JP2016139570A - Power fuse - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power fuse capable of securely shutting off an electric circuit at a preset temperature and capable of being easily manufactured with a simple configuration.SOLUTION: A power fuse 10 includes: a fuse body 13, composed of a core material 11 and a conductive part 12 formed so as to surround the core material 11; and a coating part 14 covering the fuse body 13. The fuse body 13 is formed in a long line shape as a whole. The conductive part 12 is formed in a hollow tube shape. The core material 11 is formed so as to fill the hollow part of the conductive part 12.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a power fuse that opens a circuit by fusing part of a conductor when a part of an electric circuit exceeds a predetermined temperature.

  2. Description of the Related Art Thermal power fuses are widely used for protecting electrical components and the like that constitute an electrical circuit when a part of the electrical circuit exceeds a predetermined temperature due to overcurrent or the like. Such a power fuse is inserted into a part of an electric circuit and melts when a low melting point metal forming a part of the circuit exceeds a predetermined temperature, thereby protecting the electric component from excessive Joule heat or the like.

2. Description of the Related Art Conventionally, as an example of such a temperature type electric power fuse, a linear low melting point metal sealed in a hollow glass tube is generally known.
A power fuse is also known in which a low-melting-point metal serving as a conductor is covered with an insulator such as silicon rubber to reduce heat generation during fusing (see, for example, Patent Document 1).

Japanese Patent Laid-Open No. 7-57615

However, in a general glass tube type power fuse, when mounting inside a resin molded electronic component, both ends of the glass tube are sealed and there is a space inside, so when forming the resin mold, More pressure may be applied and the glass tube may be damaged. For this reason, the melted low melting point metal (conductor serving as a fuse) may be connected again, and the electric circuit may be conducted.
On the other hand, in the electric power fuse described in Patent Document 1, since the thermal conductivity of the silicon rubber covering the low melting point metal is low, the low melting point metal is melted by the heat insulating property of the silicon rubber even if the surrounding temperature is higher than the predetermined temperature. As a result, there is a possibility that the current cannot be cut off even when the predetermined temperature is reached.

  The present invention has been made in view of the above-described circumstances, and it is possible to reliably cut off an electric circuit at a preset temperature, and the resin mold can be easily manufactured with a simple configuration. A power fuse that can be mounted is provided.

  In order to solve the above problems, a power fuse of the present invention includes a core material made of a thermoplastic resin, a conductive portion made of a conductive low-melting-point metal and formed to surround the core material, and the conductive portion. And an insulative covering portion.

  According to the power fuse of the present invention, the heat from the heat generating component mounted in the resin mold is transmitted through the resin mold, first applied to the conductive portion made of a low melting point metal, and then propagated to the core material in the center. Is done. Thereby, compared with the structure which covered the circumference | surroundings of the low melting-point metal with the thermoplastic resin, for example, heat can be added reliably to a conductive part and a conductive part can be fuse | melted reliably. Therefore, when the power fuse is heated to a predetermined temperature, it is possible to reliably cut off the energization of the electric circuit.

The melting point of the conductive part is higher than the melting point of the core material.
Thereby, the core material formed inside the conductive part can be melted simultaneously with the conductive part or earlier. As a result, when the conductive part is melted, the core material is also melted, and the low melting point metal constituting the conductive part is made spherical or elliptical by surface tension in the molten thermoplastic resin so that the conductive part is electrically connected. It can be reliably shut off.

The temperature difference between the melting point of the conductive part and the melting point of the core material is 10 ° C. or more and 150 ° C. or less.
Thereby, the core material formed inside the conductive portion can be melted at the same time or earlier than the conductive portion, and when the conductive portion is melted, the core material can also be melted.

The volume of the conductive part / the volume of the core material is in the range of 0.25-7.
As a result, the molten thermoplastic resin constituting the core material divides the molten low-melting-point metal constituting the conductive portion into a spherical shape and wraps the surroundings, and reliably prevents the conductive portion from being connected again after cooling. can do.

The core material is characterized by having a larger volume in a molten state than in a solid state under the same pressure.
Thereby, when the core material 11 is melted, the conductive portion covering the periphery thereof is destroyed by the expansion of the volume, and the conduction of the conductive portion can be reliably interrupted.

The conductive portion is formed in a hollow tube shape, and the core material is formed in a linear shape filling a hollow portion of the conductive portion.
As a result, it is possible to manufacture a power fuse easily and at low cost simply by filling the hollow portion of the hollow melting point metal with a thermoplastic resin.

The diameter of the cross section perpendicular to the longitudinal direction of the core material is 0.35 mm or more and 2 mm or less.
Thereby, formation of a hollow part can be easily manufactured.

The thickness of the cross section perpendicular to the longitudinal direction of the conductive portion is 0.05 mm or more and 0.6 mm or less.
Thereby, formation of a hollow part can be easily manufactured.

  According to the present invention, there is provided a power fuse that can be reliably cut off at a preset temperature and can be easily manufactured with a simple configuration and can be mounted inside a resin mold. be able to.

It is sectional drawing which shows an example of the power fuse of this invention. It is sectional drawing which shows the electric power fuse after fusing. It is sectional drawing which shows an example of the resistor to which the power fuse of this invention is applied.

  The power fuse of the present invention will be described below with reference to the drawings. Each embodiment described below is specifically described for better understanding of the gist of the invention, and does not limit the present invention unless otherwise specified. In addition, in the drawings used in the following description, in order to make the features of the present invention easier to understand, there is a case where a main part is shown in an enlarged manner for convenience, and the dimensional ratio of each component is the same as the actual one. Not necessarily.

FIG. 1 is a cross-sectional view showing an example of a power fuse of the present invention.
The power fuse 10 includes a core body 11, a fuse body 13 including a conductive portion 12 formed so as to surround the core material 11, and a covering portion 14 (for example, a resin mold) that covers the fuse body 13. .
The fuse body 13 is, for example, formed in an elongated linear shape as a whole. The conductive portion 12 is formed in a hollow tube shape, and the core material 11 is formed so as to fill the hollow portion of the conductive portion 12.

The core material 11 is made of a thermoplastic resin, and a low melting point resin is particularly selected. As such a thermoplastic resin, for example, a thermoplastic resin having a melting point in the range of 70 ° C. to 250 ° C. is selected. Specific examples include rosin, polystyrene, polypropylene, and PET resin. Further, the core material 11 is formed so that the diameter r in a cross section perpendicular to the longitudinal direction is 0.35 mm or more and 2 mm or less.
As the thermoplastic resin constituting the core material 11, it is preferable to select a thermoplastic resin whose volume is increased in the molten state than in the solid state under the same pressure.

  The conductive portion 12 is made of a conductive low melting point metal. As such a low melting point metal, a metal having a melting point that is the same as or close to the temperature at which the circuit of the power fuse 10 is to be shut off is selected. For example, a single metal or alloy having a melting point in the range of 150 to 330 ° C. The Specific examples include Sn, In, and Pb single metals and alloys such as Pb—Sn, Pb—In, Pb—Ag, Pb—Sn—Ag, Sn—Ag, Zn—Al, and Sn—Ag—Cu. It is done.

The melting point of the low melting point metal constituting the conductive portion 12 is preferably selected to be higher than the melting point of the thermoplastic resin constituting the core material 11. For example, the core material 11 is configured with a low melting point metal constituting the conductive portion 12 such that the temperature difference between the melting point of the conductive portion 12 and the melting point of the core material 11 is in the range of 10 ° C. or more and 150 ° C. or less. It is preferable to select a thermoplastic resin.
Such a conductive portion 12 is formed so that a thickness t in a cross section perpendicular to the longitudinal direction is 0.05 mm or more and 0.6 mm or less.

The linear fuse body 13 is preferably formed so that the volume of the conductive portion 12 / the volume of the core material 11 falls within the range of 0.25-7. For example, when the volume of the entire fuse body 13 is 10 mm ³ , the volume of the hollow tube-shaped conductive portion 12 is 7.5 mm ³ , and the volume of the core material 11 filling the hollow portion is 2.5 mm ^3. Can be mentioned.

  As a method of manufacturing the linear fuse body 13, for example, the conductive portion 12 made of a low-melting-point metal is first manufactured into a hollow pipe shape by an extrusion method, and a thermoplastic resin serving as a core material is poured into the hollow portion. The wire-shaped fuse body 13 can be manufactured by manufacturing a wire rod using the material portion as a resin and then performing a drawing process.

  The covering portion 14 that covers the fuse body 13 is made of a thermosetting resin, and a resin that is particularly insulating and has good thermal conductivity is selected. Specifically, an epoxy resin is preferable.

The operation of the power fuse of the present invention will be described.
When the power fuse 10 is incorporated in an electric circuit, the electric circuit is connected to the end portions 13a and 13b of the fuse body 13, respectively. Thus, one end 13a and the other end 13b of the fuse body 13 are electrically connected via the conductive portion 12 made of a low melting point metal.

  Then, when the fuse body 13 becomes high temperature due to external heat propagating to the fuse body 13 through the covering portion 14 or Joule heat generated by a current exceeding the rating flowing through the fuse body 13, as shown in FIG. The conductive portion 12 and the core material 11 are melted, and, for example, the low melting point metal constituting the conductive portion 12 is separated into a plurality of spheres in the thermoplastic resin constituting the core material 11. As a result, electrical conduction between the one end 13a and the other end 13b of the fuse body 13 is not possible, and the electric circuit is reliably interrupted.

  When the fuse body 13 is melted, for example, heat propagated from the outside is first applied to the conductive portion 12 made of a low melting point metal, and then propagated to the core material 11 at the center. Thereby, compared with the structure which covered the circumference | surroundings of the low melting metal with the thermoplastic resin, for example, heat is reliably applied to the conductive part 12 and the conductive part 12 can be reliably melted. Therefore, when the power fuse 10 is heated to a predetermined temperature, it is possible to reliably cut off the electrical circuit.

  In addition, by making the melting point of the conductive portion 12 higher than the melting point of the core material 11 in the range of, for example, 10 ° C. or more and 150 ° C. or less, the core material 11 formed inside (inside) the conductive portion 12 is made conductive. It can be melted simultaneously with the part 12 or earlier. As a result, when the conductive portion 12 is melted, the core material 11 is also melted, and the low melting point metal constituting the conductive portion 12 is made spherical by tension in the molten thermoplastic resin so that the conductive portion 12 is electrically connected. Make sure to shut off.

  Further, by selecting a thermoplastic resin that constitutes the core material 11 so that its volume is increased in the molten state than in the solid state, the conductive portion 12 that covers the periphery by expansion when the core material 11 is melted is provided. It is destroyed and the conduction | electrical_connection of the electroconductive part 12 can be interrupted | blocked reliably.

  Moreover, the low melting point metal melted by the molten thermoplastic resin is divided into spheres by configuring the fuse body 13 so that the volume of the conductive portion 12 / the volume of the core material 11 is in the range of 0.25-7. Thus, it is possible to reliably prevent the conductive portion 12 from being connected and re-conducted after cooling by surrounding the periphery.

FIG. 3 shows an example of a resistor to which the power fuse of the present invention is applied.
The resistor 20 includes resistors 23 and 24 arranged on one side of substrates 21 and 22 made of AIN, respectively. A thick film conductor 31 is connected to each of the resistors 23 and 24. Moreover, the heat sink 26 which consists of Al is connected to the other surface side of the board | substrates 21 and 22 through the common buffer layer 25 which consists of 4N-Al. Further, terminals 27 and 28 are formed on the substrates 21 and 22, respectively.

  The power fuse 10 shown in FIG. 1 is provided so as to connect the circuit of the substrate 21 and the substrate 22. In the resistor 20, the substrates 21 and 22 and the resistors 23 and 24 are sealed with an insulating sealing resin 29. Such a sealing resin 29 corresponds to the covering portion 14 that covers the fuse body 13 of the power fuse 10.

  By applying the power fuse 10 to the resistor 20 having such a configuration, for example, even if the resistors 23 and 24 generate excessive heat, the resistors 23 and 24 are heated by the power fuse 10 before the sealing resin 29 is burned out. The energization to 24 can be cut off and damage to the resistor 20 due to heat can be prevented beforehand. When the purpose is to prevent such burning of the sealing resin 29, the conductive portion 12 and the core material 11 of the fuse body 13 are melted at a temperature lower than the heat resistance temperature of the sealing resin 29, and the sealing resin 29. It is preferable to select a thermoplastic resin that melts at or below the heat resistant temperature.

As mentioned above, although embodiment of this invention was described, this invention is not limited to this, It can change suitably in the range which does not deviate from the technical idea of the invention.
For example, in the above embodiment, the fuse body 13 is a linear member in which the hollow portion of the hollow tube-like conductive portion 12 is filled with the core material 11, but the shape of the fuse body 13 is limited to this. The outer shape may be other than a linear shape as long as the conductive portion is formed so as to surround the core material.

A confirmation experiment conducted to confirm the effectiveness of the present invention will be described.
Using the covering portion (covering member), the core material, and the conductive portion (conductive member) shown in Table 1, fuse bodies 13 of Samples 1 to 20 were produced.

Each power fuse 10 of the obtained samples 1 to 20 was examined for the presence or absence of disconnection when heated to a temperature 10 ° C. higher than the melting point of the conductive portion (conductive member) and when heated to 310 ° C. Each of the 100 samples was evaluated, and the probability of disconnection was defined as the disconnection probability. In Table 1, the disconnection probability (1) is the disconnection probability when heated to a temperature 10 ° C. higher than the melting point of the conductive part (conductive member), and the disconnection probability (2) is the disconnection probability when heated to 310 ° C. Each is shown.
From the results shown in Table 1, the effectiveness of the power fuse of the present invention was confirmed.

DESCRIPTION OF SYMBOLS 10 Power fuse 11 Core material 12 Conductive part 13 Fuse body 14 Covering part

Claims (8)

A core made of thermoplastic resin;
A conductive portion made of a conductive low melting point metal and formed to surround the core; and
An insulating covering portion covering the conductive portion;
A power fuse characterized by comprising:   The power fuse according to claim 1, wherein a melting point of the conductive portion is higher than a melting point of the core member.   3. The power fuse according to claim 2, wherein a temperature difference between a melting point of the conductive portion and a melting point of the core member is 10 ° C. or more and 150 ° C. or less.   4. The power fuse according to claim 1, wherein a volume of the conductive portion / a volume of the core member is in a range of 0.25 to 7. 5.   The power fuse according to any one of claims 1 to 4, wherein the core material has a larger volume in a molten state than in a solid state under the same pressure.   6. The electric power according to claim 1, wherein the conductive portion is formed in a hollow tube shape, and the core material is formed in a linear shape filling a hollow portion of the conductive portion. fuse.   The power fuse according to claim 6, wherein a diameter in a cross section perpendicular to the longitudinal direction of the core member is 0.35 mm or more and 2 mm or less.   8. The power fuse according to claim 6, wherein a thickness in a cross section perpendicular to the longitudinal direction of the conductive portion is 0.05 mm or more and 0.6 mm or less.

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