JPH0922802A - Resistor - Google Patents

Abstract

(57) [Summary] [Objective] An object of the present invention is to provide a fuse resistor excellent in fast-melting property even in a low resistance value region. [Structure] A resistance film 2 having a metal resistance film in which a fine powder of a low melting point substance 3 is dispersed is formed on the surface of an insulating substrate 1, and a cap 4 is press-fitted into both ends of the insulating substrate 1 and lead wires 5 are formed.
The present invention provides a resistor which is excellent in fusing property at high speed even in a low resistance value region by welding the above and applying the insulating coating 6 around the resistor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resistor which requires a fast fusing property as a measure for protecting electronic circuits which require safety of various electronic devices.

[0002]

2. Description of the Related Art In recent years, a general current fuse is used to take measures against the problem of ensuring safety when an electronic circuit of various electronic devices typified by a television and a VTR is abnormal. Along with the progress of cost reduction and price reduction, there is an increasing demand for high-value-added resistors that have both highly reliable fixed resistors and current fuse functions.
In addition, with the power saving of electronic devices, the power saving trend of general fixed resistors is also progressing, and the demand for low resistance products with low electric resistance and low electrical resistance is increasing. The same is true of the container, and there is a strong demand for a low resistance value.

Conventionally, this type of resistor has been disclosed in Japanese Patent Laid-Open No. 53-1.
No. 5556 is a spiral groove cutting for correcting the resistance value of a film resistor, and the resistance film width of the part is narrowed by making a part of the groove cutting closer to each other. It is disclosed that when an abnormal overcurrent is applied, the abnormal heat generation of the resistance film is concentrated especially on the portion where the width of the resistance film is narrowed to improve the fusing property.

[0004]

However, in the conventional resistor structure described above, when the resistance film is grooved, the resistance value increases in proportion to the grooving, especially in the low resistance value region. Since the target resistance value is originally low, it is often unnecessary to cut the groove itself. Therefore, it is difficult to narrow down a part of the resistance film width by devising the groove cutting method itself. It is difficult to deal with the value range, and it is often effective only in the high resistance value range.In addition, when flute cutting with a narrow resistance film width is performed in consideration of the fusing characteristics, the rated power is reduced even when used within the rated load. The corresponding current was constantly concentrated in the narrow portion of the resistance film, and the resistance value was likely to change. Further, even with a transient current (pulse current) that is instantaneously applied, there is a problem that the portion where the width of the resistance film is narrowed is large and the transient current generally has a characteristic of weakening.

The present invention solves the above-mentioned conventional problems and has excellent reliability in the steady state as in a general fixed resistor, and conversely, when an abnormal overcurrent is applied, the resistance is reduced even in a low resistance value region. It is an object of the present invention to provide an excellent resistor capable of instantaneously fusing a film.

[0006]

According to the present invention, in order to achieve the above object, the resistance film is a metal film in which a fine powder of a low melting point substance containing at least PbO and B ₂ O ₃ is dispersed.

[0007]

Therefore, according to the present invention, the fine powder of the low melting point substance is directly and uniformly dispersed in the resistance film to form the resistance film, so that the melting point of the low melting point substance is reached in the steady state. Since it does not have any adverse effect on the metal film, it can ensure reliability with excellent life characteristics as with resistors.

Further, even in the thick region of the resistance film having a low resistance value, which has conventionally been melted only by a high overload, a sufficient amount of the low melting point substance necessary for melting is taken into the resistance film, so that a high resistance is obtained. As well as the value range, it can be made to have excellent fast-acting properties.Because the low-melting-point substance is present in the entire resistance film in a uniformly dispersed state, the melting point is instantly low when an abnormal overcurrent is applied. The substance melts and insulates the resistance film, which easily leads to fusing.

[0009]

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view of a resistor according to an embodiment of the present invention. In the figure, 1 is an insulating substrate made of a cylindrical ceramic. Reference numeral 2 denotes a resistance film provided on the surface of the insulating substrate 1, which is Ni-P, Ni-B, Ni-P-.
A metal film containing at least one of W, Cu-Ni, Ni-Cr, etc., containing fine powder having an average particle size of 20 μm or less among low melting point substances 3 made of PbO and B ₂ O _3. It is a thing. The resistance film 2 is formed by plating while dispersing a fine powder of the low melting point substance 3 in the plating solution, so that the surface of the insulating substrate 1 together with the metal ions of the metal film deposited during the plating operation. Since the fine powder of the low melting point substance 3 is uniformly dispersed and deposited in the resistance film during the plating operation, it is agitated by air or the liquid so that the fine powder of the low melting point substance 3 is uniformly dispersed in the resistance film. By circulating, the plating solution and the fine powder of the low melting point substance are constantly stirred to form electroless plating on the surface of the insulating substrate 1 or electroplating after the base treatment. Reference numerals 4 are metal caps provided at both ends of the insulating substrate 1 so as to be electrically connected to the resistance film 2. Reference numeral 5 is a lead wire provided so as to be electrically connected to the cap 4. Reference numeral 6 is an insulating coating made of silicon-based coating material which is provided so as to cover at least the resistance film 2 and a part of the cap 4.

The operation of the resistor configured as described above will be described below. First, when an abnormal overcurrent is applied to the resistor, the temperature of the resistor film 2 rises to a high temperature with heat generation according to the overload state of the resistor film 2 as in the conventional resistor. Then, the fine powder of the low melting point substance 3 which is uniformly dispersed and taken into the resistance coating 2 is heated to the same temperature as the resistance coating 2 as the resistance coating 2 is heated. Next, when the fine powder of the heated low-melting point substance 3 reaches its melting point of 400 to 500 ° C., the low-melting point substance 3 begins to melt and promotes the structural change of the metal film to become conductive, and the resistance film 2 The resistance value is significantly reduced. Lastly, the abnormal overcurrent increases proportionally due to the decrease in the resistance value, and the overload power instantaneously rises by 10 to 300%, which accelerates the melting of the film and accelerates the fusing to cut the circuit safely. To do.

FIG. 2 shows the fusing characteristics of a resistor in which fine powder of the low melting point substance 3 is dispersed.
The average particle size of 20
A fine powder of a low melting point substance composed of PbO and B ₂ O ₃ having a particle size of μm or less is dispersed and dispersed at a ratio of 20 wt% with respect to the resistance film composition to form a metal composite resistance film.
The plated initial resistance value was 50 mΩ, and no groove was cut for resistance value correction. As is clear from Fig. 2, even at 16 times the rated power, it melted down in about 10 seconds and was 50 mΩ.
It was confirmed that even the low resistance product of No. 1 had sufficient quick-breaking property.

FIG. 3 shows the relationship between the blending ratio of the fine powder of the low melting point substance to the resistance film and the fusing property. The composition ratio of the low melting point substance in the resistance film is 0.5 wt% to the fusing property. As a result, it was confirmed that the effect of enhancing the quick-acting property was achieved even with an extremely small composition ratio. Further, as the proportion of the low melting point substance increases, the fusing time is further shortened to improve the fast-breaking property, but when the proportion exceeds 80 wt%, the ratio of the metal composition in the resistance film is small, and therefore the metal composition of the metal is low. Since the fusing time becomes extremely short because it depends on the characteristics of the low melting point material rather than the film, and the general characteristics of the resistor such as the life characteristics are deteriorated, a design that achieves both fusing characteristics and general life characteristics Not suitable for resistors. Therefore, the composition ratio of the low melting point substance in the metal composite resistance film as the resistor is preferably 0.5 to 80 wt%.

FIG. 4 shows the difference in fusing characteristics between the metal composite resistance film of the present invention and a conventional resistor having a low melting point glass coated on the surface of the resistance film. A 0.5 W type sample was used. There is. Regarding the resistance value, the fusing characteristics were compared with the minimum resistance value (0.22Ω) of the conventional product that can be manufactured being constant. As is clear from FIG. 4, the low melting point glass-coated product on the surface of the resistance film melts at 60 times or more at 20 times or more of the rated power, whereas the metal composite resistance film product of the present invention has a rated power of 16 times. It was confirmed that the product of the present invention was excellent in quick-cutting property, because the material melted in about 10 seconds even when doubled, and there was almost no variation in the melting time.

In this embodiment, a resistor using a cylindrical ceramic insulating substrate has been described. However, by taking advantage of quick disconnection in a low resistance value area, a printed circuit board surface mounting, which has been strongly demanded in recent years, is used. It is also possible to develop a chip-shaped resistor for use as a resistance film.

Further, since the low-melting-point substance fine powder is dispersed in the metal resistance film regardless of the resistance-film base material, if the resistance film and the low-melting substance fine powder can be simultaneously deposited, another metal composite resistance film Needless to say, it can be applied to a metal oxide composite resistance film or the like.

Further, in the present embodiment, the low melting point substance composed of PbO and B ₂ O ₃ is dispersed in the resistance film to form the metal composite resistance film. However, PbF ₂ is contained in the low melting point substance. , ZnO, and SiO ₂ can be added to adjust the fusing characteristics, and similar effects can be obtained by adding them as needed.

Further, in this embodiment, after the low melting point substance fine powder is dispersed as a resistor on the surface of the ceramic insulating substrate,
If necessary, the groove is cut, and the insulation coating is applied at the end.If the low melting point substance content in the resistance film increases, the low melting point substance fine powder also exists on the surface of the metal composite resistance film. As a result, the roughness of the surface of the film increases and the surface becomes rough. Therefore, a protective film such as a silicon-based varnish may be applied to protect the surface of the metal composite resistance film, or a metal film of about several μm may be deposited on the upper surface of the metal composite resistance film for protection.

Although the low melting point substance is uniformly dispersed in the entire resistance film, only a part of the central portion of the resistor is treated for the purpose of adjusting the quick disconnection property, or the metal film and the metal composite resistance film are layered a plurality of times. A structure in which the metal composite resistance film is partially formed by depositing the film may be used.

[0020]

As described above, according to the present invention, the following effects can be obtained by uniformly incorporating the fine powder of the low melting point substance into the resistance film of the resistor.

(1) Heat generation of resistance film in the process leading to fusing-Melting of low melting point substance-Structural change of resistance film-Time required for wire breakage is instantaneous and fusing time can be shortened and fusing at the same time. It is also possible to reduce time variations.

(2) In particular, even in a low resistance value region in which the resistance film is thick in the past and has a problem of quick disconnection, it is taken into the resistance film by increasing the amount of the low melting point substance added to the plating solution. It is possible to finely adjust the amount of the low melting point substance arbitrarily, and it is possible to manufacture a resistor which is excellent in quick-acting property and easily meets the target fusing property.

(3) In the conventional resistor, there are four or more steps of the resistance film deposition film, the groove cutting for resistance value correction, the low melting point glass coating, and the low melting point glass dry curing, but in the present invention, the resistance film is formed. Production and compounding of low-melting point substances can be processed at the same time, and the process can be shortened and the cost including materials can be reduced.

(4) Since the low-melting point substance is in the form of fine powder, there is no longer the need to apply a paste that has been processed with a resin component as in the prior art, and it is easy to maintain the quality of the low-melting point substance. . In the case of a paste containing resin,
The quality control is easily affected by ambient temperature, humidity, resin quality, and solvent amount, and storage and quality control may not be easy. Further, even in the case of long-term storage, since it is in a powder state, it is stable with less quality deterioration due to storage, as compared with pasted low melting glass.

(5) Since the fine powder of the low melting point substance is dispersed over the entire resistance film, quick disconnection can be secured without being affected by the grooving process for correcting the resistance value.

(6) The structure is such that only when an abnormal overcurrent is applied, the melting point of the low melting point substance in the resistance film is reached and the resistance film is melted and broken. Basically, a metal film having stable characteristics is used as the base material. Therefore, it shows stable life characteristics when used under general load conditions.

[Brief description of drawings]

FIG. 1 is a sectional view of a resistor according to an embodiment of the present invention.

FIG. 2 is a diagram showing the same fusing characteristics.

[Fig. 3] Relationship between composition ratio of low melting point substance and fusing property

FIG. 4 is a diagram comparing the present invention and a conventional fuse resistor fusing characteristic.

[Explanation of symbols]

 1 Insulating substrate 2 Resistive film 3 Low melting point substance 4 Cap 5 Lead wire 6 Insulation coating

Claims (4)

[Claims] 1. A resistor having a resistance coating on the surface of an insulating substrate, wherein the resistance coating is a metal coating containing fine powder of a low melting point substance containing at least PbO and B ₂ O ₃ . 2. A resistance film containing an insulating substrate, a metal film formed on the surface of the insulating substrate, and a fine powder of a low melting point substance containing at least PbO and B ₂ O _3, and the resistance film. A resistor comprising caps provided at both ends of the insulating base so as to be electrically connected. 3. The metal coating is at least Ni-P, Ni-
The resistor according to claim 1 or 2, containing one of B, Ni-P-W, Cu-Ni, and Ni-Cr. 4. PbO and B ₂ O ₃ dispersed in the resistance film
3. The resistor according to claim 1, wherein the composition ratio of the low melting point substance is 0.5 to 80 wt% with respect to the composition of the resistance film.