JPH0422516Y2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to an improvement of a substrate type temperature fuse.

<Prior art and problems> Substrate-type temperature fuses include a pair of foil-like electrodes provided on one side of an insulating substrate such as a ceramic plate, and a foil-like fusible metal body bridged between these electrodes. It has a structure in which an insulating coating layer is provided on one side of the insulating substrate, and the other side of the insulating substrate is used in contact with the heat generating part of the electrical equipment to be protected. When the protected electrical equipment generates heat due to overcurrent, the fusible metal body is heated through the insulating substrate, and the fusible metal body is blown out, cutting off the power supply to the protected electrical equipment.

The fusing mechanism of a fusible metal body in a temperature fuse is that the fusible metal body melts, this molten metal becomes spheroidized due to surface tension (surface energy), and the molten metal is divided as the spheroidization progresses. If oxides are present on the surface of the molten metal body, the surface energy will be low and spheroidization will be delayed, making it impossible to quickly operate the temperature fuse. For this reason, in temperature fuses, by providing a flux layer on the fusible metal body, it is possible to prevent the oxidation of the fusible metal body during the manufacture of the temperature fuse, and even if some oxide film is formed, the fusible metal The active force of the flux under high temperature during melting melts the oxide film and promotes the spheroidization and fragmentation of the molten metal body. However, in thermal fuses, the flux layer may become fluidized due to repeated heating of the protected electrical equipment through energized heat cycles. However, in the case of substrate-type temperature fuses, the planar dimensions of the substrate cannot be made so large in order to achieve miniaturization.
Since the sealing performance between the board and the insulating coating layer is relatively low, the above-mentioned molten flux easily leaks out, and by the time it is activated (when the fusible metal body is melted), the flux escapes and the molten metal is There is a concern that spheroidization may become difficult or delayed.

In addition, in conventional board type temperature fuses,
Due to heat dissipation from the surroundings of the insulating substrate, the heating delay of the fusible metal body is quite significant, and a delay in operation is inevitable.

As described above, conventional substrate type thermal fuses suffer from operational delays due to leakage of flux, time delay until the fusible metal body melts, and time delay until disconnection after melting.

<Purpose of the invention> The purpose of the invention is to reduce the activation delay in a substrate-type temperature fuse.

<Structure of the invention> The substrate-type temperature fuse of the invention has electrodes extending from one end of the substrate to near the other end arranged in parallel on one side of an insulating substrate, a fusible metal body straddling these electrodes, and a fusible metal In a temperature fuse in which a flux layer is provided on the body and an insulating coating layer is provided on one side of an insulating substrate, grooves are provided on one side of the insulating substrate along the other end of the substrate and both sides of the substrate in the vicinity of the other end. This structure is characterized in that the above-mentioned insulating coating layer bites into the groove.

<Explanation of Examples> The present invention will be explained below with reference to the drawings.

FIG. 1 is an explanatory top view showing a temperature fuse according to the present invention, and FIG. 2 is an explanatory cross-sectional view taken from FIG.

In FIGS. 1 and 2, reference numeral 1 denotes an insulating substrate with good thermal conductivity, such as a ceramic plate.
Reference numerals 2 and 2 denote foil electrodes (for example, silver electrodes) provided in parallel on one side of the insulating substrate, and reach from one end of the substrate to the vicinity of the other end. 3, 3 are lead conductors connected to each electrode 2, 2. 4 is a foil-shaped fusible metal body provided astride the other ends of both electrodes 2, 2; for example, a Pb-Sn alloy foil can be used. 5
1 is a groove provided on one side of the insulating substrate along the other end of the substrate and both sides of the substrate near the other end; 52 is a groove provided symmetrically to the other end groove 510 with the fusible metal body 4 as the center; This groove 52 can also be omitted. These grooves 51 and 52 can be provided by laser machining or molding. 6 is a flux layer coated on the fusible metal body 4, and 7 is an insulating layer coated on one side of the substrate 1, for example, a mold layer of epoxy resin.

The substrate-type temperature fuse is used by bringing the other surface 10 of the insulating substrate 1 into contact with a heat-generating portion of an electrical device to be protected. When the device generates heat, the heat is transferred to the fusible metal body 4 of the temperature fuse through the thickness of the insulating substrate 1, and a portion of this transferred heat is radiated from the periphery of the insulating substrate 1. Therefore, if the amount of heat transferred per unit time is Q, the heat capacity of the insulating substrate is C, and the heat radiation resistance from the periphery of the insulating substrate is R, then the temperature of the insulating substrate is T.
is T=RQ(1-e-t/CR)-(1). Therefore, the transfer of heat from the fusible metal body to the peripheral edge of the substrate near the metal body can be effectively prevented due to the thinning of the substrate due to the presence of the grooves 51, and the heat dissipation resistance R can be increased. The temperature T based on Equation 1 can be increased at a high rate. Therefore, the fusible metal body can be rapidly heated in accordance with the heat generated by the equipment, and the operability of the temperature fuse can be improved.

In the above-mentioned substrate-type temperature fuse, since it is heated by the energization heat cycle of the electrical equipment to be protected, the flux layer 6 melts and thermally expands while the fusible metal body 4 is not melted, and this molten flux Although it tries to leak, the grooves 51 and 5 of the insulating coating layer 7
Since the bite into 2 acts as a dam against leakage, leakage of the molten flux can be well prevented. Therefore, the flux layer can be maintained until operation, and the molten metal can be smoothly divided into spherules.

Incidentally, since the distance from the flux 6 to one end of the substrate 1 (on the side of the lead conductors 3, 3) can be made considerably long, the groove 52 can be omitted.

<Effects of the invention> The substrate-type temperature fuse of the invention has the structure described above, and prevents leakage of flux.
Since the fusible metal body can be rapidly heated and melted quickly, and the molten metal can be smoothly divided into spheres, the operating speed can be increased.

[Brief explanation of the drawing]

Fig. 1 is a partially cutaway top view showing a substrate-type temperature fuse according to the present invention, and Fig. 2 is a -
FIG. In the figure, 1 is an insulating substrate, 2, 2 are electrodes, 4
is a fusible metal body, and 51 is a groove.

Claims (1)

[Scope of utility model registration request] Electrodes extending from one end of the substrate to near the other end are provided in parallel on one side of the insulating substrate, a fusible metal body is provided across these electrodes, a flux layer is provided on the fusible metal body, and a flux layer is provided on one side of the insulating substrate. In a temperature fuse provided with an insulating coating layer, grooves are provided on one side of the insulating substrate along the other end of the substrate and both sides of the substrate near the other edge, and the insulating coating layer is dug into the groove. Features a board-type temperature fuse.