, Sn—Ag—Bi alloy, Sn—Ag—Cu alloy, Sn—Ag—In alloy. , Sn—Zn—Al alloy, Sn—Zn—Bi alloy, Zn—Al alloy or at least one metal material selected from the group of alloys obtained by further adding Au, Ni, Ge, Ga, Mg, P to the alloy protection device according to any one of claims 5 to 7, characterized in that with. The protective element according to any one of claims 5 to 8 , wherein the joining operation temperature is 183 ° C or higher and lower than 400 ° C.

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