Fuse alloy and protection element

Abstract

To provide a protection element which has a reflow-resistant property, can maintain a low electric resistance as well after a reflow, and has a lead-free fuse element formed of a single alloy.SOLUTION: The fuse element is formed of a single alloy material as an Sn-Ag-Cu three-dimensional alloy. A flux for assisting a welding operation is applied on the fuse element. The silver content is 20-30 mass%, the copper content is 2-10 mass%, and the balance is Sn.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a fuse alloy and a protection element for electric and electronic devices.

Background Art

[0002] In recent years, with the rapid spread of small electronic devices such as mobile devices, protection elements mounted in the protection circuits of the power supplies installed therein are also of a small and thin type. For the protection circuit of a secondary battery pack, a protection element of a surface mount component (SMD) as described in Patent Document 1, for example, is preferably used. Among these protection elements, there is a non-return type protection element that detects abnormal states such as excessive heat generation and overvoltage caused by an overcurrent of a device to be protected, or senses abnormal overheating of the ambient temperature, and operates a fuse under predetermined conditions to cut off an electric circuit. In order to ensure the safety of the device, when the protection circuit detects an abnormality occurring in the device, the protection element generates heat in a resistance element by a signal current, and the heat melts a fuse element made of a fusible alloy material to cut off the circuit, or melts the fuse element by an overcurrent to cut off the circuit.

[0003] For example, as described in Patent Document 1 and the like, there is a protection element using a fuse element formed by laminating a low melting point metal material that melts at a soldering temperature and a metal structural material soluble in the low melting point metal material. The fuse element of this protection element adheres a low melting point metal material liquefied in a soldering operation to a solid-phase metal structural material at that temperature by interfacial tension and supports and holds it so as not to be melted for a certain period of time, thereby maintaining the shape of the fuse element at least during the soldering operation and preventing the fuse element from malfunctioning due to reflow soldering. When the soldering is completed and the circuit protection element is mounted on the circuit to be protected, the metal structural material of the fuse element diffuses or dissolves into the low melting point metal material as a medium due to the heat of soldering and becomes thinner, so that it easily disappears due to abnormal overheating of the installation environment or heater heating of a built-in resistance heating element, and thereafter it operates without preventing melting.

Prior Art Documents

Patent Documents

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-079608 [Summary of the Invention] [Problems to be Solved by the Invention]

[0005] The protection element used in the secondary battery is a surface-mounted component. Therefore, the fuse element used in the protection element needs to be prevented from melting during reflow soldering, and in particular, it needs to withstand two high-temperature reflow soldering processes for double-sided mounting. Conventional reflow-resistant fuse elements using lead-free solder alloys melt after passing through a solid-liquid coexistence temperature zone where the solid phase and the liquid phase coexist before reaching the temperature at which the fuse element becomes completely liquid. However, when the protection element is surface-mounted on the circuit board by reflow soldering, there is a problem that the fuse element deforms in the solid-liquid coexistence temperature zone. A flux for ensuring the fusing operation is applied to the fuse element. Usually, near the operating temperature, the flux liquefies and becomes easy to flow, but it is important to retain the required amount of flux on the fuse element until the fuse operation is completed. However, in the deformed fuse element, the flux may leak from the deformed part of the fuse element before the fuse operates, which may interfere with stable operation.

[0006] In general, for the fuse element used in the protection element, from the viewpoints of coping with high current and standby energy loss of the rechargeable battery, it is preferable to use a material with as low an electrical resistance value as possible. However, the solder alloys and metal elements available for fuse elements with a lead-free composition are limited. Conventionally, there have been extremely few single-composition easily fusible alloys or metal materials that have reflow resistance and simultaneously satisfy the desired low electrical resistance value and have a slight impact on the environment and the human body, and there has been no practical one.

[0007] As a lead-free solder alloy, Sn-based alloys, particularly ternary Sn-Ag-Cu alloys, are representative. However, in this ternary Sn-Ag-Cu alloy, it has not been possible to achieve reflow resistance that can withstand high-temperature reflow soldering even in lead-free industry-academia-government joint projects such as NEDO, and despite the efforts of solder manufacturers at home and abroad, its realization has been extremely difficult.

[0008] The present invention has been proposed to solve the above problems, and in a circuit protection element, it aims to provide a new fuse element made of a single alloy that has reflow resistance and can maintain a low electrical resistance even after reflow, and at the same time has extremely little impact on the environment and the human body, and a protection element equipped with such a fuse element.

Means for Solving the Problems

[0009] According to the present invention, there is provided a protection element comprising an insulating substrate, a first electrode and a second electrode provided on the insulating substrate, a fuse element electrically connecting at least between the first electrode and the second electrode, and a flux assisting the fusing operation of the fuse element, wherein the fuse element is made of a ternary Sn-Ag-Cu alloy, and its silver content is 20 to 30% by mass, its copper content is 2 to 10% by mass, and the balance is composed of Sn. The fuse element may contain trace elements (inevitable impurities) that are inevitable in metallurgy. On the other hand, the fuse element may contain a small amount of reducing elements such as phosphorus, zinc, aluminum, magnesium, nickel, indium, gallium, germanium, cobalt, etc., for example, less than 0.001% by mass (including 0% by mass). It is preferable that the fuse element does not contain reducing elements. Also, the fuse element may contain a small amount of elements other than reducing elements, for example, less than 1% by mass.

[0010] The protection element of the present invention may further be provided with a heating element on the insulating substrate as required, and be energized to heat the fuse element so that it can perform a fusing operation when necessary. That is, it includes an insulating substrate, a first electrode and a second electrode provided on the insulating substrate, a heating element that generates heat when energized, an energizing electrode provided for energizing the heating element, a fuse element that electrically connects between the first electrode, the second electrode, and the energizing electrode, and a flux that assists the fusing operation of the fuse element. The fuse element is made of a ternary alloy of Sn-Ag-Cu, and is characterized in that its silver content is 20 to 30% by mass, its copper content is 2 to 10% by mass, and the balance is composed of Sn. The protection element is configured to be able to energize the heating element of the insulating substrate as required and heat the fuse element so that it can perform a fusing operation when necessary.

[0011] The fuse element of the present invention can be used as a reflow-resistant fuse element with a single alloy material even though it is an alloy having a solid-liquid coexistence temperature range by using the alloy within the above-described alloy composition range. By suppressing the deformation of the fuse element even after reflow, it is possible to maintain a low electrical resistance, prevent the loss of flux that assists the fusing operation of the fuse element, and retain the flux. The Sn-Ag-Cu ternary alloy itself is a well-known alloy system, but a remarkable effect is obtained when a Sn-Ag-Cu ternary alloy with a specific composition is applied as the fuse element. The fuse element has a solidus temperature of 217°C, which is lower than the general reflow temperature, but has a liquidus temperature of around 380°C and can satisfy the reflow resistance. By setting the silver content to 20 to 30% by mass, adding 6 ± 4% by mass of copper, and the balance being tin, the solid-phase residual rate during reflow increases, thereby improving the reflow resistance compared to the conventional case. Further, the Sn-Ag-Cu ternary alloy constituting the fuse element preferably has a silver content of 22% by mass or more and 25% by mass or less, and preferably has a copper content of 4% by mass or more and 8% by mass or less. With such a preferable configuration, the solid-phase residual rate during reflow can be further improved to improve the reflow resistance, and on the other hand, since the liquidus line does not rise too much, more excellent fusing characteristics can be exhibited. Here, the solid-phase residual rate refers to the ratio of the solid phase to the liquid phase at the corresponding temperature. In the case of the fuse element, the solid-phase residual rate increases, but the liquidus line does not rise, so the deformation resistance and fusing property are extremely good. Although the reason for this has not been fully elucidated, it is presumed that by using the above alloy material within the composition range for the fuse element, the heat-resistant shape stability is improved by precipitation strengthening or crystallization strengthening of intermetallic compounds or the like of any of the metal elements tin, silver, and copper constituting the alloy. The fuse element may be provided with a bonding metal layer on a part or all of the surface on the side facing the electrode surface to be bonded for the purpose of bonding the fuse element to a desired electrode provided on the insulating substrate as required. As the bonding metal layer, any alloy material, solder material, brazing material, or metal material may be used as long as its melting temperature is lower than that of the fuse element.

Advantages of the Invention

[0012] According to the protection element according to an embodiment of the present disclosure, the fuse element is made of a single alloy with less impact on the environment and the human body, has reflow resistance, suppresses deformation of the fuse element even after reflow, maintains low electrical resistance, and prevents the flux applied on the fuse element from flowing out and holds the flux.

Brief Description of the Drawings

[0013]

Figure 1

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Figure 8

Mode for Carrying Out the Invention

[0014] According to one aspect of the present invention, there is provided a protection element comprising an insulating substrate, a first electrode and a second electrode provided on the insulating substrate, a fuse element electrically connecting at least between the first electrode and the second electrode, and a flux assisting the fusing operation of the fuse element. The fuse element is made of a ternary alloy of Sn-Ag-Cu, and is characterized in that its silver content is 20 to 30% by mass, its copper content is 2 to 10% by mass, and the balance is composed of Sn. The protection element is a protection element applicable to surface mounting. By using the fuse element within the above-described alloy composition range, the fuse element can be used as a single alloy material with reflow resistance, and by suppressing deformation of the fuse element even after reflow, it is possible to maintain a low electrical resistance and prevent loss of the flux assisting the fusing operation of the fuse element and hold the flux. For the purpose of joining the fuse element to the first electrode and the second electrode provided on the insulating substrate as required, a joining metal layer may be provided on a part or all of the fuse element plane on the side facing the electrode surface for joining the fuse element. This joining metal layer may be made of any alloy material, solder material, brazing material or metal material as long as its melting temperature is lower than that of the fuse element. For example, there are solder alloys such as Bal.Sn-3.0Ag-0.5Cu (the numerical values are in mass%, Bal. is the balance) and Bal.Sn-0.75Cu (the numerical values are in mass%, Bal. is the balance) as solder alloys. These joining alloy layers may contain trace elements (inevitable impurities) inevitable in metallurgy. Further, the joining alloy layer may contain a trace amount of reducing elements such as phosphorus, zinc, aluminum, magnesium, nickel, indium, gallium, germanium, cobalt, etc., for example, less than 0.001% by mass (including 0% by mass). It is preferable that the joining alloy layer does not contain reducing elements. Further, the joining alloy layer may contain a trace amount of elements other than reducing elements, for example, less than 1% by mass.

[0015] According to another embodiment of the present invention, there is provided a protection element comprising an insulating substrate, a first electrode and a second electrode provided on the insulating substrate, a heating element that generates heat upon energization, an energizing electrode provided for energizing the heating element, a fuse element that electrically connects between the first electrode, the second electrode, and the energizing electrode, and a flux that assists in the fusing operation of the fuse element. The fuse element is made of a ternary alloy of Sn-Ag-Cu, with a silver content of 20 to 30% by mass, a copper content of 2 to 10% by mass, and the balance being Sn. The protection element is configured to be able to energize the heating element on the insulating substrate as needed, and to heat the fuse element to perform a fusing operation when necessary. The fuse element of the present invention can be used as a reflow-resistant fuse element with a single alloy material by using the alloy composition range described above. By suppressing deformation of the fuse element even after reflow, it is possible to maintain a low electrical resistance and prevent loss of the flux that assists in the fusing operation of the fuse element, and to hold the flux. For the purpose of joining the fuse element to the first electrode, the second electrode, and the energizing electrode provided on the insulating substrate as needed, a bonding metal layer may be provided on part or all of the fuse element plane on the side facing the electrode surface for bonding the fuse element. The bonding metal layer may be made of any alloy material, solder material, brazing material, or metal material as long as its melting temperature is lower than that of the fuse element. For example, there is a solder alloy of Bal.Sn-3.0Ag-0.5Cu (the numerical values are in mass%, and Bal. is the balance) as a solder alloy.

[0016] A cap-shaped lid that covers the fuse element and the flux and is fixed to the insulating substrate may be attached to the protection element according to an embodiment of the present invention. The first electrode and the second electrode or the energizing electrode may be electrically connected to pad electrodes provided on the opposite side of the insulating substrate with the insulating substrate interposed therebetween for connection to external components. Any method may be used for the means of the electrical connection as long as it can be electrically connected. For example, surface wiring, through holes (including vias and half-through holes) may be used.

[0017] The bonding metal layer according to an embodiment of the present invention may be provided by previously bonding and laminating with a fuse element, a clad, etc. integrally. In the case of the above, during the bonding operation, it is directly placed on the electrode so that the bonding metal layer surface of the fuse element faces the electrode surface, and the fuse element and the electrode material can be easily bonded by heating as it is to melt the bonding metal layer. Further, a solder paste may be applied to a required portion of the fuse element during the bonding operation, and the solder paste may be melted to form a bonding metal layer, and at the same time, the fuse element and the electrode material may be bonded. In other words, the fuse element of the present invention is used by being bonded to an external electrode, but a bonding metal layer made of a metal material having a liquidus temperature lower than that of the fuse element may be further provided on the surface on the side where the electrode is bonded. Alternatively, the fuse element of the present invention may further be provided with a bonding metal layer made of a metal material having a liquidus temperature lower than that of the fuse element only at the bonding portion where the fuse element and the electrode are bonded. The bonding metal layer only needs to be able to bond the fuse element to the electrode, and may have a smaller film thickness (or volume or cross-sectional area) compared to the thickness (or volume or cross-sectional area) of the fuse element. The bonding metal layer is preferably composed of an alloy material having the same constituent elements as the alloy material constituting the fuse element (that is, an Sn-Ag-Cu alloy).

[0018] An example of a method for bonding a fuse element, which is a single alloy material according to an embodiment of the present invention, to each electrode on an insulating substrate will be described. Note that the bonding method between the fuse element and each electrode is not limited to these. For example, the fuse element and each electrode may be bonded to each other by a liquefied metal layer, a solder paste, or a solder reflow by passing them through a reflow furnace. In this case, the peak temperature of the reflow furnace is preferably 220°C to 240°C. Further, the fuse element and each electrode may be bonded by ultrasonic bonding using an ultrasonic horn, laser bonding using a semiconductor laser, a green laser, a YAG laser, or a UV laser, resistance welding, or a conductive adhesive. Alternatively, the fuse element in a molten state may be injected or dropped onto the electrodes using a dispenser to join the fuse element and each electrode. Alternatively, after printing a paste onto the electrodes using metal mask printing, the paste may be passed through a reflow furnace to form the fuse element.

[0019] The fuse element according to an embodiment of the present invention is made of a single alloy with low electrical resistance that has a slight impact on the environment and the human body, can withstand several reflow soldering operations, and can prevent deformation of the same fuse element even after reflow, thereby preventing the loss of flux that assists the fusing operation of the fuse element and retaining the flux.

Example

[0020] As shown in FIG. 1, the protection element 10 of Example 1 according to the present invention includes an alumina ceramic insulating substrate 11, a first electrode 12 and a second electrode 13 made of a silver alloy provided on the insulating substrate 11, a fuse element 16 that electrically connects at least between the first electrode 12 and the second electrode 13, and a flux that assists the fusing operation of the fuse element 16. The fuse element 16 is characterized by being composed of a flat plate of a ternary alloy of Bal.Sn-30Ag-10Cu (the numerical values are mass%, and Bal. is the balance) with a flux (not shown) applied to the surface. For the purpose of soldering the fuse element 16 to the first electrode 12 and the second electrode 13 provided on the insulating substrate 11 as needed, a bonding metal layer (not shown) may be provided on a part or all of the fuse element plane on the side facing the electrode surfaces of the first electrode 12 and the second electrode 13 to which the fuse element 16 is bonded. This bonding metal layer is composed of Bal.Sn-3.0Ag-0.5Cu (the numerical values are mass%, and Bal. is the balance) of a solder alloy whose melting temperature is lower than that of the fuse element. A cap-shaped cover 100 made of a liquid crystal polymer that covers the fuse element 16 and the flux and is fixed to the insulating substrate 11 is attached to the protection element 10. The first electrode 12 and the second electrode 13 are connected by through holes to pad electrodes 110 provided on opposite surfaces with the insulating substrate 11 interposed therebetween for connection to external components.

[0021] As shown in FIG. 2, the protection element 20 according to the second embodiment of the present invention includes an alumina ceramic insulating substrate 21, a first electrode 21 and a second electrode 23 made of silver alloy provided on the insulating substrate 21, and a heating element 24 provided on the insulating substrate 21 and composed of a resistor that generates heat by energization so that the fuse can operate when necessary. A current-carrying electrode 25 made of silver alloy provided for energizing the heating element 24, a fuse element 26 that electrically connects between the first electrode 22, the second electrode 23, and the current-carrying electrode 25 and is provided on a substrate surface different from the installation surface of the heating element 24, and a flux that assists the fusing operation of the fuse element 26. The fuse element 26 is characterized in that it is composed of a flat plate of a ternary alloy of Bal.Sn-30Ag-10Cu (the numerical values are mass%, and Bal. is the balance) with a flux (not shown) applied to the surface. A cap-shaped cover 200 made of liquid crystal polymer is attached to the protection element 20 so as to cover the fuse element 26 and the flux and is fixed to the insulating substrate 21. The first electrode 22, the second electrode 23, and the current-carrying electrode 25 are connected by through holes to pad electrodes 210 provided on the opposite side across the insulating substrate 21 for connection to external components.

[0022] As shown in FIG. 3, the protection element 30 according to Example 3 of the present invention includes an insulating substrate 31 made of alumina ceramic, a first electrode 32 and a second electrode 33 made of a silver alloy provided on the insulating substrate 31, and a heating element 34 provided on the insulating substrate 31 and composed of a resistor that generates heat by energization so that the fuse can operate when necessary. An energizing electrode 35 made of a silver alloy provided for energizing the heating element 34, a fuse element 36 that electrically connects between the first electrode 32, the second electrode 33, and the energizing electrode 35, and is provided on a substrate surface different from the installation surface of the heating element 34, and a flux for assisting the fusing operation of the fuse element 36. The fuse element 36 is composed of a flat plate of a ternary alloy of Bal.Sn-20Ag-2Cu (the numerical value is mass%, Bal. is the balance) with a flux (not shown) applied to the surface. On the plane of the flat plate facing the first electrode 32, the second electrode 33, and the energizing electrode 35, a bonding metal layer 37 made of Bal.Sn-3.0Ag-0.5Cu (the numerical value is mass%, Bal. is the balance) of a solder alloy having a liquidus temperature lower than that of the fuse element 36 and a thinner thickness is further provided by cladding. The first electrode 32, the second electrode 33, and the energizing electrode 35 are electrically connected through through-holes to pad electrodes 310 provided on the opposite side across the insulating substrate 31 for connection to external components. A cap-shaped cover 300 made of liquid crystal polymer is attached to the protection element 30 so as to cover the fuse element 36 and the flux and is fixed to the insulating substrate 31.

[0023] As shown in Fig. 4, the protection element 40 according to Example 4 of the present invention includes an alumina ceramic insulating substrate 41, a first electrode 42 and a second electrode 43 made of a silver alloy provided on the insulating substrate 41, and a heating element 44 provided on the insulating substrate 41 and composed of a resistor that generates heat by energization so that the fuse can operate when necessary. An energization electrode 45 made of a silver alloy provided for energizing the heating element 44, an electrical connection between the first electrode 42, the second electrode 43, and the energization electrode 45, and a fuse element 46 provided on a substrate surface different from the installation surface of the heating element 44. A flux for assisting the fusing operation of the fuse element 46 is provided. The fuse element 46 is composed of a flat plate of a ternary alloy of Bal.Sn-20Ag-10Cu (the numerical values are mass%, Bal. is the remainder) with a flux (not shown) applied to the surface. A joining solder alloy layer 47 made of Bal.Sn-3.0Ag-0.5Cu (the numerical values are mass%, Bal. is the remainder) of a solder alloy having a liquidus temperature lower than that of the fuse element 46 is further provided on each joining surface with the first electrode 42, the second electrode 43, and the energization electrode 45. The first electrode 42, the second electrode 43, and the energization electrode 45 are electrically connected between each other with the joining metal layer 47 interposed therebetween. A cap-shaped cover 400 made of a liquid crystal polymer is attached to the protection element 40 so as to cover the fuse element 46 and the flux and is fixed to the insulating substrate 41. The first electrode 42, the second electrode 43, and the energization electrode 45 are connected to pad electrodes 410 provided on the opposite side with the insulating substrate 41 interposed therebetween for connection to external components through through-holes.

[0024] As shown in FIG. 5, the protection element 50 according to Example 5 of the present invention includes an insulating substrate 51 made of alumina ceramic, a first electrode 52 and a second electrode 53 made of silver alloy provided on the insulating substrate 51, and an insulating substrate 51 provided with a heating element 54 composed of a resistor that generates heat by energization so that the fuse can operate when necessary. It also includes a current-carrying electrode 55 made of silver alloy provided for energizing the heating element 54, and a fuse element 56 that electrically connects between the first electrode 52, the second electrode 53, and the current-carrying electrode 55 and is provided on the same substrate surface as the installation surface of the heating element 54. The fuse element 56 is characterized in that it is composed of a flat plate of a ternary alloy of Bal.Sn-30Ag-10Cu (the numerical values are mass%, and Bal. is the remainder) with flux (not shown) applied to the surface. A cap-shaped lid 500 made of liquid crystal polymer is attached to the protection element 50 so as to cover the fuse element 56 and the flux and be fixed to the insulating substrate 51. The first electrode 52, the second electrode 53, and the current-carrying electrode 55 are connected to pad electrodes 510 provided on the opposite side with the insulating substrate 51 interposed therebetween for connection to external components through through-holes.

[0025] As shown in FIG. 6, the protection element 60 according to Example 6 of the present invention includes an insulating substrate 61 made of alumina ceramic, a first electrode 62 and a second electrode 63 made of silver alloy provided on the insulating substrate 61, and a heating element 64 provided on the insulating substrate 61 and composed of a resistor that generates heat by energization so that the fuse can operate when necessary. It also includes a current-carrying electrode 65 made of silver alloy provided for energizing the heating element 64, and a fuse element 66 that electrically connects between the first electrode 62, the second electrode 63, and the current-carrying electrode 65 and is provided on the same substrate surface as the installation surface of the heating element 64. The fuse element 66 is composed of a flat plate of a ternary alloy of Bal.Sn-20Ag-2Cu (the numerical value is mass%, Bal. is the balance) with flux (not shown) applied to the surface. On the plane of the flat plate facing the first electrode 62, the second electrode 63, and the current-carrying electrode 65, a bonding metal layer 67 made of Bal.Sn-3.0Ag-0.5Cu (the numerical value is mass%, Bal. is the balance) of a solder alloy having a liquidus temperature lower than that of the fuse element 66 and a thinner thickness is further provided by cladding. The first electrode 62, the second electrode 63, and the current-carrying electrode 65 are electrically connected through through-holes to pad electrodes 610 provided on the opposite side across the insulating substrate 61 for connection to external components. A cap-shaped cover 600 made of liquid crystal polymer is attached to the protection element 60 so as to cover the fuse element 66 and the flux and is fixed to the insulating substrate 61.

[0026] As shown in FIG. 7, the protection element 70 according to Example 7 of the present invention includes an insulating substrate 71 made of alumina ceramic, a first electrode 72 and a second electrode 73 made of a silver alloy provided on the insulating substrate 71, and an insulating substrate 71. A heating element 74 composed of a resistor that generates heat by energization so that the fuse can operate when necessary, a current-carrying electrode 75 made of a silver alloy provided to energize the heating element 74, and the first electrode 72, the second electrode 73, and the current-carrying electrode 75 are electrically connected, and a fuse element 76 provided on the same substrate surface as the installation surface of the heating element 74. The fuse element 76 is composed of a flat plate of a ternary alloy of Bal.Sn-20Ag-10Cu (the numerical value is mass%, Bal. is the balance) with flux (not shown) applied to the surface. A bonding metal layer 77 made of Bal.Sn-3.0Ag-0.5Cu (the numerical value is mass%, Bal. is the balance) of a solder alloy having a liquidus temperature lower than that of the fuse element 76 is further provided on each bonding surface with the first electrode 72, the second electrode 73, and the current-carrying electrode 75. The first electrode 72, the second electrode 73, and the current-carrying electrode 75 are electrically connected through the bonding metal layer 77. A cap-shaped lid 700 made of liquid crystal polymer is attached to the protection element 70 so as to cover the fuse element 76 and the flux and is fixed to the insulating substrate 71. The first electrode 72, the second electrode 73, and the current-carrying electrode 75 are connected to pad electrodes 710 provided on the opposite side across the insulating substrate 71 for connection to external components by through holes.

[0027] In addition, it was confirmed by an experiment using simulation that the Sn-Ag-Cu based alloy constituting the fuse element of the present invention is excellent in reflow resistance. Specifically, for a plurality of Sn-Ag-Cu based alloys having different Ag contents (20 mass%, 21 mass%, 22 mass%, 23 mass%, 24 mass%, 25 mass%) and Cu contents (2 mass%, 4 mass%, 6 mass%, 8 mass%, 10 mass%), analysis was performed using software for calculating a multi-component phase diagram, and the solid-phase residual ratio and the liquidus temperature at 260° C., which is a general reflow temperature, were calculated. The results are shown in FIG. 8.

[0028] As shown in Fig. 8, all Sn-Ag-Cu based alloys with an Ag content of 20% to 25% by mass and a Cu content of 2% to 10% by mass have a liquidus temperature higher than 260°C and a solid phase residual ratio at 260°C of 0.2 or more (20% or more), and it was confirmed that they can exhibit excellent reflow resistance. In particular, Sn-Ag-Cu based alloys with an Ag content of 22% to 25% by mass and a Cu content of 4% to 8% by mass have a low liquidus temperature and a high solid phase residual ratio, and it was confirmed that they exhibit particularly excellent reflow resistance.

Industrial Applicability

[0029] The protection element with an electrode filling material of the present invention can be mounted on a protected circuit board together with other surface mount components, and can be collectively soldered and mounted by a reflow method or the like, and can be used for a protection device of a secondary battery such as a battery pack.

Explanation of Symbols

[0030] Protection element 10, insulating substrate 11, first electrode 12, second electrode 13, fuse element 16, lid 100, pad electrode 110, protection element 20, insulating substrate 21, first electrode 22, second electrode 23, heating element 24, energizing electrode 25, fuse element 26, lid 200, pad electrode 210, protection element 30, insulating substrate 31, first electrode 32, second electrode 33, heating element 34, energizing electrode 35, fuse element 36, bonding metal layer 37, lid 300, pad electrode 310, protection element 40, insulating substrate 41, first electrode 42, second electrode 43, heating element 44, energizing electrode 45, fuse element 46, bonding metal layer 47, lid 400, pad electrode 410, protection element 50, insulating substrate 51, first electrode 52, second electrode 53, heating element 54, energizing electrode 55, fuse element 56, lid 500, pad electrode 510, protection element 60, insulating substrate 61, first electrode 62, second electrode 63, heating element 64, energizing electrode 65, fuse element 66, bonding metal layer 67, lid 600, pad electrode 610, protection element 70, insulating substrate 71, first electrode 72, second electrode 73, heating element 74, energizing electrode 75, fuse element 76, bonding metal layer 77, lid 700, pad electrode 710.

Claims

1. A fuse element made of a single alloy material that is a ternary alloy of Sn-Ag-Cu, coated with flux to assist in fusing action, and having a silver content of 20 to 30 mass %, a copper content of 2 to 10 mass %, and the remainder being Sn.

2. A ternary alloy of Sn-Ag-Cu is applied with a flux to assist the fusing action, the silver content of which is 20 to 30% by mass, the copper content of which is 2 to 10% by mass, and the balance being Sn; A fuse element comprising a bonding metal layer made of a metal material having a liquidus temperature lower than that of the Sn--Ag--Cu ternary alloy, the bonding metal layer being provided on a surface or portion bonding to an electrode.

3. 3. The fuse element according to claim 2, wherein the joining metal layer is provided on a surface of the fuse element which is joined to an electrode.

4. 3. The fuse element according to claim 2, wherein the joining metal layer is provided at a portion of the fuse element that is joined to an electrode.

5. a fuse element electrically connecting at least the first electrode and the second electrode provided on the insulating substrate; and a flux applied to the fuse element to assist a melting operation; The fuse element is a protective element made of a single alloy material that is a ternary alloy of Sn-Ag-Cu, and the silver content is 20 to 30 mass%, the copper content is 2 to 10 mass%, and the balance is Sn.

6. a fuse element electrically connecting at least the first electrode and the second electrode provided on the insulating substrate; and a flux applied to the fuse element to assist a melting operation; The fuse element is a protective element made of a Sn-Ag-Cu ternary alloy having a silver content of 20 to 30 mass %, a copper content of 2 to 10 mass %, and the remainder Sn, and a bonding metal layer made of a metal material having a lower liquidus temperature than the Sn-Ag-Cu ternary alloy is provided on a surface or portion where the fuse element is bonded to an electrode.

7. 7. The protection element according to claim 6, wherein the fuse element is configured as a flat plate, the bonding metal layer is provided on a plane of the flat plate facing the first electrode and the second electrode, and the first electrode, the second electrode, and the current-carrying electrode are electrically connected with each other via the bonding metal layer.

8. 7. The protection element according to claim 6, wherein the fuse element is formed of a flat plate, the bonding metal layer is provided only on each bonding surface between the first electrode, the second electrode, and the current-carrying electrode, and the first electrode, the second electrode, and the current-carrying electrode are electrically connected with the bonding metal layer sandwiched therebetween.

9. a heat generating element that generates heat when current is applied thereto; a current-carrying electrode provided for applying current to the heat generating element; a fuse element electrically connecting the first electrode, the second electrode, and the current-carrying electrode; and a flux that is applied to the fuse element to assist a melting operation; The fuse element is a protective element made of a single alloy material that is a ternary alloy of Sn-Ag-Cu, and has a silver content of 20 to 30 mass%, a copper content of 2 to 10 mass%, and the remainder being Sn.

10. a heat generating element that generates heat when current is applied thereto; a current-carrying electrode provided for applying current to the heat generating element; a fuse element electrically connecting the first electrode, the second electrode, and the current-carrying electrode; and a flux that is applied to the fuse element to assist a melting operation; The fuse element is a protective element made of a Sn-Ag-Cu ternary alloy having a silver content of 20 to 30 mass %, a copper content of 2 to 10 mass %, and the remainder Sn, and a bonding metal layer made of a metal material having a lower liquidus temperature than the Sn-Ag-Cu ternary alloy is provided on a surface or portion where the fuse element is bonded to an electrode.

11. The protection element according to claim 10 , wherein the fuse element is provided on a surface of the substrate different from a surface on which the heating element is provided.

12. The protection element according to claim 10 , wherein the fuse element is provided on the same substrate surface as the heating element.

13. 13. The protection element according to claim 10, wherein the fuse element is configured as a flat plate, the bonding metal layer is provided on a plane of the flat plate facing the first electrode, the second electrode, and the current-carrying electrode, and the first electrode, the second electrode, and the current-carrying electrode are electrically connected with the bonding metal layer sandwiched therebetween.

14. 13. The protection element according to claim 10, wherein the fuse element is formed of a flat plate, the bonding metal layer is provided only on the bonding surfaces with the first electrode, the second electrode, and the current-carrying electrode, and the first electrode, the second electrode, and the current-carrying electrode are electrically connected with the bonding metal layer sandwiched therebetween.

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