JP3182844B2 - Noise filter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a three-terminal noise filter having varistor characteristics, capacitor characteristics, and resistance characteristics, and more particularly to an improved voltage suppression capability to reliably prevent the destruction and malfunction of a semiconductor device. Also, the present invention relates to a structure capable of reducing the number of components and mounting cost and avoiding deterioration of life characteristics.

[0002]

2. Description of the Related Art IC, L employed in computer equipment
In semiconductor devices such as SI, breakdown due to intrusion of transient noise such as electrostatic surge
It is an important issue to prevent malfunction. Conventionally, as a method of protecting against the intrusion of such transient noise, the setting of the ground of the set or the substrate, the arrangement of the electronic component elements in the substrate, or the addition of a disk type varistor or an LC filter to the circuit has been conventionally performed. It is common to absorb noise. Above all, the varistor is relatively easy to add to the circuit,
In addition, because of its low voltage and low capacity, it is more suitable as a noise absorbing element than other methods. When a varistor is used as a noise absorbing element, the varistor voltage needs to be as close to the circuit voltage as possible, so that a lower voltage is required.

In recent years, computer equipment has become smaller and smaller.
As the thickness has been reduced, the varistors have been reduced in size,
It is required to respond to SMT (surface mounting). However, the above-mentioned disk varistor cannot cope with miniaturization and SMT due to its structure. As a substitute for such a disk-type varistor, a multilayer varistor has been conventionally proposed (for example, see Japanese Patent Publication No. 58-23921).

[0004]

However, although the above-mentioned conventional multilayer varistor can cope with miniaturization and SMT, the voltage suppression capability is almost the same as that of the conventional disk varistor, so that the noise is prevented from entering. In some cases, the semiconductor device cannot be completely protected, and improvement in this respect is demanded. The breakdown voltage of the above-mentioned semiconductor device differs depending on the type, but in a MOS-IC or the like,
Many break down at 40-60V. On the other hand, the voltage suppressing capability of the multilayer varistor is two to three times the varistor voltage,
Since the lower the varistor voltage is, the higher the ratio is, the suppression voltage is further increased by an impulse such as static electricity. As a result, there is a case where the multilayer varistor alone cannot be protected.

Here, by adding a resistance to the above-mentioned multilayer varistor, it is possible to obtain a voltage suppression capability equal to or higher than the actual value. In this case, if a resistive element is separately externally attached to the multilayer varistor, the cost increases as the number of the resistive elements increases, and the mounting space increases. It is also conceivable to form a resistive film on the surface of the multilayer varistor. However, in this case, the resistive film is easily damaged by an external mechanical load, and as a result, the electrical characteristics are deteriorated and the life characteristics are deteriorated. Is reduced.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional circumstances, and it is possible to improve the voltage suppression capability to reliably prevent the destruction and malfunction of a semiconductor device due to noise, further increase the cost and increase the mounting space. It is an object of the present invention to provide a noise filter which can avoid the deterioration of the lifetime characteristic while avoiding the problem.

[0007]

SUMMARY OF THE INVENTION Accordingly, a first aspect of the present invention is to form first and second side electrodes on first and second side surfaces of a semiconductor porcelain having a voltage non-linear characteristic. Forming third and fourth side electrodes on the side surface, embedding the first internal electrode inside the semiconductor ceramic, connecting both end edges of the first internal electrode to the third and fourth side electrodes, A second internal electrode overlapping with the first internal electrode is embedded in the semiconductor ceramic with a ceramic layer interposed therebetween, and one end of the second internal electrode is connected to one of the first and second side electrodes. Further, a resistor is embedded in the semiconductor ceramic, and the other end of the second internal electrode is connected to one of the first and second side electrodes via the resistor. It is a noise filter. The invention according to claim 2 is characterized in that a resistor buried inside the semiconductor ceramic is connected to one of the other end face electrodes via a conductor formed on the outer edge of the ceramic layer. .

Here, it is desirable to coat a glass film on the surface of the semiconductor ceramic except for the electrodes. Thereby, moisture resistance and chemical resistance can be improved, and leakage current can be reduced.

[0009] As a material constituting the resistor, it is suitable to use Ru as a main component, especially RuO _2.
It is preferable to mix either Pb ₂ Ru ₂ O ₇ or Bi ₂ Ru ₂ O ₇ with the mixture. This makes it possible to easily control the resistance value, and also to set a desired resistance value by appropriately changing the length, area, and number of layers of the resistor. The above Pb ₂ Ru ₂ O ₇ , Bi ₂ R
It is desirable that the added amount of u ₂ O _{7 be} up to 60 wt%. If it exceeds this, the resistance value will vary. Further, as the ceramic material constituting the above-mentioned semiconductor porcelain, it is appropriate to adopt a material containing ZnO as a main component in consideration of the temperature at the time of firing.

[0010]

According to the noise filter of the present invention, since the resistor is added to the second internal electrode, the resistance of the varistor is improved by the resistor while obtaining the voltage non-linear characteristic between the first and second internal electrodes. As a result, a voltage control capability equal to or higher than the value can be obtained, so that destruction and malfunction of the semiconductor device due to intrusion of transient noise can be reliably prevented. Further, since the resistor is buried inside the semiconductor porcelain, it is possible to avoid an increase in cost and an increase in mounting space when a resistor component is separately provided externally, and furthermore, a resistance film is formed on the surface of the semiconductor porcelain. In this case, damage due to an external mechanical load can be avoided, and the life characteristics can be improved.

[0011]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. FIGS. 1 to 4 are views for explaining a noise filter according to an embodiment of the present invention. In the figure, reference numeral 1 denotes a voltage non-linear characteristic, a capacitor characteristic,
And a three-terminal noise filter having both resistance characteristics. The semiconductor porcelain 3 of the noise filter 1 is made of ZnO
Is a rectangular parallelepiped formed by laminating a plurality of ceramic layers 2 whose main components are and sintering the laminated body integrally. Left and right end faces (first and second side faces) 3a and 3b of the semiconductor porcelain 3
Are formed with end electrodes (first and second side electrodes) 4 and 4 made of Ag for external circuit connection. The front and rear side (third and fourth side surfaces) 3c and 3d of the semiconductor ceramic 3 are formed. Are formed at the center portion of the side surface electrodes (third and fourth side surface electrodes) 5 and 5 also made of Ag for external circuit connection.

The semiconductor ceramic 3 has an Ag-
A first internal electrode 6 made of a Pd alloy is embedded. Both end edges 6a, 6b of the first internal electrode 6 are exposed on the front and rear side surfaces 3c, 3d of the semiconductor ceramic 3, respectively, and the both end edges 6a, 6b are connected to the side electrodes 5,5.

Further, a second internal electrode 7 overlapping the first internal electrode 6 in parallel with the ceramic layer 2 is embedded in the semiconductor ceramic 3. One end edge 7a of the second internal electrode 7 is exposed to the left end surface 3a of the semiconductor porcelain 3 and connected to the end surface electrode 4. The other end 6b of the second internal electrode 7 is located inside the right end face 3b of the semiconductor porcelain 3, so that the other end than the one end 7a is sealed in the semiconductor porcelain 3. The above first and second
The portion sandwiched between the internal electrodes 6 and 7 is a ceramic layer 2 'that exhibits voltage non-linear characteristics. Further, although not shown, the end face electrode 4 and the side face electrode 5 of the semiconductor ceramic 3 are provided.
A glass film is coated and formed on the outer surface except for.

The semiconductor porcelain 3 contains R
60 wt% of Pb ₂ Ru ₂ O ₇ and Bi ₂ Ru ₂ O ₇ to uO ₂
% Is buried. The resistor 8 is formed so as to be substantially flush with the second internal electrode 7. One end 8a of the resistor 8 is connected to the other end 7a of the second internal electrode 7, and the other end 8b is exposed to the right end face 3b of the semiconductor ceramic 3 and connected to the end face electrode 4. . The resistor 8 is set to a predetermined resistance value by selecting its thickness and width.

Next, one manufacturing method of the noise filter 1 of the present embodiment will be described. First, a main component 99% or more of ZnO, this _{Bi 2 O 3, CoCO 3,} MnO 2
And Sb ₂ O ₂ at 98 mol%, 0.5 mol% and 0.5 mol, respectively.
%, 0.5 mol%, and 0.5 mol%, to which pure water is added and mixed with a ball mill for 24 hours to form a slurry. Next, after filtering and drying this slurry and granulating,
Temporarily bake at 800 ° C for 2 hours.

Next, the calcined product is coarsely pulverized by a pulverizer, and pure water is added thereto, and finely pulverized by a ball mill. Next, this fine powder is filtered and dried, and then dispersed in a solvent together with an organic binder to form a slurry. Thereafter, this slurry was formed into a ceramic green sheet having a thickness of 50 μm by a doctor blade method,
The green sheet is punched into a predetermined size to form a plurality of ceramic layers 2.

Next, a first internal electrode 6 is formed by screen-printing a conductive paste made of an Ag—Pd (7: 3) alloy on the upper surface of the ceramic layer 2. The first internal electrode 6 is formed such that both end edges 6 a and 6 b are located on both longitudinal edges of the ceramic layer 2, and the other edge is located inside the ceramic layer 2. In addition, a second internal electrode 7 is formed by printing a conductive paste on the upper surface of another ceramic layer 2 in the same manner. The internal electrode 7 is formed such that one end 7a is located on the right outer edge of the ceramic layer 2, and the other end 7b and the remaining edges are located inside the ceramic layer 2.

Next, RuO ₂ is mixed with Pb ₂ Ru ₂ O ₇ and BiRu ₂ O _{7 in an amount} of 60 wt% or less, and a varnish is added thereto to form a resistive paste. This resistive paste is screen-printed on another ceramic layer 2. Thus, the resistor 8 is formed. The resistor 8 is formed such that one end 8 a thereof is located on the other end 7 b of the second internal electrode 7, and the other end 8 b is located on the outer edge of the ceramic layer 2.

Then, as shown in FIG. 3, the first internal electrode 6 and the second internal electrode 7 are overlapped so as to face each other with the ceramic layer 2 'interposed therebetween. The ceramic layer 2 on which the resistor 8 is formed is superposed on the ceramic layer 2 'on which the second internal electrode 7 is formed. In this case, one end 8a of the resistor 8 is disposed so as to slightly overlap the other end 7b of the second internal electrode 7. Further, a plurality of dummy ceramic layers 2 are stacked on the upper and lower surfaces thereof, and a pressure of ² t / cm ² is applied in the laminating direction to press-bond to form a laminate.

Next, the laminate is cut into a predetermined size,
This is fired at a temperature of 900 ° C. for 2 hours to obtain a semiconductor porcelain 3. Next, the semiconductor porcelain 3 is housed in a porcelain pot, zinc borosilicate glass is added to the pot, and heat treatment is performed at a temperature of 600 to 900 ° C. while rotating the porcelain pot. As a result, a glass film is formed on the outer surface of the semiconductor porcelain 3. Finally, the left and right end faces 3a, 3b and the front and rear side faces 3c,
After applying Ag paste on the center of 3d,
By baking for a minute, the end face electrode 4 and the side face electrode 5 are formed.
Thereby, the noise filter 1 of the present embodiment is manufactured.

As shown in the equivalent circuit diagram of FIG. 4, the noise filter 1 of this embodiment has one end face electrode 4 and one side face electrode 5.
And the other end face electrode 4 and the side face electrode 5
Is connected to the semiconductor device A. This prevents an abnormal voltage from being applied to the semiconductor device A and absorbs the overvoltage energy exceeding the voltage suppressing capability of the varistor portion Z by the resistor 8.

As described above, according to the present embodiment, since the resistor 8 is added between the second internal electrode 7 and the end face electrode 4 and this resistor 8 is embedded in the semiconductor ceramic 3, the semiconductor device Even if noise larger than the breakdown voltage of A enters, it can be suppressed by the resistor 8, and as a result, IC or LS
Destruction and malfunction of the semiconductor device such as I can be reliably avoided. In addition, since the resistor 8 is built in the semiconductor porcelain 3, the component cost can be reduced as compared with a case where a resistive component is separately externally mounted, and the mounting space can be reduced, and the computer device can be downsized. it can.
Further, as compared with the case where a resistive film is formed on the surface of the semiconductor porcelain, damage due to external force can be avoided, and the life characteristics can be improved.

[0023]

[Table 1]

Table 1 is for explaining the test results performed to confirm the effect of the noise filter 1 of the present embodiment. In this test, sample Nos. 1 and 2 were prepared by the above-described manufacturing method, and the resistance value (Ω), varistor voltage (V _{1 mA} ), nonlinear coefficient (α),
And the capacitance value (pF) were measured, and their variations were examined. The variation is 3CV = σ × 3
/ Average × 100% (σ is standard deviation).

As is clear from Table 1, according to this embodiment, both samples Nos. 1 and 2 obtain satisfactory values in all of the varistor voltage, nonlinear coefficient, and capacitance. Further, resistance values such as 231 and 201 Ω are obtained, and the variation is as small as 5.2 to 3.5%. As a result, by embedding the resistor in the semiconductor porcelain and integrally sintering, it is possible to obtain a noise filter having no change in varistor characteristics and dielectric constant, a small variation in resistance, and a good coupling stability. Understand. By the way, using the noise simulation for the resistor of each sample, 2
When a square wave of KV · 200nSEC was applied, the change of the resistor was less than 2% in each case.

FIG. 5 shows a pulse waveform when a high voltage pulse is applied to the circuit shown in FIG. As is clear from the figure, the voltage of the sample of this embodiment is about 40 V, which is approximately one fifth of that of the conventional varistor. From this point as well, it is understood that the one having a built-in resistor has a high voltage suppressing ability and is effective for protecting a semiconductor device.

FIG. 6 is a graph showing the frequency characteristics of the above-mentioned sample. As is clear from FIG. 6, it is understood that excellent frequency characteristics are obtained and the generation of stray capacitance due to the internal electrodes is small.

FIG. 7 is a diagram for explaining an embodiment of the second aspect of the present invention. In the figure, the same reference numerals as those in FIG. 3 indicate the same or corresponding parts. In the noise filter of the present embodiment, the conductor 9 is patterned on the right outer edge of the ceramic layer 2 ′ on which the second internal electrode 7 is formed, and one end 10 a of the resistor 10 is formed.
Is connected to the other end 7b of the second internal electrode 7, and the other end 1
0b is connected to the conductor 9 and to the end face electrode 4 via the conductor 9.

In this embodiment, since each edge of the resistor 10 is sealed in the semiconductor porcelain 3, it is possible to prevent the glass from diffusing into the resistor 10 when a glass film is formed on the semiconductor porcelain 3. . As a result, the fluctuation of the resistance value can be avoided, and the resistance value as designed can be obtained.

[0030]

As described above, according to the noise filter of the first aspect of the present invention, the first internal electrode is embedded in the semiconductor ceramic, and the second internal electrode overlaps the first internal electrode with the ceramic layer interposed therebetween. Since the internal electrode is buried and the second internal electrode is connected to one of the first and second side electrodes via the resistor buried in the semiconductor porcelain, the voltage suppressing capability is improved and the semiconductor device is improved. This has the effect of reliably preventing the destruction and malfunction of the device, and has the effect of reducing the number of components and the mounting cost and avoiding deterioration of the life characteristics. Further, in the noise filter according to the second aspect of the present invention, since the resistor is connected to the side electrode via the conductor, fluctuation of the resistance value when the glass is diffused can be avoided, and the resistance value as designed can be obtained. Has the effect.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a noise filter according to an embodiment of the present invention.

FIG. 2 is a perspective view showing the noise filter of the embodiment.

FIG. 3 is an exploded perspective view showing a method of manufacturing the noise filter of the embodiment.

FIG. 4 is an equivalent circuit diagram of the noise filter of the embodiment.

FIG. 5 is a characteristic diagram showing an effect of the noise filter of the embodiment.

FIG. 6 is a characteristic diagram showing an effect of the noise filter of the embodiment.

FIG. 7 is an exploded perspective view illustrating a noise filter according to an embodiment of the present invention.

[Description of Signs] 1 Noise filter 2 Ceramic layer 3 Semiconductor porcelain 3a, 3b Left and right end faces (first and second side faces) 3c, 3d Front and rear side faces (third and fourth side faces) 4 End face electrode (first , Second side electrode) 5 side electrode (third and fourth side electrode) 6 first internal electrode 6a, 6b both end edges 7 second internal electrode 7a one end edge 7b other end edge 8,10 resistor 8a, 10a one end edge 8b, 10b End edge 9 Conductor

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Yukio Sakabe 2-26-10 Tenjin, Nagaokakyo-shi, Kyoto Murata Manufacturing Co., Ltd. (56) References JP-A-1-152704 (JP, A) JP-A Sho 61-127637 (JP, A) JP-A-3-152903 (JP, A) JP-A-49-104652 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01C 7/02 -7/22 H03H 7/075

Claims (3)

(57) [Claims] 1. A semiconductor ceramic having a voltage non-linear characteristic, wherein first and second side electrodes are formed on first and second side surfaces, and third and fourth side electrodes are formed on third and fourth side surfaces. Burying a first internal electrode inside the semiconductor ceramic, connecting both end edges of the first internal electrode to the third and fourth side electrodes, and sandwiching a ceramic layer inside the semiconductor ceramic; A second internal electrode overlapping with the first internal electrode is buried, and one edge of the second internal electrode is connected to the first and second internal electrodes.
A resistor is buried inside the semiconductor porcelain connected to one of the side electrodes, and the second element is buried through the resistor.
A noise filter, wherein the other end of the internal electrode is connected to one of the first and second side electrodes. 2. The noise according to claim 1, wherein a resistor buried inside the semiconductor ceramic is connected to one of the other side electrodes via a conductor formed on an outer edge of a ceramic layer. filter. 3. The noise filter according to claim 1, wherein a surface portion of the semiconductor ceramic except for the first to fourth side electrodes is covered with a glass film.