JPH0217610A - Overload fusing type resistor - Google Patents

Abstract

PURPOSE:To form a resin layer with heat softening properties so that one part or entire part of a resistor coating may be covered, cover it with a thermal insulation object, and obtain a overload fusing type resistor with the same performance and reliability as those of a general resistor on rated operation by forming the overload fusing type resistor where a resistor film consisting of a specific amount of composition of Pb and Ag is provided on the surface of an insulating substrate. CONSTITUTION:An activation treating layer consisting of Sn, Ag or Pb is provided on an insulating substrate 1 made of a ceramic, etc., an alloy film layer 2 of Pb-Ag is formed with the layer as a ground layer, and a resin layer with heat softening properties 3 is formed on this film layer 2. With the resistance film by this alloy film layer 2 as a composition of Pb 88 to 99% and Ag 1 to 12%, the resistance film is covered with the resin layer 3 either partially or entirely. A cap 4 is injected into both edges of the substrate 1 where this kind of resistance film is formed, a lead wire 5 is welded to it, and a groove-cut part 6 is formed around the alloy film layer 2.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an overload fusing type resistor widely used in consumer equipment, industrial equipment, and the like.

Conventional technology In recent years, with the demand for smaller devices and lower power consumption, overload fusing resistors are required to be able to interrupt current even if the applied power is a low multiple of the rated power in the event of an abnormality. has been done.

Traditionally, this type of overload fusing type resistor consists of (1) a general resistance film such as a metal film, a metal oxide film, or a carbon film coated with a low melting point glass paste; (2) a resistance film and its (3) Partially narrowing the current path to cause heat concentration and melting, (4) Using a fusible resistance film. etc.

Problems to be Solved by the Invention However, with these conventional resistors, it is generally difficult to blow them out at a low magnification of, for example, 4 to 6 times the rated power. For this reason, attempts have been made to improve the resistors of the above four types, and some have been developed that fuse at a low applied power of 4 to 6 times the rated power, but the resistance film material has a low fusing temperature. There is a problem that it may melt due to excessive heat from the outside during soldering or installation.

The present invention solves these problems, and is capable of stably and accurately cutting off the current by reaching an applied power of about 4 to 6 times the rated power, and is an overload fusing type that is not easily affected by external heat. The purpose is to obtain a resistor.

Means for Solving the Problems Therefore, the present invention provides P bss ~99%,
This is an overload fusing type resistor provided with a resistance film having a composition of 1 to 12% of g.

That is, in the present invention, Pb88 to 99%, A
The present invention provides an overload fusing type resistor provided with a resistive film having a composition of 1 to 12% g, and in particular, a thermosoftening resin layer is formed so as to partially or entirely cover the resistive film.
Moreover, it is specifically realized with a structure in which the entire structure is covered with an insulating material such as a heat shrink tube.

The main characteristics that an overload fusing type resistor should have include fusing characteristics, life characteristics, and soldering heat resistance, but if the melting point of the resistance film becomes too high, the fusing characteristics tend to deteriorate.
On the other hand, if the melting point becomes too low, the life characteristics, soldering heat resistance, and other characteristics subject to the action of external heat tend to deteriorate, causing problems.

Therefore, when considering the characteristics of both, the melting point of the resistive film is 3.
Materials with a temperature of around 00°C are required. A resistive film with a composition of 5s~99% Pb and 1~12% Mg has a melting point of 30%.
Around 0℃ (especially Pb97.5wt%, Mg2.5W
The melting point of t-thickness is 304° C.), and the above-mentioned objective overload fusing type resistor can be obtained.

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a sectional view showing a part of a resistor according to the present invention. First, in FIG. 1, reference numeral 1 denotes an insulating substrate, which is made of a material such as porcelain that is commonly used in this field. Its size and shape are appropriately determined depending on the rated power of the intended resistor, etc., but typically, for example, the diameter is 1.7~
4.6MM.

Length 6.6-14. ONM's cylindrical porcelain is exemplified.

Such an insulating substrate is used after being subjected to conventional treatments such as polishing and reheating according to conventional methods. In one embodiment of the present invention, in providing the pb-λg alloy film layer,
The film was deposited on the insulating substrate by a dry method such as sputtering. There is also a wet method in which an activated layer made of Sn, Mug, or Pd is provided, and then an Ag or Sn layer is provided as a base layer, and the alloy film 2 of the PB layer Mug is provided on this base layer by electroplating. Conceivable. In the case of a wet method, a method of depositing an alloy plating film of a PB layer and a PB layer.

A possible method is to perform alloying by heat treatment after forming the Ag layer alone. Furthermore, even in dry methods such as sputtering, thermal aging may be performed after film deposition for the purpose of stabilizing the resistive film.

The resistive film obtained as described above is grooved to modify the resistance value, if necessary.

Next, in the present invention, a softening resin layer is formed over a partial range or the entire range of the resistive film, which may or may not be grooved. Second
The figure shows a state in which a thermoplastic resin layer 3 is formed on the alloy film 2 of FIG. 1. Figure 3 shows P in Figure 1.
A cap 4 is press-fitted at both ends of the insulating base 1 onto a resistance film consisting of a b-Ag alloy film 2, and a lead wire 6 is welded to this. A grooved portion 6 is provided.

The heat-softening resin layer 3 is provided in a portion of the grooved central portion (that is, the central portion of the grooved portion). The heat-softening resin layer 3 softens due to heat generated during overload, and promotes melting of the molten resistance coating due to a decrease in viscosity and a flux action. Examples include rosin, olefin, styrene, nylon, phenolic,
Examples include heat-softening resins such as xylene-based resins and modified products thereof. These thermosetting resins are preferably ones that soften and reduce viscosity near the temperature at which the resistance coating is fused (generally around 90 to 260°C), and particularly help the molten resistance coating become spherical due to surface strength. Those having action are more preferable. The thickness of the thermosoftening resin layer 3 may vary depending on the type of resin used, but generally it is 2 to 2.
The thickness may be about 0 μm, preferably about 6 to 15 μm. The heat-softening resin layer 3 is formed by applying a solution or melt of a heat-softening resin with a brush, or by a dipping method or a printing method. Finally, as shown in FIG. 4, the overload fusing type resistor is completed by covering the entire resistor with a protective layer 7 made of an insulating material commonly used in this field, such as a heat shrink tube.

Hereinafter, the present invention will be explained in more detail with reference to Examples.

A Pb-Ag film was deposited on an insulator with a diameter of 1.7 WW and a length of 6°6 mm using the sputtering method as shown below to give a resistance value of somΩ.
An overload fusing type resistor was obtained. The fusing characteristics of the overload fusing type resistor of the present invention obtained in the above examples were tested. The test method is as follows. The test will be conducted using the circuit shown in Figure 5, and a constant voltage power source will be used as the power source. Chapter S
In the figure, R1 is a resistor under test. R2 is high power
This is a stabilizing resistor, its resistance value is 30 to 50 times that of R1, and it is connected in series to R1. In advance, a high-power dummy resistor is used in place of the test resistor R1, and the voltage of the power supply is adjusted to meet the conditions specified in the fusing characteristic specifications. Next, attach the resistor to be tested instead of the dummy resistor and turn on the switch S. After turning on the switch, use an ammeter to check whether the specified current is flowing, and if the specified current is not flowing, quickly (within 1 second) make fine adjustments. However, the power supply will not be adjusted after that.

Measure the time from turning on the switch to disconnection.

The determination that the resistor has reached the disconnection state is made when the current value becomes less than 3δ of the initial test current.

The results are shown in Figure 6.

Furthermore, the resistance of the resistor of the present invention obtained in the above example to external heat was tested. That is, the resistor was immersed in silicone oil, and the rate of change in resistance value was measured when the temperature was gradually raised. The results are shown in FIG.

Effects of the Invention The overload fusing type resistor of the present invention stably and reliably fuses and interrupts current at a low power multiplier of about 4 to 6 times the rated power. The fusing mechanism is probably that the melting point of the resistive film of the present invention is relatively low, and when the temperature of the resistive film reaches its melting point due to overload heat generation, the resistive film melts, and at the same time the thermoplastic resin It is presumed that the viscosity reduction due to thermal softening of the layer and the flux action combine to cause the melted resistance film to become spherical due to the force of the surface eye, and thus fusion is achieved.

During rated operation, the resistor of the present invention becomes an overload fusing type resistor having performance and reliability equivalent to that of a general resistor. Furthermore, the resistance film of the resistor of the present invention exhibits stable resistance to external heat such as heat conduction from lead wires during soldering. In addition, since the heat-softening resin layer is formed on the resistive film, it has high fusing characteristics and a high withstand voltage after fusing. Furthermore, since the manufacturing process of conventional film resistors can be used as is, the manufacturing cost is low and advantageous.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing a part of a resistor according to an embodiment of the present invention, FIG. 2 is a cross-sectional view after forming a thermosoftening resin layer on the resistor film of FIG. 1, and FIG. FIG. 4 is a side view of the main parts of the resistor of the present invention just before completion, FIG. The figure is a frequency distribution diagram of fusing characteristics of Examples measured using this, and FIG. 7 is a characteristic diagram showing the rate of change in resistance value as the external temperature rises. 1... Insulating base, 2... Alloy film layer,
3...Thermosoftening resin layer, 4...Cap, 6...11. Lead wire, 6...Groove section, 7...Insulator. Name of agent: Patent attorney Shigetaka Awano and 1 other person Fig. (:8')

Claims (2)

[Claims] (1) An overload fusing type resistor characterized in that a resistance film having a composition of 88 to 99% Pb and 1 to 12% Ag is provided on a substrate. (2) Claim 1 in which a thermosoftening resin layer is formed so as to partially or entirely cover the resistive film, and the whole is covered with an insulating material.
Overload fusing type resistor as described.