JP2008226796A - Board type temperature fuse, and manufacturing method of board type temperature fuse - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a board type temperature fuse of an axial type which has low resistance, is stable, is excellent in fusing workability, and has high pulling strength of a lead conductor. <P>SOLUTION: A pair of membrane electrodes 2, 2 are formed on one surface of an insulating substrate 1. Respective end parts of lead conductors 4 opposing in a straight line are welded to the respective membrane electrodes 2, 2. A low melting fusible alloy piece 3 is welded between tip end surfaces of both of the lead conductors 4, 4. A protective coating 6 is provided so as to cover the low melting fusible alloy piece. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an axial type substrate-type thermal fuse and a method for manufacturing the substrate-type thermal fuse.

An alloy type thermal fuse has a low-melting-point fusible alloy piece as a fuse element, is attached in thermal contact with the protected device, and the low-melting-point fusible alloy piece is melted due to abnormal heat generation due to the overcurrent of the device, It is divided by spheroidization based on the surface tension of the molten alloy, and the power supply to the equipment is cut off. Therefore, the occurrence of accidents such as equipment fires can be prevented.
As one type of the substrate type thermal fuse, a radial type substrate type thermal fuse is widely used. (For example, Patent Documents 1 and 2)
JP 2007-59295 A JP 2004-14188 A

  FIG. 2 is a partially cut-out top view showing a conventional radial type substrate-type thermal fuse, and a pair of parallel film electrodes 2 ′, 2 ′ on one side of a heat-resistant and heat-conductive insulating substrate 1 ′ such as a ceramic substrate. Is formed by printing and baking conductor paste, and the lead conductors 4 'and 4' parallel to each other are welded to the rear end side of each membrane electrode 2 'and 2', and between the tip portions of both membrane electrodes 2 'and 2' A low melting point soluble alloy piece 3 ′ is welded to the low melting point soluble alloy piece 3 ′, a flux 5 ′ is applied to the low melting point soluble alloy piece 3 ′, and an epoxy resin is dropped on one surface of the insulating substrate to provide a protective jacket 6 ′. It is.

An axial type may be required for the radial type substrate-type thermal fuse.
However, in a board-type thermal fuse, electrical conduction from the fuse element to the lead conductor is performed through the weld interface between the fuse element and the membrane electrode → the membrane electrode → the weld interface between the membrane electrode and the lead conductor. The resistance between the lead conductor and the fuse element is higher than that of the axial type tubular thermal fuse in which the lead conductor and the fuse element are directly butt welded.

Conventionally, an alloy mainly composed of Pb is used for a fuse element of an alloy type thermal fuse. However, environmental pollution due to disposal of lead parts or lead alloy parts has been regarded as a problem, and in recent years, lead-free has been planned in many fields, and lead-free fuse elements are also being promoted in the field of thermal fuses.
Among these lead-free fuse elements, those in which Ag or Cu is added to the Bi—In—Sn system can have a specific resistance value of a low specific resistance value of 20 μΩ · cm to 25 μΩ · cm.

However, even if the conventional radial type substrate type thermal fuse is simply an axial type, the above-described high resistance portion is interposed between the fuse element and the lead conductor, so that the thermal fuse element can be rationally reduced in resistance. It is difficult.
Therefore, it is effective to butt-weld the lead conductor and the fuse element directly to make the substrate type thermal fuse axial.

  An object of the present invention is to provide an axial type substrate type thermal fuse having low resistance, stable, excellent fusing operability, and high lead conductor pull-out strength.

In the substrate type thermal fuse according to the present invention, a pair of film electrodes is formed on one surface of an insulating substrate, the ends of the lead conductors facing each other in a straight line are welded to the respective film electrodes, and the tips of both lead conductors A low melting point soluble alloy piece is welded between the end faces, and a protective jacket is provided to cover the low melting point soluble alloy piece. In the low melting point soluble alloy piece, In-Bi-Sn Any of an Al alloy, an In—Bi—Sn alloy added with Ag or Cu, a Cu—In—Sn alloy, a Bi—Sn—Sb alloy, and a Sn—Bi alloy can be used.
In the method of manufacturing a substrate-type thermal fuse according to the present invention, each of the insulating substrates having a pair of membrane electrodes on one side after welding a low melting point soluble alloy piece between the tip end faces of a pair of lead conductors facing each other in a straight line. Each of the lead conductors is fixed to the membrane electrode by welding.

(1) The resistance between the fuse element and the lead conductor is low because of direct butt welding of the two, and the low melting point fusible alloy with a low specific resistance is used for the fuse element to reduce the resistance of the thermal fuse. Can be achieved well.
(2) When the fuse element is blown, the fusing speed can be increased by wet spreading of the molten alloy to the film electrode.
(3) Since the lead conductor is fixed to the membrane electrode by welding, the pull-out strength of the lead conductor can be well maintained even if the resin jacket is thermally softened during mounting.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
1A is a partially cutaway plan view showing a substrate-type thermal fuse according to the present invention, and FIG. 1B is a cross-sectional view of FIG.
In FIG. 1, reference numeral 1 denotes an insulating substrate having heat resistance and good thermal conductivity, and a ceramic substrate can be used.
Reference numerals 2 and 2 are film electrodes formed on one surface of the insulating substrate at predetermined intervals in the longitudinal direction, and can be formed by printing and baking a conductive paste, for example, a silver paste.
Reference numeral 3 is a low melting point soluble alloy piece as a fuse element, and 4 and 4 are lead conductors butt welded to both end faces of the low melting point soluble alloy piece 3. Each lead conductor 4 is welded to each membrane electrode 2, Both end portions of the element 3 are in contact with the membrane electrodes 2 and 2. The lead conductor 4 can be a copper-plated iron wire or a copper-plated steel wire in addition to a copper wire.
5 is a flux applied to the fuse element.
Reference numeral 6 denotes a resin jacket which covers and covers the above-mentioned flux-applied fuse element on one surface of the insulating substrate 1, and an epoxy resin can be used as the resin. The performance of the thermal fuse or the like can be printed on the surface of the resin jacket.

The board-type thermal fuse according to the present invention includes (1) butt welding of a fuse element and a lead conductor, (2) welding fixing of a lead conductor of a fuse element with a lead conductor to a film electrode of an insulating substrate with a film electrode, (3 ) Manufactured through a resin coating process.
In the step (1), the end face of each lead conductor is butted against the both end faces of the low melting point soluble alloy piece, the tip of each lead conductor is heated and melted, and the lead conductor is pressed in the axial direction to weld the butt interface. can do.
In the step (2), the positive and negative pin electrodes of the resistance welding machine are brought into contact with the tip portions of the lead conductors and the membrane electrodes, and the tip portions of the lead conductors are spot-welded to the membrane electrodes by energizing a welding current. Can do.
The resin in the step (3) can be coated by a drop coating method using a room temperature curable epoxy resin.

As the alloy of the low melting point soluble alloy piece, a lead-free low resistivity alloy can be used. For example, Bi7 to 12% by weight, Sn40 to 46% by weight, remainder In, or Bi7 to 12% by weight, Sn40 to 46% by weight, 100 parts by weight of remainder In, 0.5 to 3.5 parts by weight of Ag or Cu The added one can be used. In addition, a Cu—In—Sn alloy, a Bi—Sn—Sb alloy, a Sn—Bi alloy, or the like can also be used.
By using such a low-resistivity fuse element, it is possible to provide an axial type substrate-type thermal fuse of a low-resistance fuse element, and it is possible to guarantee an accurate operation substantially without self-heating.

In the substrate-type thermal fuse according to the present invention, when the fuse element is blown, the molten alloy wets and spreads on the film electrode to promote spheroidization, so that the fusing speed can be accelerated.
In addition, when mounting the substrate type thermal fuse according to the present invention, for example, when soldering to the base substrate of the FET, even if the room temperature curing epoxy resin is thermally softened, the lead conductor is welded and fixed to the membrane electrode. As a result, the lead conductor can be well held out and the stable support by the lead conductor can be maintained.

1 is a diagram illustrating a substrate type thermal fuse according to the present invention. 1 is a diagram illustrating a conventional substrate-type thermal fuse.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Insulation board | substrate 2 Membrane electrode 3 Low melting point soluble alloy piece 4 Lead conductor 5 Flux 6 Resin jacket

Claims (3)

A pair of membrane electrodes is formed on one side of the insulating substrate, the respective ends of the lead conductors that are linearly opposed to each other are welded to the respective membrane electrodes, and a low melting point soluble alloy piece is formed between the tip end surfaces of both lead conductors. A board-type thermal fuse which is welded and has a protective jacket covering the low melting point soluble alloy piece. Low melting point soluble alloy pieces are In-Bi-Sn alloy, In-Bi-Sn alloy with Ag or Cu added, Cu-In-Sn alloy, Bi-Sn-Sb alloy, Sn-Bi 2. The substrate-type thermal fuse according to claim 1, wherein the substrate-type thermal fuse is any one of a series alloy. After welding a low melting point soluble alloy piece between the tip end faces of a pair of lead conductors facing in a straight line, each lead conductor is welded and fixed to each film electrode of an insulating substrate having a pair of film electrodes on one side. A method of manufacturing a substrate-type thermal fuse characterized by the above.

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