JP2002025402A - Temperature fuse and wire material for temperature fuse element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a temperature fuse which can secure meltdown temperature from 120 deg.C or higher to 130 deg.C or lower, and wire material for a temperature fuse element suitable for manufacturing of this temperature fuse. SOLUTION: The temperature fuse is a temperature fuse, having a fuse element melting at a given temperature, and the fuse element is formed from a fusible alloy, consisting of tin of 30 weight% or more and 48 weight% or less and the remainder being indium. Furthermore, wire material for the temperature fuse element is also formed from a fusible alloy of similar composition. That is to say, by adjusting the indium content in the fusible alloy, a temperature fuse and wire material and provided with superior fusion temperature characteristics and a moderate strength and ductility.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal fuse and a wire for a thermal fuse element, and more particularly, to a thermal fuse and a thermal fuse element wire having a thermal fuse element formed of a lead-free fusible alloy that melts at a predetermined temperature. .

[0002]

2. Description of the Related Art There are two types of fuses: an electric fuse that is blown when an overcurrent flows through an electric circuit to protect the circuit, and a thermal fuse that is blown and protected when the temperature around the electric circuit rises. Electric fuses are used in TVs, washing machines, etc.
Thermal fuses are used in mobile phones, notebook computers, etc.
Each is incorporated and has a role of protecting these electrical products. Above all, the thermal fuse must be blown reliably and quickly at the set fusing temperature to protect the electric circuit. For this reason, the thermal fuse is required to be blown with high accuracy under various temperature conditions. Recent electronic components such as semiconductors often have low heat resistance.
Many of them break at temperatures around 20 ° C to 130 ° C. Further, as in the case of a lithium ion secondary battery, the temperature is 12
Some are dangerous if the temperature rises to around 0 ° C to 130 ° C. For this reason, a thermal fuse that accurately and quickly melts in a temperature range around 120 ° C. to 130 ° C. is required.

Here, the melting temperature of the fuse depends on the melting point (liquidus temperature) of the fusible alloy constituting the fuse element in the thermal fuse, and the melting point depends on the component metals of the alloy and the compounding ratio thereof, that is, the composition. Decided. Therefore, the choice of alloy composition is extremely important.

Conventionally, as a fusible alloy for a thermal fuse having a melting point of 120 ° C. to 130 ° C., an alloy containing lead as a kind of raw material metal (hereinafter referred to as a lead alloy) has been used exclusively. However, when electric appliances are discarded in recent years, there is a problem that lead is eluted into the natural environment from a thermal fuse incorporated therein. When humans take in the lead eluted into the environment, they become poisoned, and depending on the amount of intake, toxic symptoms such as fatigue, lack of sleep, constipation, trembling, abdominal pain, anemia, neuritis, and cerebral degeneration appear. Therefore, in order to prevent environmental pollution due to lead, it is required worldwide not to use lead as an industrial material as much as possible, and studying industrial materials to replace lead is one of the important issues in the industry. I have. For this reason, Japanese Patent Application Laid-Open No. H11-25829 discloses a thermal fuse formed of an alloy composed of 52 to 100% by weight of indium and a balance of tin as a thermal fuse not using a lead alloy.

[0005]

However, indium is more expensive than other metals for thermal fuses such as lead and bismuth, and the thermal fuses and wires made of alloys having a high indium content are expensive to manufacture. There is. Further, since indium is soft, there is a problem that thermal fuses and wires made of an alloy having a high indium content are easily damaged and are inconvenient to handle. Furthermore, in order to improve the fusing property against the temperature of the fuse, the fuse element of a cylindrical fuse or a tubular fuse is often installed under a certain tension, but a fuse element made of a wire having a high indium content. Is soft and highly ductile, so it is difficult to install it under tension, and there is a problem that the fusing property of the thermal fuse deteriorates.

[0006] Therefore, as a result of intensive studies on the Sn-In alloy forming the thermal fuse and the wire, the inventor of the present invention has found that the thermal fuse element can be melted at a temperature of 120 ° C or more and 130 ° C or less, and the thermal fuse element can be manufactured at low cost. It has been found that a lead-free fusible alloy having appropriate hardness and ductility to be formed can be obtained.

A thermal fuse and a wire for a thermal fuse element of the present invention have been made based on the above findings, and an object of the present invention is to provide a thermal fuse capable of securing a fusing temperature of 120 ° C. or more and 130 ° C. or less. . It is another object of the present invention to provide a wire for a thermal fuse element suitable for manufacturing the thermal fuse.

[0008]

A thermal fuse according to the present invention is a thermal fuse having a fuse element that blows at a predetermined temperature, wherein the fuse element is 30% by weight or more and 48% or more.
It is characterized by being formed of a fusible alloy composed of tin by weight or less and the balance of indium.

Further, the wire for a thermal fuse element of the present invention is characterized in that it is formed of a fusible alloy comprising 30% by weight or more and 48% by weight or less of tin and the balance of indium.

[0010] As described above, indium has properties of being rich in ductility and low in hardness. Therefore, by adjusting the indium content in the Sn-In alloy, indium can be produced.
An alloy which melts at a relatively low temperature of from 130 ° C. to 130 ° C. and has appropriate ductility and hardness can be obtained. However,
If the ΔT of the alloy is large, it takes a long time to blow the fuse and the electronic component may be damaged. Therefore, the ΔT of the fusible alloy is required to be within 30 ° C.

The thermal fuse of the present invention, which is made of a lead-free fusible alloy having the above-mentioned composition, secures a fusing temperature of 120 ° C. or more and 130 ° C. or less, similarly to a conventional lead alloy thermal fuse, and has ΔT of 30 ° C. Within a practical thermal fuse. In addition, compared to a wire for a thermal fuse element made of an ordinary alloy containing indium, the wire for a thermal fuse element of the present invention made of the lead-free fusible alloy has a low indium content in the alloy, so that it is not too soft. Has moderate hardness. Therefore, as will be described later, there is no risk of the wire being damaged or crushed when the wire is pulled through the roll gap or wound on a bobbin in the manufacture of the wire. For this reason, the wire of the present invention can be thinned as compared with the conventional wire, and can be used in various applications such as electronic parts having low heat resistance and small electronic devices.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a thermal fuse and a thermal fuse element wire according to the present invention will be described below for each of the items of fusible alloy, thermal fuse, and thermal fuse element wire.

<Fusible Alloy> First, an embodiment of a fusible alloy which is a material for forming a thermal fuse and a wire for a thermal fuse element of the present invention will be described. The fusible alloy used for the thermal fuse and the wire of the present invention is composed of 30% by weight or more and 48% by weight or less of tin and the balance of indium. The reason why the fusible alloy has such a composition will be described with reference to the drawings.

FIG. 1 shows a phase diagram of the Sn—In binary alloy. In FIG. 1, point A indicates the eutectic point of the Sn-In alloy (48% by weight Sn-52% by weight In). The target fusing temperature (hereinafter, referred to as a target temperature) of the thermal fuse and the wire of the present invention is from 120 ° C to 130 ° C. In order to blow the fuse and the wire at this target temperature, the liquidus temperature of the fusible alloy as a material for forming the fuse and the wire should be increased from 120 ° C to 130 ° C.
C must be set. The composition in which the liquidus temperature can be set in such a range is represented by an area (Sn) on the left side of the point A in FIG.
It exists in each of a region where the content is 48% by weight or less and a right region (a region where the Sn content exceeds 48% by weight). Therefore, if it is determined only from the liquidus temperature, the composition of the alloy can be set in either region. However, ΔT is much smaller in the area to the left of point A than in the area to the right. As described above, in a thermal fuse used at a relatively low temperature, ΔT is required to be small in order to ensure quick disconnection. Therefore, a region on the left side of the point A, that is, a region having an indium content of 52% by weight or more is more suitable as a region for setting the alloy composition.

From the viewpoint of reducing ΔT,
The indium content in the alloy only needs to be at least 52% by weight, but if the content is too high, the following problems occur. That is, indium has properties of being soft, rich in ductility, and low in hardness. For this reason, if the indium content in the alloy is too high, the properties of indium also appear in the alloy, and the alloy itself becomes soft and low in hardness.
If the alloy is soft, there is a problem that the wire is damaged or crushed when the wire is pulled through a gap between rolls or wound on a bobbin in the production of a wire described below. Also, indium has a small resource reserve and is inherently expensive compared to other fuse alloys. Therefore,
If the indium content is too high, there arises a problem that the manufacturing cost of the fuse and the wire is necessarily increased.
In order to avoid such a problem, it is necessary to reduce the indium content in the alloy to such an extent that the alloy has an appropriate hardness and the manufacturing cost of the fuse and the wire can be suppressed. Must be 70% by weight or less.

ΔT of the above-mentioned alloy, and hardness of the alloy,
From the viewpoint of the manufacturing cost of the fuse and the like, the inventor of the present invention has determined that the composition of the alloy forming the fuse and the wire of the present invention is 30% by weight or more and 48% by weight or less, and the balance is indium.

By changing the mixing ratio of tin and indium within this composition range, the melting point of the alloy can be freely controlled, and a temperature fuse corresponding to an arbitrary target temperature between 120 ° C. and 130 ° C. A wire can be provided. Specifically, when the target temperature is high, the melting point of the alloy can be increased by lowering the tin content, and a fuse and a wire corresponding to a desired target temperature can be provided. For example, when the target temperature is 130 ° C., the composition of the fusible alloy is changed to the point B (30% by weight) in FIG.
(Sn-70% by weight In). On the other hand, when the target temperature is low, the melting point of the alloy can be lowered by increasing the tin content, and a fuse and a wire corresponding to the desired target temperature can be provided. For example, when the target temperature is set to 120 ° C., the composition of the fusible alloy may be set to point A (48 wt% Sn-52 wt% In) in FIG.

Incidentally, it is conceivable that unavoidable impurities from the raw material metal and the like are mixed in the fusible alloy. The fusible alloy constituting the fuse and the wire according to the present invention does not specifically exclude mixing of impurities, and the alloy having the above composition also includes a case where unavoidable impurities are mixed in the alloy.

<Thermal Fuse> An embodiment of the thermal fuse of the present invention will be described with reference to the drawings. FIG.
FIG. 1 shows a sectional view of a cylindrical thermal fuse as an example of the thermal fuse of the present invention. The thermal fuse 1 shown in FIG. 2 includes a fuse element 10 that blows at a constant temperature and a fuse element 10.
And a flux 1 filled around the fuse element 10 in a columnar shape and covering the fused surface after the fuse element is blown to prevent conduction again.
1 and a cylindrical ceramic case 12 for housing a part of the fuse element 10, the flux 11 and the lead wire 2.

In an electronic device, the thermal fuse 1 is installed between a power supply such as a battery and an electric circuit. When the temperature around the thermal fuse 1 rises for some reason and reaches the set temperature of the thermal fuse 1, the fuse element 10
Is melted, the flux 11 covers the melted section, and the conduction between the power supply and the circuit is cut off. In this way, the thermal fuse 1 can protect a power supply, an electric circuit, and the like.

The method of manufacturing the thermal fuse 1 of the present embodiment can be manufactured by various methods conventionally used for manufacturing a fuse. For example, a wire to be described later is cut to form a fuse element 10, and the fuse element 10 and the lead wire 2 are joined to form a fuse element 10.
And a method in which a ceramic case 12 for protecting the fuse element 10 and the like from the outside is provided by filling a flux 11 around the surroundings.

The thermal fuse of the present invention can be various types of thermal fuses conventionally used, such as a fuse with a nail, a tubular fuse, and a plug-type fuse, in addition to the cylindrical fuse shown in FIG. .

The thermal fuse of the present invention has a temperature of 120 ° C.
It can be blown quickly to any relatively low temperature of ~ 130 ° C. For this reason, for protection of semiconductors with low heat resistance and lithium ion secondary batteries for mobile phones, etc.
Can be used for a wide variety of applications.

<Temperature Fuse Element Wire> Next, an embodiment of the temperature fuse element wire of the present invention used for the above-described temperature fuse will be described. The wire of the present invention can be manufactured by various methods conventionally used for manufacturing wires. The drawing method will be described as an example.

The drawing method includes a raw material blending step of blending the raw material of the fusible alloy constituting the wire into a melting furnace, a step of melting the blended raw material to prepare an alloy and pouring the alloy into a mold to form a billet; An extrusion process to make the
It consists of a drawing step of forming a fine wire from a coarse wire.

First, in the raw material blending step, tin and indium ingots, which are raw materials for the wire rod, are weighed and blended so as to have a desired composition, and then put into a melting furnace. Next, in the billet preparation step, the compounded raw materials are melted at a temperature of 300 to 350 ° C. to prepare a Sn—In alloy, and the prepared alloy in a molten state is poured into a mold to prepare a columnar billet. Next, in the extrusion step, the billet is taken out of the mold, set in an extruder, and extruded to form a coarse wire. Finally,
In the wire drawing step, the coarse wire is applied to a drawing forming machine, and a thin alloy, that is, a wire is formed by drawing a linear alloy from a circular die hole provided in the forming machine. The diameter of the die holes is gradually reduced, so that a predetermined diameter can be obtained while passing through a large number of the die holes. In order to extract the alloy from the die hole and obtain a wire, it is necessary to apply tension to the wire at the exit side of the die hole. For this reason, the wire is passed through the gap between the pair of rolls on the die exit side. The tension is applied by this roll, and the alloy is pulled out of the die hole. After that, the wire rod exiting the roll is wound up on a bobbin or the like and stored.

In the method of forming a wire by tension, as in the above-mentioned drawing method, if the indium content in the wire is high, the wire becomes too soft. When wound on a bobbin, the wire may be damaged or crushed. Therefore, molding cannot be performed by such a method. On the other hand, the wire for a thermal fuse element of the present embodiment has a low indium content and an appropriate hardness,
Even if the wire is passed through the gap between the rolls or wound on a bobbin, the wire is not damaged or crushed, and the wire can be formed by such a method. The wire may have various cross-sectional shapes conventionally used, such as an elliptical shape and a polygonal shape, in addition to a true circular shape in a cross section in a direction perpendicular to the axial direction.

Further, in the case of a thermal fuse which blows at a relatively low temperature, it is required to have a quick disconnection property with respect to a set temperature in order to protect electronic parts such as semiconductors having low heat resistance. As described above, in many cases, a fuse element made of a wire is installed in a state in which a constant tension is applied in the fuse in order to ensure quick disconnection. Since the fuse element installed in this state blows more rapidly as the cross-sectional area is smaller, the wire used for such a fuse element also needs to have a smaller cross-sectional area.

Further, the wire of the present invention has a fusing temperature of 1
A fuse having a wire that is melted in this temperature range from 20 ° C. to 130 ° C. is in demand for protection of small electronic devices such as a notebook personal computer. In recent years, these electronic devices have been steadily miniaturized for convenience of use, and in order to miniaturize the devices, the thermal fuse as a component thereof has also been required to be small. A small cross-sectional area is also required.

From the above needs, the cross-sectional area of the wire is 0.3 m
m ² or less. For such a wire having a small cross-sectional area, damage or crushing of the wire is fatal. That is, if the wire is damaged or crushed, the cross-sectional area changes only at that portion, and even if the fuses have the same set temperature, the fusing time varies depending on the presence or absence of the damage and the degree of crushing. Fuse wires having a high indium content were soft and easily scratched and crushed. For this reason, the fusing time tends to vary, and many of them have low reliability. On the other hand, since the wire of the present invention is formed of the above-mentioned fusible alloy having a low indium content, it is hardly damaged and crushed. For this reason, a highly reliable wire having small variations can be obtained.

[0031]

EXAMPLE Based on the above embodiment, a sample made of an In--Sn alloy having a predetermined composition was manufactured and an experiment was conducted. This will be described as an example.

Example 1 The sample of Example 1 is composed of a fusible alloy having a composition of 32% by weight of tin and 68% by weight of indium. This sample was manufactured by the following method. First, 99.99% pure tin and 99.99% pure indium were weighed and placed in a melting furnace. Next, the raw material was melted and stirred at a temperature of 300 ° C. in a melting furnace to prepare an alloy, and the prepared alloy was poured into a mold, allowed to cool, and demolded. A sample was collected from the ingot thus manufactured, and this was designated as Example 1. When the prepared alloy was poured into a mold, the composition of the alloy was confirmed by chemical analysis.

Example 2 The sample of Example 2 is made of a fusible alloy having a composition of 35% by weight of tin and 65% by weight of indium. An ingot from which this sample was collected was manufactured in the same manner as in the ingot of Example 1 above.

<Experimental Method> In the experiment, the samples of Examples 1 and 2 were gradually heated in a heating furnace, and were measured using a thermal analyzer (hereinafter referred to as TA) and a differential scanning calorimeter (hereinafter referred to as DSC). This was performed by examining the melting temperature characteristics of each sample. The temperature rise pattern of the heating furnace was 50 ° C before the experiment,
The heating rate was 10 ° C./min, and the final holding temperature was 150 ° C.

<Experimental Results> FIG. 3 shows the measurement results by TA when the temperature of the sample of Example 1 was raised according to this temperature rising pattern.
Shown in FIG. 3 shows that the temperature curve has an inflection point when the temperature is about 126 ° C. and about 128 ° C. Also, DSC
FIG. 4 shows the results of the measurement. According to FIG.
It can be seen that the differential thermal curve has a peak starting point at 6 ° C. From these facts, the fusible alloy constituting the sample of Example 1 changes from a single-phase state of a solid phase alone to a two-phase coexistence of a solid phase and a liquid phase at about 126 ° C., and to a two-phase coexistence at about 128 ° C. It can be seen that the state changes from the state to the single phase state of the liquid phase alone.
That is, in Example 1, about 126 ° C. is the solidus temperature, about 128 ° C. is the liquidus temperature, and ΔT is about 2 ° C.

Similarly, when the sample of Example 2 was heated,
FIG. 5 shows the measurement results by TA. FIG. 5 shows that the temperature curve has an inflection point when the temperature is about 123 ° C. and about 126 ° C. FIG. 6 shows the measurement results by DSC. From FIG. 6, it can be seen that there is a peak start point in the differential thermal curve when the temperature is about 123 ° C. That is, the second embodiment
, About 123 ° C. is the solidus temperature, about 126 ° C. is the liquidus temperature, and ΔT is about 3 ° C.

Table 1 summarizes the compositions, melting points, and ΔT of the samples of Examples 1 and 2 from the above experiments.

[0038]

[Table 1]

From Table 1, it can be seen that Examples 1 and 2 have a temperature of 120 ° C. or higher.
It was found that the liquidus temperature was within a temperature range of 30 ° C. or less. ΔT in Examples 1 and 2 was 30 ° C.
It was much smaller than that.

[0040]

The thermal fuse of the present invention is a thermal fuse having a fuse element that blows at a predetermined temperature,
The fuse element is formed of a fusible alloy comprising 30% by weight or more and 48% by weight or less of tin and the balance of indium.

The wire for a thermal fuse element according to the present invention comprises:
It is characterized by being formed of a fusible alloy comprising 30% by weight or more and 48% by weight or less of tin and the balance of indium.

As described above, by selecting the Sn-In alloy as the fusible alloy and reducing the indium content in the alloy, a thermal fuse and a wire having excellent fusing temperature characteristics and appropriate hardness and ductility can be obtained. Become.

[Brief description of the drawings]

FIG. 1 is a phase diagram of a Sn—In alloy.

FIG. 2 is a sectional view of a thermal fuse.

FIG. 3 is a graph showing the results of analysis by TA in Example 1.

FIG. 4 is a graph showing the results of DSC analysis of Example 1.

FIG. 5 is a graph showing the results of analysis of Example 2 by TA.

FIG. 6 is a graph showing the results of DSC analysis of Example 2.

[Explanation of Symbols] A: eutectic point of Sn-In binary alloy B: point of 30% by weight of Sn and 70% by weight of In 1: temperature fuse 10: fuse element 11: flux 12: ceramic case 2: lead wire

Claims (2)

[Claims] 1. A thermal fuse having a fuse element that blows at a predetermined temperature, wherein the fuse element has a temperature of 30 ° C.
A thermal fuse characterized by being formed of a fusible alloy composed of at least 48% by weight of tin and at most 48% by weight of tin. 2. A temperature fuse element wire made of a fusible alloy comprising 30% by weight or more and 48% by weight or less of tin and the balance of indium.