JP3267740B2 - Substrate type temperature fuse - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an alloy-type substrate type temperature fuse using a fuse element having a low melting point as a fuse element.

[0002]

2. Description of the Related Art There is a temperature fuse as an electric component for protecting electric equipment from overcurrent and preventing thermal damage to the electric equipment and, consequently, fire. As this temperature fuse, an alloy type temperature fuse using a low melting point fusible alloy piece for a fuse element is widely used. The basic structure of this alloy type temperature fuse is such that a low melting point fusible alloy piece is bridged between the electrodes, a flux is applied on the low melting point fusible alloy piece, and the flux coated alloy piece is used as an insulator. The protection device is attached to a portion of the protected device that is likely to generate heat due to an overcurrent, and the operation process is as follows.

That is, when the device to be protected generates heat due to an overcurrent, the generated heat melts the low-melting-point fusible alloy piece, and the molten metal coexists with the flux already melted by the surface tension. The spheroidization proceeds, the spheroidization proceeds and the spheroid is cut off, and the power supply to the device is cut off. In this case, the wettability of the molten metal to the electrode is mainly involved in the spheroidization of the molten metal, and the better the wettability, the better the spheroidization is promoted, and rapid separation can be expected. Thus, the molten flux improves the wettability of the molten metal, thereby contributing to the promotion of the spheroidization of the molten metal.

The present applicant has developed a substrate-type temperature fuse as an alloy-type temperature fuse. The basic structure of this substrate-type temperature fuse is, as shown in FIG. 3A and FIG. 3B, a cross-sectional view of FIG. Layered electrodes 2 ', 2' are provided on one surface at intervals in the width direction, and a low-melting-point fusible alloy piece 3 'is bridged between the tips of these electrodes. And a lead wire 52 'is connected to each electrode 2' from the rear end side, and the entire surface of one surface of the insulating substrate is covered with an insulating layer 6 '. Is used in contact with the device to be protected.

In this substrate type temperature fuse, the ratio of the insulating substrate surface to the entire surface of the temperature fuse is high.
Compared to other types of temperature fuses, the area of contact with the equipment can be increased, and the insulating substrate, for example, a ceramic plate, has good thermal conductivity. Can receive heat.

[0006]

In the temperature fuse, a holding temperature is set as a temperature at which the temperature fuse does not operate even when the rated current is continuously supplied. (For example, a holding temperature of a temperature fuse having a nominal operating temperature of 115 ° C is 89 ° C, a holding temperature of a temperature fuse having a nominal operating temperature of 130 ° C is 102 ° C, and a temperature fuse having a nominal operating temperature of 133 ° C. The fuse has a holding temperature of 108 ° C. and a nominal operating temperature of 150 ° C. The fuse has a holding temperature of 12 ° C.
Thus, even if the temperature fuse is lower than the operating temperature, if it is heated to near the holding temperature,
Flux melting is inevitable.

In the above-mentioned substrate type temperature fuse, both ends 31 'of the low melting point fusible alloy piece are located in the middle of the width of the tip of each electrode (in the portion where the flux is applied, the insulating coating layer is insulated from the insulating coating layer). Since the bonding with the substrate and the layered electrode is not performed, and the sealing area of the insulating coating layer is reduced as the area of the non-bonded portion increases, the applied amount of the flux is a minimum enough to surround the low melting point fusible alloy piece. To the limit).

Further, the surface of the electrode 2 'and the lead wire tip 52'
At the boundary between the two, there is a corner n 'of the deep fine gap, and it is difficult to completely fill the corner with the material of the insulating coating layer. A cold-setting epoxy resin is used so that the flux applied to the piece is not melted, but the low melting point fusible alloy piece is mechanically weak and easily cut, so a pressure molding method is applied to the insulating coating. It is impossible to use a non-pressurizing method, and it is necessary to use a substantially non-pressurizing method such as dripping, so it is difficult to completely press-fit the coating material into the corner.) A capillary passage is likely to be formed at the bottom.

[0009] With the formation of such a capillary passage, when the temperature fuse is heated to near the above-mentioned holding temperature and the flux is melted, the molten flux is heated due to the thermal expansion pressure. As shown in FIG. 4, the flux flows toward the capillary passage, and the amount of flux on the low melting point fusible alloy piece must be reduced. In this case, of the fluxes of the adjacent portions a2 of the low melting point fusible alloy piece 3 'on one side adjacent to the lead wire 5' side, among the portions a1 and a2 adjacent on both sides of the low melting point fusible alloy piece 3 '.
It flows toward the capillary passage around each end 31 'of the low melting point fusible alloy piece, and the flux on the a1 side is straight.
It flows toward the capillary passage.

In this state, even if the temperature fuse is heated and the low melting point fusible alloy piece is melted, the amount of the molten flux coexisting with the molten alloy is insufficient, and the molten flux is promoted for the spheroidization of the molten alloy. No action is achieved, and a rapid cutting of the low-melting-point fusible alloy piece cannot be expected, and a decrease in the operability of the temperature fuse cannot be avoided.

[0011] It is an object of the present invention to provide a substrate type temperature heater capable of sufficiently maintaining the amount of flux on a low melting point fusible alloy piece and ensuring good operation even when the flux is melted by heating at a temperature lower than the operating temperature. -To provide

[0012]

According to the present invention, there is provided a substrate-type temperature fuse having a layered electrode provided on one side of an insulating substrate at intervals in a width direction, and a low melting point fusible alloy between the tips of these electrodes. Bridge the pieces, apply flux to the low melting point fusible alloy pieces,
A lead wire is connected from the rear end side of each electrode, and in the temperature fuse in which the entire surface of one surface of the insulating substrate is covered with an insulating layer, both ends of the low melting point fusible alloy piece protrude from the edge of the front end of each electrode. This is a configuration characterized by having

[0013]

Since each end of the low-melting-point fusible alloy piece protrudes from the edge of each electrode tip, even if the flux is melted at a temperature lower than the operating temperature of the temperature fuse and expanded and pressurized, the flux is kept low. The above-mentioned one side a2 of the fusible alloy piece (the side opposite to the lead wire 5 side)
In the above flux, the flow to the capillary passage at the boundary between the lead wire and the electrode around each end of the low melting point fusible alloy piece is suppressed .

Therefore, even if the flux is melted by heating at a temperature lower than the operating temperature, it is possible to guarantee a certain amount of flux adjacent to the one side a2 of the low melting point fusible alloy piece. Thus, at the time of operating the temperature fuse, the effect of promoting the molten flux on the spheroidization of the molten alloy is achieved, and good fracturing of the low melting point fusible alloy piece can be expected, and the temperature fuse operability is sufficient. Is guaranteed.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1A is an explanatory plan view showing an embodiment of the present invention,
FIG. 1B is a cross-sectional view of FIG. In FIGS. 1A and 1B, reference numeral 1 denotes an insulating substrate having good thermal conductivity, and a ceramic plate is usually used. Reference numerals 2 and 2 denote layered electrodes provided on one surface of the insulating substrate 1 at intervals in the width direction. The layered electrodes are formed by baking a conductive paint such as a silver paste or etching a copper foil of a copper foil laminated insulating substrate. I have. Rear end 21 of each electrode 2
Are located at a predetermined distance a from the rear end 11 of the insulating substrate.

Reference numeral 3 denotes a low-melting-point fusible alloy piece bridged between the tips of the electrodes 2 and 2 by welding or the like, and each end 31 is projected from each electrode tip end edge 22. “b” indicates the protruding distance. 4 is a flux, a low melting point fusible alloy piece 3
It is applied on the upper surface (even if it is applied on the whole of the low-melting-point fusible alloy 3, the flux may not be attached to the one end 31 because the lower surface is made of ceramics that is hardly wetted by the flux. Reference numeral 5 denotes a lead wire, which is an insulated wire obtained by extrusion-coating a single-wire conductor 51 with a plastic insulating layer. The leading end 521 of the lead-out conductor 52 approaches the low melting point fusible alloy piece 3 (interval c). Is about 0.2 mm to 1.5 mm). The electrode 2 is connected by soldering, welding, or the like.

Reference numeral 6 denotes an insulating coating layer provided on the entire surface of one surface of the insulating substrate, which is coated by, for example, a substantially pressureless method. For example, it can be coated by drop coating of an epoxy resin liquid.

The above-mentioned substrate type temperature fuse is used by being attached to a device to be protected as described above. In this case, by heating at a temperature equal to or lower than the operating temperature, only the flux 4 may be melted without melting the low melting point fusible alloy piece 3. Thus, the corner at the corner between the lead wire lead conductor 52 and the layered electrode 2 and the above-mentioned lead conductor tip 521 and the low melting point
Since it is difficult to completely fill the close gap between the fusible alloy piece 3 and the non-pressurized coating of the insulating coating material 6, for example, by drop coating, the close corner gap passes through the close gap. The capillary passage n along the hole is easily formed.

When only the flux 4 is melted by heating below the temperature fuse operating temperature, a low melting point
On the a1 side of the flux existing on both sides a1, a2 of the gold piece
The existing flux flows toward the capillary passage n.
But the flux on the side a2 opposite to the lead wire side
In addition, each end 31 of the low melting point fusible alloy piece is protruded.
It is difficult to turn around each end 31 of the low melting point fusible alloy piece,
The flow toward the pipe passage is well suppressed. Therefore, even when only the flux is melted by heating at a temperature lower than the operating temperature, the amount of the flux in contact with the low melting point fusible alloy piece can be surely held in a larger amount than in the conventional example, and therefore, the temperature fuse can be reduced. During operation, the molten flux can sufficiently coexist with the molten alloy of the low melting point fusible alloy piece, and the action of promoting the molten flux on the spheroidization of the molten alloy can be well achieved.

In the above, each end 31 of the low melting point fusible alloy piece
The protrusion distance b of the insulating substrate 1
The width is increased to about 0.1 mm to 1.0 mm. The distance d between the electrodes 2 and 2 is set to a distance necessary for ensuring the spheroidization of the low melting point fusible alloy piece, and is set to 0.9 mm to 1.5 mm at a rating of 250 V. The distance f between the electrode tip 23 and the insulating substrate tip 13 and the distance e from the low melting point fusible alloy one end 31 to the insulating substrate lateral end 12 are determined by the adhesive interface between the insulating substrate and the insulating coating layer. Is set to the interval required to prevent the pressure from being released to the outside by exfoliation. In the case of a temperature fuse rated at 250 V, e = 0.4 mm to 1.6 m
m, f = 1.3 mm to 1.6 mm are set. a is set to 0.2 mm to 1.0 mm.

FIG. 2 shows a substrate type temperature fuse according to another embodiment of the present invention. The width of the electrode tip 2a for bridging the low melting point fusible alloy piece 3 is connected to the lead wire lead conductor 52. Electrode part 2
b, the gap from one end 31 of the low-melting-point fusible alloy to the lateral end 12 of the insulating substrate is melted by the low-melting-point fusible alloy to peel off the adhesive interface between the insulating substrate and the insulating coating layer and pressurize to the outside. The electrode portion 2 is set at the interval e necessary to prevent the
The distance g between b and the insulating substrate lateral end 12 is determined by the substrate type temperature hue.
The distances required to insulate the ground voltage when both lateral ends of the capacitor are held at the ground potential are set to other dimensions a, b, c, and
d, f, etc. are the same as in the embodiment shown in FIG.

In the substrate type temperature fuse of the present invention,
Even if the flux is melted and pressurized by thermal expansion before this operation, a sufficient amount of flux adjacent to the low melting point fusible alloy piece can be secured. This can be confirmed from the following test results. Test results In the example product, a = 0.5 mm and d = 1.1 in FIG.
mm, e = 1.2 mm, f = 1.4 mm, electrode tip 2a width =
0.8 mm, electrode part 2b width = 1.5 mm, a 0.6 mm thick ceramic plate is used for the insulating substrate, layered electrodes are provided by baking silver paste, and the conductor diameter is set to the insulating coated lead wire. Use a 0.51 mm long conductor with a lead length of 2.6 mm, a low melting point fusible alloy piece with a thickness of 0.3 mm, a width of 0.4 mm, a rectangular cross section, and a melting point of 98 ° C. The projecting distance b of each end of the low melting point fusible alloy piece is 0.5 mm, and the distance c from the tip of the lead conductor to the low melting point fusible alloy piece is c = 0.5 mm.
This is a substrate type temperature fuse for a rated voltage of 250 V, which is coated with an insulating coating by drop coating of a 1.8 mm thick epoxy resin. On the other hand, the comparative example was the same as the example except that each end of the low-melting-point fusible alloy piece was positioned at the center of the width of the electrode tip 2a.

Fifty pieces each of a comparative example product and an example product were manufactured, heated at a temperature of 80 ° C. for 100 hours, cooled, disassembled, and the amount of flux adjacent to the low melting point fusible alloy piece was measured. As a result, in the example product, the initial amount of 7
Although it was 0% or more, it was 60% to 50% in the comparative example product.

[0024]

The substrate-type temperature fuse of the present invention has the above-described structure. Even if the flux is melted by heating before operation and pressurized by its thermal expansion, it can be formed into a low melting point fusible alloy piece. The amount of flux in contact can be sufficiently maintained, and the operability of the temperature fuse can be sufficiently ensured.

[Brief description of the drawings]

FIG. 1A is an explanatory view showing an embodiment of the present invention;
FIG. 1 (B) is a cross-sectional view of FIG. 1 (A).

FIG. 2 is an explanatory view showing another embodiment of the present invention.

3A is an explanatory view showing a conventional example, and FIG. 3B is a cross-sectional view of FIG.

FIG. 4 is an explanatory diagram showing a flow state of a molten flux at a temperature lower than an operating temperature of the conventional example shown in FIG. 3;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Insulating substrate 2 Layered electrode 22 Electrode tip edge 3 Low melting point fusible alloy piece 31 Low melting point fusible alloy piece end 4 Flux 5 Lead wire 52 Lead wire electrode connection part 6 Insulation coating layer

Continuation of the front page (56) References JP-A-3-81921 (JP, A) JP-A-63-99643 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01H 37 / 76

Claims (1)

(57) [Claims] 1. A layered electrode is provided on one surface of an insulating substrate at intervals in the width direction, a low melting point fusible alloy piece is bridged between the tips of these electrodes, and a flux is applied to the low melting point fusible alloy piece. Is applied, a lead wire is connected from the rear end side of each electrode, and in the temperature fuse in which an insulating layer is coated on one entire surface of the insulating substrate,
A substrate type temperature fuse characterized in that both ends of a low melting point fusible alloy piece protrude from the edge of each electrode tip.