JP2015022827A - Temperature fuse - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a temperature fuse that enables even a decrease in size without degrading shielding characteristics even when an increase in current is coped with.SOLUTION: A temperature fuse comprises: a pair of metal terminals 12 made of metal plates and oppositely arranged with a space between the leading end parts 13 of the metal terminals 12; and a fusible body 14 joined by being bridged between the leading end parts 13 of the metal terminals 12. Each metal terminal 12 includes a main part 17 and a wet spread preventing part 19 formed on the opposite faces 18 of the metal terminals 12. The wet spread preventing part 19 is made of a material inferior in the wettability of the fusible body 14 that has been fused, to the metal material composing the main part 17.

Description

  The present invention relates to a thin thermal fuse used for overheat protection of a lithium ion battery or the like.

  In recent years, pack batteries using secondary batteries such as high-capacity lithium ions and lithium polymers have been frequently used for portable devices such as mobile phones and notebook computers.

  Since these secondary batteries have high energy density and may generate abnormal heat when overcharged or suddenly discharged, a temperature fuse is attached to the battery can of the battery pack by resistance welding or spot welding to detect abnormal heat generation. The circuit is cut off.

  As such battery packs become thinner and smaller, there is a growing demand for thinner and smaller thermal fuses.

  In response to this demand, as shown in FIG. 6, the fusible alloy 2 is bridged and joined between the terminals 1 made of opposing metal plates, and these are sealed by being sandwiched between the base film 3 and the cover film 4. Thermal fuse is used.

  As prior art document information related to the invention of this application, for example, Patent Document 1 is known.

JP 2002-42621 A

  As the performance of portable devices continues to increase, there is a growing demand for higher currents for thermal fuses, and there has been a demand for higher currents from 2-4A to 4-10A. Yes.

  In order to cope with a large current in the thermal fuse, it is necessary to reduce the electrical resistance of the thermal fuse, and it is important to reduce the electrical resistance of the terminal among the thermal fuses.

  Usually, nickel material with high corrosion resistance is used for the battery can of the battery pack, so that the nickel material is also used for the terminal of the thermal fuse that is welded to the battery can to facilitate welding. In order to increase the current of the thermal fuse, it is conceivable to reduce the electrical resistance by making the terminal material a material having a higher conductivity than that of the nickel material, and a material having a high conductivity includes a copper material.

  However, in the above-described conventional thermal fuse configuration, the copper material has better wettability of the molten alloy compared to the nickel terminal, and the molten alloy melts on the opposing surface of the terminal and spreads between the opposing terminals. Since the molten fusible alloy is likely to stay, there is a problem that the breaking characteristic of the thermal fuse may be deteriorated and the miniaturization cannot be performed.

  SUMMARY OF THE INVENTION The present invention solves these problems, and an object of the present invention is to provide a thermal fuse that can be downsized without deteriorating the breaking characteristics even when the current is increased.

  In order to solve the above-mentioned problems, the present invention includes a pair of metal terminals made of a metal plate and arranged to face each other with a gap between the tip portions, and a fusible body joined by bridging between the tip portions of the metal terminals. The metal terminal is composed of a main part and a wetting and spreading preventing part formed on the opposing surface of the metal terminal, and the wetting and spreading preventing part is a material in which the fusible material melted is worse than the metal material constituting the main part. It is composed of

  With the above configuration, the metal terminal is composed of a main part and a wetting and spreading preventing part formed on the opposing surface of the metal terminal, and the wetting and spreading preventing part is a wettability of a fusible material melted from the metal material constituting the main part. However, because the surface of the pair of metal terminals facing the pair of metal terminals has a poor wet-spread surface of the melted soluble body, it has good wettability with the melted coalescence of the main part of the metal terminal. Even when a copper material is used, it is possible to cope with an increase in current without impairing the interruption characteristics of the thermal fuse, and further, the distance between a pair of metal terminals facing each other can be reduced to enable miniaturization.

1 is a top plan view of a thermal fuse in an embodiment of the present invention. Side surface sectional view of the AA line in FIG. Section C enlarged sectional view in FIG. The side expanded sectional view of another thermal fuse in one embodiment of the present invention The side expanded sectional view of another thermal fuse in one embodiment of the present invention Side sectional view of a conventional thermal fuse

  Hereinafter, a thermal fuse in an embodiment of the present invention will be described with reference to the drawings.

  1 is a top plan view of a thermal fuse according to an embodiment of the present invention, FIG. 2 is a side sectional view taken along line AA in FIG. 1, and FIG. 3 is an enlarged sectional view of a portion C in FIG. A thermal fuse according to an embodiment of the present invention includes a pair of metals made of a metal plate having a thickness of 0.1 mm on the upper surface of a plate-like first insulating film 11 made of polyethylene naphthalate having a thickness of 0.1 mm. The terminal 12 is disposed opposite to the front end portion 13 with a space therebetween, and the front end portion 13 side of the opposing metal terminal 12 is placed on the first insulating film 11 and fixed by heat fusion or the like.

  Between the front end portions 13 of the metal terminals 12, a fusible body 14 made of an Sn-In-Bi alloy that melts at a predetermined temperature is placed so as to straddle the front end portion 13, and is welded by laser welding or the like. A fusible body 14 is bridged between the front end portions 13 of the metal terminals 12.

  Around the fusible body 14, a flux 15 is applied to promote melting of the melted fusible body 14 due to surface tension when the fusible body 14 is melted at a predetermined temperature.

  Then, the fusible body 14 to which the flux 15 is applied is covered with a second insulating film 16 made of polyethylene naphthalate having a thickness of 0.1 mm and the opening is embossed in a substantially rectangular shape. The fusible body 14 and the flux 15 are sealed by ultrasonically welding the film 11 and the second insulating film 16.

  In FIG. 1, a part of the first insulating film is cut away along the line BB to show the inside of the first insulating film.

  Here, the metal terminal 12 will be described in more detail.

  The metal terminal 12 is composed of a main portion 17 and a wetting and spreading prevention portion 19 formed on the opposing surface 18 of the metal terminal 12, and the wetting and spreading prevention portion 19 is more meltable than the metal material constituting the main portion 17. The solution 14 is made of a material with poor wettability, and the surface 18 of the metal terminal 12 is formed with a surface with poor wet spread of the melted soluble material 14 by the wet spread preventive portion 19.

  As a material of the main portion 17 of the metal terminal 12, it is important to use a material having a higher conductivity than that of a conventional nickel material in order to cope with an increase in current of the battery pack, and a conductivity higher than that of the nickel material. Examples of the large material include a copper material, a silver material, and a gold material, and a copper material is preferable from the viewpoint of material cost.

  Examples of the material for the wetting and spreading preventing unit 19 include a melted soluble material and a poorly wettable aluminum material or nickel material than the copper material of the main portion of the metal terminal 12, and a nickel material having poorer wettability is preferable. .

  The main part 17 made of the copper material and the wetting and spreading preventing part 19 made of the nickel material are bonded by cutting a part of the copper hoop material and forming a clad material rolled with the nickel material inserted therein. The wet spread preventing portion 19 made of a nickel material is formed by cutting the nickel material and cutting the nickel material.

  By doing so, the thermal fuse of one embodiment of the present invention is configured so that the metal terminal 12 includes the main portion 17 and the wetting and spreading preventing portion 19 formed on the opposing surface 18 of the metal terminal 12. Since the spread preventing portion 19 is made of a material having a poor wettability of the fusible body 14 melted than the metal material constituting the main portion 17, the wetting spread preventing portion 19 melts the opposing surfaces 18 of the pair of metal terminals 12. Since the surface of the fusible body 14 that does not spread well is formed, the melted fusible body 14 is prevented from spreading on the facing surfaces 18 of the pair of metal terminals 12, and the fusible body 14 melted between the metal terminals 12 It is possible to prevent the blocking characteristic from deteriorating and deteriorating.

  Thereby, it is possible to cope with an increase in current by using a copper material or the like for the main portion 17 of the metal terminal 12, and it is also possible to reduce the facing distance of the metal terminal 12 and to reduce the temperature fuse. Can do.

  In this case, by using a copper material for the main portion 17 of the metal terminal 12, a nickel plating layer 20 plated with a nickel material is provided on the upper and lower surfaces of the metal terminal 12 to facilitate welding with the battery can. It is desirable to form it, and in order to facilitate the joining of the fusible body 14 to the nickel plating layer 20, a tin plating layer 21 plated with a tin material is formed in a portion where the fusible body 14 is joined. Is desirable.

  The wetting and spreading preventing portion 19 is formed along the edge of the metal terminal 12 on the fusible body 14 side, and is formed at 30% or more in the thickness direction of the metal terminal 12.

  When the wetting and spreading preventing portion 19 is formed by plating like the nickel plating layer 20, the thickness can be formed only about several μm, and the melted soluble body 14 easily gets over and spreads. In this embodiment, since the wetting and spreading preventing portion 19 having a thickness of 0.03 mm or more is formed with respect to the thickness of the metal terminal of 0.1 mm, wetting and spreading of the meltable fusible body 14 can be prevented. It is.

  Moreover, as shown in FIG. 3, the dimension of the terminal side of the metal terminal 12 from the opposing surface 18 of the metal terminal 12 of the wetting spread prevention part 19 is (i), and the dimension in which the metal terminal 12 and the fusible body 14 overlap is (ii). It is desirable that (i) <(ii).

  By doing in this way, the electric current which flows between the fusible body 14 and the metal terminal 12 from the main part 17 of the metal terminal 12 to the fusible body 14 (solid line arrow in FIG. 3), It is possible to disperse the current flowing from the portion 17 to the fusible body 14 via the wetting and spreading preventing portion 19 (broken arrows in FIG. 3), and the metal terminal 12 is simply formed as the wetting and spreading preventing portion 19. In the case where only the copper material is used, the electric resistance of the metal terminal 12 is smaller than that of the fusible body 14 made of the Sn—In—Bi alloy. Although it concentrates on the front end and partial heat generation increases, in this embodiment, the wetting and spreading prevention portion 19 has a higher electrical resistance than the copper material of the main portion 17 of the metal terminal 12, and therefore flows. In which the effect of the flow is dispersed suppress partial heat generation is obtained.

  In this case, it is more preferable that (i) <(ii) × 0.5 so as not to affect the electrical resistance of the thermal fuse.

  In the present embodiment, the example in which the wetting and spreading preventing portion 19 on the facing surface 18 is formed on the fusible body 14 side of the metal terminal 12 has been described. However, as shown in FIG. The prevention part 19 may be formed. Thus, as a method of forming the wetting and spreading preventing portion 19 on the entire surface of the opposing surface 18, it can be formed by using a so-called edge clad material in which a nickel material is abutted and bonded to a copper hoop material. The same effect as the form can be obtained.

  As another example of forming the wetting and spreading preventing portion 19 on the entire facing surface 18, a nickel plating layer 20 may be formed on the entire facing surface 18 of the metal terminal 12, as shown in FIG. As a method of forming the nickel plating layer 20 on the entire surface of the metal 18, nickel plating is applied to the entire surface of the copper hoop material so that the edge portion of the hoop material on which the nickel plating layer 20 is formed becomes the opposing surface 18 of the metal terminal 12. In this case, the same effect as the present embodiment can be obtained.

  The thermal fuse according to the present invention can cope with an increase in current without deteriorating the interruption characteristic, and further enables downsizing, and is industrially useful.

DESCRIPTION OF SYMBOLS 11 1st insulating film 12 Metal terminal 13 Tip part 14 Soluble body 15 Flux 16 2nd insulating film 17 Main part 18 Opposite surface 19 Wet spreading prevention part 20 Nickel plating layer 21 Tin plating layer

Claims (3)

A pair of metal terminals made of a metal plate and arranged to face each other with a gap between the front end portions, and a fusible body joined by bridging between the front end portions of the metal terminals, the metal terminal, It comprises a wetting and spreading preventing portion formed on the opposing surface of the metal terminal, and the wetting and spreading preventing portion is composed of a material having poor wettability of the fusible material melted than the metal material constituting the main portion. Thermal fuse characterized by. 2. The thermal fuse according to claim 1, wherein the wetting and spreading preventing portion is formed along an edge of the metal terminal on the fusible body side, and is formed at 30% or more in the thickness direction of the metal terminal. . 2. The thermal fuse according to claim 1, wherein the wetting and spreading preventing portion is formed on the entire surface of the opposing surface of the metal terminal.

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