JP2001143589A - Alloy fuse - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an alloy fuse that ensures the effective operation at about 80 deg.C with effectively inhibiting dispersion as well as having a significant heat cycle resistance. SOLUTION: A fuse element is made of an alloy composed of 20 to 40 wt.% of Pb, 10 to 25 wt.% of Sn, 3 to 10 wt.% of In, 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 80.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 sealed with a case or resin and 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 heat generated. The phase is phased, and the molten metal is sphericalized by surface tension in the coexistence with the already molten flux.

[0003] The basic requirements for the low melting point fusible alloy are that the alloy has a predetermined melting point determined from the allowable temperature of the equipment, and the solid-liquid coexistence zone between the solidus line and the liquidus line. It is narrow. That is, usually, in an alloy, a solid-liquid coexistence region exists between the solidus line and the liquidus line, and this region is in a state in which solid particles are dispersed in the liquid phase and has a liquid-like property. , The above-mentioned spheroidization may occur. Therefore, the temperature range (here, ΔT) belonging to the solid-liquid coexistence region before the liquidus temperature (this temperature is T). Therefore, there is a possibility that the low melting point fusible alloy piece is spheroidized and divided. Thus,
In a temperature fuse using such a low melting point fusible alloy piece, the fuse element temperature must be treated as operating within a temperature range of (T-ΔT) to T, and ΔT is small. In other words, the smaller the solid-liquid coexistence area, the smaller the variation in the operating temperature range of the temperature fuse, and the more the temperature fuse can be operated at a predetermined set temperature.

[0004]

Conventionally, an operating temperature of 10
Melting temperature 95 ° C as alloy type temperature fuse below 0 ° C
A Bi-Pb-Sn-based eutectic alloy as a fuse element, and a Bi-Pb-Sn-Cd alloy (Bi50) having a melting temperature of 72 ° C (solidus temperature 70 ° C, liquidus temperature 72 ° C).
Wt%, Pb 25 wt%, Sn 12.5 wt%, Cd1
(2.5% by weight) as a fuse element is widely used. However, the separation between the operating temperatures of these temperature fuses has reached 20 ° C. or more, and the development of temperature fuses having an operating temperature of 80 ° C., an intermediate temperature between them, is required.

Conventionally, as a low melting point fusible alloy having a solid-liquid coexistence region at 80 ° C., a Bi-In—Sn eutectic alloy (eutectic point temperature 81 ° C., eutectic composition Bi: 54.02% by weight, In: 2
9.68% by weight, Sn: 16.3% by weight). However, solid-state transformation occurs at about 54 ° C., and an apparatus having an allowable temperature of about 80 ° C. exceeds this solid-state transformation point. Exposure to heat cycles in the temperature range up to
The fuse element is easily broken at an early stage due to repeated transformation strain.

An object of the present invention is to provide an alloy-type temperature fuse which can be operated sufficiently accurately at around 80 ° C. with good suppression of variation, and which is excellent in heat cycle resistance.

[0007]

The alloy type temperature fuse according to the present invention is a low melting point fusible alloy having a composition of 20 to 40% by weight of Pb, 10 to 25% by weight of Sn, 3 to 10% by weight of In and the balance of Bi. Is a fuse element, and 0.5 to 5 parts by weight of Ag can be added to 100 parts by weight of the alloy composition.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The reference composition of the fuse element of the temperature fuse according to the present invention is Pb 30% by weight, Sn1.
The composition has a liquidus temperature of 82 ° C. and a solid-liquid coexistence zone width of 4 ° C. In the alloy composition of the fuse element of the temperature fuse according to the present invention, 20 to 40% by weight of Pb and 10 to 25% by weight of Sn impart the ductility necessary for wire drawing to the alloy, and the balance B
i and In of 3 to 10% by weight bring the liquidus temperature close to 80 ° C. and keep the solid-liquid coexistence range within 5 ° C. while maintaining this ductility. The fuse element has a liquidus temperature of 80 ° C. to 76 ° C. and a solid-liquid coexistence width of 4 ° C. or less.
Between the fuse element of the temperature fuse and the device,
A temperature difference of about 2 ° C. is generated due to the thermal resistance during this time, and the operating temperature of the temperature fuse under the solid-liquid coexistence zone width of 4 ° C. and the liquidus temperature of 80 ° C. to 76 ° C. is 82 ° C. to 74 ° C. ° C.

In the temperature fuse according to the present invention, a low specific resistance can be adjusted by adding 0.5 to 5 parts by weight of Ag to 100 parts by weight of the above alloy composition.

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.

The type of the alloy type temperature fuse of the present invention includes:
Any of a case type, a substrate type, and a resin dipping type can be used. 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 tube is inserted and each end of the tube and each lead wire are sealed with an adhesive, for example, an epoxy resin, or a linear piece is attached to the end between parallel lead wires. The fuse element is welded, a flux is applied on the fuse element, a flat ceramic cap is placed on the flux-coated fuse element, and an opening of the cap and a lead are provided.
A radial type in which the space between the conductor and the lead wire is sealed with an epoxy resin 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.

In the above substrate type, a fuse element of a linear piece is welded to a tip between the electrodes of an insulating substrate having a pair of layered electrodes provided on one side, 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 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.

According to the present invention, it is possible to provide an alloy type temperature fuse having an excellent heat cycle resistance at an operating temperature of about 80 ° C. with a good yield. This is clear from the following examples.

[0016]

EXAMPLES Example 1 The alloy composition was Pb: 30% by weight,
Sn: 16% by weight, In: 6% by weight, Bi: 48% by weight
The liquidus temperature is 82 ° C., and the solid-liquid coexisting liquid width is 4 ° C. The base material of this alloy composition was drawn and processed into a line having a diameter of 0.6 mm. The drop rate for one die was 6.5%, and the drawing speed was 30 m / min, but there was no disconnection. When the specific resistance of this wire was measured, it was 55 μΩ
Cm. Cut this line to a length of 6 mm and
A cylindrical temperature fuse was prepared as a cooling element. Lee
For the lead wire, a tin-plated copper wire with an outer diameter of 0.6 mm, for the cylinder, a ceramic cylinder with an inner diameter of 1.5 mm, for the flux, a composition of 80 parts by weight of rosin and 20 parts by weight of stearic acid, and for the adhesive, An epoxy resin cured at room temperature was used.

Fifty samples of this example were immersed in an oil bath at a temperature-raising rate of 1 ° C./min while applying a current of 0.1 amperes. Within a range of ± 2 ° C., it was possible to operate sufficiently accurately at a predetermined temperature while suppressing variations. In addition, about 50 items of this example, 65 ° C. × 30 minutes and −40 ° C. × 3
A heat cycle test was performed 500 times with 0 minute as one cycle, but no breakage of the fuse element or a remarkable change in specific resistance was observed, and excellent heat cycle resistance was exhibited. Further, a sample 50 subjected to this heat cycle test was used.
No breakage or remarkable fluctuation in resistance value was observed for any of the sections, and the oil bath immersion and fusing test was performed. The oil temperature at the time of power interruption was within the range of 82 ± 2 ° C. as described above. .

[Comparative Example 1] Bi-In-Sn eutectic alloy (eutectic point temperature 81 ° C, eutectic composition Bi: 54.02 wt%, In: 29.68 wt%, Sn: 16.3 wt% )
Using the alloy composition of
A cylindrical temperature fuse was manufactured by processing the wire into a mm line. FIG.
Shows a DSC curve of this alloy composition (reference sample: aluminum oxide 8.700 mg, heating rate 10 ° C./min),
The solidus temperature is 80.1 ° C, the liquidus temperature is 81.1 ° C, and the solid state transformation occurs between 50.6 ° C and 56.6 ° C. 50 pieces of this comparative example 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 was measured when the current was cut off by fusing.
The temperature was within the range of 1 ± 3 ° C., and the operation was able to be performed at a predetermined temperature while suppressing the variation. However, this comparative example 50
When 500 heat cycle tests were carried out for each of the test items, one cycle consisting of 65 ° C. × 30 minutes and -40 ° C. × 30 minutes, most of the fuse elements were disconnected and remarkable fluctuations in specific resistance occurred. . This is presumed to be caused by the occurrence of stress at each heat cycle based on the solid phase transformation, deformation or fatigue rupture due to repeated stress, and is not suitable as a temperature fuse.

Comparative Example 2 The alloy composition was Pb: 32% by weight, Sn: 16% by weight, In: 2% by weight, and Bi: 50% by weight. This alloy composition has a solidus temperature of 90 ° C. or higher and an alloy mold temperature hue having an operating temperature of about 80 ° C.
Is ineligible.

Comparative Example 3 The alloy composition was as follows: Pb: 28% by weight, Sn: 14% by weight, In: 12% by weight, Bi: 46
% By weight. This alloy composition has a liquidus temperature of 70 ° C. or less, and is unsuitable as an alloy-type temperature fuse having an operating temperature of around 80 ° C.

[0021]

According to the present invention, it is possible to provide an alloy-type temperature fuse having an operating temperature of about 80 ° C., which can guarantee high-precision operation and has excellent heat cycle resistance.

[Brief description of the drawings]

FIG. 1 is a drawing showing a DSC curve of a Bi-In-Sn eutectic alloy.

Claims (2)

[Claims] An alloy mold temperature characterized by using a low melting point fusible alloy having a composition of 20 to 40% by weight of Pb, 10 to 25% by weight of Sn, 3 to 10% by weight of In, and the balance of Bi as a fuse element. Fuse. 2. A low melting point fusible alloy having a composition in which 20 to 40% by weight of Pb, 10 to 25% by weight of Sn, 3 to 10% by weight of In, and 0.5 to 5 parts by weight of Ag are added to 100 parts by weight of Bi. Is a fuse element.