JPH0638350Y2 - 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> Conventionally, when soldering an electric circuit component to a printed wiring board, a lead conductor of the circuit component is formed in a spiral shape,
It is possible to protect the circuit components from the heat of soldering by increasing the heat conduction distance along the lead wire from the soldering point to the circuit component body to prevent heat during soldering from being transmitted to the circuit component body. It is known (Japanese Utility Model Publication No. 40-14494).

By the way, attach a thermal fuse to the printed wiring board,
When a circuit component mounted on the same board, such as a resistor, overheats, the generated heat heats the fuse element (low melting point fusible metal body) of the thermal fuse to heat the printed wiring board due to overcurrent. In order to protect the fuse element from heat, an insulating case (for example, a ceramic case) that surrounds the fuse element is heated, and this case heating heats the internal fuse element by radiation and heat conduction through the lead conductor. The fuse element is heated by this, and the fuse element is blown out.

Therefore, if the lead conductor of the thermal fuse is formed in a spiral shape and the fuse element is protected from heat during soldering, the thermal conductivity of the lead conductor during the fusing operation of the fuse element is reduced. Therefore, the operability of the thermal cutoff is unavoidably lowered.

An object of the present invention is to maintain sufficient operability of the thermal fuse even when the lead conductor is formed in a spiral shape in order to protect the fuse element from heat when soldering the thermal fuse to the printed wiring board. It's about tightening if possible.

<Structure of Device> The temperature fuse according to the present invention is configured such that a low melting point metal body is joined between a pair of lead conductors, and the metal body is surrounded by a case.
In the temperature fuse in which the lead conductor end can be drawn out from the case, a heat sink is provided in the lead conductor portion in the case.

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

In FIG. 1, reference numeral 1 designates an insulating case having heat resistance and good heat conductivity, and for example, a ceramic case can be used. Reference numerals 2 and 2 are a pair of lead conductors (made of copper), which are introduced into the case 1. 3 is a low melting point metal body such as a lead-tin alloy body, which is connected between the lead conductors 2 and 2,
It is stored in Case 1. 4 is the Frax. 2
Reference numerals 0 and 20 denote heat sinks attached to the lead conductor portion in the case, and the lead conductor is formed in a coil shape to reduce the length of the lead conductor. Reference numeral 5 denotes an insulator added to the heat sink 20, for example, an epoxy resin, which guarantees insulation between the heat sinks when the low melting point fusible metal body 3 is melted. 6 is a sealing material such as an epoxy resin, which is used for insulating the heat-conductive insulating case 1 to the lead conductor ends 21 and 2.
1 is derived airtightly.

FIG. 2 shows another embodiment of the present invention, in which the lead conductor 2
A conductor wire having an insulating coating is used for the coil-shaped heat sink 20, the insulation (5 in FIG. 1) is not added, and a sealing material is provided between the low melting point metal body 3 and the heat sink 20. Thus, the airtight partition wall 61 is formed. An insulating lid 6 for closing the case 1 has a hole 62, and the lead conductor end 21 is led out from this hole. 4 is a flux.

<Effects of the Invention> The thermal fuse of the present invention has the above-described configuration, and the volume of the conductor is increased between the lead conductor end that can be led out of the case and the low melting point metal body in the case to absorb heat. Since a heat sink with a large capacity is provided, it is possible to sufficiently prevent the heat of soldering from being transferred to the low melting point fusible metal body when soldering the ends of the lead conductors, and to prevent the fuse element from melting Can prevent damage well.

In addition, even though a heat sink is provided on the lead conductor, the length of the lead conductor protruding from the case can be sufficiently shortened, and soldering can be performed by the reflow method in the same manner as ordinary chip parts. Good contact between the fuse and the printed wiring board can be ensured, and the thermal fuse can operate satisfactorily.

[Brief description of drawings]

1 and 2 are explanatory views showing an embodiment of the present invention. In the figure, 1 is a case, 2 and 2 are lead conductors, 3 is a low melting point fusible metal body, 20 and 20 are heat sinks, and 21 and 21 are lead conductor ends.

Claims (1)

[Scope of utility model registration request] 1. A thermal fuse in which a low melting point fusible metal body is joined between a pair of lead conductors, the metal body is surrounded by an insulating case having good thermal conductivity, and the lead conductor ends can be led out from the case. A thermal fuse characterized in that a heat sink is attached to the lead conductor portion in the case.