JPH07201265A - Thin type fuse - Google Patents

Abstract

PURPOSE:To provide such a thin type fuse as having excellent sealing property against inner pressure and operativeness by bridging a low melting point fusible metal strip between the exposed portions of band conductors and applying an insulating layer on the surface of an insulating plate. CONSTITUTION:The ratio S1/S0 of the contact area S0 of an insulating plate 1 with a band conductor 2 to the area S1 of the exposed portion 22 of the band conductor 2 is set 0.01-0.2 and the ratio S2/S1 of the area S2 of the exposed portion 22 of the band conductor 2 when jointed to a low melting point fusible metal strip 3 to the area S1 is set 0.7 or lower. A relationship (S1+S2)L>=4 holds among an interval L between the exposed portions of the band conductors, the Volume V of the low melting point fusible metal strip, the area S1 of the exposed portion of the band conductor and the area S2 of the exposed portion of the band conductor when jointed to the low melting point fusible metal strip.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to thin fuses, for example,
The present invention relates to an alloy type thin temperature fuse.

[0002]

2. Description of the Related Art In an alloy type temperature fuse, it is used by being attached to an electric device to be protected, and when the electric device generates heat due to an overcurrent, the generated heat is melted by a low melting point which is a fuse element. It is transmitted to the metal piece, the low melting point metal piece is melted and the electric power to the electric equipment is cut off,
It is possible to prevent abnormal heat generation of the electric device and eventually a fire.

In this alloy type temperature fuse, a flux having a melting point lower than that of the metal piece is applied onto the low melting point fusible metal piece, and the molten low melting point fusible metal is already melted. Under the coexistence with, the spheroidization is caused by the interfacial energy, the molten metal is divided by the progress of the spheroidization, and when the arc generated during this division disappears due to the increase in the distance between the divisions, the current is cut off. The above-mentioned interruption of energization is completed, and the divided molten metal is cooled and solidified as the electric equipment is cooled.

In the spheroidization of the molten fuse element, the contact angle of the molten metal to the lead wire end or the electrode is small, and the molten metal is often wetted to the lead wire end or the electrode. It greatly contributes to the promotion of the division.

In the spheroidization of the molten fuse element, internal pressure is generated due to vaporization of flux by arc heat and vaporization of the fuse element. Also,
Due to a heat cycle based on turning on and off of a load current of an electric device, the flux may be repeatedly heated within a temperature range higher than the operating temperature of the temperature fuse to expand the flux to generate an internal pressure. Therefore, the insulating coating in the alloy type temperature fuse must be applied so as to withstand these internal pressures.

With the recent miniaturization of electrical equipment, the fuses are also required to be smaller and thinner. However,
In the present inventor, each end portion of the pair of strip-shaped conductors is brought into contact with the back surface of the insulating plate, and the substantially central portion of each end portion is exposed on the surface of the insulating plate and the insulating plate. And a band-shaped conductor are adhered to each other, a fuse element (low melting point fusible metal piece) is bridged between the exposed parts of the band-shaped conductor, and an insulating layer is coated on the surface of the insulating plate. -I have already proposed.

[0007]

In this thin fuse, expansion of the flux based on the heat cycle of the above-mentioned equipment, vaporization of the flux during operation of the temperature fuse, or vaporization of the fuse element. As a leakage path against internal pressure due to the internal pressure, there is a path that passes through the boundary between the exposed portion of the strip-shaped conductor and the insulating plate and passes through the adhesive interface between the insulating plate and the strip-shaped conductor. In order to secure it, it is necessary to considerably increase the adhesion area between the insulating plate and the strip conductor, and it is inevitable that the exposed portion of the strip conductor becomes considerably small.

However, when the area of the exposed portion of the strip-shaped conductor is reduced, the amount of the molten fuse element wetted by the exposed portion of the strip-shaped conductor is reduced during the operation of the fuse, and the fused fuse is melted.
Spherical element splitting is less likely to occur and temperature
This leads to a decrease in the operability of the mouse.

An object of the present invention is to bring the ends of a pair of strip-shaped conductors into contact with the back surface of the insulating plate so that the substantially central portions of these ends are exposed on the surface of the same insulating plate. A thin fuse in which a plate and a band-shaped conductor are bonded to each other, a low melting point fusible metal piece is bridged between the exposed parts of the band-shaped conductor, and an insulating layer is coated on the surface of the insulating plate. At the same time, the expansion of the flux and the temperature
It is an object of the present invention to provide a thin fuse having excellent sealability and operability against internal pressure due to vaporization of flux during vaporization operation or vaporization of a fuse element.

[0010]

According to the thin fuse of the present invention, the ends of a pair of strip-shaped conductors are brought into contact with the back surface of the insulating plate, and substantially the center of each of these ends is the same as the insulating plate. On the surface of the insulating plate and bonding the insulating plate and the band-shaped conductor to each other, and bridging a low melting point metal piece between the exposed parts of the band-shaped conductor. In the fuse covered with the insulating layer, the ratio S ₁ / S ₀ of the adhesive area S ₀ between the insulating plate and the strip conductor and the strip conductor exposed area S ₁ was set to 0.
01 to 0.2, and the ratio S of the area S _{2 of} the portion of the strip-shaped conductor exposed portion where the low melting point soluble metal piece is joined to the area S _1
2 / S ₁ is 0.7 or less, the interval L between the exposed portions of the strip conductor,
Between the volume V of the low melting point soluble metal piece, the area S _{1 of the} strip-shaped conductor exposed portion and the area S _{2 of} the portion of the striped conductor exposed portion where the low melting point soluble metal piece is joined, (S ₁ + S ₂ ) L ≧ 4.7
The configuration is characterized in that the relationship of V is added.

The configuration of the present invention will be described below in detail with reference to the drawings. 1A is a cross-sectional explanatory view showing an example of the configuration of the present invention, and FIG.
Similarly, (C) is a bottom view. In FIGS. 1A to 1C, 1 is an insulating plate made of a thermoplastic. 2 and 2 are a pair of strip-shaped conductors, and each conductor end portion 21 is brought into contact with the back surface of the insulating plate 1,
A bulging portion 22 formed substantially in the center of the abutting end portion 21 is exposed on the surface of the insulating plate 1 and the contact surface between the insulating plate 1 and the strip conductor 2 is adhered. The length of the strip-shaped conductor end portion 21 abutting on the back surface of the insulating plate 1 is usually 0.5 to 3 times the strip-shaped conductor width, and the shape of the bulging portion 22 is not necessarily rectangular. But is not limited to
In the case of a quadrangle, the length / width ratio is 1 to 3.5. The ratio S ₁ / S ₀ of the adhesion area S ₀ between the insulating plate 1 and the strip conductor 2 to the strip conductor exposed portion area S ₁ is 0.01 to.
It is set as 0.2.

Reference numeral 3 denotes a low melting point fusible metal piece bridged by welding or brazing between the strip-shaped conductor exposed portions 22 and 22. The low melting point fusible metal piece 3 in the strip-shaped conductor exposed portion 22 is joined. an area S ₂ and a ratio S ₂ / S ₁ between said area S ₁ 0.7
It is as below. Further, the interval L between the strip-shaped conductor exposed portions 22 and 22, the volume V of the low-melting point soluble metal piece 3, the strip-shaped conductor exposed portion area S _{1 and} the low-melting point soluble metal piece in the strip-shaped conductor exposed portion were joined. Between the area S _{2 of the} part, 6000>
The relationship of (S ₁ + S ₂ ) L / V ≧ 4.7 is given. Four
Is the flux applied on the low melting point metal piece. 5
Is an insulating layer coated on the surface side of the insulating plate 1 and can be provided by heat fusion of a thermoplastic film.

As the thermoplastic film for the insulating plate 1 and the insulating coating 5 made of the above thermoplastics, polyethylene, vinyl chloride, polypropylene, polystyrene, ethylene-propylene, polyimide, polyethylene terephthalate, etc. are used. It is preferable to use the same material for the insulating plate and the thermoplastic film for insulating coating, but it is also possible to use different materials.

In the above-mentioned strip-shaped conductor 2, a single body of copper, or, as shown in FIG. 2, the surface abutting against the back surface of the insulating plate is copper 201 and the other portion 202 is made of a different metal. It is also possible to use a composite with nickel, for example.

In order to bond the end portion of the strip-shaped conductor exposed portion to the insulating plate, a swollen portion is pressed on the end portion of the strip-shaped conductor, and a hole slightly smaller than the swollen portion is formed in the insulating plate. A method of contacting the end portion of the strip-shaped conductor with the back surface of the insulating plate, fitting the bulging portion of the end portion of the strip-shaped conductor into the hole of the insulating plate, and pressing and heat-sealing both contact surfaces, The bulging part is pressed on the end of the band-shaped conductor, the end of the band-shaped conductor is brought into contact with the back surface of the insulating plate, and pressed under heat to press the bulged part toward the surface of the insulating plate and insulate it. The plate and the belt-shaped conductor are heat-sealed, and the resin on the exposed portion is removed by grinding,
In contrast to these methods such as the method of exposing the exposed portion, instead of heat-sealing the insulating plate and the band-shaped conductor, a method of bonding with an adhesive can be used.

The above-described configuration example of the present invention is a strip-shaped conductor (lead).
Is a so-called axial type in which the strip conductors are arranged in a straight line, but a radial type in which strip conductors are arranged in parallel can be used as shown in FIG. In FIG. 3, 1 is an insulating plate, 2 and 2 are a pair of strip-shaped conductors, 21 is an end of each strip-shaped conductor 2, and 22 is a substantially central strip-shaped conductor exposed portion of each end. Is a low melting point soluble metal piece, 4 is a flux applied to the low melting point soluble metal piece, and 5 is an insulating layer coated on the surface side of the insulating plate. Insulating plate 1 and each strip-shaped conductor The ratio S ₁ / S ₀ of the adhesion area S ₀ between the surface of the belt-shaped conductor and the exposed area S ₁ of the strip-shaped conductor is set to 0.
01 to 0.2, and the ratio S of the area S _{2 of} the portion of the strip-shaped conductor exposed portion where the low melting point soluble metal piece is joined to the area S _1
2 / S ₁ is 0.7 or less, and the interval L between the strip-shaped conductor exposed portions, the volume V of the low melting point fusible metal piece, the strip-shaped conductor exposed portion area S _{1 and} the low-melting point in the strip-shaped conductor exposed portion Between the area S _{2 of} the portion where the soluble metal pieces are joined, 6000> (S ₁ +
The relationship of S ₂ ) L / V ≧ 4.7 is given.

[0017]

Function: Expansion of the flux based on the heat cycle of the equipment, vaporization of the flux 4 at the time of fuse operation, or vaporization of the fuse element (low melting point soluble metal piece) 3 causes an internal pressure, resulting in a strip shape. Around the conductor exposed portion 22 and the insulation
Even if leakage occurs from the boundary with the insulating plate 1 through the adhesive interface between the insulating plate 1 and the band-shaped conductor 2, the bonding area S ₀ between the insulating plate 1 and the band-shaped conductor 2 and the band-shaped conductor expression. The ratio S ₁ / S ₀ to the partial area S ₁ is set to 0.01 to 0.2 to sufficiently widen the adhesive interface between the insulating plate 1 surrounding the strip-shaped conductor exposed portion 22 and the strip-shaped conductor 2. Since the front and rear and left and right bonding distances (sealing distances) of the strip-shaped conductor exposed portions 22 are sufficiently long, such leakage can be prevented well.

During operation of the fuse, the melted low melting point metal piece coexists with the molten flux to reduce the interfacial energy.
The molten metal is spheroidized due to the wetting phenomenon and the spheroidization is progressed while the molten metal is pulled by the wetting phenomenon. In this case, between the insulating plate 1 and the strip-shaped conductor 2 as described above. As a result of widening the bonding area of the strip conductor, the area of the strip conductor exposed portion 22 becomes considerably small, which becomes a negative factor against the wetting of molten metal to the strip conductor exposed portion 22. the ratio S ₂ / S ₁ between the area S ₂ of the portion joining the low-melting-soluble metal piece 3 and the area S ₁ is 0.7 or less in addition to this condition, preferably, between strip conductor exposed portion Between the distance L, the volume V of the low melting point soluble metal piece, the area S _{1 of the} strip-shaped conductor exposed portion and the area S _{2 of} the portion where the low melting point soluble metal piece is joined in the strip-shaped conductor exposed portion, (S ₁ + S ₂ ) L
The relationship of /V≧4.7 is given so that even if the exposed portion of the strip-shaped conductor is small, the molten metal is fragmented sufficiently quickly, so that a good operating speed can be guaranteed. This is clear from the operation test results of the examples described below. It should be noted that 6000> (S ₁ + S ₂ ) L / V is a condition for ensuring the compactness of the insulating plate, and it is possible to achieve sealability and operability against internal pressure while ensuring miniaturization. . The operation of the fuse is when the low melting point metal piece reaches its melting point T, that is, the temperature rise due to the Jule heat generation of the low melting point metal piece is Δt ₁ , and the heat generated by the equipment is received. If the temperature rise of the low melting point soluble metal piece is Δt ₂ and the ambient temperature is t ₀ , then t ₀ + Δt ₁ + Δt ₂ = T, and if the energizing current is large, Δt ₁ becomes large, and Δt ₁ becomes large. _The fuse operates when ₂ is relatively small, and in this case, the energizing current is large and the arc energy is high, and as a result, the above internal pressure becomes particularly high. The thermoplastic film for the plate 1 and the insulating coating 5 can absorb internal pressure well due to the excellent flexibility (expandability) of the thermoplastic film for the insulating coating 5, and the above-mentioned excellent sheet. Combined with the flexibility, the fuse can be held safely by avoiding explosion.

[0019]

EXAMPLES In any of the following examples, the insulation
The length is 10.5 mm, width: 6 mm, thickness: 0.19
mm polyethylene terephthalate film, and for the strip-shaped conductor, the copper-nickel composite shown in FIG. 2 having a width of 3.5 mm and a thickness of 0.1 mm is used, respectively, and is applied to the back surface of the insulating plate of each strip-shaped conductor. The contact length was 4.85 mm.
In manufacturing the temperature fuse, a bulging portion is press-formed in the center of the end portion of the strip-shaped conductor, a hole slightly smaller than the bulging portion is formed in the insulating plate, and the end portion of the strip-shaped conductor is formed. Abut the back surface of the insulating plate and connect the bulging part of the end of the strip conductor to the insulating plate.
To the end of the strip-shaped conductor on the insulating plate by press-fitting the contact surfaces of the both and attaching it to the hole of the belt.
A mm mm polyethylene terephthalate film was heat fused around the surface of the insulating plate to provide an insulating coating.

The dimensions of each part in the embodiment are as shown in FIG. In FIG. 4, a _{1 and} b ₁ are the length and width of the strip-shaped conductor exposed portion 22, and L is the strip-shaped conductor exposed portion 2.
The distance between 2 and 22 and h and d respectively indicate the length and diameter of the low melting point fusible metal piece (circle line) 3 used.

Example 1 a ₁ : 1.62 mm, b ₁ : 0.8 mm, and the area S ₁ of the strip-shaped conductor exposed portion was 1.296 mm ² . Area S _{2 of} the portion where the low melting point soluble metal piece is joined in the exposed portion of the strip conductor
Is 0.781 mm ² . The melting point of the low melting point fusible metal piece (eutectic alloy) is 93 ° C., and L is 2.5 mm.
h: 6.0 mm, d: 0.446 mm, and V is 0.
It is 937 mm ³ . Therefore, S ₁ / S ₀ is 0.08, S ₂ / S ₁ is 0.60, and (S ₁ + S ₂ ) L / V =
5.4> 4.7.

Comparative Example 1 a ₁ : 1.62 mm, b ₁ : 0.8 mm, and the strip conductor exposed portion area S ₁ was 0.845 mm ² . Area S _{2 of} the portion where the low melting point soluble metal piece is joined in the exposed portion of the strip conductor
Is 0.781 mm ² . The melting point of the low melting point fusible metal piece (eutectic alloy) is 93 ° C., and L is 2.5 mm.
h: 6.0 mm, d: 0.446 mm, and V is 0.
It is 937 mm ³ . Therefore, S ₁ / S ₀ is 0.04, S ₂ / S ₁ is 0.92, and (S ₁ + S ₂ ) L / V =
4.3 <4.7.

50 samples for each of Example 1 and Comparative Example 1
The test pieces were immersed in an oil bath at a temperature of 94 ° C. in a state where a small amount of electric current was applied, and the number of cut-off currents was measured within 20 seconds after the immersion. Although the number of rejects was 0, it was 17% for the comparative example product.
Was rejected.

Example 2 a ₁ : 1.39 mm, b ₁ : 0.5 mm, and the strip conductor exposed surface area S ₁ was 0.695 mm ² . Area S _{2 of} the portion where the low melting point soluble metal piece is joined in the exposed portion of the strip conductor
Is 0.332 mm ² . The melting point of the low melting point fusible metal piece (eutectic alloy) is 88 ° C., and L is 3.5 mm.
h: 5.0 mm, d: 0.446 mm, and V is 0.
It is 767 mm ³ . Therefore, S ₁ / S ₀ is 0.04, S ₂ / S ₁ is 0.48, and (S ₁ + S ₂ ) L / V =
It is 4.7.

Comparative Example 2 a ₁ : 1.39 mm, b ₁ : 0.5 mm, and the strip conductor exposed portion area S ₁ was 0.695 mm ² . Area S _{2 of} the portion where the low melting point soluble metal piece is joined in the exposed portion of the strip conductor
Is 0.442 mm ² . The melting point of the low melting point fusible metal piece (eutectic alloy) is 88 ° C., and L is 3.0 mm.
h: 5.0 mm, d: 0.446 mm, and V is 0.
It is 767 mm ³ . Therefore, S ₁ / S ₀ is 0.04, S ₂ / S ₁ is 0.64, and (S ₁ + S ₂ ) L / V =
4.4 <4.7.

50 samples for each of Example 2 and Comparative Example 2
The test pieces were immersed in an oil bath at a temperature of 89 ° C. in a state where a small amount of electric current was applied, and the number of cut-off currents was measured within 20 seconds after the immersion. Although the number of rejects was 0, it was 43% for the comparative example product.
Was rejected.

[0027]

According to the present invention, the ends of the pair of strip-shaped conductors are brought into contact with the back surface of the insulating plate so that the substantially central portions of these ends are exposed on the surface of the insulating plate and insulated. In a fuse in which a plate and a band-shaped conductor are bonded to each other, a low melting point fusible metal piece is bridged between the exposed parts of the band-shaped conductor, and an insulating layer is coated on the surface of the insulating plate. Since the adhesive area between the insulating plate and the band-shaped conductor is wide enough to ensure the sealing property against the internal pressure, the expansion of the flux based on the heat cycle of the equipment and the flux at the time of fuse operation It is possible to well prevent leakage under the internal pressure due to the vaporization of or the fuse element.

Since the bonding area between the insulating plate and the strip-shaped conductor is made sufficiently wide, the area of the exposed portion of the strip-shaped conductor becomes small and the molten fuse element is wet when the fuse is in operation. Although the area is small, the area S _{2 of} the portion where the low melting point fusible metal piece is joined in the exposed portion of the strip-shaped conductor and the area S _{1 are}
To the ratio S ₂ / S ₁ , the interval L between the exposed portions of the strip conductor, the volume V of the low melting point soluble metal piece, the area S _{1 of the} exposed portion of the strip conductor and the low melting point soluble metal piece in the exposed portion of the strip conductor. Since a specific relationship based on the experimental result is given to the area S _{2 of} the portion where the is joined, the molten metal can be fragmented sufficiently quickly even if the strip-shaped conductor exposed portion is small. Can assure a good operating speed.

[Brief description of drawings]

1A is a cross-sectional explanatory view showing an example of a fuse according to the present invention, FIG. 1B is a plan explanatory view thereof, and FIG. 1C is a bottom explanatory view thereof. is there.

FIG. 2 is a perspective view showing an example of a strip-shaped conductor used in the present invention.

FIG. 3 is an explanatory plan view showing another example of the fuse according to the present invention.

FIG. 4 is an explanatory diagram used for expressing the dimensions of the embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Insulation pre-2 Band-shaped conductor 21 Band-shaped conductor end 22 Band-shaped conductor exposed part 3 Low melting point fusible metal piece 4 Flux 5 Insulation coating layer

Claims (1)

[Claims] 1. An end face of a pair of strip-shaped conductors is brought into contact with the back surface of an insulating plate, and a substantially central part of each end part is exposed on the surface of the insulating plate. In a fuse in which a band-shaped conductor is adhered, a low melting point fusible metal piece is bridged between the exposed parts of the band-shaped conductor, and an insulating layer is coated on the surface of the insulating plate, The ratio S ₁ of the adhesion area S ₀ between the belt and the strip conductor and the area S _{1 of the} exposed portion of the strip conductor
The S ₀ and 0.01 to 0.2, a ratio S ₂ / S ₁ between the partial area S ₂ of bonding the low melting point soluble metal pieces in strip conductor exposed portion and the area S ₁ 0.7 or less And the space L between the exposed portions of the strip-shaped conductor, the volume V of the low melting point soluble metal piece, the area S _{1 of the} exposed portion of the strip conductor and the area S of the portion where the low melting point soluble metal piece is joined in the exposed portion of the strip conductor. between the _{2, (S 1 + S 2} )
A thin fuse having a relationship of L ≧ 4.7V.