KR20180130597A - Production method for mounting body, mounting method for temperature fuse elements, and temperature fuse element - Google Patents

Abstract

Thereby preventing melting and deformation of the fuse element even when the thermal fuse element is exposed to the mounting temperature. A thermal fuse element (1) is subjected to heat treatment at least once in a manufacturing method of a package (3) in which a thermal fuse element (1) is mounted on a circuit board (2) Melting metal (20) having a melting point lower than the heat treatment temperature and a high melting point metal (21) having a melting point higher than the heat treatment temperature and having a melting point of not lower than the melting point of the low melting point metal (20) The fuse element 13 is melted in a temperature atmosphere, and the heat treatment is performed at a temperature equal to or higher than the melting point of the low melting point metal 20.

Description

TECHNICAL FIELD [0001] The present invention relates to a manufacturing method of a mounting body, a mounting method of a thermal fuse element, and a thermal fuse element,

The present invention relates to a mounting body in which a thermal fuse element is mounted on a circuit board and is provided with a fuse element which is not fused in a high temperature environment exposed during manufacture of the mounting body and which fuses in accordance with the ambient temperature atmosphere during use A method of manufacturing a thermal fuse element, and a thermal fuse element.

The present application claims priority based on Japanese Patent Application No. 2014-197631, filed on September 26, 2014, which is hereby incorporated by reference in its entirety.

A large number of rechargeable secondary batteries that can be recharged and recharged are processed into battery packs and provided to the user. Particularly, in a lithium ion secondary battery having a high weight energy density, in order to secure the safety of users and electronic equipment, some protection circuits such as overcharge protection and over discharge protection are generally incorporated in the battery pack, And the output of the battery pack is cut off.

In this type of protection circuit, the output of the FET (Field Effect Transistor) switch incorporated in the battery pack is turned ON / OFF to perform overcharge protection or over-discharge protection operation of the battery pack. However, when the FET switch is short-circuited for some reason, when a lightning surge or the like is applied and an instantaneous large current flows, or when the output voltage abnormally decreases due to the life of the battery cell, or when an over- , Battery packs and electronic devices must be protected from accidents such as ignition. Therefore, in order to safely shut off the output of the battery cell in such an abnormal state that can be assumed, a protection element composed of a protection element having a function of cutting off the current path by an external signal is used.

As a protection element for such a protection circuit for a lithium ion secondary battery or the like, as described in Patent Document 1, a structure in which a heating element is provided inside a protection element, and a fuse element on the current path is fused by the heating element is generally .

As a related art of the present invention, a protection element 100 is shown in Figs. 17A and 17B. The protection element 100 includes an insulating substrate 101, a heat generating element 103 which is laminated on the insulating substrate 101 and covered with an insulating member 102 such as glass and a pair of heaters 103 formed on both ends of the insulating substrate 101 Electrodes 105a and 104b which are laminated so as to overlap the heating element 103 on the insulating member 101 and both ends of the heating element lead electrode 105 are connected to a pair of electrodes 104a and 104b, And a fuse element 106 connected to the heating element lead-out electrode 105.

One end of the heating-element lead-out electrode 105 is connected to the first heating-element electrode 107. The other end of the heating element 103 is connected to the second heating element electrode 108. The protection element 100 is also coated with the flux 111 on substantially the entire surface of the fuse element 106 in order to prevent the fuse element 106 from being oxidized. In addition, the protection element 100 is placed on the insulating substrate 101 in order to protect the inside thereof.

Such a protective element 100 is formed in such a manner that a pair of electrodes 104a and 104b formed on the surface of the insulating substrate 101 are electrically connected to the insulating substrate 101 through the conductive through hole 109 formed in the side surface of the insulating substrate And is electrically connected to the external connection electrode 110 formed on the back surface. The protection element 100 constitutes a part of the current path of the protection circuit by connecting the external connection electrode 110 on a substrate of a protection circuit for a lithium ion secondary battery or the like.

When the abnormal voltage or the like of the battery pack is detected, the protection element 100 is energized between the second heating element electrode 108 and the electrode 104a or the electrode 104b, so that the heating element 103 generates heat. In the protection element 100, the fuse element 106 is melted by the heat of the heating element 103, and the melting element coalesces on the heating element withdrawing electrode 105. Thereby, the protective element 100 is interrupted between the pair of electrodes 104a and 104b connected by the fuse element 106, and the feeding path of the heating element 103 is blocked, The heat generation is stopped.

Japanese Laid-Open Patent Publication No. 2010-003665

In order to operate such a protection device 100, a heating element 103 serving as a heat source for melting the fuse element 106 and the fuse element 106 is formed inside the element, and the protection element 100 is connected to a heating element It is necessary to connect on the energizing path for the electrodes 103 and 103. The circuit board on which the protection element 100 is mounted may be provided with a control element for controlling energization of the heating element 103 on the energizing path to the heating element 103, It is necessary to energize the heating element 103 when the operating condition is satisfied.

However, in overcharge protection due to failure of the FET for energization control, the abnormal temperature of the FET is detected by a temperature sensor such as PTC (Positive Temperature Coefficient), and the secondary protection IC judges a change in the resistance value, In this case, the temperature fuse for directly detecting the abnormal temperature and interrupting the energization of the protective device 100 is not heated by the heat generation It is preferable for safety design.

However, the thermal fuse of this kind has a disadvantage in that it has a low heat-resistant temperature and is a lead part, so that it is mounted by hand so that the packaging cost becomes high. In the step of mounting the thermal fuse on the circuit board, if the surface mounting can be performed by reflow soldering or the like, a package in which the thermal fuse is easily mounted can be manufactured. Here, in order to mount the semiconductor device by a process involving heat treatment such as reflow soldering, it is required that the fuse element mounted on the thermal fuse be provided with heat resistance that does not melt or deform even at the mounting temperature. If the fuse element is melted in a high temperature environment at the time of mounting, there is a fear that the temperature fuse may fluctuate in rating, and if the current path of the circuit board is cut off, the device can not be used.

For this reason, it is required that the fuse element has a high melting point capable of maintaining its shape without being melted even when exposed to a mounting temperature such as reflow.

On the other hand, when the protection element is constituted as a thermal fuse element which cuts off according to the surrounding high-temperature environment, if the fuse element is formed of a metal having a high melting point, it hinders the fast-

Thus, the present invention is a manufacturing method of a mounting body in which a thermal fuse element that can be operated in a temperature atmosphere at a temperature equal to or higher than the melting point of the fuse element is mounted, wherein, even when the thermal fuse element is exposed to the mounting temperature, A method of manufacturing a thermal fuse element, and a thermal fuse element.

In order to solve the above-described problems, a manufacturing method of a mounting body according to the present invention is a manufacturing method of a mounting body in which a thermal fuse element is mounted on a circuit board, wherein the thermal fuse element is subjected to heat treatment at least once Wherein the thermal fuse element has a low melting point metal having a melting point lower than the heat treatment temperature and a high melting point metal having a melting point higher than the heat treatment temperature and a melting point of the low melting point metal, And the heat treatment is performed at a temperature equal to or higher than the melting point of the low melting point metal.

A method for mounting a thermal fuse element according to the present invention is a method for mounting a thermal fuse element on a circuit board, wherein the thermal fuse element is subjected to heat treatment at least once, Melting metal having a melting point lower than the heat treatment temperature and a high melting point metal having a melting point higher than the heat treatment temperature and having a melting point higher than the melting point of the low melting point metal and lower than the melting point of the high melting point metal, Element, and the heat treatment is performed at a temperature equal to or higher than the melting point of the low melting point metal.

A thermal fuse element according to the present invention is a thermal fuse element constituting a mounting body by being mounted on a circuit board and subjected to at least one heat treatment step in the manufacturing step of the mounting body, Melting metal having a melting point lower than the temperature of the heat treatment step and a refractory metal having a melting point higher than the temperature of the heat treatment step, the first and second electrodes formed on the insulating substrate, And a fuse element mounted between the electrodes and interposed between the first and second electrodes by melting in a temperature atmosphere of a melting point of the low melting point metal or higher and lower than a melting point of the high melting point metal.

According to the present invention, since the fuse element has a low melting point metal having a melting point lower than the heat treatment temperature and a high melting point metal having a melting point higher than the heat treatment temperature, Even when exposed, deformation and dissolution of the low melting point metal are prevented, and variations in rating and melting point characteristics can be prevented.

1 is a cross-sectional view showing a mounting body according to the present invention.
2 is a cross-sectional view showing an example of a fuse element.
3 is a sectional view showing an example of a fuse element.
Fig. 4 is a perspective view showing an example of a fuse element, where (A) shows a structure in which a refractory metal layer is laminated on the top and back surfaces of a refractory metal layer, Fig. (C) is formed in a ring-shaped shape.
5 is a perspective view showing a fuse element protected by a protective member;
Fig. 6 is a diagram showing a thermal fuse element using a fuse element having a plurality of fusing parts, wherein (A) is an exploded perspective view and (B) is a plan view.
Fig. 7 is a plan view showing a fuse element having a plurality of fusing parts, and Fig. 7 (B) is a plan view of a fuse element having free ends at one end of the fusing part.
Fig. 8 is a diagram showing a thermal fuse element in which a fuse element having a plurality of fusing ends is used and an insulating wall is formed between the fusing parts, wherein (A) is an exploded perspective view and Fig.
FIG. 9 is a cross-sectional view showing a thermal fuse element in which an insulating wall is formed on the surface of an insulating substrate, using a fuse element having a plurality of fused ends.
10 is a cross-sectional view showing a thermal fuse element in which a fuse element having a plurality of fused ends is used and an insulating wall is formed on the cover member.
11 is a cross-sectional view showing a thermal fuse element in which an insulating wall is formed by applying a liquid or paste-like insulating material between the free ends and curing it.
Fig. 12 is a view showing a thermal fuse element using a fuse element in which a terminal portion connected to an external circuit is integrally formed, Fig. 12 (A) is a perspective view showing a state before the cover member is mounted, (C) is a perspective view showing an insulating substrate.
13 is a perspective view showing a thermal fuse element in which a plurality of fuse elements are fitted on a surface of an insulating substrate.
FIG. 14 is a view showing a thermal fuse element in which the terminal portion of the fuse element is protruded to the surface side of the insulating substrate, FIG. 14 (A) is a perspective view showing a state before the cover member is mounted, (C) is a perspective view showing a state of mounting by face down, and (D) is a perspective view showing an insulating substrate.
Fig. 15 is a view showing a thermal fuse element in which an end portion of a fuse element is connected to an electrode by a conducting wire, Fig. 15 (A) is a plan view showing a state before the cover member is mounted, to be.
Fig. 16 is a view showing a thermal fuse element in which an end portion of a fuse element is connected to an electrode by soldering, wherein Fig. 16A is a perspective view showing a state before the cover member is mounted, and Fig. 16B is a cross- .
17A is a plan view and FIG. 17B is a cross-sectional view taken along the line AA 'in FIG. 17A.

Hereinafter, a manufacturing method of a mounting body to which the present invention is applied, a mounting method of a thermal fuse element, and a thermal fuse element will be described in detail with reference to the drawings. It is needless to say that the present invention is not limited to the following embodiments, and various modifications are possible within the scope of the present invention. Also, the drawings are schematic, and the ratios of the dimensions and the like may be different from those of the real world. The specific dimensions and the like should be judged based on the following description. Needless to say, the drawings also include portions having different dimensional relationships or ratios with each other.

[Thermal fuse element]

1, the thermal fuse element 1 to which the present invention is applied is constituted by surface mounting on a circuit board 2 to constitute a mounting body 3, A thermal fuse element that undergoes a heat treatment process of a plurality of thermal fuses and includes an insulating substrate 10, first and second electrodes 11 and 12 formed on the insulating substrate 10, and first and second electrodes 11 and 12 And a fuse element 13 mounted between the first and second electrodes 11 and 12 by melting in a predetermined temperature atmosphere.

In the temperature fuse element 1, the fuse element 13 is melted in a temperature atmosphere equal to or higher than the melting temperature of the fuse element 13 and self-heating due to an overcurrent equal to or higher than the rated current, , And the second electrodes 11 and 12 coagulate to block the gap between the first and second electrodes 11 and 12.

[Temperature Atmosphere]

The thermal fuse element 1 melts the fuse element 13 by heat transmitted from an external heat source. The temperature atmosphere refers to a temperature environment in which the fuse element 13 made by the external heat source of the thermal fuse element 1 is melted. For example, (Enthalpy heat) is transmitted to the inside of the thermal fuse element 1. The temperature atmosphere above the melting point of the fuse element 13 may be made by the heat of the electronic appliance in which the thermal fuse element 1 is used or the heat generated by the surrounding fire is transmitted to the inside of the thermal fuse element 1 . The temperature atmosphere above the melting point of the fuse element 13 is a normal use for not only an emergency such as an accident or a disaster but also a current path inevitably to interrupt the current path, 1), as shown in Fig.

[Heat transfer member]

The temperature atmosphere in which the fuse element 13 is melted is made by functioning as air inside the thermal fuse element 1 or a constituent component inside the element serving as a heat transfer member for transferring heat outside the device. The heat transfer member conveys the heat of the heat source outside the thermal fuse element 1 and is connected to the external casing of the thermal fuse element 1 or the insulating substrate 10, the first and second electrodes 11 and 12, And other constituent members can be used and directly or indirectly connected to the fuse element 13 to heat the fuse element 13. [ The heat transfer member can be formed by, for example, an electrode pattern, a wire or a heat pipe connected to the first electrode 11 and / or the second electrode 12, a heat conduction grease / adhesive, Or indirectly through the first electrode 11 and / or the second electrode 12 to the fuse element 13 and melts it.

When a conductive member such as a heat pipe is used as the heat transfer member, it is preferable that at least the surface of the heat transfer member is coated with an insulating material in order to insulate the periphery.

[Insulation Substrate]

The insulating substrate 10 is formed in a substantially circular shape using an insulating member such as alumina, glass ceramics, mullite, or zirconia, for example. As the insulating substrate 10, a material used for a printed wiring board such as a glass epoxy substrate or a phenol substrate may be used, but it is necessary to pay attention to the temperature at the time of fusing the fuse element 13.

It is preferable that the insulating substrate 10 be an insulating material having excellent thermal conductivity such as a ceramic substrate or a metal substrate whose surface is coated with an insulating material. Thereby, the insulating substrate 10 functions as a heat transfer member for transferring the heat of the external heat source to the fuse element 13. The heat of the external heat source is transmitted directly to the fuse element 13 through the first electrode 11 via the insulating substrate 10 and indirectly as the row heat in the thermal fuse element 1 by the fuse element 13 ). Thereby, the thermal fuse element 1 is allowed to melt the fuse element 13 by creating a temperature atmosphere above the melting point of the fuse element 13.

[First and Second Electrodes]

The first and second electrodes 11 and 12 are conductive patterns such as Cu and Ag formed on the surface 10a of the insulating substrate 10 and are formed of Ni / Au plating or Sn plating A protective layer 14 is formed. The first and second electrodes 11 and 12 are connected to the external connection terminals 11a and 12a formed on the back surface 10b of the insulating substrate 10. The thermal fuse element 1 is inserted into various external circuits such as a power supply circuit and a digital signal circuit by connecting these external connection terminals 11a and 12a to the land portion 2a of the circuit board 2. [

The first and second electrodes 11 and 12 are formed on the same plane by printing or firing a high melting point metal paste such as Ag on the insulating substrate 10, for example.

[Fuse element]

The fuse element 13 mounted between the first and second electrodes 11 and 12 has a low melting point having a melting point lower than the temperature of the heat treatment in the manufacturing process of the mounting member of the thermal fuse element 1, (20) and a refractory metal (21) having a melting point higher than the temperature of the heat treatment. When the refractory metal (21) is in use, it is heated to a temperature of not lower than the melting point of the low melting point metal (20) And the molten element 13a coagulates on the first and second electrodes 11 and 12 to block the gap between the first and second electrodes 11 and 12. The fuse element 13 is fused by self heating (juxtaposition) when a current exceeding the rating is applied to the thermal fuse element 1 and the fuse element 13 is fused by the current between the first electrode 11 and the second electrode 12 It is blocking the path.

The fuse element 13 is a laminated structure composed of an inner layer and an outer layer and has a low melting point metal layer 20a made of a low melting point metal 20 as an inner layer and a high melting point metal 21 as an outer layer laminated on the low melting point metal layer 20a. Melting-point metal layer 21a made of a material having a high melting point, and is formed in a substantially rectangular plate-like shape. The fuse element 13 is mounted between the first and second electrodes 11 and 12 via an adhesive material 15 such as solder for connection and then connected to the insulating substrate 10 by reflow soldering or the like do.

The low melting point metal 20 is preferably a metal containing Sn as a main component and is a material commonly called " Pb-free solder ". The melting point of the low melting point metal 20 may be lower than the temperature of the heat treatment in the manufacturing process of the mounting body and may be melted at about 200 캜 which is lower than the reflow temperature, for example. When a Sn-Bi based solder alloy is used as the low melting point metal 20, the melting point can be lowered to about 138 占 폚 and further the melting point can be lowered. When a Sn-In based solder alloy is used, The fusing element 13 can be fused in a temperature atmosphere which does not reach the temperature of the heat treatment process. The refractory metal 21 is laminated on the surface of the low melting point metal layer 20a and is made of, for example, Ag or Cu or a metal mainly composed of any of them, and the fuse element 13 is subjected to heat treatment such as reflow It has a high melting point that is not melted even when mounted on the insulating substrate 10 by the process.

The fuse element 13 is formed by laminating a refractory metal layer 21a as an outer layer on a refractory metal layer 20a serving as an inner layer so that even when the reflow temperature exceeds the melting temperature of the refractory metal 20, It does not reach the melting point as the element 13. Therefore, the thermal fuse element 1 and the fuse element 13 can be efficiently mounted by reflow.

The fuse element 13 melts in a temperature atmosphere not lower than the melting point of the low melting point metal 20 and the melting element 13a cuts off the current path between the first and second electrodes 11 and 12. At this time, the fuse element 13 melts at a temperature lower than the melting point of the high melting point metal 21 by melting the low melting point metal 20 by melting the melting point metal 21 . Therefore, the fuse element 13 can be fused in a short time by utilizing the erosion action of the refractory metal 21 by the low melting point metal 20. In addition, the molten metal of the fuse element 13 can be quickly and surely separated from the first and second electrodes 11 and 12 in that the molten metal of the fuse element 13 is divided into right and left by the physical pulling action of the first and second electrodes 11 and 12. [ It is possible to cut off the current path between the electrodes 11 and 12.

Here, the fuse element 13 can be fused in a temperature atmosphere that does not reach the temperature of the heat treatment step by using Sn-Bi-based solder alloy or Sn-In-based solder alloy as the low melting point metal 20. Therefore, when the temperature of the mounting body using the thermal fuse element 1 is raised to a temperature at which a serious influence is exerted on other devices such as the electronic device or the like using the circuit board 2 or the mounting body 3, 13) can be melted, and safety can be improved.

Further, the fuse element 13 is not fused even by self-heating while a predetermined rated current flows. Then, when a current having a value higher than the rated value flows, it is melted by self-heating and blocks the current path between the first and second electrodes 11 and 12. At this time, the fuse element 13 is also formed in such a manner that the fused low melting point metal 20 erodes the high melting point metal 21, so that the high melting point metal 21 can be rapidly heated at a temperature lower than the melting point of the high melting point metal 21 ≪ / RTI >

Since the fuse element 13 is formed by laminating the refractory metal layer 21a on the refractory metal layer 20a serving as the inner layer, the fusing element 13 is greatly reduced in the refractory temperature from that of the conventional refractory metal chip fuse . Therefore, the fuse element 13 can have a larger cross-sectional area than the chip fuse of the same size, and can significantly improve the current rating. In addition, the chip fuse can be made smaller and thinner than the conventional chip fuse having the same current rating, and is excellent in fast-forwarding.

Further, the fuse element 13 can improve the resistance (resistance to impulse) to surges where an abnormally high voltage is momentarily applied to the electric system in which the thermal fuse element 1 is embedded. That is, the fuse element 13 should not be fused until, for example, a current of 100 A flows for a few milliseconds. In this respect, the fuse element of the present invention, which is made of Sn and Ag, has a resistivity lower by about 1/4 to 1/3 than a conventional Pb-based fuse element and has a low resistance, and a large current flowing in a very short time is a point (Skin effect), the fuse element 13 is formed with the refractory metal layer 21a such as Ag plating having a low resistance value as the outer layer. Therefore, the current applied by the surge easily flows, Can be prevented. Therefore, the fuse element 13 can greatly improve the resistance to surge as compared with a conventional fuse made of a Pb-based solder alloy.

The fuse element 13 preferably has a volume of the low melting point metal layer 20a larger than that of the high melting point metal layer 21a. By increasing the volume of the low melting point metal layer 20a, the fuse element 13 maintains the rated value without melting or deforming at the temperature of the heat treatment in the manufacturing process of the mounting body, and at the time of use, It is possible to effect fusing in a short time by effectively eroding the refractory metal layer 21a in a temperature atmosphere of the melting point of the refractory metal layer 20 or more.

Specifically, the fuse element 13 has a structure in which the inner layer is the low melting point metal layer 20a, the outer layer is the coating structure of the high melting point metal layer 21a, and the layer thickness ratio of the low melting point metal layer 20a and the high melting point metal layer 21a is Melting point metal layer: high melting point metal layer = 2.1: 1 to 100: 1. Thereby, the fuse element 13 can prevent melting and deformation at the temperature of the heat treatment in the manufacturing process of the mounting body.

That is, the fuse element 13 has a layer thickness ratio of a low melting point metal layer: a high melting point metal layer = 2.1: 1 or more in that the high melting point metal layer 21a is laminated on the upper and lower surfaces of the low melting point metal layer 20a constituting the inner layer The volume of the low melting point metal layer 20a can be made larger than the volume of the high melting point metal layer 21a as the low melting point metal layer 20a is thickened.

The fuse element 13 defines the resistance to heat treatment in the manufacturing process of the mounting body by setting the film thickness ratio between the low melting point metal layer 20a and the high melting point metal layer 21a. That is, since the fuse element 13 is exposed to a temperature atmosphere at a temperature equal to or higher than the melting point of the low melting point metal 20 constituting the inner layer in the heat treatment process, the fuse element 13 has the high melting point metal 21, The resistance to heat treatment can be improved. Therefore, the fuse element 13 has heat resistance for at least one heat treatment step, for example, by adjusting the film thickness ratio of the low melting point metal layer 20a and the high melting point metal layer 21a, Is performed by a specific heat treatment process such as ultrasonic welding to prevent fusing or deformation when reflow is performed when the thermal fuse element 1 is mounted on the circuit board 2. [ The fuse element 13 has heat resistance for at least two heat treatment steps by adjusting the film thickness ratio between the low melting point metal layer 20a and the high melting point metal layer 21a, It is possible to prevent fusing or deformation even when reflowing is performed when the thermal fuse element 1 is mounted on the circuit board 2 and when the thermal fuse element 1 is mounted on the circuit board 2. [ The fuse element 13 has heat resistance for at least three heat treatment steps by adjusting the film thickness ratio between the low melting point metal layer 20a and the high melting point metal layer 21a, Even when reflowing is performed when other electronic components are mounted on the back surface of the circuit board 2 when the thermal fuse element 1 is mounted on the circuit board 2 when the circuit board 2 is mounted on the circuit board 2, Can be prevented.

When the layer thickness ratio of the fuse element 13 is such that the low melting point metal layer 20a is thick and the high melting point metal layer 21a is thinner than the low melting point metal layer: high melting point metal layer = 100: 1, ) May be eroded by the low melting point metal 20 melted by the heat at the time of reflow mounting.

[Manufacturing method]

The fuse element 13 can be manufactured by laminating the refractory metal layer 21a by depositing a refractory metal 21 on the surface of the refractory metal layer 20a by a plating technique. The fuse element 13 can be efficiently produced, for example, by applying Ag plating to the surface of a long-length solder foil, and can be easily used by cutting according to the size at the time of use.

The fuse element 13 may be manufactured by bonding a low melting point metal foil and a high melting point metal foil. The fuse element 13 can be manufactured by, for example, pressing two sheets of rolled Cu foil or Ag foil with the same rolled solder foil interposed therebetween. In this case, it is preferable to select a material having a lower melting point than that of the high melting point metal foil. Thereby, the deviation of the thickness can be absorbed, and the low melting point metal foil and the high melting point metal foil can be brought into close contact with each other without gaps. Further, since the low-melting point metal foil is thinned by pressing, it is preferable to increase the thickness beforehand. When the low-melting-point metal foil is pushed out of the end face of the fuse element by the press, it is preferable to cut out and shape the low-melting point metal foil.

The fuse element 13 may be formed by forming a fuse element 13 in which a refractory metal layer 21a is laminated on the low melting point metal layer 20a by using a thin film forming technique such as vapor deposition or other well- Can be formed.

Further, as shown in Fig. 2, the fuse element 13 may be formed by alternately forming a plurality of layers of the low melting point metal layer 20a and the high melting point metal layer 21a. In this case, the outermost layer may be either the low-melting-point metal layer 20a or the high-melting-point metal layer 21a, but it is preferable that the outermost layer is the low-melting-point metal layer 20a. When the outermost layer is the low-melting-point metal layer 20a, the high-melting-point metal layer 21a is eroded by the low-melting-point metal layer 20a from both surfaces in the melting process. In the case where the outermost layer is the low-melting-point metal layer 20a, an appropriate amount of solder paste may be applied to the front / back surface of the fuse element at the time of mounting the fuse element and coated simultaneously with the connection to the electrode by reflow heating.

3, when the refractory metal layer 21a is the outermost layer, the fuse element 13 further includes an oxidation preventing film 23 on the surface of the refractory metal layer 21a in the outermost layer . The fuse element 13 is covered with the oxidation preventing film 23 in the outermost layer of the refractory metal layer 21a so that even when Cu plating or Cu foil is formed as the refractory metal layer 21a, The oxidation of Cu can be prevented. Therefore, the fuse element 13 can prevent a situation in which the melting time is prolonged due to the oxidation of Cu, and the fuse element 13 can be fused in a short time.

In addition, the fuse element 13 can use a low-cost but easily oxidized metal such as Cu as the refractory metal layer 21a, and can be formed without using an expensive material such as Ag.

The oxidation preventive film 23 of the refractory metal may be made of the same material as the low melting point metal 20 constituting the inner layer. For example, a Pb-free solder containing Sn as a main component may be used. The oxidation preventing film 23 can be formed by tin plating the surface of the refractory metal layer 21a. In addition, the oxidation preventing film 23 may be formed by Au plating or free flux.

4 (A), the fuse element 13 may be formed by laminating the refractory metal layer 21a on the upper and lower surfaces of the low melting point metal layer 20a, Likewise, the outer circumferential portion of the low melting point metal layer 20a excluding the two opposite end faces may be covered with the high melting point metal layer 21a.

The fuse element 13 may be a square type fuse element or a ring-shaped fuse element as shown in Fig. 4 (C). The entire surface including the end face may be covered with the refractory metal layer 21a in the fuse element 13.

Further, as shown in Fig. 5, the fuse element 13 may be provided with the protection member 24 at least in part of the outer periphery. The protective member 24 prevents the inflow of the connecting solder and the outflow of the low melting point metal layer 20a of the inner layer at the time of reflow mounting of the fuse element 13 to maintain the shape, The flow of the molten solder is prevented so that the lowering of the fastness due to the rise of the rating is prevented.

That is, by forming the protective member 24 on the outer periphery of the fuse element 13, it is possible to prevent the outflow of the molten low melting point metal 20 under the reflow temperature and to maintain the shape of the element. In particular, in the fuse element 13 in which the refractory metal layer 21a is laminated on the upper and lower surfaces of the refractory metal layer 20a and the refractory metal layer 20a is exposed from the side surface, The outflow of the low melting point metal 20 from the side is prevented, and the shape can be maintained.

Further, the fuse element 13 can prevent the inflow of molten solder when a current exceeding the rated value flows, by forming the protective member 24 on the outer periphery. When the fuse element 13 is connected to the first and second electrodes 11 and 12 by soldering, the fuse element 13 is exposed to a high temperature atmosphere in a heat treatment process such as a reflow soldering, The solder 15 and the low melting point metal 20 for connection to the first and second electrodes 11 and 12 are melted by the heat generated when the current flowing through the fuse element 13 flows, There is a fear that it may be introduced. When the molten metal such as solder flows into the fuse element 13, the fuse element 13 may not be fused in a predetermined temperature atmosphere, and the fusing time may be prolonged. In addition, the fuse element 13 is not fused at a predetermined current value, the heating time is prolonged or the first and second electrodes 11, 12 may be deteriorated. Thus, the fuse element 13 prevents the inflow of molten metal, fixes the resistance value, and quickly fuses the fuse element 13 to a predetermined current value by forming the protective member 24 on the outer periphery, Insulation reliability between the electrodes 11 and 12 can be ensured.

For this reason, as the protective member 24, a material having heat resistance at an insulation property or a reflow temperature, and having resistibility to molten solder or the like is preferable. For example, the protective member 24 can be formed by using a polyimide film and sticking it to the central portion of the fuse element 13 on the tape with the adhesive 25 as shown in Fig. The protective member 24 can be formed by applying ink having insulation property, heat resistance, and resistibility to the outer periphery of the fuse element 13. Alternatively, the protective member 24 can be formed by applying the solder resist to the outer periphery of the fuse element 13.

The protection member 24 made of the above-mentioned film, ink, solder resist or the like can be formed by adhering or coating on the outer periphery of the elongated fuse element 13, The element 13 can be cut off and the handling property is excellent.

[Flux coating]

1, for preventing oxidation of the refractory metal layer 21a or the low melting point metal layer 20a in the outer layer and removing the oxide during melting and improving the fluidity of the solder, the fuse element 13 is fused The flux 17 may be applied to the substantially entire surface of the outer layer on the element 13. [ By applying the flux 17, it is possible to increase the wettability of the low-melting-point metal (for example, solder), remove the oxide while the low-melting-point metal is dissolved, Action can be used to improve the fastness.

Even when the oxidation film 23 made of Sn-based Pb-free solder or the like is formed on the surface of the refractory metal layer 21a on the outermost layer by applying the flux 17, The oxidation of the refractory metal layer 21a can be effectively prevented, and the fast-spinning can be maintained and improved.

The fuse element 13 can be connected to the first and second electrodes 11 and 12 by reflow soldering as described above. In addition, the fuse element 13 can be connected to the first and second electrodes 11 and 12 by ultrasonic welding 1 and the second electrodes 11 and 12, respectively.

[Cover member]

The thermal fuse element 1 also has a cover member 10 on the surface 10a of the insulating substrate 10 on which the fuse element 13 is formed for protecting the inside and preventing scattering of the melted fuse element 13, (Not shown). The cover member 19 has a leg portion 19a connected to the surface 10a of the insulating substrate 10 and a top surface 19b covering the surface 10a of the insulating substrate 10, Plastic, ceramics, or other insulating material.

[Mounting process]

Next, the assembling process of the thermal fuse element 1 and the mounting process of the thermal fuse element 1 will be described. The thermal fuse element 1 is formed by connecting a fuse element 13 on an insulating substrate 10 and covering it with a cover member 19. The first and second electrodes 11 and 12 are formed on the surface 10a of the insulating substrate 10 and the external connection terminals 11a and 12a are formed on the back surface 10b. The first and second electrodes 11 and 12 and the external connection terminals 11a and 12a are formed by printing a high melting point metal paste such as Cu or Ag on the surface 10a and the back surface 10b of the insulating substrate 10 , And firing. The first and second electrodes 11 and 12 and the external connection terminals 11a and 12a are electrically connected through a casting formed on the side surface of the insulating substrate 10.

An adhesive material 15 such as Pb-free solder is formed on the first and second electrodes 11 and 12 and the fuse element 13 is mounted between the first and second electrodes 11 and 12. The fuse element 13 is then solder connected to the first and second electrodes 11 and 12 by passing the insulating substrate 10 through the reflow furnace so that the first and second electrodes 11 , 12) are electrically connected through the fuse element (13).

At this time, since the fuse element 13 has the low melting point metal 20 having a melting point lower than the reflow temperature and the high melting point metal 21 having a melting point higher than the reflow temperature, in the reflow mounting step Even when exposed to a temperature equal to or higher than the melting point of the low-melting-point metal 20, deformation and elution of the low-melting-point metal 20 are prevented, and variations in rating and melting point characteristics are prevented.

Thereafter, the thermal fuse element 1 is completed by mounting the cover member 19 on the surface 10a of the insulating substrate 10.

The thermal fuse element 1 is connected on the current path of the external circuit. Specifically, in the thermal fuse element 1, after the external connection terminals 11a and 12a are mounted on the land portion 2a formed on the circuit board 2 via solder for connection such as Pb pre-solder, And is inserted into the current path of the external circuit by passing through the furnace.

At this time, too, the thermal fuse element 1 has a structure in which the fuse element 13 has the low melting point metal 20 having a melting point lower than the reflow temperature and the high melting point metal 21 having a melting point higher than the reflow temperature , The deformation of the fuse element 13 and the elution of the low melting point metal 20 are prevented even if they are exposed to a temperature equal to or higher than the melting point of the low melting point metal 20 in the reflow soldering process, have.

The electronic component is reflowly mounted on the surface of the circuit board 2 on which the thermal fuse element 1 is mounted suitably also on the surface opposite to the mounting surface of the thermal fuse element 1. [ Even in this case, even if the fuse element 13 is exposed to a temperature equal to or higher than the melting point of the low-melting-point metal 20, the thermal fuse element 1 can prevent the deformation of the fuse element 13 and the elution of the low- So that the fluctuation of the rating and the melting point characteristics is prevented.

Also, even if the circuit board 2 on which the thermal fuse element 1 is mounted is embedded in another device and is further subjected to a heat treatment process such as reflow soldering, the fuse element 1 of the thermal fuse element 1 13 are prevented from being deformed or leaching of the low-melting-point metal 20, and the fluctuation of the rating and the melting point characteristics is prevented.

When the device is placed in a high temperature environment such as abnormal heat generation of the mounted device, the fuse element 13 starts melting in a temperature atmosphere of the melting point of the low melting point metal 20 or higher. Thereby, the thermal fuse element 1 can melt the fuse element 13 prematurely and block the current path of the circuit board 2. At this time, since the fuse element 13 is melted at a low temperature below the melting point of the refractory metal 21 by melting the refractory metal 21 (solder erosion) by the refractory metal 21, The current path can be cut off.

As described above, the thermal fuse element 1 is constituted by the fuse element 13 having the low melting point metal 20 having the melting point lower than the heat treatment temperature and the high melting point metal 21 having the melting point higher than the heat treatment temperature The heat treatment process such as the reflow process can be repeatedly performed by adjusting the film thickness ratio of the low melting point metal layer 20a and the high melting point metal layer 21a appropriately together with the fuse element 13 and the low melting point metal 20 is prevented from being eluted, and variation in the rating and melting point characteristics can be prevented. When the package 3 with the thermal fuse element 1 mounted thereon is exposed to a temperature atmosphere of the melting point of the low melting point metal 20 or more, the fuse element 13 starts to melt, 2).

[Variation 1 of fuse element: parallel type]

Further, in the fuse element related to the present invention, a plurality of fuse terminals may be arranged in parallel so that a plurality of fuse elements may be used. In the following description, the same components as those of the above-described temperature fuse element 1 are denoted by the same reference numerals, and the details thereof are omitted.

The thermal fuse element 30 shown in Figs. 6A and 6B has an insulating substrate 10 and first and second electrodes 11 and 12 formed on the surface 10a of the insulating substrate 10 And has a fuse element 31 connected thereto. The fuse element 31 has a plurality of fusing parts. For example, as shown in Fig. 3 (a), the three fusing parts 32A to 32C are arranged in parallel, thereby having a plurality of energizing paths. The fuse element 31 has a low melting point metal 20 having a melting point lower than the temperature of the heat treatment in the manufacturing process of the mounting member of the thermal fuse element 30, And has a refractory metal (21) having a melting point higher than the temperature of the heat treatment. Each of the terminal ends 32A to 32C is connected between the first and second electrodes 11 and 12 formed on the surface 10a of the insulating substrate 10 and serves as a conduction path of electric current.

The fuse element 31 is mounted between the first and second electrodes 11 and 12 via an adhesive material 15 such as Pb-free solder and then is subjected to heat treatment such as reflow soldering, And is connected to the substrate 10. The fuse element 31 is the same as the above-described fuse element 13 except for the material and lamination structure of the low melting point metal layer 20a and the high melting point metal layer 21a and the manufacturing method thereof,

The fusing element 31 is formed such that the fusing elements 32A to 32C are melted in a temperature atmosphere at a temperature not lower than the melting point of the low melting point metal 20 at the time of use and the molten element is melted on the first and second electrodes 11 and 12 So that the first and second electrodes 11 and 12 are cut off. When the current exceeding the rating is applied to the thermal fuse element 30, the fuse element 31 is fused to the fusible element 31 by the self-heating (juxtaposition), and the fuse element 31 is fused with the first electrode 11 Thereby blocking the current path between the second electrodes 12.

At this time, even if an arc discharge occurs when the current exceeding the rating is energized and the arc discharge occurs, the fused element 31 spreads over a wide range, and a current path is newly generated by the scattered metal It is possible to prevent the formed or scattered metal from adhering to a terminal or surrounding electronic parts or the like.

That is, since the fuse element 31 has a plurality of fused ends 32A to 32C mounted in parallel between the first and second electrodes 11 and 12, when a current exceeding the rating is energized, A large amount of current flows through the lower end portion 32 having a lower value and is sequentially fused by the self heat generation and arcing discharge occurs only when the last remaining end portion 32 is fused. Therefore, even when an arc discharge is generated during the fusing of the last remaining end portion 32, the fuse element 31 is small in size depending on the volume of the fusing end portion 32, so that explosive scattering of the molten metal is prevented It is possible to greatly improve the insulation after melting. Since the fuse element 31 is fused for each of the plurality of fusing ends 32A to 32C, the thermal energy required for fusing the fusing end portions 31 is minimal and can be cut off in a short time.

The fuse element 31 may have a relatively high resistance by making the cross-sectional area of a part or all of the single fused ends 32 of the plurality of fused ends 32 smaller than the cross sectional area of the other fused ends. By making the one fusing end portion 32 relatively higher in resistance, when a current exceeding the rated value is supplied to the fuse element 31, a large amount of current is passed from the fusing end portion 32 of relatively low resistance to fuse. Thereafter, the current is concentrated on the remaining high resistance end portion 32, and finally the arc discharge accompanies the firing. Therefore, the fuse element 31 can blow out the fusing end portion 32 sequentially. In addition, arc discharge occurs at the time of fusing of the fusing end portion 32 having a small cross-sectional area, so that it is small in size depending on the volume of the fusing end portion 32, and explosive scattering of the molten metal can be prevented.

In addition, it is preferable that the fuse element 31 forms three or more fuse portions and finally fuses the inner fuse portion. For example, as shown in Fig. 6, it is preferable that the fuse element 31 forms three fusing ends 32A, 32B and 32C and finally fuses the fusing end 32B in the center Do.

When a current exceeding the rated value is supplied to the thermal fuse element 30, the fuse element 31 flows first through the two fused ends 32A and 32C and melts by self heat generation. Since the fusing of the fusing ends 32A and 32C does not involve arc discharge due to self heat generation, there is no explosive scattering of the molten metal.

Then, a current is concentrated on the free end portion 32B in the center, and the arc is fired with the arc discharge. At this time, the fuse element 31 finally fuses the distal end portion 32B in the center, so that even if arc discharge occurs, the molten metal of the fusing end portion 32B is fused to the outer fusing end portion 32A , And 32C, respectively. Therefore, scattering of the molten metal of the fusing end 32B can be suppressed, and short-circuit by the molten metal can be prevented.

At this time, the fuse element 31 is formed such that the cross-sectional area of a part or the entirety of the fused end portion 32B located at the inner side among the three fused ends 32A to 32C is defined by the other fused ends 32A, 32C), it is possible to relatively increase the resistance, thereby finishing finally the fusing end portion 32B in the center. In this case as well, since the cross-sectional area is made relatively small, the arc is finally fired, so that the arc discharge degree becomes small according to the volume of the fusing end portion 31B, and the explosive scattering of the molten metal can be further suppressed.

[Preparation of fuse element]

As shown in Fig. 7 (A), the fuse element 31 having the plurality of fusing ends 32 formed thereon is divided into a plurality of fusing elements 31, for example, Can be produced by punching two points in a rectangular shape. As shown in Fig. 7 (B), the fuse element 31 may have one end of the three fused ends 32A to 32C connected in parallel to each other, and the fuse element 31 may have a free end at the other end.

[Insulation Wall]

8, the thermal fuse element 30 may be provided with an insulating wall 35 between the plurality of free ends 32 to prevent connection of the free ends 32 in parallel. By forming the insulating wall 35, the fuse element 31 is melted and expanded by the ambient temperature atmosphere or its own heat generation when the fusing end portion 32 is fused, and the fusing element 31 contacts the adjacent fusing end portion 32 Thereby preventing aggregation. As a result, the fuse element 31 is enlarged by melting and aggregation of the adjacent free ends 32, and the fuse element 31 is increased in the melting time required by the increase of the heat amount required for melting, Or explosive scattering of the molten metal due to the enlargement of the arc discharge occurring at the time of melting due to the self-heating accompanying the overcurrent can be prevented.

The insulating wall 35 is formed on the surface 10a of the insulating substrate 10, for example, as shown in Fig. The insulating wall 35 is formed by printing an insulating material such as a solder resist or glass. Since the insulating wall 35 has insulating property, it does not have wettability with respect to the molten element, and therefore it is not absolutely necessary to completely collapse the adjacent free ends 32. That is, even if the clearance between the top surface 19b of the cover member 19 and the top surface 19b of the cover member 19 does not act due to the wettability, the molten element does not flow into the side of the fused portion 32 parallel to the clearance. When the molten solder portion 32 is melted, the molten solder portion 32 swells in a cross-sectional dome-like shape in a region between the first and second electrodes 11 and 12. [ Therefore, if the insulating wall 35 has a height at least half as high as the height from the surface 10a of the insulating substrate 10 to the top surface 19b of the cover member 19, 32 from contacting with each other. Of course, the insulating wall 35 may be formed to have a height reaching the top face 19b of the cover member 19 so that the fused ends 32 may be collapsed.

The insulating wall 35 may be formed on the ceiling surface 19b of the cover member 19 as shown in Fig. The insulating wall 35 may be formed integrally with the ceiling surface 19b of the cover member 19 or may be formed by printing an insulating material such as solder resist or glass on the ceiling surface 19b. In this case as well, if the insulating wall 35 has a height of at least half the height from the top surface 19b of the cover member 19 to the surface 10a of the insulating substrate 10, 32 from contacting with each other.

11, insulating walls 35 may be formed between a plurality of fused ends 32 arranged in parallel to each other, as shown in Fig. 11 Or may be formed by applying a liquid or paste-like insulating material to be constituted and curing it. As the insulating material constituting the insulating wall 35, a thermosetting insulating adhesive such as an epoxy resin, a solder resist, or a glass paste can be used. In this case, the insulating material constituting the insulating wall 35 may be applied and cured after the fuse element 31 is connected to the insulating substrate 10, or may be formed by mounting the fuse element 31 on the insulating substrate 10 Or may be applied to the heat treatment process together with the fuse element 31 to be cured.

The liquid or paste-like insulating material is filled by a capillary action between a plurality of fused ends 32 arranged in parallel, and when the fused ends 32 are fused by curing, the connection of the fused ends 32 in parallel . Therefore, the insulating material constituting the insulating wall 35 is required to have heat resistance against the heat generation temperature of the free end portion 32 by curing.

[Installation position of insulation part]

In the thermal fuse element 1, the insulating wall 35 may be formed along the fused portion of the fusing end portion 32. [ 8, each fuse element 31 is connected to the first and second electrodes 11 and 12 formed on the insulating substrate 10 so that the first and second electrodes 11 and 12, (11, 12). The heat is diffused to the first and second electrodes 11 and 12 having a light area at both end portions connected to the first and second electrodes 11 and 12 in each of the terminal ends 32, It does not. Each of the fusing end portions 32 is formed in such a manner that current does not concentrate at both ends connected to the first and second electrodes 11 and 12 and is concentrated at the middle portion between the first electrode 11 and the second electrode 12 So that current is concentrated and melted by heat generation at a high temperature.

The thermal fuse element 30 is formed by forming the insulating wall 35 adjacent to the intermediate portion between the first electrode 11 of each free end portion 32 and both end portions connected to the second electrode 12, It is possible to prevent the molten element from coming into contact with the adjacent free end portion 32.

In order to form the insulating wall 35 between the free ends 32 on the surface 10a of the insulating substrate 10 as described above, at least the molten material is applied on the surface 10a of the insulating substrate 10 The height of the insulating wall 35 may be less than half of the height from the surface 10a of the insulating substrate 10 to the top face 19b of the cover member 19. [

The thermal fuse element 30 preferably forms an insulating wall 35 between each free end 32 of the fuse element 31. As a result, it is possible to prevent the plurality of fusing ends 32 from melting and aggregating, and to prevent the aggregation of the molten element from increasing after the fusing time or the fusing of the first and second electrodes 11 , 12) can be prevented from deteriorating continuously.

The thermal fuse element 30 sequentially fuses the plurality of fusing ends 32 and fuses at least the fusing end portion 32 for first fusing and the fusing end portion adjacent to the first fusing end portion 32 It is preferable to form the insulating wall 35 between the insulating walls 35 and 32. As described above, the fuse element 31 is configured such that the cross-sectional area of a part or the whole of one fusing end portion 32 of the plurality of fusing end portions 32 is made smaller than the cross-sectional area of the other fusing end portion, When a current exceeding the rating is energized, a large amount of current is first energized and fused from the fusing end portion 32 of relatively low resistance.

At this time, the thermal fuse element 30 has the insulating wall 35 formed between the melting end portion 32 of the relatively low resistance melting firstly melting and the melting end portion adjacent to the melting end portion 32, So that it can be prevented from being brought into contact with the adjacent free end portions 32 and flocculating. Thereby, the thermal fuse element 30 is capable of fusing the fusing end portions 32 in a predetermined fusing sequence and increasing the fusing time due to integration of adjacent fusing end portions 32, It is possible to prevent deterioration of the insulating property by the insulating film.

Specifically, in the thermal fuse element 30 in which the fuse element 31 composed of the three fused ends 32A, 32B and 32C shown in Fig. 8 is mounted, the cross-sectional area of the fused end 32B A larger amount of current is preferentially flowed from the outer fusing end portions 32A and 32C and fused, and finally the fusing end portion 32B in the center is fused. At this time, the thermal fuse element 30 is provided with the insulating wall 35 between the free ends 32A and 32B and between the free ends 32B and 32C, It is possible to heat the terminal end portion 32B at the end while melting the terminal end portion 32B in a short time without contacting the adjacent free end portion 32B. The free end portion 32B having a small cross-sectional area has no contact with the adjacent free end portions 32A and 32C and has a small arc discharge at the time of melting.

In the case where three or more fuse elements are formed, it is preferable that the fuse element 31 first fuse the outer fuse element and fuse the inner fuse element last. For example, as shown in Fig. 6, it is preferable that the fuse element 31 forms three fusing ends 32A, 32B and 32C and finally fuses the fusing end 32B in the center Do.

As described above, when a current exceeding the rating is applied to the fuse element 31, a large amount of current flows first to the two fused ends 32A and 32C formed on the outside, and the fuse element 31 is fused by self heat generation. Since the fusing of the free ends 32A and 32C does not involve arc discharge due to self heat generation, there is no explosion of molten metal. As described above, the fused ends 32A and 32C are initially fused without contact with the adjacent fused ends 32B by the insulating wall 35. [0064]

Subsequently, the current is concentrated on the fused end portion 32B formed on the inner side, and the firing is carried out with the arc discharge. At this time, the fuse element 31 finally fuses the fused end portion 32B formed on the inner side so that the molten metal of the fused end portion 32B is fused to the outer fused end portion 32A , 32C and the insulating walls 35 formed between the free ends 32A, 32C. Therefore, scattering of the molten metal of the fusing end 32B can be suppressed, and short-circuit by the molten metal can be prevented.

At this time, the fuse element 31 is also formed so that the cross-sectional area of a part or the entirety of the fused end portion 32B located at the inner side among the three fused ends 32A to 32C is set to the other fused ends 32A, 32C), it is possible to relatively increase the resistance, thereby finishing finally the fusing end portion 32B in the center. In this case as well, since the cross-sectional area is made relatively small, the arc is finally fired, so that the arc discharge degree becomes small according to the volume of the fusing end portion 32B, and explosive scattering of the molten metal can be further suppressed.

[Manufacturing process of the thermal fuse element]

The thermal fuse element 30 using the fuse element 31 is assembled by the same process as the thermal fuse element 1 using the fuse element 13 and mounted on the circuit board 2. [ At this time, the thermal fuse element 30 is constituted by the low melting point metal 20 having a melting point lower than the heat treatment temperature and the high melting point metal 21 having a melting point higher than the heat treatment temperature , The thickness ratio of the low melting point metal layer 20a and the high melting point metal layer 21a can be appropriately adjusted so that the fuse element 31 can be deformed or the low melting point metal 20 is prevented from being eluted, and variation in the rating and melting point characteristics can be prevented.

When the mounted device mounted with the thermal fuse element 30 is placed in a high temperature environment such as a case where the mounted device abnormally generates heat as in the case of the mounted device of the thermal fuse element 1, The element 31 starts melting in a temperature atmosphere of the melting point of the low melting point metal 20 or higher. Thereby, in the thermal fuse element 30, each fuse element 32 of the fuse element 31 is melted prematurely, and the current path of the circuit board 2 can be cut off. Since the fuse element 31 is melted at a low temperature below the melting point of the refractory metal 21 by melting the refractory metal 21 by erosion (soldering erosion) of the refractory metal 21, The current path can be cut off.

[Modification example 2 of the fuse element: terminal part]

Further, the fuse element related to the present invention may be formed integrally with a terminal portion connected to an external circuit. In the following description, the same components as those of the above-described temperature fuse elements 1 and 30 are denoted by the same reference numerals, and the details thereof are omitted.

The thermal fuse element 40 shown in Fig. 12 (A) has an insulating substrate 10 and a fuse element 41 fitted to the surface 10a of the insulating substrate 10. The fuse element 41 is provided with a plurality of fusing ends 42A to 42C in parallel and a plurality of fusing elements 42A to 42C disposed at both ends of the fusing end portions 42A to 42C in a land portion of the circuit board 2 on which the thermal fuse element 40 is mounted A terminal portion 43 connected to the terminals 2a and 2a is formed. The fuse element 41 is made of a low melting point metal 20 having a melting point lower than the temperature of the heat treatment in the manufacturing process of the mounting member of the thermal fuse element 40 like the fuse elements 13 and 31 described above, And a refractory metal (21) having a melting point higher than the temperature of the heat treatment. The plurality of fusing end portions 42A to 42C are formed between the pair of terminal portions 43 to constitute a current carrying path and cut off the current path by fusing the entire fusing end portions 42A to 42C.

The terminal portion 43 is connected to the land portion 2a of the circuit board 2 on which the thermal fuse element 40 is mounted via an adhesive member such as Pb pre-solder, It constitutes a part. The fuse element 41 is bent so that both ends of the fuse element 41 on which the terminal portions 43 are formed are bent along the side surface of the insulating substrate 10 so that the fuse element 41 fits on the insulating substrate 10, As shown in Fig.

When the cover member 19 is mounted on the surface 10a of the insulating substrate 10 as shown in Fig. 12 (B), the thermal fuse element 40 is electrically connected to the insulating substrate 10 and the cover member 19 To the back surface 10b side of the insulating substrate 10. [0053] Thereby, the thermal fuse element 40 becomes a mount surface for the external circuit board 2 on the back surface 10b of the insulating substrate 10 and the pair of terminal portions 43 of the fuse element 41 And is connected to the land portion 2a of the circuit board 2, thereby being inserted into the external circuit.

Since the fuse element 40 has the terminal portion 43 to be a connection terminal to an external circuit, the temperature fuse element 40 can be improved in rating. That is, in a configuration in which a surface electrode, a back electrode, and a through hole for connecting the front surface electrode and the like that draw the current path of the fuse element to the external circuit are formed on the insulating substrate, the diameter of the through hole, casting, Or the resistivity of the conductive paste or the film thickness, it is difficult to achieve the resistance value of the fuse element equal to or lower than the resistance value of the fuse element.

On the other hand, the thermal fuse element 40 is formed by forming a through hole or the like in the insulating substrate 10 so as not to lead the current path of the fuse element 41 to the external circuit but to connect the fuse element 41 to the external circuit The conduction resistance between the external circuit and the fuse element 41 is determined by the rating of the fuse element 41 itself and the resistance of the fuse element 41 on the side of the insulating substrate 10 It does not. Therefore, with the thermal fuse element 40, the current path of the entire element can be made low resistance, and the rating can be easily improved.

[Preparation of fuse element]

The fuse element 41 in which the plurality of fusing ends 42 and the terminal portions 43 are formed is obtained by swaging two central portions of the plate-shaped low melting metal and the high melting metal in a rectangular shape See Fig. 7 (A)), and can be produced by bending both ends. The fuse element 41 is integrally supported on both sides of the three fused ends 42A to 42C in parallel by the terminal portion 43. [ The fuse element 41 may be manufactured by connecting a plate member constituting the terminal portion 43 and a plurality of plate members constituting the fusing end portion 42. [ The fuse element 41 is formed by bending both end portions of the plate member shown in Fig. 7B so that one end of the three fused ends 42A to 42C connected in parallel is supported integrally by the terminal portions 43, The terminal portions 43 may be formed.

Since the fuse element 41 and the external circuit are connected via the terminal portion 43 to the thermal fuse element 40, the thermal fuse element 40 is connected to the first and second electrodes 11 12 and external connection terminals 11a, 12a may not be formed.

[Fitting recess]

12 (C), it is preferable that the insulating substrate 10 be formed with a fitting recess 45 in a pair of side edge portions to which the terminal portion 43 of the fuse element 40 is fitted . The thermal fuse element 40 does not expand the mounting area of the fuse element 41 with respect to the circuit board 2 by forming the fitting recess 45 in the insulating substrate 10, Can be fixed.

Further, the fuse element 41 is directly bonded to the surface 10a of the insulating substrate 10. As the adhesive for connecting the fuse element 41 to the insulating substrate 10, it is not necessary to have conductivity, and for example, a thermosetting adhesive or the like can be used. The thermal fuse element 40 also has a thermally conductive adhesive agent for bonding the fuse element 41 to the insulating substrate 10 in that the fuse element 41 is fired by a temperature atmosphere caused by heat of an external heat source Excellent.

[Heat dissipating electrode]

The thermal fuse element 40 on which the fuse element 41 is mounted may be formed with the heat radiation electrode 46 on the surface 10a of the insulating substrate 10. The heat dissipating electrode 46 is formed near a pair of side edges of the insulating substrate 10 on which the fuse element 41 is fitted and is connected to each of the fuse terminals 42, The heat of the heat exchanger 41 can be efficiently absorbed and the molten element can be agglomerated. The heat radiating electrode 46 can be formed using an electrode material such as Ag or Cu and is subjected to heat treatment such as reflow through a connecting material such as Pb pre-solder, . The heat radiating electrode 46 may be a common electrode to which the respective fusing ends 42A to 42C are connected as shown in Fig. 12 (C), or a plurality of fusing electrodes may be formed along each fusing end 42A to 42C .

The thermal fuse element 40 can prevent the heat in the vicinity of the terminal portion 43 of the fuse element 41 from flowing to the insulating substrate 10 side And the heat generating region of each free end portion 42 is concentrated at the central portion. As a result, the fusing element 41 is limited to the central portion of each free end portion 42, so that the current path can be quickly cut off. In addition, even when the fuse element 41 is accompanied by an arc discharge, the heat generating region is limited so that explosive melting and scattering of the molten element can be prevented, and the insulating characteristic is not hindered.

The heat radiating electrode 46 may be connected to a heat radiating electrode (not shown) formed on the back surface 10b of the insulating substrate 10 through a through hole formed in the insulating substrate 10. Thereby, the thermal fuse element 40 can dissipate the heat of the fuse element 41 more efficiently.

[Manufacturing process of the thermal fuse element]

The thermal fuse element 40 using the fuse element 41 is assembled by the same process as that of the thermal fuse element 1 and is mounted on the circuit board 2. [ At this time, the thermal fuse element 40 comprises the fuse element 41 composed of the low melting point metal 20 having a melting point lower than the heat treatment temperature and the high melting point metal 21 having a melting point higher than the heat treatment temperature The heat treatment process such as the reflow process can be repeatedly performed by adjusting the film thickness ratio of the low melting point metal layer 20a and the high melting point metal layer 21a appropriately together with the deformation of the fuse element 41 or the low melting point metal 20 is prevented from being eluted, and variation in the rating and melting point characteristics can be prevented.

When the mounted device with the thermal fuse element 40 is placed in a high temperature environment such as a case where the mounted device is abnormally heated, as in the case of the mounted device of the thermal fuse element 1, the fuse element 41 has a low melting point The melting is started in a temperature atmosphere not lower than the melting point of the metal (20). Thereby, each of the fuse elements 42 of the fuse element 41 is melted in the thermal fuse element 40, and the current path of the circuit board 2 can be cut off. Since the fuse element 41 is melted at a low temperature below the melting point of the refractory metal 21 by melting the refractory metal 21 by erosion (soldering erosion) of the refractory metal 21, The current path can be cut off.

[Variation 3 of fuse element: multiple fuse elements in parallel]

The fuse element related to the present invention may be arranged in such a manner that a plurality of fuse elements corresponding to the free ends 31 are fitted between a pair of side edges of the insulating substrate 10 facing each other. In the following description, the same components as those of the above-described temperature fuse element (1, 30, 40) are denoted by the same reference numerals, and the details thereof are omitted.

The thermal fuse element 50 shown in Fig. 13 has an insulating substrate 10 and a fuse element 51 fitted to the surface 10a of the insulating substrate 10. The fuse element 51 has a plurality of, for example, 51A, 51B and 51C, arranged in parallel on the surface 10a of the insulating substrate 10. [ Each of the fuse elements 51A to 51C has a melting point lower than the temperature of the heat treatment in the manufacturing process of the mounting member of the thermal fuse element 50 as in the case of the fuse elements 13, Melting metal (20) and a refractory metal (21) having a melting point higher than the temperature of the heat treatment. Each of the fuse elements 51 is formed in a rectangular plate shape and has a fusing end portion 52 for fusing in a temperature atmosphere equal to or higher than the melting point of the low melting point metal 20 and a fusing end portion 52 formed at both ends of the fusing end portion 52, And a terminal portion 53 connected to the land portion 2a of the circuit board 2 is formed.

The fusing end portion 52 is connected to the heat radiation electrode 46 formed on the surface 10a of the insulating substrate 10 via a heat treatment process such as reflow through an adhesive material such as Pb free solder .

The terminal portion 53 is connected to the land portion 2a of the circuit board 2 on which the thermal fuse element 50 is mounted via an adhesive member such as Pb free solder, And each of the free ends 52 cuts off the current path by melting. The fuse element 51 is bent so that both ends of the fuse element 51 on which the terminal portions 53 are formed are bent along the side surface of the insulating substrate 10 so that the fuse element 51 is fitted to the insulating substrate 10, As shown in Fig. Thereby, the thermal fuse element 50 becomes a mounting surface for the circuit board 2 on the outer side of the back surface 10b of the insulating substrate 10 and the pair of terminal portions 53 of the fuse element 51 And is connected to the land portion 2a of the circuit board 2, thereby being inserted into the external circuit.

The thermal fuse element 50 is configured such that the cross sectional area of the center fuse element 51B formed inside is made smaller than the cross sectional area of the other fuse elements 51A and 51C formed on the outside, And may be fused at the end when the self heat generation accompanying the overcurrent is interrupted.

Further, the thermal fuse element 50 may form the insulating wall 35 between the respective fuse elements 51A to 51C. By forming the insulating wall 35, the thermal fuse element 50 is melted and expanded by the ambient temperature atmosphere or its own heat generation when the respective fuse elements 51 are fused, So as to prevent agglomeration. As a result, the thermal fuse element 50 becomes larger as the adjacent fuse elements 51 are melted and agglomerated, and the increase of the melting time due to an increase in the amount of heat required for melting, It is possible to prevent the explosion of molten metal from scattering due to the enlargement of the arc discharge occurring at the time of melting due to the self heat generation accompanying the overcurrent.

The thermal fuse element 50 can be formed by arranging a plurality of plate-like fuse elements not provided with the terminal portions 53 in parallel between the first and second electrodes 11 and 12 formed on the insulating substrate 10 do.

[Variation 4 of fuse element: flip type]

Further, the fuse element related to this technique may protrude the terminal portion of the fuse element to the surface 10a side of the insulating substrate 10. In the following description, the same components as those of the above-described temperature fuse element 1, 30, 40, 50 are denoted by the same reference numerals, and the details thereof are omitted.

The thermal fuse element 60 shown in Fig. 14 (A) has an insulating substrate 10 and a fuse element 61 connected to the surface 10a of the insulating substrate 10. The fuse element 61 is provided with a plurality of fusing ends 62A to 62C in parallel and at both ends of the fusing end portions 62A to 62C with the land portions of the circuit board 2 on which the thermal fuse elements 60 are mounted 2a are formed in the terminal portion 63. [ The fuse element 61 has a low melting point having a melting point lower than the temperature of the heat treatment in the manufacturing process of the mounting member of the thermal fuse element 60 like the fuse element 13, 31, 41, Metal 20 and a refractory metal 21 having a melting point higher than the temperature of the heat treatment.

The plurality of fusing ends 62A to 62C are connected to the surface 10a of the insulating substrate 10 via an adhesive material such as Pb free solder to constitute a current conduction path of the current, To 62C cut off the current path by blowing.

The terminal portion 63 is connected to the land portion 2a of the circuit board 2 on which the thermal fuse element 60 is mounted so as to form a part of the current path of the circuit board 2. [ The fuse element 60 is mounted on the surface 10a of the insulating substrate 10 so as to face the surface 10a side of the insulating substrate 10.

When the cover member 19 is mounted on the surface 10a of the insulating substrate 10 as shown in Fig. 14 (B), the thermal fuse element 60 is electrically connected to the insulating substrate 10 and the cover member 19 To the side of the surface 10a of the insulating substrate 10. Thereby, the thermal fuse element 40 becomes a mounting surface for the external circuit board 2 on the surface 10a of the insulating substrate 10, and as shown in Fig. 14 (C) A pair of terminal portions 63 of the fuse element 61 are connected to the land portion 2a of the circuit board 2 and inserted into the external circuit.

Since the thermal fuse element 60 has the terminal portion 63 which is a connection terminal to the external circuit in the fuse element 60 like the temperature fuse element 40, the rating can be improved.

14 (D), the thermal fuse element 60 is arranged on the surface of the insulating substrate 10 along the fusing end portion 62 of the fuse element 61, like the thermal fuse element 40 A plurality of heat dissipating electrodes 46 may be formed on the upper and lower ends 10a and 10a and connected to the respective fusing ends 62 through heat treatment such as reflow through a connecting material such as Pb pre-solder.

The fuse element 60 may be a fuse element composed of a single fuse element 62 and a pair of terminal parts 63 formed at both ends of the fuse element 62.

[Manufacturing process of the thermal fuse element]

The thermal fuse element 60 using the fuse element 61 is assembled by the same process as that of the thermal fuse element 1 and mounted on the circuit board 2. [ At this time, the thermal fuse element 60 comprises the fuse element 61 composed of the low melting point metal 20 having a melting point lower than the heat treatment temperature and the high melting point metal 21 having a melting point higher than the heat treatment temperature , The thickness ratio of the low melting point metal layer 20a and the high melting point metal layer 21a can be appropriately adjusted so that the fuse element 61 is deformed or the low melting point metal 20 is prevented from being eluted, and variation in the rating and melting point characteristics can be prevented.

When the mounted device mounted with the thermal fuse element 60 is placed in a high temperature environment such as a case where the mounted device abnormally generates heat as in the case of the mounted device of the thermal fuse element 1, The melting is started in a temperature atmosphere not lower than the melting point of the metal (20). Thereby, in the thermal fuse element 60, each free end portion 62 of the fuse element 61 is melted in an early stage, and the current path of the circuit board 2 can be cut off. Since the fuse element 61 is melted at a low temperature below the melting point of the refractory metal 21 by melting the refractory metal 21 by erosion (soldering erosion) of the refractory metal 21, The current path can be cut off.

[Modification Example 5 of Fuse Element: Wire Bonding Type]

Further, in the fuse element related to the present invention, both ends of the fuse element may be connected to the first electrode and the second electrode via a connection material. In the following description, the same components as those of the above-described temperature fuse elements 1, 30, 40, 50, and 60 are denoted by the same reference numerals, and the details thereof are omitted.

The thermal fuse element 70 shown in Figs. 15A and 15B includes an insulating substrate 10 and a first electrode 11 and a second electrode (not shown) formed on the surface 10a of the insulating substrate 10 A fuse element 71 placed on the surface 10a of the insulating substrate 10 and a connection material connecting the opposite ends of the fuse element 71 to the first electrode 11 and the second electrode 12, In wires 72 and 73, respectively. The fuse element 71 has a melting point lower than the temperature of the heat treatment in the manufacturing process of the mounting member of the thermal fuse element 70, similarly to the fuse elements 13, 31, 41, 51 and 61 described above Melting metal (20) and a refractory metal (21) having a melting point higher than the temperature of the heat treatment.

The fuse element 71 has a rectangular plate-like structure and does not form a terminal portion by bending or the like. The fuse element 71 is fixed to the surface 10a of the insulating substrate 10 with an adhesive material and is connected to the first electrode 11 and the second electrode 12 by wire bonding. Thereafter, a necessary and sufficient amount of the flux 17 is applied to constitute a current conduction path for current, and the current path is cut off by fusing the distal end portion.

4 (B), the fuse element 71 has a structure in which the inside is made of a low melting point metal 20 and the outside is covered with a high melting point metal 21. The fuse element 71 is made of a low melting point metal 20, This is the structure that has been revealed.

The fuse element 71 is formed on the surface 10a of the insulating substrate 10 such that the cut surface at which the low melting point metal 20 is exposed is parallel to both sides of the current flowing direction.

The wires 72 and 73 are wire members formed of a conductive metal or the like and connect both ends of the fuse element 71 to the first electrode 11 and the second electrode 12, respectively. In particular, the wires 72 and 73 can be easily formed by wire bonding. As the material, Au, Al, Cu, or the like can be used.

The wires 72 and 73 are connected to both ends of the fuse element 71 in the energizing direction. Since both ends of the fuse element 71 in the energizing direction are covered with the refractory metal 21, It is preferable to use a member having good connectivity with the melting point metal 21.

Here, the position where the fuse element 71 is connected to the first electrode 11 and the second electrode 12 will be described. As shown in Fig. 15A, the connection position by the wires 72 and 73 is a position facing the energizing direction. However, the connection positions by the wires 72 and 73 may be shifted appropriately to avoid the position of the through hole. That is, the wires 72 and 73 may be diagonal positions of the rectangular fuse elements. In the case of taking a diagonal position, the workability of wire bonding can be improved by avoiding the through hole of the insulating substrate 10 shown in Fig. 15 (A). The wires 72 and 73 are not limited to a pair of opposing pairs, but may be connected by a plurality of wires.

The thermal fuse element 70 having such a structure simultaneously acts not only at the terminal end of the fuse element 71 itself but also at the connection point between the fuse element 71 and the wires 72 and 73, Can be blocked. More specifically, when the material of the wires 72 and 73 is Au, the high melting point metal 21 to be connected is rapidly eroded into the low melting point metal 20, The metal 20 contacts. When the molten low melting point metal 20 is brought into contact with the wires 72 and 73, the wires 72 and 73 are melted into the melted low melting point metal 20 so that the current path can be blocked more quickly and reliably .

[Modification example 6 of fuse element: solder connection type]

Further, in the fuse element related to the present invention, both ends of the fuse element may be connected to the first electrode and the second electrode via a connection material. In the following description, the same components as those of the above-described temperature fuse elements 1, 30, 40, 50, 60, and 70 are denoted by the same reference numerals, and the details thereof are omitted.

The thermal fuse element 80 shown in Figs. 16A and 16B includes an insulating substrate 10 and a first electrode 11 and a second electrode (not shown) formed on the surface 10a of the insulating substrate 10 A fuse element 81 mounted on the surface 10a of the insulating substrate 10 and a connecting material 81 for connecting both ends of the fuse element 81 to the first electrode 11 and the second electrode 12, And solder paste 82, 83, respectively. The fuse element 81 has a melting point lower than the temperature of the heat treatment in the manufacturing process of the mounting member of the thermal fuse element 80, like the above-described fuse elements 13, 31, 41, 51, 61, Melting metal (20) having a melting point higher than that of the heat treatment and a refractory metal (21) having a melting point higher than the temperature of the heat treatment. Although not shown, a sufficient amount of flux is applied to the surface of the fuse element 81.

The fuse element 81 has a rectangular plate-like structure, and the terminal portion is not formed by bending or the like. The fuse element 81 is mounted on the surface 10a of the insulating substrate 10 and connected to the first electrode 11 and the second electrode 12 by the solder paste 83 and 84, And the current path is blocked by melting the fusing part.

The fuse element 81 has a structure in which the inside is made of a low melting point metal 20 and the outside is covered with a high melting point metal 21 as in the case described in FIG. This is the structure that has been revealed.

The fuse element 81 is formed on the surface 10a of the insulating substrate 10 such that the cut surface at which the low melting point metal 20 is exposed is perpendicular to the current flowing direction.

The solder paste 83 or 84 is formed on the protruding portion 11a of the first electrode 11 and the protruding portion 12a of the second electrode 12 by Pb-free solder or the like, And both ends of the fuse element 81 are connected to the first electrode 11 and the second electrode 12, respectively. Further, the connection portion of the fuse element 81 may be constituted by the solder bumps.

The solder paste 83 and the solder paste 84 are respectively connected to both sides of the fuse element 81 in the energizing direction so as to face the surface 10a of the insulating substrate 10. The fuse element 81 is a non- It is preferable to use a member having good connectivity with the refractory metal 21 because the both ends of the refractory metal 21 are covered with the refractory metal 21. [ It is also possible to suppress the outflow of the low melting point metal 20 to the first electrode 11 and the second electrode 12 by connecting the solder paste 83 and 84 to only the refractory metal 21, 81 can be stabilized and the rated current can be prevented from decreasing.

Here, the position where the fuse element 81 is connected to the first electrode 11 and the second electrode 12 will be described. The connection positions by the solder paste 83 and 84 are respectively located at positions opposed to the central portion in the direction orthogonal to the energization direction, as shown in Figs. 16A and 16B. The protruding portion 11a of the first electrode 11 and the protruding portion 12a of the second electrode 12 are also disposed at the center in the direction perpendicular to the energizing direction of the fuse element 81 and facing each other in the energizing direction have.

The connection positions by the solder paste 83 and 84 are not limited to the opposing arrangement as shown in Figs. 16A and 16B, and the projecting portion 11a of the first electrode 11 and the connection portion The solder paste 83 or 84 may be positioned at the diagonal position of the rectangular fuse element depending on the position of the protruding portion 12a of the fuse element 12. The solder paste 83 and the solder paste 84 are not limited to a pair of opposed ones but may be formed in the same manner as in the case of forming the plurality of projections of the first electrode 11 and the second electrode 12, A plurality of solder pastes may be used depending on the number.

1 Thermal fuse element,
10 Insulation board,
11 first electrode,
11a protrusions,
12 second electrode,
12a protrusion,
13 Fuse element,
13a melting element,
14 protective layer,
15 adhesive material,
17 flux,
19 cover member,
20 Low melting point metal,
20a Low melting point metal layer,
21 High melting point metal,
21a high melting point metal layer,
23 Oxidation prevention film,
24 protective member,
25 adhesive,
30 Thermal fuse element,
31 Fuse element,
32 terminal portion,
34 plateau,
35 Insulation wall,
40 Thermal fuse element,
41 Fuse element,
42 terminal portion,
43 terminal portion,
44 Plate,
45 fitting recess,
46 heat dissipation electrode,
50 Thermal fuse element,
51 Fuse element,
52 terminal portion,
53 terminal portion,
60 Thermal fuse element,
61 Fuse element,
62 terminal portion,
63 terminal portion,
70 Thermal fuse element,
71 Fuse element,
72 wire,
73 wire,
80 Thermal fuse element,
81 Fuse element,
82 solder paste,
83 Solder Paste.

Claims (28)

A method of manufacturing a mounting body in which a thermal fuse element is mounted on a circuit board,
The thermal fuse element is subjected to heat treatment at least once,
Wherein the thermal fuse element has a low melting point metal having a melting point lower than the heat treatment temperature and a high melting point metal having a melting point higher than the heat treatment temperature and having a melting point higher than the melting point of the low melting point metal, A fuse element which is melted in a temperature atmosphere,
Wherein the heat treatment is performed at a temperature equal to or higher than the melting point of the low melting point metal. The method according to claim 1,
In the heat treatment,
The thermal fuse element is mounted on a land portion of the circuit board via a connection material,
And heating the circuit board on which the thermal fuse element is mounted in a heating furnace and mounting the thermal fuse element on the circuit board via the connection material. 3. The method according to claim 1 or 2,
Wherein the fuse element has resistance not to be fused even by the heat treatment at least three times. 3. The method according to claim 1 or 2,
Wherein the low melting point metal is solder. 3. The method according to claim 1 or 2,
Wherein the low melting point metal is an alloy containing Sn or Sn as a main component and the high melting point metal is an alloy containing Ag, Cu, or Ag or Cu as a main component. 3. The method according to claim 1 or 2,
Wherein the low-melting-point metal is an Sn / Bi-based or Sn / In-based alloy. 3. The method according to claim 1 or 2,
Wherein the low melting point metal has a larger volume than the high melting point metal. 3. The method according to claim 1 or 2,
Wherein the fuse element is laminated with the low melting point metal and the high melting point metal. 3. The method according to claim 1 or 2,
Wherein the fuse element has the low melting point metal covered with the high melting point metal. 3. The method according to claim 1 or 2,
Wherein said fuse element is formed by plating said refractory metal on the surface of said low melting point metal. 3. The method according to claim 1 or 2,
Wherein the fuse element is formed by adhering a metal foil of the refractory metal to the surface of the low melting point metal. 3. The method according to claim 1 or 2,
Wherein the fuse element is formed by forming the refractory metal on the surface of the low melting point metal by a thin film forming step. 3. The method according to claim 1 or 2,
Wherein an oxidation preventing film is formed on the surface of the refractory metal. 3. The method according to claim 1 or 2,
Wherein the fuse element is formed by laminating a plurality of layers of the refractory metal and the refractory metal alternately. 3. The method according to claim 1 or 2,
Wherein the fuse element is formed by coating an outer peripheral portion of the low melting metal except a pair of opposing end faces thereof with the high melting metal. 3. The method according to claim 1 or 2,
Wherein the fuse element includes a terminal portion connected to a land portion of the circuit board. 17. The method of claim 16,
And the terminal portion is a surface mounting terminal. 17. The method of claim 16,
Wherein the land portion of the circuit board is connected only to the refractory metal portion of the terminal portion via the connecting material. 3. The method according to claim 1 or 2,
Wherein at least a part of an outer periphery of the fuse element is protected by a protection member. 3. The method according to claim 1 or 2,
Wherein the film thickness of the low melting point metal is 30 占 퐉 or more and the film thickness of the high melting point metal is 3 占 퐉 or more. 3. The method according to claim 1 or 2,
Wherein the film thickness ratio of the low melting point metal and the high melting point metal is from 2.1: 1 to 100: 1. 21. The method of claim 20,
Wherein the film thickness ratio of the low melting point metal and the high melting point metal is from 2.1: 1 to 100: 1. 3. The method according to claim 1 or 2,
Wherein the fuse element is melted in a temperature atmosphere of the melting point of the low melting point metal or higher and lower than or equal to the heat treatment temperature. 22. The method of claim 21,
Wherein the fuse element is melted in a temperature atmosphere of the melting point of the low melting point metal or higher and lower than or equal to the heat treatment temperature. A mounting method for mounting a thermal fuse element on a circuit board,
The thermal fuse element is subjected to heat treatment at least once,
Wherein the thermal fuse element has a low melting point metal having a melting point lower than the heat treatment temperature and a high melting point metal having a melting point higher than the heat treatment temperature and having a melting point higher than the melting point of the low melting point metal, A fuse element which is melted in a temperature atmosphere,
Wherein the heat treatment is performed at a temperature equal to or higher than the melting point of the low melting point metal. A thermal fuse element constituting a mounting body by being mounted on a circuit board and undergoing at least one heat treatment step in the manufacturing step of the mounting body,
An insulating substrate,
First and second electrodes formed on the insulating substrate;
Melting metal having a melting point lower than the temperature of the heat treatment step and a high melting point metal having a melting point higher than the temperature of the heat treatment step and is mounted between the first and second electrodes, And a fuse element which melts when the temperature of the fuse element is lower than the melting point of the refractory metal, thereby blocking the first and second electrodes. 27. The method of claim 26,
Wherein the first and second electrodes are connected only to the refractory metal of the fuse element via a connection material in connection of the first and second electrodes and the fuse element. 28. The method of claim 26 or 27,
And a heating element formed on the insulating substrate, wherein the fuse element is fused by heat generation of the heating element.

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