JPH05226184A - Noise filter - Google Patents

Abstract

PURPOSE:To effectively prevent damage, erroneous operation of a semiconductor device, to reduce the number of components and a mounting cost, to avoid deterioration of life characteristics and to avoid a variation in a resistance value when glass is diffused. CONSTITUTION:End face electrodes 4 are formed on left and right end faces 3a, 3b of a semiconductor porcelain 3 having voltage nonlinear characteristics, and side face electrodes 5 are formed on the other both side faces 3c, 3d. A first inner electrode 6 is buried in the porcelain 3, and only its one edge 6a is connected to the one electrode 4. A second inner electrode 7 superposed with the electrode 6 through a ceramic layer 2 is buried in the porcelain 3, and its both edges 7a, 7b are connected to the electrodes 5. Further, a resistor 8 superposed with the electrode 6 through a ceramic layer 2 is buried in the porcelain 3, and lead electrodes 9 to be connected to the electrode 4 are formed on left and right outer edges 2a, 2b of the layer 2. Left and right edges 8a, 8b of the resistor 8 are connected to the electrodes 9 to constitute a noise filter 1. In addition, a glass film is formed on a surface part except the end face and side face electrodes.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a three-terminal type noise filter having both varistor characteristics, capacitor characteristics, and resistance characteristics, and in particular, voltage suppression control capability is improved to reliably prevent destruction and malfunction of semiconductor devices. The present invention relates to a structure capable of reducing the number of parts and mounting cost, and avoiding deterioration of life characteristics.

[0002]

2. Description of the Related Art ICs and Ls used in computer equipment
In semiconductor devices such as SI, destruction due to intrusion of transient noise such as electrostatic surge,
Preventing malfunctions has become an important issue. As a method to prevent such intrusion of transient noise, conventionally, by setting the ground of the set or the board, arranging the electronic component elements in the board, or adding a disk type varistor or an LC filter to the circuit. It is common to absorb noise. Above all, the above varistor is relatively easy to add to the circuit,
Moreover, since it has a low voltage and a low capacity, it is more suitable as a noise absorbing element than other methods. When a varistor is used as the noise absorbing element, the varistor voltage of the varistor needs to be as close to the circuit voltage as possible, so that a low voltage is required.

In recent years, miniaturization of computer equipment,
As thinning advances, the varistor also becomes smaller,
It is required to support SMT (surface mounting). However, the above-mentioned disc type varistor cannot support downsizing and SMT due to its structure. As an alternative to the disc type varistor, a laminated type varistor has been conventionally proposed (see, for example, Japanese Patent Publication No. 58-23921).

[0004]

However, although the above-mentioned conventional laminated varistor can be made compact and SMT, its voltage suppression capability is almost the same as that of the conventional disk varistor, so that it is not susceptible to noise intrusion. In some cases, semiconductor devices cannot be completely protected, and improvement in this respect is required. In addition, although the breakdown voltage of the semiconductor device varies depending on its type, in a MOS-IC or the like,
Many are destroyed at 40-60V. On the other hand, the voltage suppressing ability of the above laminated varistor is 2 to 3 times the varistor voltage,
Since the lower the varistor voltage, the larger the ratio, the suppression voltage is further increased by impulses such as static electricity, and as a result, the laminated varistor alone may not be protected.

Here, by adding a resistance to the laminated varistor, it is possible to obtain a voltage suppression capability higher than the actual value. In this case, if a resistance element is externally attached to the laminated varistor, the cost increases and the mounting space increases due to the increase in the number of elements. It is also conceivable to form a resistance film on the surface of the laminated varistor. However, in this case, the resistance film is easily damaged by an external mechanical load, resulting in deterioration of electrical characteristics and life characteristics. Occurs.

The present invention has been made in view of the above-mentioned conventional circumstances, and it is possible to improve the voltage suppressing ability to reliably prevent the semiconductor device from being damaged or malfunctioning due to noise, and further increase the cost and the mounting space. It is an object of the present invention to provide a noise filter capable of avoiding the above and avoiding deterioration of life characteristics.

[0007]

SUMMARY OF THE INVENTION Therefore, according to the present invention, the first and second side surface electrodes are formed on the first and second side surfaces of the semiconductor porcelain having the voltage non-linear characteristic, which face each other, and the third and third electrodes face each other. , Forming third and fourth side surface electrodes on the fourth side surface, burying the first internal electrode inside the semiconductor porcelain, and applying one end edge of the first internal electrode to one of the first and second side surface electrodes. A second internal electrode, which is connected to and overlaps with the first internal electrode with a ceramic layer sandwiched therebetween, is embedded inside the semiconductor porcelain, and both end edges of the second internal electrode are connected to the third and fourth internal electrodes.
A resistor which is connected to the side surface electrode and which overlaps the first internal electrode with a ceramic layer sandwiched therein is embedded in the semiconductor porcelain, and both end edges of the resistor are connected to the first and second side surfaces through lead electrodes. It is a noise filter characterized by being connected to electrodes.

Here, it is desirable to form a glass film on the surface portion of the semiconductor ceramic except the electrodes. This is because moisture resistance and oxidation resistance can be improved, leakage current can be reduced, and life characteristics can be improved.

Further, as a material forming the resistor, it is appropriate to use Ru as a main component, and particularly RuO ₂
It is desirable to mix with either Pb ₂ Ru ₂ O ₇ or Bi ₂ Ru ₂ O ₇ . This is because the resistance value can be easily controlled, and in addition, the resistance value can be set to a desired resistance value by appropriately changing the length, the area, and the number of laminated layers of the resistor. Also, the above Pb ₂ Ru ₂ O ₇ , Bi ₂ R
The amount of u ₂ O ₇ added is preferably up to 60 wt%. This is because if it exceeds this value, the resistance value varies. Further, as the ceramic material forming the above-mentioned semiconductor porcelain, it is suitable to use a material containing ZnO as a main component in consideration of the temperature during firing.

[0010]

According to the noise filter of the present invention, since the resistor is connected between the first and second side electrodes of the semiconductor porcelain with the lead-out electrode interposed therebetween, the voltage nonlinearity between the first and second inner electrodes is increased. While obtaining the characteristics, the resistor can obtain the voltage suppressing ability which is equal to or more than the actual value of the varistor, so that the destruction or malfunction of the semiconductor device due to the intrusion of transient noise can be surely prevented. Further, since the resistor is embedded inside the semiconductor porcelain, it is possible to avoid an increase in cost and an increase in mounting space when a resistance component is externally attached, and further, to form a resistance film on the surface of the semiconductor porcelain. of the case,
Damage due to external mechanical load can be avoided and life characteristics can be improved. Furthermore, in the present invention, the resistor is enclosed in the semiconductor porcelain, and the resistor is connected to the first and second side surface electrodes on the end face via the lead-out electrode. Therefore, when the glass film is formed on the semiconductor porcelain. It is possible to prevent the glass from diffusing into the resistor. As a result, it is possible to avoid variations in resistance value, and it is possible to obtain the resistance value as designed.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 4 are views for explaining a noise filter according to an embodiment of the present invention. In the figure, reference numeral 1 is a three-terminal type noise filter having the voltage non-linear characteristic, the capacitor characteristic, and the resistance characteristic of this embodiment. The semiconductor porcelain 3 of the noise filter 1 has a rectangular parallelepiped shape obtained by laminating a plurality of ceramic layers 2 containing ZnO as a main component and integrally sintering the laminated body. This semiconductor porcelain 3
On the left and right end faces (first and second side faces) 3a and 3b, end face electrodes (first and second side face electrodes) 4 and 4 made of Ag for external circuit connection are formed. Before,
At the central portions of the rear side surfaces (third and fourth side surfaces) 3c and 3d, side surface electrodes (third and fourth surface electrodes) also made of Ag for connecting an external circuit are formed.
Lateral electrodes 5 and 5 are formed.

Inside the semiconductor porcelain 3, Ag-
The first internal electrode 6 made of Pd alloy is embedded. One end edge 6a of the first internal electrode 6 is exposed at the left end surface 3a of the semiconductor porcelain 3 and connected to the end surface electrode 4, and the other end edge 6b is located inside the right end surface 3b of the semiconductor porcelain 3. It is enclosed in the semiconductor porcelain 3.

Further, inside the semiconductor porcelain 3, there is embedded a second internal electrode 7 which overlaps the first internal electrode 6 in parallel with the ceramic layer 2 interposed therebetween. Both end edges 7a, 7b of the second internal electrode 7 are exposed at the front and rear side surfaces 3c, 3d of the semiconductor porcelain 3 and connected to the side surface electrodes 5, 5, whereby the first and second internal electrodes 6 are formed. The ceramic portion sandwiched between the electrodes 7 and 7 is the ceramic layer 2 that exhibits a voltage non-linear characteristic. Further, although not shown, a glass film is formed on the outer surface of the semiconductor porcelain 3 excluding the left and right end surface electrodes 4 and the front and rear side surface electrodes 5.

Inside the semiconductor porcelain 3, R
A resistor 8 formed by mixing Pb ₂ Ru ₂ O ₇ and Bi ₂ Ru ₂ O ₇ in a predetermined amount in uO ₂ is embedded. The resistor 8 has the second internal electrode 7 with one ceramic layer 2 interposed therebetween.
It is arranged so as to overlap in parallel with. All the edges of the resistor 8 are located inside the end faces 3a, 3b and the side faces 3c, 3d, and are enclosed in the semi-conductive magnet 3. The resistor 8 is set to a predetermined resistance value by selecting its thickness and width.

Further, lead electrodes 9 are formed on the left and right outer edge portions 2a and 2b of the ceramic layer 2 on which the resistor 8 is formed. One end of the lead-out electrode 9 is connected to the end face electrode 4, and the other end is the left and right end edges 8 of the resistor 8.
a and 8b are connected. As a result, the resistor 8 is connected to the left and right end face electrodes 4 via the lead electrode 9.

Next, a method of manufacturing the noise filter 1 of this embodiment will be described. First, ZnO having a purity of 99% or more is used as a main component, and Bi ₂ O ₃ , CoCO ₃ , and MnO _{2 are} added to the main component.
And Sb ₂ O ₂ are 98mol%, 0.5mol%, 0.5mol
%, 0.5 mol%, and 0.5 mol% are weighed, pure water is added thereto, and they are mixed in a ball mill for 24 hours to form a slurry. Next, after filtering and drying this slurry and granulating,
Pre-baking is performed at a temperature of 800 ° C for 2 hours.

Next, the calcined product is roughly pulverized by a pulverizer, pure water is added thereto, and then 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. After this, this slurry was formed into a ceramic green sheet with a thickness of 50 μm by the doctor blade method,
This green sheet is punched into a predetermined size to form a plurality of ceramic layers 2.

Next, a conductive paste made of an Ag-Pd (7: 3) alloy is screen-printed on the upper surface of the ceramic layer 2 to form the first internal electrode 6. The first inner electrode 6 is formed so that only one end edge 6a thereof is located on the outer edge of the ceramic layer 2, and the other end edge 6b and the remaining end edge are located inside the ceramic layer 2. Further, a conductive paste is printed on the upper surface of another ceramic layer 2 to form the second internal electrode 7. This internal electrode 7 has both edges 7a, 7
b is located on both outer edges of the ceramic layer 2 in the longitudinal direction, and the remaining edges are located inside the ceramic layer 2. Furthermore, the left and right outer edges 2 of the upper surface of another ceramic layer 2
Similarly, a conductive paste is printed on a and 2b to form the lead electrode 9
To form.

Then, RuO ₂ is mixed with Pb ₂ Ru ₂ O ₇ and Bi ₂ Ru ₂ O ₇ in an amount of 0 to 60 wt%, and varnish is added to the mixture to prepare a resistance paste. The resistor 8 is formed by screen-printing on the upper surface of the formed ceramic layer 2. The resistor 8 is formed such that both end edges 8a and 8b of the resistor 8 slightly overlap the lead-out electrodes 9.

Then, as shown in FIG. 3, the respective ceramic layers 2 are stacked so that the first internal electrode 6 and the second internal electrode 7 face each other with the ceramic layer 2 ′ interposed therebetween. The ceramic layer 2 on which the resistor 8 is formed is stacked on the upper surface with the dummy ceramic layer 2 interposed therebetween, and a plurality of dummy ceramic layers 2 are stacked on the upper surface and the lower surface thereof. Then, a pressure of ² t / cm ² is applied in the stacking direction to press-bond the stack to form a stack.

Next, the above laminated body is cut into a predetermined size,
This is fired at a temperature of 900 ° C. for 2 hours to obtain a semiconductor ceramic 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. Thereby, a glass film is formed on the outer surface portion of the semiconductor porcelain 3. And finally, the left and right end faces 3a and 3b of the semiconductor porcelain 3 and the front and rear side faces 3c,
After applying Ag paste to the center of 3d,
It is baked for a minute to form the end face electrode 4 and the side face electrode 5.

The noise filter 1 of this embodiment has one end face electrode 4 and one side face electrode 5 as shown in the equivalent circuit diagram of FIG.
A power source is connected between the other end face electrode 4 and the side face electrode 5
The semiconductor device A is connected between and. As a result, an abnormal voltage is prevented from being applied to the semiconductor device A, and the overvoltage energy exceeding the voltage suppression capability of the varistor portion Z is absorbed by the resistor 8.

As described above, according to this embodiment, since the resistor 8 is added between the end face electrodes 4 of the semiconductor porcelain via the lead-out electrode 9, and the resistor 8 is embedded in the semiconductor porcelain 3, the semiconductor Even if noise larger than the breakdown voltage of the device A enters, it can be suppressed by the resistor 8, and as a result, the IC
It is possible to surely avoid breakage and malfunction of semiconductor devices such as LSIs and LSIs. Further, since the resistor 8 is built in the semiconductor porcelain 3, the component cost can be reduced and the mounting space can be reduced as compared with the case where the resistor component is externally attached, which corresponds to downsizing of computer equipment. it can. Further, compared with the case where a resistance film is formed on the surface of the semiconductor porcelain, damage due to an external force can be avoided and the life characteristics can be improved.

Further, in this embodiment, the semiconductor porcelain 3 is used.
The resistor 8 enclosed in the inside is connected to the end face electrode 4 via the lead-out electrode 9.
Since it is connected to, when the glass film is formed on the semiconductor porcelain 3, the glass can be prevented from diffusing into the resistor 8 and the fluctuation of the resistance value can be avoided.

[0025]

[Table 1]

Table 1 is for explaining the result of the test conducted to confirm the effect of the noise filter 1 of this embodiment. In this test, a sample No. 1 not covered with a glass film and a sample No. 2 covered with a glass film were prepared by the above-mentioned manufacturing method, and the resistance value (Ω) and varistor voltage (V) of both samples were prepared. _1mA ), non-linear coefficient (α), and capacitance value (pF),
Each variation was examined. Also, the variation is 3 CV
= Σ × 3 / average × 100% (σ indicates standard deviation).

As is clear from Table 1, according to the present embodiment, both Sample Nos. 1 and 2 have satisfactory values for varistor voltage, nonlinear coefficient, and capacitance. In addition, resistance values of 232 and 235 Ω were obtained, and the variation was as small as 4.3 and 4.7%. As a result, by embedding the resistor in the semiconductor porcelain and sintering it integrally,
It can be seen that it is possible to obtain a noise filter which does not change in varistor characteristics and permittivity, has small resistance variation, and has good coupling stability. Further, in the case of Sample No. 2 in which the semiconductor porcelain was coated with the glass film, the environment resistance against humidity and oxidation was improved, and the life characteristics were improved. By the way, when a square wave of 2 KV · 200 nSEC was applied to the resistors of the above samples using noise simulation, the change in the resistors was less than 2% in all cases.

FIG. 5 shows a pulse waveform when a circuit as shown in FIG. 4 is constructed by using the above sample and a high voltage pulse is applied thereto. As is clear from the figure, the sample of this example has a voltage of about 40 V, which is about 1/5 of that of the conventional varistor. From this point as well, it can be seen that the one having the built-in resistor has a high voltage suppressing ability and is effective in protecting the semiconductor device.

FIG. 6 is a diagram showing the frequency characteristics of the above sample. As is clear from this figure, excellent frequency characteristics are obtained, and it can be seen that the stray capacitance generated by the internal electrodes is small.

[0030]

As described above, according to the noise filter of the present invention, the first internal electrode is embedded inside the semiconductor porcelain, and the second internal electrode that overlaps with the ceramic layer is embedded. Since a resistor is embedded inside the resistor and both end edges of the resistor are connected to the end face electrodes (first and second side face electrodes) through the lead-out electrodes formed on the outer edge of the ceramic layer, the voltage suppressing ability is improved. As a result, it is possible to reliably prevent breakage and malfunction of the semiconductor device, reduce the number of parts and mounting cost, and avoid the deterioration of the life characteristics. Also, it is possible to avoid the fluctuation of the resistance value when diffusing the glass. There is an effect that the resistance value as designed can be obtained.

[Brief description of drawings]

FIG. 1 is a sectional view for explaining a noise filter according to an embodiment of the present invention.

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

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

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

FIG. 5 is a characteristic diagram showing the effect of the noise filter of the above-described embodiment.

FIG. 6 is a characteristic diagram showing the effect of the noise filter of the above-described embodiment.

[Explanation of symbols]

 1 noise filter 2 ceramic layer 3 semiconductor porcelain 3a, 3b left and right end faces (first and second side faces) 3c and 3d front and rear side faces (second and third side faces) 4 end face electrodes (first and second side face electrodes) ) 5 side surface electrodes (third and fourth side surface electrodes) 6 first inner electrode 6a one end edge 7 second inner electrodes 7a, 7b both end edges 8 resistors 8a, 8b both end edges 9 lead electrode

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yukio Sakabe 2 26-10 Tenjin Tenjin, Nagaokakyo-shi, Kyoto Murata Manufacturing Co., Ltd.

Claims (2)

[Claims] 1. A semiconductor porcelain having a voltage non-linear characteristic has first and second side electrodes formed on first and second side surfaces facing each other, and third and fourth side surfaces facing each other. 4 side surface electrodes are formed, a first internal electrode is embedded inside the semiconductor porcelain, one end edge of the first internal electrode is connected to one of the first and second side surface electrodes, and inside the semiconductor porcelain. A second internal electrode that overlaps the first internal electrode is embedded with a ceramic layer sandwiched in between, and both end edges of the second internal electrode are connected to the third and fourth side surface electrodes, and the ceramic is provided inside the semiconductor porcelain. A noise filter in which a resistor that overlaps the first internal electrode is embedded with a layer sandwiched in between, and both ends of the resistor are connected to the first and second side electrodes through lead electrodes. 2. The noise filter according to claim 1, wherein a surface portion of the semiconductor porcelain except for the first to fourth side electrodes is covered with a glass film.