JP2001143590A - Alloy fuse - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an alloy temperature fuse that ensures the accurate operation at about 70 deg.C even with a diameter below 500 μm. SOLUTION: A fuse element is made of an alloy composed of 29 to 40 wt.% of Pb, 13 to 18 wt.% of Sn, 7 to 25 wt.% of Cd, and the remaining part of Bi.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an alloy type temperature fuse having an operating temperature of about 70.degree.

[0002]

2. Description of the Related Art In an alloy type temperature fuse, a low melting point fusible alloy piece (fusing element) is connected between a pair of lead wires, and a flux is applied on the low melting point fusible alloy piece. The flux coated alloy piece is surrounded by an insulator, and it is used by attaching it to the electrical equipment to be protected.When the electrical equipment generates heat due to overcurrent, the low melting point fusible alloy piece is liquefied by the generated heat, In the coexistence of the molten metal and the flux that has already been melted, the molten metal is spheroidized by surface tension.

[0003] The basic condition required for the above low melting point fusible alloy is that it has a melting point determined from the permissible temperature of the equipment to be protected, and has a melting point between the solidus and liquidus at that melting point. The width of the liquid coexistence area is narrow. That is, in an alloy, there is usually a solid-liquid coexistence zone width between the solidus line and the liquidus line. In this area, the solid phase particles are dispersed in the liquid phase, and the liquid phase Because of the above-mentioned properties, the above-mentioned spheroidization may occur. Therefore, the temperature range (ΔT) belonging to the solid-liquid coexistence zone width before the liquidus temperature (T is this temperature) is considered. ), There is a possibility that the low-melting-point fusible alloy piece is spheroidized and divided. Therefore, the temperature fuse using such a low melting point fusible alloy piece must be treated as operating at a temperature range in which the fuse element temperature is (T-ΔT) to T. , .DELTA.T, that is, the narrower the solid-liquid coexistence area width, the smaller the variation in the operating temperature range of the temperature fuse, and the more accurately the temperature fuse can be operated at a predetermined set temperature. .

Conventionally, as an alloy type temperature fuse having an operating temperature of approximately 70 ° C., a melting temperature of 72 ° C. (solidus temperature of 70 ° C.,
Bi-Pb-Sn-Cd alloy (liquidus temperature 72 ° C) (B
i 50% by weight, Pb 25% by weight, Sn 12.5% by weight,
Cd 12.5% by weight).
A known element (for example, Japanese Patent Application Laid-Open No. 3-236130) is known, and its solid-liquid coexistence width is as narrow as 2 ° C., so that high-precision operation can be guaranteed.

[0005]

In recent years, in order to make the temperature fuse thinner, the fuse element has been required to be thinner, for example, as thin as 300 μmφ.
However, the wood metal described above has a high brittleness due to a large amount of Bi and is difficult to draw, and it is extremely difficult to reduce the fuse element diameter to 300 μmφ.

Therefore, it is conceivable to reduce the amount of Bi. Naturally, the decrease in the amount of Bi increases the amount of other metal components to be added. Fluctuations in the coexistence width of solid and liquid and fluctuations in the specific resistance are inevitable. Particularly, when the fuse element is thinned, the electric resistance of the fuse element dramatically increases due to the increase in the specific resistance. However, even at the time of rated energization, the fuse element is heated to a considerably high temperature due to Joule heat, which may cause a malfunction. That is, the temperature rise due to the Joule heat of the fuse element is Δθ,
Assuming that the melting point of the fuse element is T, the temperature (T-Δ
Since the temperature fuse is operated at θ), if the electrical resistance of the fuse element becomes too high to ignore Δθ, the power is cut off before the device reaches a predetermined allowable temperature. In some cases, it is necessary to lower the electric resistance value to minimize the above Δθ.

SUMMARY OF THE INVENTION An object of the present invention is to provide an alloy type temperature fuse capable of guaranteeing accurate operation even under a small diameter fuse element having a diameter of less than 500 μm in an alloy type temperature fuse having an operating temperature of about 70 ° C. To provide.

[0008]

The alloy type temperature fuse according to the present invention is composed of a fuse element composed of 29-40% by weight of Pb, 13-18% by weight of Sn, 7-25% by weight of Cd, and the balance of Bi. It is a configuration characterized by that
It is also possible to add 0.5 to 10 parts by weight of In to 100 parts by weight of the alloy composition, and further add 0.5 to 5 parts by weight of Ag.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION In the temperature fuse according to the present invention, a circular wire having an outer diameter of less than 500 μmφ and a diameter of 200 μmφ or more or a flat wire having the same cross-sectional area as the circular wire can be used as the fuse element.

[0010] The alloy composition of the fuse element is P
b 29 to 40% by weight, Sn 13 to 18% by weight, Cd 7 to
25% by weight, the balance Bi is preferably 30 to 40% by weight of Pb, 13 to 18% by weight of Sn, 7 to 25% by weight of Cd, and the balance of Bi. The reference compositions are 30% by weight of Pb and Sn14.
% Of Cd, 710% by weight of Cd, and 46% by weight of Bi. The liquidus temperature of the reference composition is 74 ° C., and the solid-liquid coexistence zone width is 4 ° C.
And the specific resistance is 49 μΩ · cm.

In the alloy composition of the fuse element, Sn is contained in an amount of 13 to 18% by weight and Pb is contained with respect to the amount of Sn (12.5% by weight) and the amount of Pb (25% by weight) of the wood metal. By increasing the content of Pb to as large as 29 to 40% by weight, the drawability and low specific resistance (45 to 55 μΩ · c) can be obtained while maintaining the solid-liquid coexistence region of the wood metal.
m), and in the composition range of 25 to 25% by weight of Cd 7 to 25% by weight, the amount of Cd in wood metal (1
(2.5% by weight), and is a composition region having a particularly low specific resistance. The highest liquidus temperature of the alloy composition of this fuse element is 74 ° C, and the lowest solidus temperature is 68 ° C.
° C, and the solid-liquid coexistence region width is about 5 ° C on average. Since a temperature difference of about 2 ° C. occurs between the fuse element of the temperature fuse and the equipment due to thermal resistance therebetween, the operating temperature of the temperature fuse using this reference composition is 76 ° C. ~
70 ° C.

Alloy composition of the fuse element 100
By adding 0.5 to 10 parts by weight of In to the parts by weight, the specific resistance of the fuse element can be lowered while sufficiently maintaining the drawability and the melting point characteristics,
For example, by adding 3 parts by weight of In to 100 parts by weight of the reference composition, the specific resistance can be reduced from 49 μΩ · cm of the reference composition to 42 μΩ · cm. Further, the above alloy composition 1
By adding 0.5 to 5 parts by weight of Ag to 00 parts by weight, the specific resistance can be made much lower than that of 45 to 55 μΩ · cm. For example, by adding 2 parts by weight, the specific resistance becomes 40 μΩ・ It can be as low as about cm.

The fuse element of the temperature fuse according to the present invention is manufactured by drawing an alloy base material, and can be used as it is in a round cross section or in a flattened form.

FIG. 1A is an explanatory plan view showing a thin alloy-type temperature fuse according to the present invention, and FIG. 1B is a cross-sectional view taken along the line in FIG. Thickness 100-30
A 100 μm thick plastic base film 11
The band-shaped lead conductors 3 to 3 having a thickness of about 200 μm are fixed by an adhesive or fusion bonding, and the wire diameter is 500 μmφ between the band-shaped lead conductors.
And a flux 5 is applied to the fuse element 4, and the flux-coated fuse element is fixed to the plastic cover film 12 having a thickness of 100 to 300 μm by an adhesive or fusion. Sealed with.

The alloy type temperature fuse of the present invention can be implemented in a case type, a substrate type or a resin dipping type. As a case type, a fuse element of a linear piece is welded between lead wires that are opposed to each other in a straight line, a flux is applied on the fuse element, and a flux is applied on the fuse-coated fuse element. An axial type in which a ceramic cylinder is inserted and each end of the cylinder and each lead wire are sealed with an adhesive, for example, an epoxy resin, or a line-shaped piece is attached to the end between parallel lead wires. Welding the fuse element, applying a flux on the fuse element, placing a flat ceramic cap on the flux-coated fuse element, and applying an epoxy resin between the opening of the cap and the lead wire. A sealed radial type can be used.

As the resin dipping type, a radial type in which an epoxy resin coating layer is provided on a flux-coated fuse element by immersion in an epoxy resin liquid, instead of surrounding the ceramic cap, can be used.

In the above-mentioned substrate type, a fuse element of a linear piece is welded to an end between the electrodes of an insulating substrate having a pair of layered electrodes provided on one surface, and a flux is applied on the fuse element. A structure in which a lead wire is connected to the rear end of each electrode and an epoxy resin coating layer is provided on one surface of an insulating substrate can be used, and either an axial or radial system can be used.

As the above-mentioned flux, a flux whose melting point is lower than that of the fuse element is usually used, for example, 90 to 60 parts by weight of rosin, 10 to 40 parts of stearic acid.
Parts by weight, 0 to 3 parts by weight of activator can be used. in this case,
As the rosin, natural rosin, modified rosin (for example, hydrogenated rosin, disproportionated rosin, polymerized rosin) or these purified rosins can be used. As the activator, diethylamine hydrochloride, hydrobromide, or the like can be used. Can be used.

[0019]

[Example 1] Pb: 30% by weight, Sn: 14
The alloy composition used was 1% by weight, 10.0% by weight of Cd, and 47% by weight of Bi. The liquidus temperature of this alloy is 74 ° C., and the solid-liquid coexistence zone width is 4 ° C. The base material having this alloy composition was drawn and processed into a wire having a diameter of 300 μmφ. The area reduction rate per die is 6.5%, and the drawing speed is 30 m / mi.
n, but there was no disconnection. When the specific resistance of this wire was measured, it was 49 μΩ · cm. This wire was cut into a length of 4 mm to form a fuse element, and a substrate-type temperature fuse was prepared. A composition of 80 parts by weight of rosin, 20 parts by weight of stearic acid, and 1 part by weight of diethylamine hydrobromide was used as a flux, and an epoxy resin cured at room temperature was used as a resin material.

When 50 amps of this embodiment were energized for 1 amp in an atmosphere of 65 ° C., which is 5 ° C. lower than the solidus temperature of 70 ° C., even after 1000 hours, there was no fusing and there was no self-heating. No malfunction was observed. Further, these 50 samples were immersed in an oil bath at a heating rate of 1 ° C./min while applying a current of 0.1 amperes, and the oil temperature at the time of shutting off the current by fusing was measured to be 73 ± 2 ° C. , And the operation was able to be performed accurately while suppressing variations in the operating temperature.

Example 2 The alloy composition of Example 1 was used in which 3 parts by weight of In was added to 100 parts by weight of the alloy composition. The liquidus temperature of this alloy is 69 ° C., and the solid-liquid coexistence zone width is 4 ° C. When the base material having this alloy composition was drawn in the same manner as in Example 1 and processed into a wire having a diameter of 300 μmφ, there was no disconnection. When the specific resistance of this line was measured, 42 μm was obtained.
Ω · cm. This wire was cut into a length of 4 mm to form a fuse element, and a substrate-type temperature fuse was prepared in the same manner as in Example 1.

When 50 amps of this embodiment were energized for 1 amp in an atmosphere of 60 ° C., which is 5 ° C. lower than the solidus temperature of 65 ° C., even after 1000 hours, there was no fusing and there was no self-heating. No malfunction was recognized. Furthermore, while immersing in an oil bath at a heating rate of 1 ° C./min while applying a current of 0.1 amperes to each of the 50 specimens and measuring the oil temperature at the time of energization interruption by fusing, 68 ± 3 ° C. , And could be operated at a sufficiently accurate temperature.

Comparative Example 1 A Bi-Pb-Sn-Cd alloy (Bi50% by weight, Pb2) having a melting point of 72 ° C. (solidus temperature 70 ° C., liquidus temperature 72 ° C.) was added to a low melting point fusible alloy.
(5% by weight, Sn 12.5% by weight, Cd 12.5% by weight)
, Using a surface reduction rate of 5.0% and a drawing speed of 20 m / min.
Was tried to draw a thin wire having a diameter of 300 μmφ. However, the wire was frequently broken and it was extremely difficult. The specific resistance of this line is
It was 69 μΩ · cm. A substrate-type temperature fuse was prepared using the thin wire as a fuse element in the same manner as in the embodiment.
Immersed in an oil bath per minute and the oil temperature at the time of energization cutoff due to fusing was measured. It is presumed that this is because a thick oxide film is formed on the surface of the fuse element due to the rotary drum spinning method, and the oxide film becomes a sheath, making it difficult for the fuse element to be blown.

Comparative Example 2 Pb: 25% by weight, Sn: 1
2.5% by weight, Cd: 15.5% by weight, Bi: 47.0
A weight percent alloy composition was used. In this composition, Cd was increased by an amount corresponding to a decrease in Bi amount with respect to wood metal, and the solidus temperature reached nearly 60 ° C., and the operating temperature was 70 ° C.
It was ineligible as a class alloy type temperature fuse.
In the same manner as in the embodiment, the substrate was processed into a wire having a diameter of 300 μmφ by drawing, and a substrate-type temperature fuse was manufactured.
When 1 ampere of electricity was supplied for 1000 hours in an atmosphere of ° C., malfunctions due to self-heating frequently occurred. In addition, while passing a current of 0.1 amps for each of these 50,
It was immersed in an oil bath at a temperature rise rate of 1 ° C / min, and the oil temperature was measured when the power was cut off by fusing. The oil temperature was 65 ° C or less, and it was not suitable as a temperature fuse in the operating temperature class of 70 ° C. There was found.

[0025]

The alloy-type temperature fuse according to the present invention can eliminate malfunctions due to self-heating well to a predetermined temperature of 70 ° C. even if the fuse element diameter is as small as 300 μmφ. The power of the equipment can be cut off by
It is extremely useful as a thin alloy type temperature fuse in the class of ° C.

[Brief description of the drawings]

FIG. 1 is a drawing showing an example of an alloy type temperature fuse according to the present invention.

[Explanation of symbols]

 4 fuse element

Claims (4)

[Claims] 1. An alloy-type temperature fuse comprising an alloy having a composition of 29 to 40% by weight of Pb, 13 to 18% by weight of Sn, 7 to 25% by weight of Cd, and the balance Bi as a fuse element. 2. An alloy having a composition in which 29 to 40% by weight of Pb, 13 to 18% by weight of Sn, 7 to 25% by weight of Cd, and 0.5 to 5 parts by weight of Ag are added to 100 parts by weight of the remaining Bi. Alloy type temperature hue characterized by
Z. 3. An alloy having a composition obtained by adding 0.5 to 10 parts by weight of In to 100 parts by weight of Pb, 29 to 40% by weight of Pb, 13 to 18% by weight of Sn, 7 to 25% by weight of Cd, and the remaining Bi.
Alloy type temperature fuse characterized by using
Z. 4. A composition comprising 29 to 40% by weight of Pb, 13 to 18% by weight of Sn, 7 to 25% by weight of Cd, and 0.5 to 10 parts by weight of In and 0.5 to 5 parts by weight of Ag to 100 parts by weight of the remaining Bi. An alloy type temperature fuse characterized by using an alloy as a fuse element.