JP3901028B2 - Lead-free thermal fuse - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a protective element, and more particularly to a temperature fuse using a low melting point soluble alloy that is used in electric / electronic devices and melts at a specific temperature.
[0002]
[Prior art]
A thermal fuse that operates at a specific temperature and shuts off a circuit is used as a protective element that protects electrical and electronic devices from overheating damage. A fusible alloy type thermal fuse uses a low-melting-point alloy that melts at a specific temperature as a temperature-sensitive material, energizes this low-melting-point alloy, and melts the low-melting-point alloy due to excessive ambient temperature, thereby interrupting the circuit. It is.
[0003]
Usually, a conventional fusible alloy type thermal fuse is constructed by housing a low melting point fusible alloy having terminal leads connected to both ends in an insulating case and sealing the lead-out portion of the terminal lead. Further, there is a protective element called a resistance built-in type thermal fuse that includes a low melting point soluble alloy and a resistor and forcibly blows off the low melting point soluble alloy by energization heating to the resistor.
[0004]
The above-mentioned fusible alloy type temperature fuse is used as a protective element in home appliances such as heat insulation kotatsu and rice cookers, OA equipment such as liquid crystal televisions and copiers, and lighting equipment. Among these, soluble alloys having an operating temperature in the range of 80 to 89 ° C include conventional 48Bi-30Pb-15Sn-7In (mass%) quaternary alloy (84 ° C) , 42-50In, 10-15Cd, 0.8 -5Zn, residual Sn (mass%) A material containing 10 mass% or more of lead or cadmium, which is a heavy metal harmful to the human body, such as a quaternary alloy (85 ° C.). Recently, the fact that hazardous metals are eluted from discarded electrical and electronic equipment by the action of rainwater and the like has caused serious pollution in groundwater has become a global environmental problem and needs to be improved.
[0005]
The fusible alloy of the thermal fuse is preferably a eutectic alloy composition having a single melting point if possible, because it requires liquefaction at a specific temperature to cause spheroidization and fusing. Furthermore, due to the characteristics of thermal fuses mounted in series in the power supply circuit, the internal resistance value of such thermal fuses does not change even after long-term high-temperature storage, and is 10 mΩ or less. Also desirable from above.
[0006]
[Problems to be solved by the invention]
An object of the present invention is to provide an environment-friendly fusible alloy type thermal fuse that does not use Pb and Cd in the above-described fusible alloy so as not to cause problems due to Pb and Cd.
[0007]
[Means for Solving the Problems]
The fusible alloy type temperature fuse according to claim 1 of the present invention uses a fusible alloy having a composition of Bi of 57 mass%, In of 26 mass%, and the balance of Sn of 17 mass% for the temperature sensitive element. To do. Namely, Bi is 50 to 60% by mass, In is 20 to 30% by mass, and the balance is Sn, and a soluble alloy having an operating temperature of 75 to 85 ° C. by using a soluble alloy having the above specific composition. The mold temperature fuse is made possible.
[0008]
In order to improve the plastic workability of the wire, Cu is added to the fusible alloy within the range described in claim 2 for the purpose of improving the plastic workability of the wire. You can also
[0009]
In addition to the Bi-In-Sn ternary alloy, Ag may be added to the above-mentioned fusible alloy within the range described in claim 3 without affecting the operating temperature for the purpose of reducing internal resistance. it can.
[0010]
Comparing the effects of adding Cu and Ag to the base metal alloy of claim 1, both can improve the plasticity of the base metal alloy and reduce the internal resistance, but Cu has a remarkable effect of improving the plastic workability of the wire. On the other hand, it was found that Ag is superior in the effect of reducing the internal resistance of the wire.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
The present invention is axial type thermal fuse, radial type thermal fuse, thin thermal fuse, can be used for resistance built - in fuse or the like, but are not limited to a particular type, axial type thermal fuse as an example of an embodiment below This will be described using the example .
[0012]
FIG. 1 shows an embodiment of a thermal fuse, and is a cross-sectional view of an axial type thermal fuse.
1, 2: Terminal lead (Sn-Cu plated copper wire)
3: Soluble alloy 4: Flux (rosin, wax, activator)
5: Insulator case (alumina ceramic tube)
6, 7: Sealing resin (epoxy resin)
[0016]
In the embodiment, after the fusible alloy 3 is joined to the terminal leads 1 and 2 made of Sn—Cu plated copper wire by resistance welding, the fusible alloy 4 is covered with the flux 4 made of rosin, wax and activator. Then, it can be formed by being inserted into the alumina ceramic soot tube 5 and sealing the case end with the epoxy-based sealing resins 6 and 7. The Sn-Cu plated copper wires of the terminal leads 1 and 2 can be changed to Ag plated copper wires, Sn plated copper wires, Ni plated copper wires, etc. as required, and are limited to Sn-Cu plated copper wires. It is not something.
[0017]
In the thermal fuse of the above embodiment, a φ0.3 to 0.7 mm wire can be used for the fusible alloy 3, and a rectangular strip of a tape-like alloy having the same cross-sectional area can be used if necessary.
[0018]
The temperature fuse fusible alloy of the present invention can be manufactured by extruding an alloy ingot and then rolled into a tape shape as necessary.
[0019]
In addition, the wire diameter of the fusible alloy 3 can be reduced to φ0.3 or less as required in the range not departing from the gist of the present invention in the future, and further changed to φ0.7 mm or more as required. You can also.
[0020]
【Example】
(Embodiment 1) A fusible alloy 3 is joined to terminal leads 1 and 2, this fusible alloy 3 is covered with a flux 4, inserted into an insulator case 5, and the terminal lead 1 2 in a temperature fuse formed by sealing the ends of the case 5 with sealing resins 6 and 7, the fusible alloy contains 57% by mass of Bi, 26% by mass of In, Sn A φ0.6 mm wire having a composition of 17 mass% was prepared by extrusion, and this alloy wire was applied to the temperature fuse of the embodiment. When operating in a thermostatic chamber (gas phase) where the temperature rises at a rate of 1 ° C./min while supplying a detection current of 10 mA to 30 temperature fuses of Example 1, the operating temperature range is 81 ± 2 ° C. Met. In addition, when 10 temperature fuses of Example 1 stored at 71 ° C. for 500 hours, 1000 hours, and 2000 hours were tested, the internal resistance range of 9 ± 2 mΩ could be maintained, and the operating temperature was 81 after high temperature storage. It was found that the initial range of ± 2 ° C can be maintained.
[0021]
(Example 2) A φ0.6 mm wire having a composition in which 1 part by mass of Cu is added to 100 parts by mass of the three alloys of Example 1 is produced by extrusion, and this alloy wire is applied to the temperature fuse of the embodiment. did. Evaluation of 30 temperature fuses in the same manner as in Example 1 revealed that the internal resistance value could be lowered to 7 ± 2 mΩ in the operating temperature range of 85 ± 5 ° C. Furthermore, as a result of examining the addition amount of Cu in detail, when the addition amount of Cu is preferably within the range of 0.1 to 1.5 parts by mass with respect to 100 parts by mass of the alloy of Example 1, the operation in the target range Temperature could improve the wire workability of the alloy.
[0022]
(Example 3) A φ0.6 mm wire having a composition in which 0.5 parts by mass of Ag was added to 100 parts by mass of the three alloys of Example 1 was produced by extrusion, and this alloy wire was used as the temperature fuse of the embodiment. Applied to. When 30 temperature fuses were evaluated in the same manner as in Example 1, it was found that the internal resistance value could be lowered to 5 ± 2 mΩ without changing the operating temperature range. Furthermore, as a result of examining the addition amount of Ag in detail, when the addition amount of Ag is preferably in the range of 0.1 to 2.5 parts by mass with respect to 100 parts by mass of the alloy of Example 1, the operating temperature is changed. The internal resistance value was able to be lowered.
[0023]
[Comparative example]
Alloy composition in which the amount of Bi is 49% by mass or less: The temperature fuse of the embodiment using 48Bi-30In-22Sn does not stabilize the operating temperature range of 75 to 90 ° C., leading to a practical temperature fuse. There wasn't. In addition, an attempt was made to extrude a composition of 62Bi-30In-8Sn having a Bi content of 61% by mass or more by extrusion, but the alloy strength was too poor and could not be produced.
[0024]
【The invention's effect】
As described above, the present invention realizes a reliable lead-free thermal fuse operable at 75 to 85 ° C. by adding three alloys not containing Pb or Cd, or further adding Cu or Ag. It is.
[0025]
[Brief description of the drawings]
FIG. 1 is a sectional view of an axial type thermal fuse according to an embodiment of the present invention.
1, 2 Terminal lead 3 Soluble alloy 4 Flux 5 Insulator case 6, 7 Sealing resin

Claims (3)

A fusible alloy is joined to the terminal lead, the fusible alloy is coated with a flux, inserted into an insulator case, and the end of the case leading out the terminal lead is sealed. A temperature fuse having an operating temperature of 75 to 85 ° C. encapsulated with a resin, wherein the fusible alloy is 57% by mass of Bi, 26% by mass of In, and 17% by mass of the remaining Sn. A lead-free temperature fuse characterized by comprising: The lead-free temperature fuse according to claim 1, wherein 0.1 to 1.5 parts by mass of Cu is added to 100 parts by mass of the fusible alloy to improve the wire workability of the alloy. . 2. The lead-free temperature fuse according to claim 1, wherein 0.1 to 2.5 parts by mass of Ag is added to 100 parts by mass of the fusible alloy to lower the internal resistance value.

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