JPH0638351Y2 - Temperature fuse - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention relates to improvement of temperature fuse.

<Prior Art and Problems> One of the methods of using the thermal fuse is to dispose the thermal fuse close to a heat-generating circuit element, for example, a resistance element, and activate the temperature fuse by the heat generated by the heat-generating element due to overcurrent. This may protect the circuit from abnormal heat generation of the heat generating circuit element. As one of such temperature fuses, a pair of electrodes is provided on one surface of an insulating substrate, a low melting point soluble metal body is provided between these electrodes, and the low melting point soluble metal body is coated with a flux. The one in which an insulating coating is provided on one surface of the insulating substrate so as to cover the electrodes is known as a so-called substrate type thermal fuse.

By the way, recently, as a circuit element to be mounted on a printed wiring board, a chip-type circuit element having no lead wire is rapidly used for increasing the packaging density. In this chip-type circuit element, cap-shaped terminals are fixed to both ends, the element is brought into close contact with the printed wiring board, and the terminals are soldered to conductors on the board.

Therefore, when the chip-type circuit element is a heat-generating element such as a resistance element, it is required to attach a thermal fuse to the chip-type circuit element in close thermal contact.

It is known in the art to use a thermally conductive metal combination to thermally attach a thermal fuse to an exothermic circuit element. However, in the above-mentioned substrate type thermal fuse, when the flux thermally expands due to the heat of the arc generated when the low melting point fusible metal body is melted, the flux is generated between the insulating substrate and the insulating coating. The molten metal flows out together with the expansion flux, and the molten metal flowing out adheres to the metal joint, the lead wire of the thermal fuse and the metal joint are electrically connected, and the space between the lead wires of the thermal fuse is metal. In some cases, the circuit will not be able to reliably cut off the current due to short-circuiting with the manufactured coupling body.

The object of the present invention is to use the back surface of the insulating substrate of the substrate type thermal fuse for mounting the chip type heat generating circuit element, and to thermally connect the temperature fuse and the chip type heat generating circuit element without using a joint. Allows for close coupling.

<Structure of device> The thermal fuse of the present invention has a pair of electrodes provided on one surface of an insulating substrate, a lead wire is connected to each electrode, and a low melting point fusible metal body is provided between the electrodes. An electrode for mounting a chip-type heat-generating circuit element is provided on the other surface of the insulating substrate of a substrate-type thermal fuse having an insulating coating so as to cover the electrode, and a lead wire different from the lead wire is connected to the electrode. The configuration is characterized in that

<Description of Embodiments> The present invention will be described below with reference to the drawings.

FIG. 1A is a partially cutaway top view showing a temperature fuse according to the present invention, and FIG. 1B is a back view showing the temperature fuse.

In FIGS. 1A and 1B, 1 is an insulating substrate, for example, a ceramic plate. 2 and 2 are foil-like electrodes provided on one surface of the insulating substrate 1, 3 is a low melting point soluble metal layer bridged between the electrodes, 4 is a flux layer coated on the low melting point soluble metal layer 3, and 5 is insulating It is an insulating layer covering the entire one surface of the substrate 1. Reference numerals 6 and 6 are lead wires that can be connected to the electrodes 2.2. 7,7
Is a foil electrode provided on the other surface of the insulating substrate 1, and 8 and 8 are electrodes 7 and 7, respectively.
Is the lead wire connected to.

FIG. 2A is a partially cutaway top view showing another embodiment of the present invention, and FIG. 2B is a rear view of the other embodiment.

FIG. 3A is a partially cutaway top view showing another embodiment of the present invention,
FIG. 3B is a rear view of the same embodiment.

In FIG. 2A, FIG. 2B, FIG. 3A, and FIG. 3B, the components having the same reference numerals as those in FIG. 1A and FIG. 1B are the components in FIG. 1A and FIG. 1B. Technically virtually the same.

FIG. 4 shows a usage state of the temperature fuse according to the present invention.

In FIG. 4, A is a printed wiring board, 9 is a printed circuit conductor, and 101, 102, ... Are chip type circuit elements connected (soldered) to predetermined positions of the printed circuit conductor.
B is a temperature fuse according to the present invention. Reference numeral 100 denotes a chip-type heat-generating circuit element that should be connected between the rounds 91, 91 of the printed circuit conductor 9, and is attached between the electrodes 7, 7 on the back surface of the insulating substrate of the temperature fuse B with a conductive adhesive, and each electrode 7 , 7 lead wires 8, 8 are soldered to each round 91, 91 of the printed circuit conductor 9. Lead wires 6,6 for the low melting point soluble metal body 3 of the temperature fuse B are connected in series to the printed circuit.

In the above, when the chip-type heat generating circuit element 100 generates heat, the heat is transferred to the low melting point soluble metal body 3 through the path of the electrode 7 → the insulating substrate 1 of the thermal fuse B → the low melting point soluble metal body 3 of the fuse B. Transmitted to the electrode 7 due to the good thermal conductivity of the electrode 7.
Becomes almost the same as the heat generation temperature of the chip-type heat-generating circuit element 100, and the thermal contact area between the chip-type heat-generating circuit element 100 and the insulating substrate of the thermal fuse B can be substantially increased. The heat generated by the exothermic circuit element 100 can be efficiently transferred to the substrate type thermal fuse B, and the heat generated by the chip type exothermic circuit element 100 quickly melts the low melting point metal body of the substrate type thermal fuse to energize the circuit. Can be shut off immediately.

<Effects of the Invention> The thermal fuse of the present invention has the configuration as described above, and the chip type heat generating circuit element is attached to the electrode on the other surface of the insulating substrate, and the lead wire of the electrode is attached to the chip mounting type printed wiring board. By connecting to the conductor, the chip type heat generating circuit element to which the thermal fuse is attached can be easily mounted on the chip mounting type printed wiring board. In addition, the heat generated by the chip-type heat-generating circuit element can be efficiently transferred to the board-type thermal fuse by using the mounting electrode of the chip-type heat-generating circuit element as a heat-sensitive plate, and the board-type temperature is increased by the overcurrent heat generated by the heat-generating circuit element. The low melting point fusible metal body of the fuse can be quickly blown. Further, since no metal coupling body is required, even if the molten metal of the low melting point fusible metal body flows out to the surroundings during the operation of the substrate type thermal fuse, conduction between the lead wires of the thermal fuse cannot occur.

[Brief description of drawings]

FIG. 1A is a partially cutaway top view showing a thermal fuse of the present invention, FIG. 1B is a rear view of the same temperature fuse, and FIGS. 2A and 2B show another embodiment of the present invention. 3A and 3B are partial cutaway top and bottom views showing another embodiment of the present invention, and FIG. 4 shows the use state of the temperature fuse of the present invention. It is an explanatory view shown. In the figure, 1 is an insulating substrate, 2 and 2 are electrodes, 3 is a low melting point soluble metal body, and 7 and 7 are electrodes for soldering.

Claims (1)

[Scope of utility model registration request] 1. A pair of electrodes is provided on one surface of an insulating substrate, a lead wire is connected to each electrode, a low melting point metal body is provided between the electrodes, and insulation is performed so as to cover the metal body and the above electrodes. An electrode for mounting a chip type heat generating circuit element is provided on the other surface of the insulating substrate of the substrate type thermal fuse provided with a coating, and a lead wire different from the lead wire is connected to the electrode. Thermal fuse.