JP3074527B2 - Chip type fuse resistor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a chip type fuse resistor mainly composed of a thick film glaze.

[0002]

2. Description of the Related Art Conventionally, the following types of chip-type fuse resistors function as general-purpose resistors in a normal state and have a fusing function to interrupt a circuit when a circuit overload is abnormal.

That is, a resistive film is formed between electrodes arranged on an insulating substrate having a rectangular parallelepiped chip shape by a vapor deposition method, a sputtering method or an electroless plating method, and a fusing narrow portion is formed at the center of the resistive film by a trimming method. Is formed, a heat storage layer made of glass is partially interposed between the insulating substrate and the fusing portion, and the fusing time is shortened by overcurrent concentration on the trimmed fusing narrow portion and assisting the heat storage of the glass. Known structures are known.

Further, an activation layer is formed on an insulating substrate having a rectangular parallelepiped chip shape, a resistance film is formed by an electroless plating method, and a fusing narrow portion is formed at the center of the resistance film by a trimming method. Another structure in which a fusing material is provided on the fusing narrow portion is known.

[0005]

In recent electronic devices, information processing and control by computers have become widespread not only in communication devices and data processing devices but also in general electronic devices, and connection with transmission lines has been frequently used. There is an urgent need to ensure safety against signal malfunctions due to extraneous surge noise and overload abnormalities.Accordingly, it functions as a general-purpose resistor in normal conditions, and also withstands surges caused by induced lightning. There is a need for a chip-type fuse resistor that reliably melts and interrupts a circuit when an overload is abnormal.

However, as described above, in the conventional chip type fuse resistor, 1) a fusing narrow portion is provided at the center of the resistive film by a trimming method, and the heat storage effect and the fusing narrowing of the glass provided below the fusing narrow portion are provided. With the aid of the fusing material provided to cover the portion, the fusing speed can be obtained quickly, but since the fusing characteristics are given priority, the inflow of the surge easily leads to disconnection.

2) Since the resistive film is formed by a vapor deposition method, a sputtering method or an electroless plating method, the number of steps is increased and the construction method is complicated.

[0008] 3) The resistance film is hardly formed uniformly due to the step due to the partial formation of the heat storage layer made of glass, and the reproducibility of the fusing material is poor.

4) Since the resistive film is formed by a vapor deposition method, a sputtering method or an electroless plating method, the protective film covering the resistive film is made of a resin-based paint in consideration of heat resistance and moisture resistance of the resistive film. This has to be adopted, and as a result, heating from an overload abnormality causes smoke from the protective film, combustion, or causes a sustained arc due to carbonization when used in a high voltage circuit.

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to solve the problems by focusing on the problems of the prior art.

That is, if a simple structure is used, the number of construction methods is small, and a stable surge resistance contrary to the fusing characteristics is provided. An object of the present invention is to provide a chip-type fuse resistor having a wide degree of freedom in value.

[0012] The chip type fuse resistor according to the present invention comprises:
A chip-type fuse resistor in which a resistive film connecting between a pair of electrodes provided at both ends of a rectangular chip-shaped insulating substrate and a protective film covering the resistive film are formed in a thick film glaze, wherein the resistive film is Are divided into a central portion having a high sheet resistance and both side portions having a low sheet resistance, and a trimming groove to be formed on the resistive film is traversed through the center in a direction between the electrodes, and a turning point and a terminal point of the trimming groove. Are located on both sides.

In the present invention, the resistive film is disposed so that the sheet resistance at the center (in the direction between the electrodes) is higher than the sheet resistance at both sides of the center, and is formed by thick film glaze. Paying attention to the softening point temperature of the glass component contained in the resistive film and the protective film, a thick glaze of the glass component is selected such that the softening point temperature of the protective film is lower than that of the resistive film.
As described above, the Joule heat caused by the overcurrent at the time of an overload abnormality is concentrated at the central portion of the resistive film, and the heating due to the heat concentration first melts the protective film portion covering the central portion, and then melts the central portion of the resistive film. I do. At this time, since the concentration gradients of the respective melted glass components are different, the glass flows so that the concentration becomes uniform, whereby the conductive components (ruthenium oxide particles and the like) at the center of the resistive film are also diffused, and the resistance value becomes high. And
This acts to interrupt the circuit. In addition, in order to suppress the variation of the fusing characteristics due to the non-uniform thickness, the thickness of the resistive film is 5 μm to 15 μm, and the thickness of the protective film is 10 μm to 2 μm.
It is desirable that the thickness be 5 μm.

In the present invention, the form of the trimming groove to be formed on the resistive film is L-shaped, J-shaped or U-shaped.
The direction change and the end point are applied so that the center part is traversed in the direction between the electrodes and the end points are located on both sides. This suppresses the non-uniformity of the current density between the electrodes, prevents the variation of the fusing time and the deterioration of the surge resistance, and acts to secure the reliability as a resistor. If the trimming structure is L-shaped (see FIG. 1), J-shaped (see FIG. 5) or U-shaped (see FIG. 6) having a turning point of 90 ° or more, the current density around the turning point can be increased. Can be made more uniform, which contributes to an improvement in surge resistance.

As the conductive component of the resistive film, particularly the thick film glaze at the center, silver-palladium-based materials can be used in addition to ruthenium oxide-based materials. Since the resistance value is low, the resistance value is limited to a low range, and it is desirable to use a ruthenium oxide-based material from the viewpoint of the degree of freedom of the completed resistance value range, the residual resistance value after fusing, and the like. The point temperature is 550 ° C to 900 ° C, preferably 630 ° C to 660 ° C.

For the purpose of avoiding smoke, burning or carbonization due to heat generation at the time of an overload abnormality, it is desirable to use a lead borosilicate glass-based material as the thick film glaze of the protective film. From 500 ° C to 800 ° C,
Preferably it is 590-600 degreeC.

In the chip type fuse resistor according to the present invention, the area resistance value ratio between the both sides and the central part is 1:
It is desirably 1.5 to 3. When the sheet resistance of the central part with respect to the sheet resistance of both sides is less than 1.5, the heat concentration in the center at the time of an overload abnormality becomes slow, and the unfusing and the variation of the blowing increase, and 3 If it exceeds, the heat concentration becomes excessive, and it becomes difficult to secure the surge resistance.

[0018]

FIG. 1 is a plan view showing one embodiment of a chip type fuse resistor 10 according to the present invention, and FIG.
FIG. 2 is a sectional view taken along line AA ′ of FIG. The resistor 10 includes a rectangular chip-shaped insulating substrate (alumina 96%) 1 and a pair of left and right front electrodes 2 provided on both right and left ends of the front and back surfaces of the insulating substrate 1.
And a back electrode 2 ′, a resistance film R communicating between the front electrodes 2 on the insulating substrate 1, and a trimming groove 3 formed in the resistance film R.
A protective film 4 for covering and protecting the resistive film R; an end surface electrode 5 partially overlapped on the front and back electrodes 2 and 2 ′ and provided on the left and right end surfaces of the insulating substrate 1; And a plating layer electrode 6 covering the electrode 5 as a basic structure.

The resistive film R and the protective film 4 are formed by a thick film glaze, and the resistive film R is divided into a central part R1 and both side parts R2, and is provided independently. As shown in FIGS. 3 and 4, both side portions R2 'are superimposed on the lower resistive film R' connecting between the front electrodes 2 (portions common to FIGS. 1 and 2 are denoted by the same reference numerals). Then, the lower resistance film R ′ between them may be used as the central portion R1 ′.

Further, the sheet resistance of the central portion R1 is the same as that of the both sides R1.
2, the softening point temperature of the glass component of the protective film 4 is set lower than the softening point temperature of the glass component of the central portion R1. Further, the film pressures of the central portion R1, the side portions R2, and the protective film 4 are adjusted to be constant.

The trimming groove 3 is L-shaped so as to traverse the central portion R1 in the direction between the electrodes, and that the turning point 3 and the terminal point 3 ″ of the trimming groove 3 are located only on both side portions R2.
Note that the trimming groove is J-shaped (reference numeral 53 in FIG. 5) or U-shaped.
It can also be in the shape of a letter (reference numeral 63 in FIG. 6).

An embodiment of the above-mentioned chip type fuse resistor will be described below.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The external dimensions of a chip type fuse resistor are 6.3 mm in length and 3.2 mm in width, and the rated power is 1
Table 1 shows the test results of the fusing characteristics and the surge resistance, which were prepared as samples having W of 4.7Ω, 47Ω and 470Ω as the W.

The central portion R1 of the resistive film R has a thick film glaze containing ruthenium oxide-based lead ruthenate as a conductive component.
It was formed by baking at 50 ° C. to obtain a film thickness of 8 μm. Also,
Effective length ratio L1: of central portion R1 and both side portions R2 of resistance film R
L2 (× 2) was set to 1: 4, and the sheet resistance ratio was set to 1: 3.

As the protective film 4, a thick film glaze of lead borosilicate glass was fired at 600 ° C. to obtain a film thickness of 12 μm.

The trimming groove 3 has a laser output of 2 W, a Q switch frequency of 6 kHz, and a beam position moving speed of 3 kHz.
The moving distance (width direction) P of the laser spot is set to W with respect to the width W
/ 5, W / 3 and W / 2.

In the fusing characteristic test, a voltage corresponding to an overload of 25 times the rated power value assuming an abnormal overload is applied.
The fusing time was measured. The surge resistance test was performed using the test circuit shown in FIG.
0) A voltage of 10 kV peak voltage (open voltage of the terminal aa ′ shown in FIG. 7) in μs, and (10 × 100
0) A voltage of 1 kV peak voltage in μs (terminal a shown in FIG. 7)
-A 'open-circuit voltage) was measured for the rate of change from the initial value after each application of 10 times.

The number of samples was 10 for each completed resistance value.

[0029]

[Table 1]

As is clear from Table 1, each of the completed resistance values was reliably blown in 0.3 to 2.9 seconds against a predetermined overload, and good blowing characteristics were obtained.

In the surge resistance, according to the aspect of the present invention, the conventional chip type fuse resistor is disconnected by one application of both the waveform A and the waveform B.
-0.02% to + 0.11% for waveform B, and -0.02% for waveform B.
The rate of change was 2% to + 0.02%, and an extremely stable effect was obtained.

[0032]

As described above, in the chip-type fuse resistor according to the present invention, the resistive film and the protective film are formed by the thick film glaze, and the area resistance between the central portion and both side portions of the resistive film is determined by the former. By adopting a trimming structure that sets the direction change point and terminal point of the trimming groove on both sides, the Joule heat at the time of overload abnormality is concentrated in the center, and the protective film and the resistive film are The central part can be reliably and quickly blown by the flow / diffusion during melting due to the difference in softening point, the current density between the electrodes becomes uniform, the deterioration of surge resistance is prevented, and the resistance is reduced. The reliability as a container can be improved.

Further, since the resistive film and the protective film are formed into a thick film glaze through a screen printing and firing process, the manufacturing process can be simplified, and the film thickness of the protective film and the resistive film can be adjusted to be constant. Various effects can be obtained, such as reducing the variation in the fusing characteristics, avoiding smoke and burning from the protective film, and increasing the degree of freedom in the completed resistance value range.

[Brief description of the drawings]

FIG. 1 is a plan view showing a chip type fuse resistor according to the present invention.

FIG. 2 is a sectional view taken along line A-A 'of FIG.

FIG. 3 is a plan view showing another embodiment of the chip type fuse resistor according to the present invention.

FIG. 4 is a sectional view taken along line A-A 'of FIG.

FIG. 5 is a plan view showing a chip-type fuse resistor provided with a J-shaped trimming groove.

FIG. 6 is a plan view showing a chip-type fuse resistor provided with a U-shaped trimming groove.

FIG. 7 shows a surge resistance test circuit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Insulating substrate 2 Front electrode 2 'Back electrode R Resistive film R' Lower resistive film R1, R1 'Central part R2, R2' Side parts 3, 53, 63 Trimming groove 3 'Turning point 3 "End point 4 Protective film 5 Edge electrode 6 Plating layer electrode 10 Chip type fuse resistor SG Surge generator Rid Impedance matching resistance Ab1 Surge absorber (discharge start voltage 700V) Ab2 Surge absorber (discharge start voltage 125V) Rx Test sample RL Load resistance

Claims (3)

(57) [Claims] 1. A chip-type fuse resistor in which a resistive film connecting between a pair of electrodes provided at both ends of a rectangular chip-shaped insulating substrate and a protective film covering the resistive film are formed by a thick film glaze. The resistive film is divided into a central portion having a high sheet resistance and both side portions having a low sheet resistance, and a trimming groove to be formed on the resistive film is traversed in the direction between the electrodes through the central portion in the direction of the trimming groove. A chip type fuse resistor, wherein a turning point and a termination point are located on both sides. 2. The chip type fuse resistor according to claim 1, wherein an area resistance value ratio between said both side portions and said central portion is 1: 1.5-3. 3. The chip type fuse resistor according to claim 1, wherein said trimming groove is L-shaped, J-shaped or U-shaped.