JPH11306940A - Thermal fuse and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the diameter and length of a case as mush as possible by forming a metallic thin film consisting of one or more elements selected from Sn, Pb, Bi, In, Sb, Ag, and Cd and having a specific thickness on the surface of a lead wire. SOLUTION: In the central part of the inside of a case 15 in a thermal fuse 10, a low melting point metallic pellet 11 supported from the both sides by means of a lead wire 12 is arranged, while both ends of the case 15 are sealed by sealing resin 16. This thermal fuse 10 features a thickness and material of a metallic thin film formed on the surface of the lead wire 12, that is, the metallic thin film is provided with a thickness of 5-10 μm and constructed of one or more elements selected from Sn, Pb, Bi, In, Sb, Ag, and Cd. Formation of this metallic thin film is required for improving adhesion of the low melting point metallic pellet 11 supported by the lead wire 12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal fuse in which leads are joined by low-melting metal pellets, that is, a so-called alloy type thermal fuse. The present invention relates to a technology for providing a highly reliable thermal fuse.

[0002]

2. Description of the Related Art A thermal fuse has a small and robust structure capable of detecting a temperature abnormality and interrupting a circuit.
Detects an abnormal rise in the heat of household or industrial electrical equipment and immediately shuts off the circuit to prevent equipment damage and fire. The heat-sensitive element includes a type using a temperature-sensitive pellet and a type using a low-melting alloy, that is, a low-melting metal pellet. The general operating temperature range is about 70 to 240 ° C. using the temperature-sensitive pellet, and 70 to 180 ° C. to 190 using the low melting point alloy, that is, the low melting point metal pellet.
C., and the rated current corresponds to a wide current range of about 0.5 to 15 amperes.

The characteristics of a thermal fuse are that it is compact and has excellent temperature sensitivity to the ambient temperature, that it has high operating accuracy due to its airtight structure and that its characteristics do not change over time, and that it is non-return type and operates once. Then, even if the temperature is lowered, it does not return, so that high security can be ensured, and its application can be optimized by selecting several kinds of thermal fuses according to the application. In particular, in recent years, high security has been required for so-called home appliances and industrial electronic devices, and this type of thermal fuse has been widely used in homes and industries. .

[0004] More specifically, electric kotatsu, electric stove, electric carpet, iron and trouser press, hair dryer, air conditioner and fan, gas bath and gas water heater, pencil sharpener, sewing machine, LCD TV and game machine, color TV and stereo It is used in various products such as video, refrigerators, electric rice cookers, microwave ovens, fluorescent lamps, desk lamps, transformers and power supplies, inverters, chargers and rechargeable batteries, pack batteries, copiers and printers. It is also used in other types of manufacturing equipment and processing equipment as industrial machines.

As described above, the present invention relates to a thermal fuse, and more particularly to a thermal fuse in which a lead wire is joined to a low melting point metal pellet, a so-called alloy type thermal fuse. This will be described below. First, FIG. 17 is a cross-sectional view showing a normal state and an operating state of a thermal fuse 170 using a conventional low melting point metal pellet. First, this thermal fuse 1
The function of 70 will be briefly described. FIG. 7A shows a normal state as described above, but lead wires 177 and 178 are joined to both ends of a low melting point metal pellet 175 arranged at the center, and the low The portion of the melting point metal pellet 175 and a portion including the lead wires 177 and 178 are housed in a case 171, and both ends of the case 171 are sealed with a sealing resin 176 to maintain airtightness.

The current may flow from any direction. For example, the current passes through the sealing resin 176 from the lead 177 on the left side of the drawing, enters the low melting point alloy pellet 175 as it is, and then passes from the low melting point metal pellet 175 to the right side lead 178. And a current flows from the right lead 178 to another electronic device. This current is connected to a power supply or a control circuit of a device or the like that generates heat in the electronic device. When the temperature fuse 170 operates, that is, the state as shown in FIG. Melting point metal pellet 17
When the current circuit 5 is melted and the current circuit is cut off, heat generation is stopped, and destructive damage to equipment or disasters such as fire can be prevented.

More specifically, the structure under normal conditions will be described in detail. Generally, these lead wires 177 and 178 are made of copper or a metal wire of a good conductor close to copper, and have a surface of about 1 to 2 microns. Plating. This plating is used to improve the solderability when connecting the thermal fuse 170 to the controlled circuit and to improve the lead 1
77 and 178 are formed in order to improve the bonding property with the low-melting-point metal pellet 175 which is sandwiched and arranged at the central part of the metal pellets 177 and 178. The periphery of the low melting point metal pellet 175 is covered with a so-called flux 174.

Although this flux 174 is not directly related to the gist of the present invention, in brief, as shown in FIG. 1B, during operation, the low melting point metal pellet 175 is in a molten state and is in a high temperature state. The surface of the low-melting metal pellet 175 in the high temperature state has extremely high activity and is easily oxidized. If the flux 174 is not used as it is, it reacts with the gas contained in the case 171 of the hermetic terminal to form an oxide layer on the surface. Is formed.

When an oxide layer is formed on the surface, melting or spheroidal shrinkage is difficult to progress, which is a factor preventing complete interruption of a current circuit. Therefore, as shown in FIG.
4 is applied, and by the reducing action of the flux 174, the oxide film on the surface of the low melting point metal pellet 175 can be removed even if the low melting point metal pellet 175 is in a molten state. The spheroidization of the 175 and the interruption of the circuit are made easy and reliable.
As described above, the case 171 for accommodating the low-melting metal pellet 175 is generally made of nonconductive ceramics or other similar materials, and has a cylindrical shape. In an open state.

In the manufacturing process, when the lead 177, the low-melting metal pellet 175, and the one joined to the lead 178 are inserted from the opening and the low-melting metal pellet 175 is arranged at the center, both ends of the case 171 are sealed. The resin 176 is used for sealing. The sealing with the sealing resin 176 is performed in order to prevent the low-melting-point metal pellets 175 from being combined with components in the atmosphere and causing the surface to be altered such as an oxide film. Since the low-melting metal pellet 175 is completely sealed with the sealing resin 176 in this manner, even if the low-melting metal pellet 175 itself is easily oxidized and has low corrosion resistance, the entire thermal fuse 170 is extremely severe. Even under the environment, reliable operation is always guaranteed.

Next, the operation state will be described. FIG. 6B shows a state in which the normal temperature fuse 170 of FIG. 7A operates by being heated as described above, and the current circuit is cut off. In the thermal fuse 170 at the time of operation shown in FIG. 7B, a low melting point metal pellet 175 is drawn into a spherical shape and shrunk on both sides near the center of the case 171.

As described above, the ambient temperature of the low-melting metal pellet 175 rises, and the temperature of the low-melting metal pellet 175 itself becomes a melting point or a temperature close to the melting point due to heat transfer or heat radiation. An operation of retreating to the leads 177 and 178 side while fusing at the center by the force of surface tension and spheroidizing on both sides is performed. In this way, the low-melting metal pellet 175 is melted and spheroidized and receded from the center to both sides, so that the left lead 1
A space that does not contain a conductive material is generated between 77 and the lead wire 178 on the right side, and the current circuit is cut off at this portion, so that the current for the thermal fuse 170 can be cut off.

An important point in this case is that a certain space must be provided inside the case 171 in order to promote the spheroidization, and that the spheroidization is promoted and the left and right leads are respectively located from the center. Even when the spheroidized melt of the low-melting alloy pellet 175 recedes toward the lines 177 and 178, if the gap between them is small, the current is not necessarily completely shut off and the spark is Dangerous conditions such as instantaneous current flow due to or other causes. Therefore, the retreat of the low melting point metal in the molten state in which the spheroidization is promoted to the left and right sides from the central portion must be sufficiently separated. Therefore, also from this viewpoint, the space inside the case is designed under certain restrictions.

Next, the one shown in FIG. 18 will be described.
FIG. 18 shows a so-called flat alloy-type thermal fuse 180, that is, a low-melting metal pellet 185 disposed on a substrate 184 made of ceramics and the like, and lead wires 187 on both sides thereof.
188 is a thermal fuse 180 formed by joining the thermal fuse 180. FIG.
In the conventional thermal fuse 170 shown in FIG. 7, the low melting point metal pellet 175 disposed at the center of the lead wires 177 and 178 on both sides is disposed in the space inside the case 171 without contacting any side surface of the case 171. However, in the case of the low melting point alloy type thermal fuse 180 shown in FIG. 18, the low melting point metal pellet 185 is directly disposed on the substrate 184, at which point the low melting point metal when the central portion is blown is melted. FIG. 17 also shows the state of spheroidization of pellet 185
Will be different.

However, even in the case of the low melting point alloy type thermal fuse 180 shown in FIG. 18, the basic principle is the same as that of the thermal fuse 170 shown in FIG.
The low-melting metal pellet 185 disposed on the substrate 184 in the central portion is melted from the substantially central portion in a state where the temperature has reached the melting point due to heat transfer due to an increase in ambient temperature and heat radiation, and the left and right lead wires are caused by surface tension. The circuit is interrupted by the retreat of the low-melting metal spheroidized on the 187 and 188 sides. Note that the thermal fuse 1 shown in FIG. 18 is similar to that described in the thermal fuse 170 shown in FIG.
Also at 80, a so-called flux 186 is disposed around the low melting point metal pellet 185 to prevent oxidation.
In order to ensure airtightness, a high degree of reliability and specifications in a severe environment are secured by arranging a certain resin on the substrate and hermetically sealing the low melting point metal pellet 185 itself from the surrounding atmosphere.

Next, the specifications of the conventional low melting point alloy type thermal fuse, such as dimensions, will be described. Currently, electronic devices are being improved toward further miniaturization, and thermal fuses are no exception. If a device is downsized, the electronic components included in the device must be downsized. Particularly in the case of a thermal fuse, the outer diameter of the case and the total length of the thermal fuse mainly including the case are subject to downsizing. Becomes

Therefore, for this purpose, it is necessary to make the lead wire thinner and to make the metal pellet disposed in the case smaller, but at present, the outer diameter of the case is small even if the size is small. About 2mm and total length is 10m
m, and it is difficult to realize dimensions smaller than this without some improvement for further miniaturization. In general, an organic stearin sun or the like is used as a material of the flux, but a material having a carbon number of about 15 to 20 is particularly preferable, and stearin sanamide or rosin is preferably used as an activator. At present, an epoxy resin or the like is used as a resin for sealing the case.

[0018]

As described above, in recent years, there has been a high demand for miniaturization of electronic devices and electronic components used in the electronic devices. Is growing. However, thermal fuses are required to have extremely high reliability, and must be able to withstand use even in a severe environment. From this point of view, there has been a certain limit to miniaturization.

Specifically, in order to reduce the size, it is necessary to ensure a sufficient space between the spherical low-melting metal pellets in the molten state inside the case as described above, and also to prevent vibration or external The low melting point metal pellet supported on the lead wire by force or the like must not come off or be broken from the lead wire. From this viewpoint, the low-melting metal pellet must be firmly fixed to the lead wire. Generally, the low-melting metal pellet is sufficiently heated and covered from the end of the lead wire to a certain area with the low-melting metal pellet. In this case, the lead wire and the low melting point metal pellet are joined.

The outer diameter of the case is also sufficient so that the spheroidized low-melting metal that has been melted due to high temperature can be separated from the case with a sufficient distance secured in the case. It was necessary to secure a space that could be stored in the car. These points are the same as those in FIG.
The same applies to the thermal fuse as shown in FIG. Therefore, in the prior art, it was impossible to reduce the wire diameter of the lead wire or to reduce the size of the low melting point metal pellet in order to ensure the joining between the lead wire and the low melting point metal. Also, since the low-melting point metal ball in the molten state must separate from the central portion to the left and right lead wires and retreat, it is difficult to reduce the inner diameter of the case or the outer diameter of the case and the total length of the case. there were.

According to the present invention, the joining between the low melting point metal pellet and the lead wire is made small enough so that even if the low melting point metal pellet is made small, the joining can be performed sufficiently securely.
The diameter of the low-melting-point metal pellet and the lead wire joined to it were reduced as much as possible. In addition, since the diameter of the ball of the molten low-melting metal pellet in the molten state retreating left and right from the center of the case can be reduced, the inner and outer diameters of the thermal fuse should be reduced as much as possible. And the overall length of the case could be shortened. Hereinafter, these will be sequentially described.

[0022]

According to the present invention, there is provided a thermal fuse comprising a low melting point metal pellet and a lead wire joined thereto.
n, Pb, Bi, In, Sb, Ag, Cd.
Provide a thermal fuse formed below 0 microns.

Further, Sn, P
forming a metal thin film made of any one or more of b, Bi, In, Sb, Ag, and Cd from 5 μm to 10 μm; a lead wire on which the metal thin film is formed and a low melting metal pellet And a method of manufacturing a thermal fuse.

A low-melting-point metal pellet is formed by joining a pair of leads to a low-melting-point metal pellet. Provide a thermal fuse formed less than 10 microns.

A step of forming a low-melting point alloy thin film on the surface of the pair of lead wires of 5 μm to 10 μm; and forming the low-melting point metal pellet and the low-melting point metal pellet on the low melting point metal pellet. Bonding a metal thin film having substantially the same composition as the metal thin film.

A method of manufacturing a thermal fuse in which a pair of lead wires is joined to a low melting point metal pellet, wherein Sn, Pb, Bi, A step of forming a metal thin film made of any one or more of In, Sb, Ag, and Cd elements of 2 μm or more and 10 μm or less, and joining a lead wire on which the metal thin film is formed and a low melting point metal pellet; And a method for manufacturing a thermal fuse comprising the steps of:

A thermal fuse comprising a low melting point metal pellet and a pair of lead wires joined thereto, wherein the pair of the lead wire and the low melting point metal pellet have a junction cross section of 30% or more in a sectional area ratio. Sn, Pb, Bi, In, Sb,
A step of forming a low-melting-point metal thin film composed of one or more of Ag and Cd elements of 2 to 10 microns, and a lead wire and a low-melting-point metal pellet formed with the low-melting-point metal thin film, Bonding a material having substantially the same composition as the low-melting-point metal thin film.

A low-melting-point metal pellet is formed by joining a pair of leads to a low-melting-point metal pellet. A cross-sectional thin film forming step of forming a low-melting-point metal thin film having the same composition as the low-melting-point metal pellet, in a range of 2 μm to 10 μm; And a method for manufacturing a thermal fuse comprising the steps of:

A method of manufacturing a thermal fuse comprising joining a pair of lead wires to a low melting point metal pellet, wherein the low melting point metal pellet is formed on a surface of the metal wire before being cut as the lead wire. Forming a low melting point metal thin film having substantially the same composition, cutting the metal wire into the lead wire having a predetermined length, and spreading the low melting point metal thin film on a cut surface; Bonding a metal pellet and the cut surface of the lead wire to each other.

A method of manufacturing a thermal fuse comprising joining a pair of leads to a low-melting metal pellet, wherein Sn, Pb, Bi, Sn, Pb, Bi, Forming a metal thin film made of any one or more of In, Sb, Ag, and Cd; cutting the metal wire into the lead wire having a predetermined length; And a step of joining the low-melting-point metal pellet and the cut surface of the lead wire to each other.

A method of manufacturing a thermal fuse in which a pair of lead wires are joined to a low melting metal pellet, wherein the surface of the metal wire before being cut as the lead wire contains 63% by weight of Sn in advance. % Or more, and a balance is formed, if necessary, of a metal thin film composed of one or more elements of Pb, Bi, In, Sb, Ag, and Cd and unavoidable impurities. Cutting the length of the lead wire, spreading the metal thin film on a cut surface, and joining the low melting point metal pellet and the cut surface of the lead wire. A manufacturing method is provided.

A method of manufacturing a thermal fuse comprising joining a pair of lead wires to a low-melting-point metal pellet, wherein the surface of the metal wire before being cut as the lead wire contains 63% by weight of Sn in advance. % Or more, and Pb contains 37% or less by weight if necessary, with the balance being Bi, In, Sb, Ag,
Forming a metal thin film composed of one or more elements of Cd and unavoidable impurities, cutting the metal wire into the lead wire having a predetermined length, and spreading the metal thin film on the cut surface; Extending, and joining the low-melting metal pellet and the cut surface of the lead wire,
A method for manufacturing a thermal fuse comprising:

A method of manufacturing a thermal fuse comprising joining a pair of leads to a low-melting metal pellet, wherein a thin metal film made of Sn is previously formed on the surface of the metal wire before being cut as the lead. Forming and cutting the metal wire into the lead wire having a predetermined length,
Spreading the metal thin film made of Sn on a cut surface;
Bonding the low-melting point metal pellet and the cut surface of the lead wire to each other.

A method of manufacturing a thermal fuse comprising joining a pair of lead wires to a low melting point metal pellet, wherein the joining between the low melting point metal pellet and the lead wire is performed mainly by using a cut surface of the lead wire. Provided is a method for manufacturing a thermal fuse that is joined only by using a thermal fuse.

A method for manufacturing a thermal fuse in which a pair of lead wires are joined to a low melting point metal pellet, wherein the surface of the metal wire before being cut as the lead wire contains 63% by weight of Sn in advance. %, And forming a metal thin film composed of any one or more of Pb, Bi, In, Ag, and Cd as necessary, and replacing the metal wire with the lead wire having a predetermined length. And cut it into
The step of spreading the metal thin film on the cut surface and the joining of the low melting point metal pellet and the lead wire provide a method of manufacturing a thermal fuse in which the lead wire is joined mainly by only the cut surface.

A method of manufacturing a thermal fuse comprising joining a pair of lead wires to a low-melting metal pellet, wherein a metal thin film made of Sn is previously formed on the surface of the metal wire before being cut as the lead wire. Forming and cutting the metal wire into the lead wire having a predetermined length,
Spreading the metal thin film made of Sn on a cut surface;
The present invention provides a method for manufacturing a thermal fuse in which the low melting point metal pellet and the lead wire are joined mainly by only a cut surface of the lead wire.

[0037]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As described above, in the present application, by providing a thermal fuse and a method of manufacturing a thermal fuse according to claims 1 to 15, the problem to be solved by the invention can be surely solved. I got it. Hereinafter, the contents of the present invention will be sequentially described along with the claims. First, as described above, the invention according to claim 1 is a thermal fuse in which a lead wire is joined to a low melting point metal pellet, and Sn, Pb, Bi, In,
An object of the present invention is to provide a thermal fuse in which a metal thin film made of one or more of Sb, Ag, and Cd elements is formed in a range of 5 to 10 microns.

The point of difference between the present invention and the conventional invention is that the thickness of the metal thin film formed on the lead wire supporting the low melting point metal pellet from both sides is about three times to about five times the conventional one. The point is that it is thicker. By increasing the thickness in this way, the bonding strength between the low melting point metal pellet and the lead wire was sufficiently increased as compared with the conventional case, and the bonding strength was increased. Even if the diameter is increased, sufficient mechanical strength can be ensured, and the size of the thermal fuse can be reduced as much as possible.

Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1A is a sectional view showing a thermal fuse 10 according to the first aspect of the present invention. As shown in the figure, most of the structure is basically the same as a conventional so-called alloy type thermal fuse, that is, a thermal fuse using a low melting point alloy pellet. A low-melting metal pellet 11 supported by lead wires 12 from both sides is disposed at the center of the inside of the case 15, and both sides of the case 15 are sealed with a sealing resin 16, but not shown in the drawing. 11
A so-called flux is applied to the periphery of the metal pellet 11 to remove the oxide film of the low-melting metal pellet 11 or to protect the low-melting metal pellet 11 from the environment and to reliably and reliably cut off the target circuit even in a bad environment. It has become.

The features of the present invention are that the thickness of the metal thin film of the lead wire 12 is reduced from about 1 to 2 μm to 5 μm or more and 10 μm or less, and Sn, Pb, Bi is used as the material of the metal thin film. , In, Sb, Ag,
This is in that the metal thin film is made of one or more elements of Cd. FIG. 1B shows the joint 1
4 is enlarged and conceptually shown including the state of the metal thin film 13. As seen here, a metal thin film 13 made of an element such as Sn, Pb, Bi, etc.
The formation of the metal thin film 13 is particularly required in the present invention in order to improve the bonding of the low melting point metal pellet 11 to be supported by the lead wire 12. is there.

FIG. 2 illustrates this point in more detail. As described in the section of the prior art, the bonding between the lead wire 22 and the low melting point metal
In particular, a metal thin film 23 that is easy to bond with the low melting point metal pellet 21 is formed on the surface of about 1 to 2 μm, and the vicinity of the bonding of the low melting point metal pellet 21 to the lead wire 22 is semi-molten so that the A sheath-like structure 21a of a low-melting metal pellet 21 is formed on the entire end, and a lead wire 2
2 and the low melting point metal pellet 21 were physically and mechanically joined.

However, the low-melting metal pellet 21 as the thermal fuse body is made of a low-melting metal, and even if it is at the end, the main part of the low-melting metal pellet 21 is altered or deformed by increasing the temperature. This may impair the originally required high precision and high reliability. From this point of view, in the actual work, the lead wire 22 and the low melting point metal pellet 21 are joined by the minimum required temperature rise without sufficiently raising the temperature.

For such a reason, as shown in FIG. 2A, it is considered that there are a portion where the lead wire 22 and the low melting point metal pellet 21 are effectively bonded and a portion where the lead wire 22 is not so. It is. As shown in FIG.
In the end 21a, the portion 21a covered by the low melting point metal pellet 21 in a sheath shape includes a joining effective portion 23a (shown by hatching) and a portion other than the joining effective portion not shown by hatching. If the molten metal of the low-melting-point metal pellet 21 is sufficiently mixed with the end of the lead wire 22 by sufficiently raising the temperature, the joining effective portion 23a becomes sufficiently large to have sufficient strength for joining. As it is not possible from the viewpoint of guaranteeing the performance of the low melting point metal pellet 21,
The effective joint portion 23a and the other portion are distributed.

Therefore, if the lead wire diameter is reduced for the so-called miniaturization required in the industry and the low melting point metal pellet is reduced, the effective bonding portion appears at the same ratio. The bonding strength with the pellet becomes insufficient. This is because the physical strength as an absolute quantity is insufficient due to the decrease in the area of the effective bonding portion. Therefore, in the present invention, as described above, a specific metal thin film is selected, and at the same time, the thickness of the metal thin film for joining with the low-melting metal pellet at the end of the lead wire is set to 5 μm or more and 10 μm or less. As a result, the joint effective area is made sufficiently larger than the conventional one, and even if the lead wire diameter is small and the low melting point metal pellet is small, sufficient mechanical strength can be secured. is there.

FIG. 2C shows this state. It can be seen that the portion shown in FIG. 2 (c) has a larger number of effective bonding portions 23a, that is, the portion shown by oblique lines, as compared with the one shown in FIG. 2 (b). By increasing this portion, sufficient mechanical strength of the joint between the lead wire 22 and the low-melting metal pellet 21 can be ensured even in the case of joining at a low temperature. Therefore, the overall size of the thermal fuse can be reduced as much as possible. By setting the thickness of the metal thin film 23 to 5 μm or more and 10 μm or less as described above, for example, the following dimensions and shapes of the thermal fuse can be realized.

That is, the diameter of the lead wire is set to 0.3 mm to 0.1 mm.
About 6mm In addition, the diameter of low melting metal pellet is 0.3 ~
About 0.6mm, and the length of low melting metal pellet is 2-4
mm and the outer diameter of the case is about 0.7 to 1.5 mm. For example, the outer diameter of the case is 1.5m
Even if m, the outer diameter is only about 外 of that of the conventional one, so that the entire volume of the thermal fuse can be extremely reduced. FIG. 3 shows this series of flows simply with a diagram. That is, a feature of the present invention is that a metal thin film is formed on
Formed below micron. Then, the effective bonding area between the lead and the low-melting metal pellet increases, and accordingly, the bonding strength between the lead wire and the low-melting metal pellet increases.

Since the bonding strength is increased, the diameter of the lead wire can be reduced as much as possible, and the bumps at the portion covered by the low melting point metal pellet of the lead wire in a sheath shape, that is, the bonding portion can be reduced. If the bumps at the joint can be reduced and the volume of the low-melting metal pellet can be reduced, the diameter of the molten ball in the operating state can be reduced as a result. Can be smaller. At the same time, the reliability can be improved. The above is the content of the invention according to claim 1.

The reason why the thickness is set to 5 μm or more is that the effective bonding area cannot be sufficiently increased to the required mechanical strength unless the thickness of the metal thin film is about 5 μm or more. In the above, the same effect is obtained, but when it is larger than that, the size is limited to 10 microns or less from the viewpoint of cost. Of course, if there is no problem in this respect, it is needless to say that it may be 10 microns or more. Further, it can be said that the range of the metal thin film is preferably 6 μm or more and 8 μm or less, and more preferably about 7 μm.

Further, Sn, Pb,
Bi, In, Sb, Ag, and Cd were selected in order to maintain consistency with the material of the so-called low-melting metal pellets. From such a viewpoint, these materials contained Sn and Pb as main components, and contained Bi and In. , Sb, Ag, and Cd as needed.

Next, the second aspect of the present invention will be described. According to the second aspect of the present invention, as described above, a metal thin film made of any one or more of Sn, Pb, Bi, In, Sb, Ag, and Cd is formed on the surface of the lead wire in a range of 5 to 10 microns. And a step of joining the lead wire on which the metal thin film is formed and the low-melting metal pellet to each other. Actually, the invention according to claim 1 is characterized by a metal thin film, but the role of the metal thin film is to increase the effective bonding area between the lead wire and the low melting point metal pellet, which directly contributes to the bonding. The plating of the part not to be performed is not so important in the present invention.

Therefore, when the completed thermal fuse is structurally viewed, the thickness of the metal thin film in the portion of the lead wire covered with the low melting point metal pellet in a sheath shape is important. However, the present applicant also claims a method of manufacturing a thermal fuse according to claim 2 from the viewpoint that these are substantially difficult to detect as a thermal fuse structure. That is, as described above, claim 2
The described invention is a method for manufacturing a thermal fuse, comprising the steps of forming the above-mentioned metal thin film of 5 μm or more and 10 μm or less, and joining the lead wire on which the metal thin film is formed and a low melting point metal pellet. This is a method for manufacturing a thermal fuse.

The invention according to claim 2 is substantially the same as the invention according to claim 1, and the applicant of the present invention can easily detect the implementation in the method for manufacturing a thermal fuse by the invention according to claim 2. Claim in a simple way. Claim 2
FIG. 4 is a simplified illustration of the described invention.
FIG. 4 shows two methods (a) and (b), which will be described in order. In the invention according to claim 2 shown in FIG. 1A, first, a long metal wire is prepared. This is cut to a predetermined length. This predetermined length is the length of the lead wire,
Determined from the required dimensions of the completed thermal fuse.

A metal thin film is formed on the metal wire cut to a predetermined length. Various methods such as plating, vapor deposition, and sputtering are used for forming the metal thin film. A metal wire on which a metal thin film is formed, that is, a lead wire, and a low-melting metal pellet prepared separately, which is processed to a predetermined size, is joined and sealed in a case to complete a thermal fuse. This is the first embodiment of the present invention. Next, a second embodiment will be described with reference to FIG. First, a long metal wire is prepared in the same manner as shown in FIG. A metal thin film is formed on this long metal wire. This is a point different from the one shown in FIG.

When the metal thin film is formed, the metal wire is not cut yet, and the metal thin film is formed on the surface in a long state. The formation of this metal thin film is shown in FIG.
In the same manner as described above, the formation is performed by various methods such as vapor deposition sputter plating. The long metal wire on which the metal thin film is formed is cut into a predetermined length. This length is determined by the desired design size of the thermal fuse as described above. The lead wire cut to a predetermined length is joined to a low-melting-point metal pellet prepared in another predetermined size. This joining is performed in the same manner as in the case of FIG. 1A, except that the lead wires are joined to both ends of the low-melting metal pellet by heating.

In general, the low melting point metal pellet has a cylindrical shape or a rectangular parallelepiped shape having a rectangular cross section, and lead wires are joined to both ends in the middle direction. The lead wire is housed in a case in a joined state, and both ends of the case are sealed to complete a thermal fuse. In the expression of claim 2, the step of forming a metal thin film made of one or more elements on the surface of a lead wire is described.
Although it seems that only the manufacturing process of FIG. 4A included therein falls under the claims, the present inventors describe claim 2 as including the process shown in FIG. doing.

Next, the third aspect of the present invention will be described. According to a third aspect of the present invention, there is provided a thermal fuse comprising a low melting point metal pellet and a lead wire bonded thereto, and a low melting point metal thin film having substantially the same composition as that of the low melting point metal pellet is formed on the surface of the lead wire at 5 μm or more. Provide a thermal fuse formed less than 10 microns. The invention described in claim 3 can be described in detail with reference to Table 1. That is, the feature of the invention described in the present claim is that the composition of the metal thin film is made to be substantially the same as the composition of the low melting point metal pellet. The inventors have found that the bonding strength between the lead wire and the low-melting-point metal pellet can be made higher than usual when the compositions are substantially the same. Table 1 shows this in a table.

[0057]

[Table 1]

[0058] Of the many experiments we performed, sample N
O1 to O14 are displayed as representatives. Sn, Pb, Bi, In, S
b, Ag, and Cd were selected, and the bonding strength was measured while varying the values of these components. The outer shape of the metal wire and the low-melting metal pellet used in the experiment are both cylindrical and have a diameter of 0.3 mm and a length of 2.5 mm for the low-melting metal pellet.
mm, the outer diameter of the case is 0.9 mm, and if the strength is judged to be less than 1 in 1,000 pieces, it is ◎. 〇, 3-5 out of 1,000
The specimen was evaluated as Δ when the specimen was damaged, and was evaluated as × when the specimen was damaged 6 or more out of 1,000 pieces.

As can be seen from the results of the compositions and strengths of Samples Nos. 1 to 14, all of those marked with ◎ are the metal thin film formed on the surface of the lead wire and the low metal supported by the lead wire. It is limited to those having substantially the same composition as the melting point metal pellet. In the case of the substantially same material as described above, it is considered that such an improvement in strength occurs because the effective bonding area of the bonding portion between the low melting point metal pellet and the lead wire is increased as already shown in FIG. . Accordingly, in the third aspect of the present invention, there is provided a thermal fuse in which a lead wire is joined to a low melting point metal pellet, and a low melting point metal thin film having substantially the same composition as that of the low melting point metal pellet is formed on the surface of the lead wire. Provide sub-micron formed thermal fuse.

Next, the invention according to claim 4 will be described. According to a fourth aspect of the present invention, as described above, a step of forming a low melting point alloy thin film on a surface of a lead wire in a range of 5 μm to 10 μm is provided. And bonding a thin film having substantially the same composition as the low melting point metal thin film. The invention described in claim 4 is claim 1
The claimed invention is claimed for the same purpose as the claimed invention is claimed.

That is, in the third aspect of the present invention, it is difficult to ascertain the actual implementation, and therefore, it is possible to ascertain the implementation by claiming the same invention by the manufacturing method. . FIG. 5 shows the invention of claim 4 similarly to the invention of claim 2 with a diagram. FIG. 5A shows claim 4.
It is a typical example of the described invention. That is, first, a low melting point metal material is prepared. One of the low melting point metal materials is processed into a pellet, and the other is processed as, for example, a material for a vapor deposition source. Processing one low melting point metal material into two materials in this way means processing the same lot into two materials.

This is because, if the same low melting point metal material is used, the composition of the two materials will be almost the same even when the two materials are processed. The material processed into a pellet and the material processed into an evaporation source material are divided, and the material processed into an evaporation source material is used to deposit a low melting point metal thin film on a lead prepared by another method. By joining the lead on which the metal thin film is thus formed and the pellet processed as described above, a series of joined bodies of the main body of the thermal fuse, the low-melting-point metal pellet, and the lead are formed. To complete the thermal fuse.

The invention described in claim 4 is not limited to this, but includes a method as shown in FIG. 5B. What is included in FIG. 5B will be described. In the case of FIG. 5B, a low-melting metal material is first prepared as in the case of FIG. 5A. The low melting point metal materials are of the same lot, one of which is processed as a pellet and the other is processed as an evaporation source material. A long metal wire is prepared for the material processed as the vapor deposition source material, and the low melting metal material processed as a vapor deposition source is vapor-deposited on the entire long metal wire to form a low melting metal material on the metal wire. Is formed.

Next, the long metal wire on which the thin film of the low melting point material is formed is cut into a predetermined length to form a lead. The lead formed in this manner is joined to the pellet processed as described above, and the resultant is sealed in a case to manufacture a thermal fuse. That is, (a) in FIG.
The difference between the manufacturing methods described in FIGS.
(B) prepares a lead that has been cut to a predetermined length and deposits a metal thin film on it, whereas the one shown in FIG. (B) prepares a long metal wire and cuts it after depositing it. The point is to prepare the lead wire. Claim 4
In the invention described in the description, a step of forming a metal thin film on the surface of the lead is performed by forming a metal thin film of 5 μm or more and 10 μm or less on a long metal wire in a state before the lead wire. The purpose is to include the step of performing

Next, the invention according to claim 5 will be described. The invention according to claim 5 is a method of manufacturing a thermal fuse in which a lead wire is joined to a low-melting metal pellet as described above, wherein Sn, Pb, Bi, In, Sb, Ag, Cd
A step of forming a metal thin film made of any one or two or more elements of 2 μm or more and 10 μm or less, and a step of joining a lead wire on which the metal thin film is formed and a low melting point metal pellet. It is a manufacturing method of.

The most important difference between the invention described in claim 5 and the invention described in claims 1 to 4 is that the portion where the metal thin film is formed is connected to the end of the lead wire, that is, the bonding between the lead wire and the low melting point metal pellet. It is a cross section. Thus, 2
By forming a sufficient amount of the metal thin film of not less than 10 μm and not more than 10 μm, the joining cross section and the low melting point metal pellet can be easily and reliably joined with sufficient strength. This is shown in FIG.
It is.

FIG. 6 (a) shows a simplified process of manufacturing a thermal fuse using the invention of claim 5, and its characteristic feature is that a sectional portion 6 of a lead wire 62 is formed.
2a and the low melting point metal pellet 61. FIG. 4B is an enlarged view of a cross-sectional portion 62a of the lead wire 62. As shown in FIG. 3B, a metal thin film 63 which plays an important role in joining the low melting point metal pellet to the lead wire 62 is formed thick in a cross section 62 a of the lead wire 62. That is, Sn, Pb, Bi,
A cross section 62 a of the lead wire 62, which is a joining portion between the low melting point metal pellet and the lead wire 62, is formed by forming a metal thin film 63 made of any one or more elements of In, Sb, Ag, and Cd.
In this case, a thickness of 2 to 10 microns was formed.

The invention of claim 5 does not necessarily limit the formation of the metal thin film 63 to only the cross section 62a. A metal thin film 63 is formed on the entire lead wire 62.
Is formed, and the same effect as that of the present invention can be obtained if the cross-sectional portion 62a is also formed at 2 μm or more and 10 μm or less, and the gist of the present invention is also in that respect. FIG. 7 clarifies how the leads are formed at the ends of the lead wires. The present invention is intended to include any of the examples shown in FIGS.

This will be described in order. FIG. 7A shows a metal thin film 73 which is a low melting point metal only in a junction section 72 a between the low melting point metal pellet and the lead wire 72 in the lead wire 72.
Is formed, that is, the metal thin film 73 is a metal thin film 73 composed of one or more of Sn, Pb, Bi, In, Sb, Ag, and Cd. Also, the one shown in FIG.
The cross section 72 on the side completely unrelated to the joining, not just the cross section
b shows an example in which the metal thin film 73 is formed. In this case, there is an advantage that the manufacturing process can be simplified since there is no need to identify the bonding surface when manufacturing the thermal fuse as compared with the one shown in FIG.

FIG. 7 (c) shows not only the cross section of the lead wire 72 but also the entire metal thin film 7 as described above.
3 shows a state in which the coating is performed. Actually, the metal thin film 73 is used only for bonding with the low melting point metal pellet, so that the portion of the metal thin film 73 that does not contribute to the bonding is practically useless technically. The structure shown in FIG. 3C may be used because of the easiness of the forming process of forming the metal thin film 73. FIG. 4D shows that the shape of the cross section 72 a of the lead wire 72 is not necessarily limited to a circular shape. FIG. 3D shows a rectangular shape, but a triangular shape, an elliptical shape, a pentagonal shape, and various shapes can be allowed.

Next, the invention according to claim 6 will be described. The invention according to claim 6 is a thermal fuse formed by joining a lead wire to a low-melting metal pellet as described above,
30% or more of Sn, Pb, Bi, In, and the like in the cross-sectional area of the joint section of the lead wire with the low-melting metal pellet.
A step of forming a low-melting metal thin film made of one or more of Sb, Ag, and Cd elements of 2 μm or more and 10 μm or less; a lead having the low-melting metal thin film formed thereon and a low-melting metal pellet. And bonding a thin film having substantially the same composition as the low melting point metal thin film.

The feature of the present invention lies in a process for forming a metal thin film on a lead wire. FIG. 8 is a diagram schematically showing the features of the invention described in claim 6. The invention described in claim 6 will be described with reference to the drawings in order of steps in a simple manner. First, a low melting point metal pellet (not shown) is prepared. An evaporation source 85 having the same composition as the low melting point metal pellet is also prepared. Then, a long metal wire 820 is prepared, and the metal wire 820 is cut into a length of the lead wire 82 having predetermined design dimensions.
Process with 6. Next, as shown in FIG. 3B, for example, a metal wire having a dimension of a lead wire 82 processed in a basket 81 rotating in a vacuum evaporation apparatus is stored, and vapor deposition is performed on the entire lead wire 82 while rotating the basket 81. The metal thin film 83 is formed by skipping the low melting point metal from the source 85.

Then, as shown in FIG. 7C, the metal thin film 83 is formed at a desired position, that is, at the cross-sectional portion 82a of the lead wire 82 bonded to the low melting point metal pellet. Generally, the cross section 82a of the above-described lead wire 82 is formed by such a method.
Low melting metal materials Sn, Pb, Bi, In, S
Although it is possible to form the metal thin film 83 made of b, Ag, Cd or the like, it is necessary to perform deposition for a considerably long time in order to spread this deposition over the entire lead wire 82 from the technical experience of the inventors. Yes, this is not very favorable for the manufacturing process. Therefore, we need to find out at least how much of the metal thin film 83 can be bonded to the low melting point metal pellet 82a of the lead wire 82 within the time allowed by the manufacturing process.
It was investigated whether it should be formed in.

As a result, in order to realize the required mechanical strength, a metal thin film 83 having a cross-sectional area ratio of 30% or more is formed in the cross section 82a of the lead wire 82 joined to the low melting point metal pellet. It has been found that the bonding between the low-melting metal pellet having sufficient strength and the lead wire 82 can be ensured if it is performed. From this viewpoint, in the invention according to the sixth aspect, the bonding section 8 of the lead wire 82 with the low melting point metal pellet is
The area of the metal thin film 83 required for 2a is set to 30% or more in the total cross-sectional area.

It is necessary that this thickness is formed in a range from 2 μm to 10 μm. If it is less than 2 microns, a sufficient bonding effective area cannot be secured. However, it is preferably from 4 microns to 8 microns. If the film thickness is too large, the vacuum deposition process will take a long time and the production efficiency will be reduced. Also, a film thickness of about 6 to 7 microns is preferable as the optimum film thickness. We confirmed that if the thickness of about 6 to 7 microns is secured in the cross section of the low melting point metal pellet of the lead wire by 30% or more, the mechanical strength required for the thermal fuse will be sufficient. doing.

Next, the invention according to claim 7 will be described. The invention according to claim 7 is a thermal fuse formed by joining a lead wire to a low melting metal pellet as described above,
Forming a low-melting metal thin film having a composition substantially the same as that of the low-melting metal pellet in a cross-sectional area of not less than 2% and not more than 10 microns in a cross-sectional area of a bonding section of the lead wire with the low-melting metal pellet; And a step of joining the lead wire on which the low-melting-point metal thin film is formed and the low-melting-point metal pellet to each other.

FIG. 9 is a schematic diagram showing the seventh embodiment of the present invention. That is, in the invention shown in FIG. 9, first, a low-melting metal pellet is prepared, and a long metal wire is prepared. The long metal wire is cut into a predetermined length and stored in a basket rotating in a vacuum device, for example, as described above, and a low melting point metal thin film is formed on the surface of the cut metal wire while rotating the basket. Forming a metal thin film on this surface is intended to include forming a metal thin film on a cross section. In this manner, a thermal fuse is realized by joining, integrally forming, and enclosing a case in which the metal of the predetermined material is formed in the range of 2 μm to 10 μm and the low melting point metal pellet.

Next, the invention according to claim 8 will be described. The invention according to claim 8 is a method for manufacturing a thermal fuse in which a lead wire is joined to a low-melting metal pellet as described above, wherein the low-melting metal pellet is formed on a surface of the metal wire before being cut as the lead wire. Forming a low melting point metal thin film having substantially the same composition as the melting point metal pellet, cutting the metal wire into the lead wire having a predetermined length, and spreading the low melting point metal thin film on a cut surface; Bonding the low-melting-point metal pellet and the cut surface of the lead wire.

The present invention has different features from the first to seventh aspects of the present invention. The greatest feature of the invention is that, in the invention according to claim 8, a claim is made for the first time by defining the order of cutting a long metal wire and forming a metal thin film on the surface of the lead wire, and The point that it has been made clear that the step of forming the metal thin film on the cross section is performed by the step of spreading the metal thin film on the cut surface as described in claim 8. FIG. 10 shows the invention of claim 8 with a diagram.

As shown in FIG. 10A, a long metal wire 1020 is prepared, and the entire surface of the metal wire is covered with the evaporation source 1.
From 05, a low melting point metal is skipped to form a metal thin film having a sufficient thickness. This metal thin film is processed as a lead wire 102 having a predetermined length by a metal cutter 106. When processing as the lead wire 102, a long metal wire 102
The thin metal film formed on the surface of the lead wire 102 is spread by the blade of the cutter 106 and extends from the surface to the cross section of the lead wire 102. Serves as a metal thin film.

The lead wire 102 thus prepared
As shown in FIG. 2B, the cut surface 102a of the lead wire 102 and the low melting point metal pellet 101 are joined to form the lead wire 102 with the low melting point metal pellet 101 and the lead wire 10 as shown in FIG.
A thermal fuse body 2 is prepared and sealed in a case to form a thermal fuse. In the invention according to claims 7 to 6, a process of cutting a long lead wire and then forming a metal thin film on the whole by vapor deposition is introduced. After forming a metal thin film on the metal wire by vapor deposition sputtering or the like, cut it, extend the metal thin film to the cross section of the lead wire by spreading at the time of cutting, and thereby form a lead wire and a low melting point metal pellet with this metal thin film. The aim is to improve the bonding strength of the steel.

In the case of the present invention, since a predetermined metal thin film can be formed on a cut surface of a lead wire by a simple and very inexpensive manufacturing process, the present invention has an excellent effect on cost. FIG. 11 illustrates the present invention in more detail. FIGS. 11A, 11B, and 11C show a long lead wire 11.
2, a predetermined metal thin film 113 is formed on the surface, and when the metal thin film 113 is cut by a metal cutter 116, the metal thin film 113 formed on the surface spreads in the cross-sectional direction while the cross section 112a is formed.
This shows a step of forming a metal thin film 113 thereon.

As shown in FIG. 9A, a long metal wire 1 is used.
12, the metal cutter 116 is swung down at the cut portion, the metal film 113 formed on the surface by the cutter 116 is sequentially spread on the cut surface 112a, and the cutter 116 is retracted upward. In this state, a sufficient amount of the metal thin film 113 extends in the cross section 112a. Further, the method of cutting the long metal wire 112 by the cutter 116 is not limited to the method shown in FIG. 11, but may be, for example, a method shown in FIG.

FIG. 12 (a) shows a method similar to that shown in FIG. 11, but FIG. 12 (b) shows a blade of a cutter 126 for cutting a long metal wire 122. Is swung down toward the metal wire 122 from above and below. As the blade of the cutter 126 is swung down from above and below, not only the upper metal thin film 123 but also the lower metal thin film 123 among the metal thin films 123 formed on the surface of the long metal wire 122 are formed. Effectively cut surface 122
Thus, the metal thin film 123 on the surface can be spread on the cut surface 122a over a wider area than that shown in FIG.

FIG. 9C is a further improvement of the one shown in FIG. 9B, and the blade of the cutter 126 for cutting the long metal wire 122 is up and down. It swings down so as to cut the metal wire 122 not only from the direction but also from three directions. In this case, the metal thin film 123 on the surface is spread by the blades of the cutter 126 not only from above and below but also from three sides, so that the metal thin film 123 on the surface can be more efficiently spread on the cut surface. It is possible to secure the amount of the metal thin film 123 on the cut surface.

The invention of claim 8 also includes a step of bonding the low melting point metal pellet and the cut surface after the metal thin film is spread on the cut surface in this manner. FIG. 13 illustrates this step. FIG. 13 shows a lead wire 132 formed by extending a metal thin film 133 to a predetermined cross section on the left side, and a low melting point metal pellet 131 to be supported by the lead wire 132 on the right side. The lead wire 132 is sandwiched from above and below by a member 137 made of a suitable material such as a ceramic material.
The vicinity of the bonding surface 132a with the base 31 is heated.

In this state, the low melting point metal thin film 133 is softened, and the lead wire 132 and the low melting point metal pellet 131 are pressed close to each other from both sides as shown in FIG. By joining the low melting point metal thin film 133 on the 132 side to the cut surface portion 131a of the low melting point metal pellet 131, the joining between the lead wire 132 and the low melting point metal pellet 131 is completed. In this way, the joining of the low melting point metal pellet of the invention of claim 8 and the cut surface of the lead wire is completed. FIG. 14 shows the features of the thermal fuse completed in this manner, which have already been described and arranged.

In the present invention, the low melting point metal pellet 141 is used.
And the lead wire 142 are joined to each other by the cut surfaces 141a and 142a, so that a bump 175a is generated when a part of the low melting point metal pellet 175 covers the lead wire 178 in a sheath shape as in the conventional invention. No phenomenon is seen. Accordingly, the volume of the low melting point metal pellet 141 can be reduced accordingly. If the volume of the low melting point metal pellet 141 can be reduced, the volume of the molten ball of the low melting point metal during operation can be reduced.
The inner diameter and length of 45 can also be made smaller and shorter. Further, as described above, if sufficient mechanical bonding strength can be secured at this portion, the diameter of the lead wire 142 can be reduced, and from this viewpoint, the size of the thermal fuse 140 can be reduced.

As described above, in the present invention, FIG.
A predetermined metal thin film is sufficiently formed on the cross section of the lead wire as compared with the conventional one shown in (b), whereby the bonding strength between the lead wire and the low melting point metal pellet is secured, and the lead wire is reduced in diameter.
Since the volume of the metal pellet can be reduced, the size can be considerably reduced as compared with the conventional thermal fuse shown in FIG. 14B. The numerical dimensions of this miniaturization have already been described. As described above, FIG. 15 shows how much space is required when the low-melting metal pellets are balled in a molten state in comparison with the conventional one.

As shown in FIG. 15, the ball 15 in the molten state
1a can be reduced because the cross-sectional area of the low-melting metal pellet can be reduced by reducing the bonding cross-section and the cross-sectional area of the lead wire 152 can be reduced. Since the volume can be reduced, the diameter and length of the case 155 can also be reduced. This is a feature point compared with the conventional one. As can be seen by comparing FIGS. 15 (a) and 15 (b) with such a small size, the tip of the ball 151a of a molten state or a low-melting metal pellet which has been solidified by lowering the temperature from the molten state. The distance between the conventional fuselage and the conventional fuselage is not different. From this viewpoint, it can be seen that miniaturization is possible without causing a problem that an undesired current flows in the thermal fuse 150 due to sparks or the like. .

Next, the ninth aspect of the present invention will be described. The invention according to claim 9 is a method for manufacturing a thermal fuse in which a lead wire is joined to a low-melting metal pellet as described above, wherein the surface of the metal wire before being cut as the lead wire has Sn, Pb, Bi, In, Sb, Ag,
Forming a metal thin film made of any one or more elements of Cd, cutting the metal wire into the lead wire having a predetermined length, and spreading the metal thin film on a cut surface; Bonding the low-melting-point metal pellet and the cut surface of the lead wire.

The difference between the invention according to claim 9 and the invention according to claim 8 is that the material of the metal thin film to be formed on the lead wire has a low melting point having substantially the same composition as the low melting point metal pellet in the case of claim 8. In the present invention, the metal thin film is characterized in that the metal thin film is made of any one or more of Sn, Pb, Bi, In, Sb, Ag, and Cd. The reason why the material of the metal thin film formed on the cross section is not necessarily substantially the same as the material composition of the low melting point metal pellet is that the cross section coverage of the metal thin film formed on the cross section is not necessarily 100%, In this case, copper or silver, which is the material of the lead wire itself, or a compound thereof appears.

Therefore, since the joining is not necessarily made of the metal thin film and the low melting point metal pellet but also of the material including the material of the lead wire and the low melting point metal pellet, for example, the same composition as this is used. When Ag or the like is contained, the same composition as the material composition of the low-melting-point metal pellet is finally obtained by reducing the amount of Ag formed in this portion without having the same composition as the material of the low-melting-point metal pellet. It is to be able to obtain.

Next, the tenth aspect of the present invention will be described. The invention according to claim 10 is a method for manufacturing a thermal fuse in which a lead wire is joined to a low-melting metal pellet as described above, wherein Sn is previously applied to the surface of the metal wire before being cut as the lead wire. A step of forming a metal thin film containing at least 63% by weight and the balance being one or more of Pb, Bi, In, Sb, Ag, and Cd, and unavoidable impurities; The wire is cut into a predetermined length of the lead wire, and the step of spreading the metal thin film on a cut surface, and the step of joining the low melting point metal pellet and the cut surface of the lead wire, This is a method of manufacturing a thermal fuse.

The feature of the invention described in claim 10 is that of claim 9
Compared with the described invention, the composition of the metal thin film to be formed on the surface of the metal wire is limited to a main material having Sn of 63% or more. The purpose of setting the Sn content to 63% or more is that such a solder material becomes a eutectic material when the Sn content is 63% or more. Therefore, the transformation from the solid phase to the liquid phase occurs in a very short time, so that the amount of heat given to the lead wire when joining the lead wire and the low melting metal pellet is minimized, and the damage to the low melting metal pellet is also minimized. The feature is that it can be stopped with. The other points are the same as those of the ninth aspect. Incidentally, in the case of such an alloy, unavoidable impurities are always contained, and therefore, even if unavoidable impurities are contained, a desired action or effect can be realized. Is substantially the same as

Next, the invention according to claim 11 will be described. The invention according to claim 11 is a method for manufacturing a thermal fuse in which a lead wire is joined to a low melting point metal pellet as described above, wherein Sn is previously applied to the surface of the metal wire before being cut as the lead wire. 63% or more by weight, Pb as needed by 37% or less by weight, and the balance Bi, I
forming a metal thin film comprising one or more elements of n, Sb, Ag, and Cd and unavoidable impurities;
Cutting the metal wire into a predetermined length of the lead wire, spreading the metal thin film on a cut surface, and bonding the low melting point metal pellet to the cut surface of the lead wire; And a method for manufacturing a thermal fuse comprising:

The present invention is substantially the same as the tenth invention. This purport is intended to claim a case in which a so-called Pb is formed on a lead wire with a metal thin film of 0% in consideration of the influence of Pb on the environment.

The twelfth aspect of the present invention will be described.
According to a twelfth aspect of the present invention, there is provided a method of manufacturing a thermal fuse in which a lead wire is joined to a low melting point metal pellet as described above, wherein the surface of the metal wire before being cut as the lead wire is formed from Sn in advance. Forming a metal thin film,
Cutting the metal wire into the lead wire of a predetermined length, spreading the thin metal film made of Sn on the cut surface, and joining the low melting point metal pellet to the cut surface of the lead wire. And a method of manufacturing a thermal fuse.

The present invention is different from the tenth to eleventh aspects in that the composition of the metal thin film to be formed on the surface of the lead wire is limited to Sn. Thus, Sn
It is possible to realize a product that can sufficiently secure the bonding strength with the low melting point metal pellet even if only Sn is used and that does not have an adverse effect on the environment because it does not contain Pb. This is because it can be done. Although not described in claim 12, the metal thin film made of Sn is substantially S
A material consisting of n and containing unavoidable impurities is substantially the same as this.

Next, the invention according to claim 13 will be described. The invention according to claim 13 is a method of manufacturing a thermal fuse in which a lead wire is joined to a low-melting metal pellet as described above, wherein the joining between the low-melting metal pellet and the lead wire is performed by using the lead wire. This is a method for manufacturing a thermal fuse mainly joined only by a cut surface. A feature of the invention according to claim 13 is that the joining between the low melting point metal pellet and the lead wire is performed only by the cut surface.

Although the advantage of performing the joining of the low melting point metal pellet and the lead wire at the cut surface has already been described in the invention described in the twelfth aspect of the present invention, the present invention particularly provides that the joining is performed only at the cut surface. When the invention is a featured invention and is performed only on the cut surface, the advantages obtained by the above-described thermal fuse can be maximized. FIGS. 16A to 16D show this in a diagram. FIG.
(A) is a cross-sectional view showing a state where the lead wire 162 and the low melting point metal pellet 161 are joined with only the cut surfaces 161a and 162a. In the claims, "mainly" means that although the low melting point metal is slightly melted,
There is a case where it extends to the 62nd side, but it is intended that what is joined by only the cut surface 162a is the invention of claim 13.

As described above, the method of joining the lead wire and the low melting point metal pellet only by the cut surface is shown in FIG.
(B) (c) and (d) are conceivable. 16 (b), (c) and (d), a lead wire 162 is disposed on the left side, and a low-melting metal pellet 161 is disposed on the right side. The surface of the lead wire 162 disposed on the left side has a predetermined surface. 3 shows a state in which a metal thin film (not shown) is formed. As shown in FIG. 6B, the vicinity of the end of the lead wire 162 is gripped by the gripping member 167 in the same manner as described above, and the heat is transferred from the end to the low melting point metal pellet 161 of the lead wire 162. Only the vicinity of the joint is heated, and the gripped cross section 162a
And a predetermined cross section 161a of the low-melting metal pellet 161 by pressing and joining the low-melting metal pellet 1
It is assumed that a part of 61 and the metal thin film formed on the cut surface 162a of the lead wire 162 are melted and bonded to complete the joining of the two.

FIG. 11C shows the lead wire 162.
The laser beam 169 is radiated while aiming at the cut surface 162a, and the temperature of the portion is increased by the energy of the laser beam 169. Immediately after that, the lead wire 162 and the low-melting metal pellet 161 are pressed against each other by cross section to join them. That is. If sufficient heating is performed by the laser beam 169, the end of the lead wire 162 is also heated as in the case shown in FIG. 4B, and the metal thin film formed on the cut surface 162a is softened and melted, With this heat, bonding with the low melting point metal pellet 161 is performed. In addition, bonding can also be performed by a method as shown in FIG.

In the case shown in FIG. 11D, the lead wire 162 is gripped from above and below by a gripping member 167. What is transmitted to the lead wire 162 by the gripping member 167 is not heat but current. When an electric current flows from the top to the bottom of the gripping member 167, the end of the lead wire 162 is heated by Joule heat, and when this portion reaches a predetermined temperature, the metal thin film formed on the surface of the lead wire 162 softens and melts. Then, in this state, if the cross sections of the lead wire 162 and the low melting point metal pellet 161 are pressed quickly, the two are joined to join the lead wire 162 and the low melting point metal pellet 16.
1 is completed. In this manner, the lead wire 162 is added to the low melting point metal pellet 161 according to the invention of claim 13.
A method for manufacturing a thermal fuse, comprising joining the low-melting metal pellet 161 and the lead wire 162 only with the cut surface 162a of the lead wire 162 alone. You can do it.

Next, the invention according to claim 14 will be described. According to a fourteenth aspect of the present invention, there is provided a method for manufacturing a thermal fuse in which a lead wire is joined to a low melting point metal pellet as described above, wherein Sn is previously applied to the surface of the metal wire before being cut as the lead wire. A step of forming a metal thin film containing 63% or more by weight, with the balance being one or more of Pb, Bi, In, Ag, and Cd, if necessary, Cutting the lead wire and spreading the metal thin film on the cut surface, and joining the low-melting metal pellet and the lead wire only with the cut surface of the lead wire. This is a method for manufacturing a thermal fuse.

The invention described in claim 14 is obtained by applying the invention described in claim 13 to the invention described in claim 12, or by applying the invention described in claim 13 to the invention described in claim 11. And so on. In particular, the invention described in claim 13 is applied to the invention described in claim 12 as the invention described in claim 14. Further, claim 15 described later.
The invention described in claim 13 corresponds to the invention described in claim 11
This is an application of the described invention.

According to a fifteenth aspect of the present invention, there is provided a method of manufacturing a thermal fuse in which a lead wire is joined to a low melting point metal pellet as described above, wherein the surface of the metal wire before being cut as the lead wire is formed. Forming a metal thin film made of Sn in advance, cutting the metal wire into the lead wire having a predetermined length, and spreading the metal thin film made of Sn on a cut surface; The joining of the pellet and the lead wire is a method of manufacturing a thermal fuse in which the lead wire is joined mainly with only a cut surface.

[0108]

As described above, the present invention is characterized in that a predetermined thin metal film is formed with a sufficient thickness on the surface of a lead wire, particularly near the joint surface with a low melting point metal pellet. The effective joining portion for joining the lead wire and the low-melting metal pellet can be increased, so that the joining strength between the lead wire and the low-melting metal pellet can be sufficiently increased as much as possible. The diameter and size of the low-melting metal pellet can be reduced, and the bumps between the lead wire and the low-melting metal pellet can be eliminated, so the volume of the low-melting metal pellet can be reduced and the temperature can be reduced as much as possible. The volume of the fuse case, that is, the case diameter and the case length can be reduced,
As a result, a highly reliable and extremely small thermal fuse can be provided.

[Brief description of the drawings]

FIG. 1 is a side sectional view and an enlarged view of a main part of a thermal fuse of the present invention.

FIG. 2 is a conceptual perspective view showing a state of a metal thin film at a bonding portion.

FIG. 3 is a diagram simply showing a flow of miniaturization of a thermal fuse.

FIG. 4 is a diagram showing a method for manufacturing a thermal fuse of the present invention.

FIG. 5 is a diagram showing another method of manufacturing the thermal fuse of the present invention.

6A and 6B are a manufacturing process diagram and an enlarged perspective view of a main part of the thermal fuse of the present invention.

FIG. 7 is a diagram showing a method of forming a metal thin film on an end of a lead wire.

FIG. 8 is a view showing characteristics of a process of forming a metal thin film on a lead wire.

FIG. 9 is a view showing another method of manufacturing the thermal fuse of the present invention.

FIG. 10 is a diagram showing a method for forming a lead wire according to the present invention.

FIG. 11 is a view showing a method of forming a metal thin film on a cut surface of a lead wire.

FIG. 12 is a view showing another method for forming a metal thin film on a cut surface of a lead wire.

FIG. 13 is a view showing a step of joining a lead wire and a low-melting metal pellet at a cut surface.

FIG. 14 is a side sectional view comparing the thermal fuse of the present invention with that of the conventional thermal fuse.

FIG. 15 is a diagram comparing a thermal fuse of the present invention with a conventional ball.

FIG. 16 is a view showing various methods for joining a lead wire and a low-melting metal pellet only at a cut surface.

FIG. 17 is a cross-sectional view of a conventional thermal fuse using a low melting point metal pellet.

FIG. 18 is a front and side view of a conventional plate-shaped alloy type thermal fuse.

[Explanation of symbols]

10, 60, 140, 150 Thermal fuse 11, 21, 61, 101, 131, 141, 161
Low melting metal pellets 12, 22, 62, 72, 82, 102, 112, 13
2, 142, 152, 162 Lead wire 13, 23, 63, 73, 83, 113, 123, 16
3 Metal thin film 14, 62a, 72a, 82a, 102a, 112a,
122a, 132a, 142a, 162a Junction cross section 133 Low melting point metal thin film 820, 1020 Metal wire

Claims (15)

[Claims] 1. A thermal fuse comprising a low melting point metal pellet and a lead wire joined thereto, wherein the surface of the lead wire has an S
n, Pb, Bi, In, Sb, Ag, Cd.
Thermal fuse formed below 0 microns. 2. The method according to claim 1, wherein Sn, Pb, B
forming a metal thin film made of any one or two or more elements of i, In, Sb, Ag, and Cd from 5 μm to 10 μm; and forming a lead wire and a low melting point metal pellet on which the metal thin film is formed. A method for manufacturing a thermal fuse, comprising: joining. 3. A thermal fuse comprising a low melting point metal pellet and a pair of lead wires joined to each other, wherein a low melting point metal thin film having substantially the same composition as the low melting point metal pellet is formed on a surface of the lead wire by 5 μm or more. Thermal fuse formed less than 10 microns. 4. A step of forming a low melting point metal thin film on the surface of a pair of lead wires in a range of 5 μm to 10 μm; and forming the low melting point metal thin film on a lead wire and a low melting point metal pellet. Bonding a metal thin film having substantially the same composition as the metal thin film. 5. A method of manufacturing a thermal fuse comprising joining a pair of leads to a low-melting metal pellet, wherein a cross section of the pair of leads and the low-melting metal pellet is bonded to each other.
n, Pb, Bi, In, Sb, Ag, Cd.
A method for manufacturing a thermal fuse, comprising: forming a metal wire having a thickness of 0 μm or less; 6. A thermal fuse formed by joining a pair of lead wires to a low melting point metal pellet, wherein a ratio of the cross section of the pair of lead wires to the low melting point metal pellet in a sectional area is 30% or more. Sn, Pb, Bi, In, Sb, Ag,
Forming a low melting point metal thin film made of any one or two or more elements of Cd from 2 μm to 10 μm; and forming a lead wire and a low melting point metal pellet on which the low melting point metal thin film is formed, Bonding a metal thin film having substantially the same composition as the metal thin film. 7. A thermal fuse formed by joining a pair of lead wires to a low melting point metal pellet, wherein a ratio of the cross section of the pair of lead wires to the low melting point metal pellet in a sectional area is 30% or more. A cross-sectional thin film forming step of forming a low-melting-point metal thin film having the same composition as the low-melting-point metal pellet, in a range of 2 μm to 10 μm; And a method of manufacturing a thermal fuse. 8. A method for manufacturing a thermal fuse comprising joining a pair of leads to a low melting point metal pellet, wherein said low melting point metal pellet is formed on a surface of the metal wire before being cut as said lead wire. Forming a low melting point metal thin film having substantially the same composition, cutting the metal wire into the lead wire having a predetermined length, and spreading the low melting point metal thin film on a cut surface; Bonding the metal pellet and the cut surface of the lead wire to each other. 9. A method for manufacturing a thermal fuse comprising joining a pair of lead wires to a low-melting metal pellet, wherein a surface of the metal wire before cutting as the lead wire is formed on the surface of the metal wire in advance.
forming a metal thin film made of any one or more of n, Pb, Bi, In, Sb, Ag, and Cd;
Cutting the metal wire into a predetermined length of the lead wire, spreading the metal thin film on a cut surface, and bonding the low melting point metal pellet to the cut surface of the lead wire; And a method for manufacturing a thermal fuse. 10. A method of manufacturing a thermal fuse comprising joining a pair of lead wires to a low-melting metal pellet, wherein a surface of the metal wire before cutting as the lead wire is previously coated with S
n is not less than 63% by weight and the balance is P
a step of forming a metal thin film made of any one or more of b, Bi, In, Sb, Ag, and Cd and unavoidable impurities, and cutting the metal wire into the lead wire having a predetermined length. And a step of spreading the metal thin film on a cut surface and a step of joining the low melting point metal pellet to the cut surface of the lead wire. 11. A method of manufacturing a thermal fuse comprising joining a pair of lead wires to a low-melting metal pellet, wherein a surface of the metal wire before being cut as said lead wire is previously coated with S
n is not less than 63% by weight and Pb is not more than 37% by weight if necessary, and the balance is Bi, In, Sb, Ag, Cd.
Forming a metal thin film composed of any one or two or more elements and unavoidable impurities, cutting the metal wire into the lead wire having a predetermined length, and spreading the metal thin film on the cut surface. And bonding the low-melting-point metal pellet to the cut surface of the lead wire. 12. A method of manufacturing a thermal fuse comprising joining a pair of lead wires to a low melting point metal pellet, wherein a surface of the metal wire before cutting as the lead wire is previously coated with S
forming a metal thin film consisting of
A step of cutting the lead wire of a predetermined length, a step of spreading the metal thin film made of Sn on a cut surface, and a step of joining the low melting point metal pellet and the cut surface of the lead wire. A method of manufacturing a thermal fuse. 13. A method for manufacturing a thermal fuse, comprising joining a pair of lead wires to a low melting point metal pellet, wherein the joining between the low melting point metal pellet and the lead wire is performed mainly by using a cut surface of the lead wire. A method of manufacturing a thermal fuse to be joined only by 14. A method for manufacturing a thermal fuse comprising joining a pair of lead wires to a low-melting metal pellet, wherein a surface of the metal wire before cutting as the lead wire is previously coated with S
n is not less than 63% by weight and the balance is P
b, Bi, In, Ag, a step of forming a metal thin film made of any one or two or more elements of Cd, and cutting the metal wire into the lead wire of a predetermined length,
A method of manufacturing a thermal fuse in which the step of spreading the metal thin film on a cut surface and the bonding between the low melting point metal pellet and the lead wire are mainly performed only by the cut surface of the lead wire. 15. A method for manufacturing a thermal fuse comprising joining a pair of lead wires to a low-melting metal pellet, wherein a surface of the metal wire before being cut as the lead wire is previously coated with S
forming a metal thin film consisting of
Cutting the lead wire of a predetermined length and spreading the thin metal film made of Sn on the cut surface; and joining the low melting point metal pellet and the lead wire mainly by cutting the lead wire. A method of manufacturing a thermal fuse that is bonded only on its surface.