JPH10112404A - Resistor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To fuse a resistance coating instantly even in low resistance region when abnormal over-current is applied, by forming a resistance coating containing at least fine powder of thermoplastic resin in metal. SOLUTION: On a metal provided on the surface of a base body 11 comprising a cylindrical ceramics, etc., a resistance coating 12 containing fine powder of a flame-retardant thermoplastic resin 13 is provided, and a metal cap 14 is provided on both ends of the base body 11 so as to be electrically connected to the resistance coating 12. When an abnormal over-current is applied to the resistor, the resistance coating 12 generates heat corresponding to over-load condition, to be high temperature. When the heated fine powder of the thermoplastic resin 13 reaches its melting point or decomposition temperature, resin 13 expands, causing a large stress at the resistance coating 12 for generating cracks. The current which flows after disconnection which results from intrusion of molten thermoplastic resin into crack-generated parts is surly shut down.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resistor having an overload fusing characteristic used in an electronic circuit of various electronic devices for protecting against heat generation, smoke generation and ignition due to overcurrent.

[0002]

2. Description of the Related Art In recent years, there is a type using a general current fuse from the viewpoint of ensuring safety when an electronic circuit of various electronic devices such as a television and a VTR is abnormal. As price increases, demand for high value-added resistors having overload fusing characteristics with excellent reliability is increasing.

[0003] In addition, as the power consumption of electronic devices is reduced, the power saving trend of general fixed resistors is also progressing, and the demand for low-power products having low electric resistance and low resistance is increasing. The same applies to resistors having overload fusing characteristics, and there has been a strong demand for lower resistance, lighter, thinner and shorter.

Hereinafter, a conventional resistor will be described with reference to the drawings. A conventional resistor is disclosed in
No. 43701 discloses that "a substrate is provided with a resistive film and an upper electrode on a surface thereof, a load concentrating portion is formed on the resistive film by trimming, and the load concentrating portion is covered with a melting agent".

FIG. 5A is a perspective view of the upper surface of a conventional resistor, and FIG. 5B is a sectional view taken along line AA.

In FIG. 1, reference numeral 1 denotes an insulating substrate made of alumina or the like. Reference numeral 2 denotes an activation layer provided on the upper surface of the insulating substrate 1 and containing palladium as a main component. Reference numeral 3 denotes a resistance film provided by electroless plating a resin-silver paste provided on the upper surface of the activation layer 2. Reference numeral 4 denotes a first kerf in which the activation layer 2 and the resistive film are formed by grooving to form the load concentrating portion 5. Reference numeral 6 denotes a second cut groove provided to make the resistance film 3 have a desired resistance value. Reference numeral 7 denotes a pair of upper electrodes provided on the side of the upper surface of the resistance film 3 of the insulating substrate 1. Reference numeral 8 denotes a molten material made of glass or non-carbonized resin provided so as to cover the load concentrating portion 5. Reference numeral 9 denotes a protective film made of a heat-resistant epoxy resin provided so as to cover the resistance film 3 on which the upper electrode 7 is not formed on the upper surface and the molten material 8. Reference numeral 10 denotes a side electrode provided on the opposite side of the insulating substrate 1 so as to be electrically connected to the upper electrode 7. Reference numeral 11 denotes nickel plating provided so as to cover the side surface electrode 10. Reference numeral 12 denotes solder plating provided so as to cover the nickel plating 11.

With respect to the resistor formed as described above,
The operation will be described below. When a conventional resistor is mounted on a printed circuit board on which various electronic components are mounted and is affected by an overcurrent or the like, the load concentrating portion 5 of the resistive film 3 is overheated, and a resin-silver paste forming the resistive film 3 and When the temperature of the molten material 8 covering the load concentrating portion 5 becomes equal to or higher than its melting point, the resistance film 3 is melted, broken, and overloaded.

[0008]

However, in the above-described conventional resistor structure, when the first kerf 4 is formed by grooving the resistance film 3, the resistance value is proportional to the amount of grooving. However, especially in the low-resistance region, the target resistance is inherently low, so the grooving itself is often unnecessary.Therefore, devising the grooving method to narrow a part of the width of the resistive film The method itself is difficult, and it is difficult to cope with a low resistance value region by devising a groove cutting method, and there is a problem that it can be performed only in a high resistance value region.

Further, the resistance film 3 and the molten material 8 are not melted and melted unless they reach a high temperature higher than the melting point of each material. Therefore, it takes a long time to melt, and the resistors become high temperature before being melted, and various electronic parts are formed. There is a problem that a printed circuit board on which is mounted or an electronic component in the vicinity becomes high in temperature.

An object of the present invention is to solve the above-mentioned conventional problems, and an object of the present invention is to provide a resistor capable of instantaneously blowing a resistance film even in a low resistance value region when an abnormal overcurrent is applied.

[0011]

In order to achieve the above object, the present invention has a resistive film comprising a metal containing at least a fine powder of a thermoplastic resin.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present invention is directed to a resistive film comprising a base, a metal provided on the surface of the base and fine powder of a thermoplastic resin, And a cap provided at both ends of the base so as to be electrically connected to the resistance film.

Further, the invention according to claim 2 of the present invention provides:
A substrate, a pair of upper electrodes provided on side portions of the upper surface of the substrate, a resistive film containing a metal and a thermoplastic resin so as to be electrically connected to the upper electrode, and both sides of the substrate; And a side electrode electrically connected to the upper surface electrode.

Further, the invention according to claim 3 of the present invention provides:
The metal of the resistance film according to claim 1 or 2 is at least Ni-P, Ni-B, Ni-PW, Cu-Ni, Ni
-Cr, Ni-P-B.

The invention according to claim 4 of the present invention provides:
The fine powder of the thermoplastic resin for the resistive film according to claim 1 or 2 contains any one of PTFE, PMMA, nylon, and polystyrene.

(Embodiment 1) Hereinafter, a resistor according to Embodiment 1 of the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view of a resistor according to the first embodiment of the present invention. In the figure, reference numeral 11 denotes a base made of a cylindrical ceramic or the like. Reference numeral 12 denotes Ni-P, Ni-B, Ni-P-W, and Cu-N provided on the surface of the base 11.
i, Ni-Cr, Ni-P-B and other metals containing at least one of them, and PTFE (Poly Tetra).
Fluoro Ethylene), PMMA (Pol
This is a resistance film containing a fine powder having a particle diameter of 20 μm or less made of any one of flame-retardant thermoplastic resin 13 such as yMethyl Meth Acrylate, nylon, and polystyrene. Reference numeral 14 denotes a metal cap provided at both ends of the base 11 so as to be electrically connected to the resistance film 12. Reference numeral 15 denotes a lead wire provided so as to be electrically connected to the cap 14. Reference numeral 16 denotes a protective film made of an insulating nonflammable paint or the like provided so as to cover at least the resistance film 12.

A method of manufacturing the resistor having the above-described configuration according to the first embodiment of the present invention will be described below.

FIG. 2 is a diagram showing a method of manufacturing the resistor according to the first embodiment of the present invention. First, as shown in FIG. 2A, a resistance film 12 is formed on a surface of a base (not shown) made of a cylindrical ceramic or the like by plating or the like.
At this time, by plating while dispersing the fine powder of the thermoplastic resin 13 such as PTFE, PMMA, nylon, and polystyrene in the plating solution, the metal film on which the fine powder of the thermoplastic resin 13 is deposited during the plating operation Ni-P, N
i-B, Ni-P-W, Cu-Ni, Ni-Cr, Ni
—PB precipitates on the surface of the substrate together with any one of the metal ions, and is uniformly dispersed and taken into the resistance film 12. The thermoplastic resin 13 is treated with a suitable surfactant so as to be uniformly dispersed in the plating solution to increase the wettability, and then is introduced into the plating solution. The plating solution is subjected to air stirring or solution circulation, and the plating solution and the fine powder of the thermoplastic resin 13 are constantly stirred to form a plating on the surface of the base by electroless plating or electroplating after the undercoat treatment.

Next, as shown in FIG. 2 (b), metal caps 1 are provided at both ends of a substrate having a resistance film 12 formed on the surface.
After fixing 4, groove 17 for adjusting the resistance value is formed in resistance film 12.

Next, as shown in FIG. 2C, a lead wire 15 is formed by welding so as to be electrically connected to the cap 14.

Finally, as shown in FIG. 2D, a protective film 16 made of an insulating and nonflammable paint is formed so as to cover at least the resistive film 12, thereby manufacturing a resistor.

The operation of the resistor constructed and manufactured as described above according to the first embodiment of the present invention will be described below.

First, when an abnormal overcurrent is applied to the resistor, the temperature of the resistive film 12 rises with the heat generated in accordance with the overload state of the resistive film 12 and rises to a high temperature, similarly to the conventional resistor.

Next, the fine powder of the thermoplastic resin 13 uniformly dispersed and taken into the resistance film 12 with the heat generation of the resistance film 12 is heated to the same temperature as the resistance film 12.

Next, when the heated fine powder of the thermoplastic resin 13 reaches its melting point or decomposition temperature, the thermoplastic resin 13 melts or decomposes and expands, and a large stress acts on the resistance film 12.

Finally, cracks are generated in the resistive film 12 by stress, and the molten thermoplastic resin penetrates into the portions where the cracks occur to break the wires, thereby reliably shutting off the flowing electricity.

(Embodiment 2) Hereinafter, a resistor according to Embodiment 2 of the present invention will be described with reference to the drawings.

FIG. 3 is a sectional view of a resistor according to the second embodiment of the present invention. In the figure, reference numeral 21 denotes a substrate made of ceramic or the like. Reference numeral 22 denotes a pair of upper electrodes formed by printing a conductive paste such as Ag-Pd provided at least on the side of the upper surface of the substrate 21. Reference numeral 23 denotes Ni-P, Ni-B, Ni-PW, and Cu-N formed on the upper surface of the substrate 21 so as to partially overlap the pair of upper electrodes 22.
i, at least one of Ni-Cr and Ni-P-B
PTFE (Poly Tetra F)
fluoro Ethylene), PMMA (Poly
It is a resistance film containing fine powder having a particle size of 20 μm or less, which is made of a flame-retardant thermoplastic resin 24 such as methyl methacrylate, nylon, or polystyrene. Reference numeral 25 denotes a lower surface electrode formed by printing an Ag paste or the like on the lower surface of the substrate 21 facing the upper electrode 22. Reference numeral 26 denotes a trimming groove formed by a laser trimmer or the like for correcting a resistance value and forming a load concentrated portion. 2
Reference numeral 7 denotes a protective film made of an insulating and nonflammable paint provided so as to cover at least the resistance film 23. Reference numeral 28 denotes the substrate 2 so that the upper electrode 22 and the lower electrode 25 are electrically connected.
1 is a pair of side electrodes provided on opposing side surfaces.
29 denotes an upper electrode 22, a side electrode 28 and a lower electrode 25.
And nickel plating provided so as to cover. 30
Is a solder plating provided so as to cover the nickel plating 29.

The method of manufacturing the resistor configured as described above according to the second embodiment of the present invention will be described below.

FIG. 4 is a diagram showing a method of manufacturing a resistor according to the second embodiment of the present invention. First, as shown in FIG. 4A, Ag-Pd is formed so as to straddle the slits 31 of the sheet substrate 32 in which the slits 31 are formed in advance.
The upper surface electrode 22 is similarly formed on the lower surface of the sheet substrate 32 by printing a conductive paste such as the above on the upper surface of the sheet substrate 32, drying and firing.

Next, as shown in FIG. 4 (b), a plating resistant paint is printed on the upper surface of the sheet substrate 32 except for a portion where a resistive film is formed in a later step, and a mask for resistive film plating (not shown). After the formation of the resistor film 23, the resistance film 23 is formed by a plating method. At this time, PTFE, PM
By plating while dispersing fine powder of thermoplastic resin 24 such as MA, nylon, polystyrene, etc., Ni-P, Ni-B, Ni of a metal film on which fine powder of thermoplastic resin 24 is deposited during plating operation -P-W, Cu-Ni, Ni
-It precipitates on the upper surface of the sheet substrate 32 together with any one metal ion of -Cr, Ni-P-B, is uniformly dispersed, and is taken into the resistance film 23. The thermoplastic resin 24 is treated with a suitable surfactant so as to be uniformly dispersed in the plating solution to increase the wettability, and then charged into the plating solution. The plating solution is subjected to air stirring or solution circulation, and the plating solution and the fine powder of the thermoplastic resin 24 constantly stirred to form a plating on the upper surface of the sheet substrate 32 by an electroless plating method or an electroplating method after a base treatment. I do.

Next, as shown in FIG. 4C, a trimming groove 26 for correcting the resistance value and forming the load concentration portion is formed in the resistance film 23 by using a laser trimmer or the like.

Next, as shown in FIG. 4D, a protective film 27 is formed by printing with an insulating and nonflammable paint so as to cover a part of the resistive film 23 and the upper electrode 22 and firing it.

Next, as shown in FIG. 4E, the sheet substrate 32 is formed on the side of the slit 31 where the upper electrode 22 is formed.
Is primarily divided into strips, and a metal thin film such as Ni or Cr or Cu is sputtered on the side surface of the strip-shaped substrate so as to be electrically connected to the upper electrode 22 and the lower electrode.
The side electrodes 28 are formed by vapor deposition or the like, or by printing and baking a conductive paste such as a resin-Ag paste.

Finally, as shown in FIG. 4F, the substrate divided into strips is subdivided and nickel-plated (not shown) so as to cover the upper electrode 22, the side electrode 28 and the lower electrode. Then, a solder plating 30 is formed so as to cover the nickel plating to manufacture a resistor.

The operation of the second embodiment is the same as that of the first embodiment, and a description thereof will not be repeated.

[0038]

As described above, according to the present invention, the following advantageous effects can be obtained by uniformly incorporating the thermoplastic resin into the resistance film of the resistor.

(1) The thermoplastic resin taken into the resistance film melts or decomposes and expands, causing cracks in the resistance film, thereby breaking the wire due to an abnormal overcurrent. The wire can be accurately disconnected at a desired power value.

(2) By changing the amount of thermoplastic resin introduced into the plating solution, the amount of thermoplastic resin taken into the resistance film can be arbitrarily fine-tuned, and the desired fusing characteristics can be easily obtained. A matching resistor can be manufactured.

(3) By changing the type of the thermoplastic resin, the melting point or the decomposition temperature of the thermoplastic resin can be adjusted, and a resistor matching the desired fusing characteristics can be easily manufactured. Things.

(4) Since the formation of the resistive film and the blending of the thermoplastic resin can be performed at once without using a molten material in the load concentration portion, the process can be shortened and the cost including materials can be reduced.

(5) Resistive film Since the metal film used for the ordinary resistor is used as the base material, the metal exhibits stable resistance characteristics when used under general load conditions.

[Brief description of the drawings]

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

FIG. 2 is a view showing the same manufacturing method.

FIG. 3 is a sectional view of a resistor according to a second embodiment of the present invention.

FIG. 4 is a view showing the same manufacturing method.

FIG. 5A is a perspective view of a top view of a conventional chip fuse resistor. FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Substrate 12 Resistance film 13 Thermoplastic resin 14 Cap 15 Lead wire 16 Protective film 21 Substrate 22 Upper surface electrode 23 Resistance film 24 Thermoplastic resin 25 Lower electrode 26 Trimming groove 27 Protective film 28 Side electrode 29 Nickel plating 30 Solder plating

Claims (4)

[Claims] 1. A substrate, a resistance film containing a metal and a fine powder of a thermoplastic resin provided on the surface of the substrate, and two ends of the substrate so as to be electrically connected to the resistance film. A resistor comprising a cap provided. 2. A substrate, a pair of upper electrodes provided on a side of an upper surface of the substrate, and a resistance film containing a metal and a thermoplastic resin so as to be electrically connected to the upper electrodes. And a side electrode electrically connected to the upper surface electrode on a side surface of the substrate. 3. The metal of the resistance film is at least Ni-
P, Ni-B, Ni-P-W, Cu-Ni, Ni-C
The resistor according to claim 1, wherein the resistor includes any one of r, Ni—P—B. 4. The fine powder of the thermoplastic resin of the resistance film is P
The resistor according to claim 1, comprising one of TFE, PMMA, nylon, and polystyrene.