JPH09134839A - Laminated ceramic passive device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a laminated ceramic passive device from being damaged even if an anomalous voltage is applied by a method wherein the total thickness of the uppermost layer and lowermost layer of a ceramic layer is set smaller than the thickness of a part of the ceramic layer sandwiched in between inner electrodes, and an insulating layer is formed on all the surface of a device except its outer electrodes. SOLUTION: Ceramic layers 1a, 2, and 1b and inner electrodes 3a and 3b are alternately laminated, and the one ends of the inner electrodes 3a and 3b are connected to the opposed outer electrodes 4 respectively. The total thickness of the uppermost and the lowermost ceramic layer, 1a and 1b, is set smaller than the thickness of the ceramic layer 2 sandwiched in between the inner electrodes 3a and 3b, and an insulating film 5 is formed on all the surface of a laminated ceramic passive device except the outer electrodes 4. The ceramic layers 1a, 1b, and 2 contain SrTiO3 as a main component or SrTiO3 where Sr is partially substituted with one or more elements selected out of Ca, Mg, and Ba, whereby the laminated ceramic passive device of this constitution can be possessed of the characteristics of both a capacitor and a varistor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention protects semiconductor devices such as ICs and LSIs and circuits of electronic devices and electric devices from abnormal high voltage such as noise, pulse and static electricity generated in electronic devices and electric devices and high frequency noise. The present invention relates to a monolithic ceramic passive element used for the purpose of

[0002]

2. Description of the Related Art In recent years, semiconductor devices such as ICs and LSIs have been widely used for electronic devices and electric devices in order to realize miniaturization and multifunctional functions. The withstand voltage against abnormally high voltage is low. Therefore, film capacitors, electrolytic capacitors, semiconductor ceramic capacitors, monolithic ceramic capacitors, etc. are used to ensure resistance to abnormally high voltages such as noise, pulses, and static electricity of these electronic devices and electric devices. It has excellent characteristics for absorbing and suppressing relatively low noise and high frequency noise, but it does not show its effect for high voltage pulses and static electricity, and may cause malfunction or destruction of semiconductor elements.

On the other hand, SiC and ZnO type varistors are used for absorbing and suppressing high voltage pulses and static electricity, but they are effective for absorbing and suppressing noise of relatively low voltage and high frequency noise. However, it may cause malfunction of the semiconductor element.

As a complement to these two drawbacks, JP-A-57-27001 and JP-A-57-35303 are known.
An SrTiO ₃ based varistor as disclosed in Japanese Patent Publication has been developed and used.

[0005]

Regarding the laminated SrTiO ₃ type varistor, various material compositions and manufacturing methods have been developed as shown in the above-mentioned conventional example, but in any case, the process is complicated. However, there was a problem in that the environment resistance was poor and the practical level was not reached. Also, the characteristics of the obtained device show its effect in absorbing and suppressing high voltage pulses and static electricity applied to the power supply line, but the problem that absorption and suppression of high frequency noise applied to the signal line is insufficient. Had.

The present invention solves the above-mentioned problems of the prior art. It is capable of absorbing and suppressing high-frequency noise applied to a signal line and does not break even when an abnormal voltage such as an electrostatic pulse is applied, and has environmental resistance characteristics, particularly humidity resistance. The object is to obtain a monolithic ceramic passive element having excellent properties.

[0007]

The laminated ceramic passive element of the present invention is provided with two internal electrode layers so that ceramic layers and internal electrode layers are alternately laminated, and each of the two internal electrode layers is provided. One end is connected to the opposing external electrode, the total thickness of the uppermost and lowermost ceramic layers is configured to be smaller than the thickness of the ceramic layers sandwiched by the internal electrode layers, and the surface of the element excluding the external electrodes An insulative film is formed on the entire surface, thereby achieving the initial purpose.

[0008]

According to the structure of claim 1 of the present invention, since there is only one ceramic layer sandwiched by the internal electrode layers of the monolithic ceramic passive element, the distance between the electrodes can be increased and the capacitance can be reduced. can do. Also, since the total thickness of the uppermost and lowermost ceramic layers of the monolithic ceramic passive element is smaller than the thickness of the ceramic layers sandwiched by the internal electrode layers, the voltage applied across the electrodes faces the internal electrodes of the element. The resistance of the element surface is increased by forming an insulative coating on the entire surface of the element except the external electrodes, and the element is provided between the opposing internal electrodes of the monolithic ceramic passive element. Can function.

Further, the effective electrode area can be changed according to the purpose of use by variously changing the shape of the internal electrode layer, and the electrostatic capacitance can be reduced by increasing the distance between the electrodes and decreasing the effective electrode area. You can

As a result, it is possible to increase the resonance frequency at which the noise attenuation rate is maximized as the electrostatic capacitance becomes smaller, and it is possible to absorb and suppress the high frequency noise riding on the signal line. Further, by varying the shape of the effective electrode surface, the amount of noise energy that can be absorbed can be adjusted without changing the electrostatic capacitance.

Further, the main component of the ceramic layer is SrTi.
O ₃ or part of Sr of the SrTiO ₃ is replaced with Ca, Mg,
By using Ba substituted with at least one element, it is possible to have characteristics of both a capacitor and a varistor, and even if an abnormal high voltage with a sharp rise such as an electrostatic pulse is applied by this. The element will not be destroyed.

(Embodiment 1) First, Sr is used as the first component.
CO_Three, CaCO_Three, TiO_Two(Sr_0.98Ca_0.02)
_0.995TiO_Three99.2 mol as the composition ratio of
%, Nb as the second component _TwoO_Five0.3 mol%, the third component
As MnCO_Three0.2 mol%, Cr_TwoO_Three0.1 mo
%, SiO as the fourth component_Two0.2 mol% is weighed,
Mix with 2OHr using a ball mill, crush and dry
After that, it was calcined in air at 800 ° C for 2 hours and then ball-milled again.
The average particle size is 1.0 μm or less after mixing and crushing 8OHr.
So that it is below. Butyler on the powder thus obtained
Organic resin and other organic binders and organic solvents
Sheet forming such as doctor blade method with rally shape
A green sheet 1 having a thickness of about 50 μm is obtained by the method.

Next, a predetermined number of the green sheets 1 are laminated to form a lowermost ineffective layer 1b shown in FIGS.
(0.4 mm thick) is formed, and an internal electrode 3a made of Pd or the like in which one of the electrodes is rectangular is printed by screen printing or the like and dried, and the green layer for the effective layer 2 is further formed thereon. Lay a specified number of sheets 1 to 1.2
After the thickness is set to mm, the internal electrode 3b having a triangular shape whose bottom is a portion where the other electrode made of Pd or the like is connected to the external electrode is printed and dried by screen printing or the like. At this time, printing is performed so that the internal electrodes 3a and 3b face each other and reach different edges. Finally, a predetermined number of the green sheets 1 are stacked to form the uppermost invalid layer 1a (0.4 mm
(Thickness), pressurize and press-bond while heating, and cut into a predetermined shape.

Next, defatting calcining is performed in air at 800 ° C. for 20 hours, and for example 121 in a reducing atmosphere of N ₂ : H ₂ = 9: 1.
After baking for 10 hours at 0 ° C, 2 hours at 930 ° C in air
Reoxidize. After that, a paste for the external electrode 4 made of Ag or the like is applied to both end surfaces of the internal electrodes 3a and 3b exposed at different edges, and the paste is baked in air at 700 ° C. for 10 minutes. Then, an electrically insulating substance 5 made of epoxy resin or the like is applied to the entire surface of the element except the external electrode,
Heat at 30 ° C. for 30 minutes to cure.

Next, the external electrode 4 is formed on the external electrode 4 paste by, for example, Ni plating and solder plating by an electrolytic method.

The shape of the monolithic ceramic passive element shown in this embodiment is W3.20 mm × D1.60 mm × T2.
It is called a 1 × 3 type formed to a size of 00 mm. The initial characteristics and reliability test results of the monolithic ceramic passive element thus obtained are shown in (Table 1).

[0017]

[Table 1]

Regarding the electrical characteristics of (Table 1), the voltage applied across the element when a current of 0.1 mA flows through the monolithic ceramic passive element is represented by V _{0.1 mA} , and the capacitance and tan δ are 1 kHz. The measured value is shown. Also, for the reliability test, 85 ° C, 85RH%, charge rate 90
%, The rate of change after 500 hours is shown. Here, the charge rate is a value obtained by dividing the voltage applied to the element by the initial V _{0.1 mA} of the element.

(Second Embodiment) A second embodiment will be described below with reference to FIGS. 3 and 4. In the same manner as in Embodiment 1, the internal electrode layers 3a and 3b have a triangular shape whose bases are the portions where both electrodes are connected to the external electrodes. After applying an organic resist, it is dried, and the laminated ceramic passive element is dipped in a coating agent composed of an alkoxide solution containing Si as a main component, pre-dried at 100 ° C., and then immersed in an organic solvent such as toluene. The resist is dissolved and removed, and then baked at 250 ° C. for 10 minutes to form coatings 6a and 6b.

Next, Ni is formed on the external electrodes by, for example, an electrolytic method.
Plating Further solder plating is applied. The results of the initial characteristics and the reliability test of the monolithic ceramic passive device thus obtained are shown in (Table 2). Further, in FIG. 3, 6a and 6b are coating films formed by a coating agent.

[0021]

[Table 2]

In the first and second embodiments, the composition of the ceramic powder is shown only for some combinations.
Any composition may be used as long as it has SrTiO ₃ as a main component and functions as both a capacitor and a varistor. Further, the ineffective layers 1a and 1b and the effective layer 2 are formed by laminating thin sheets, but one thick sheet may be formed.

Although the electrically insulating substances shown in the first and second embodiments are shown only for some kinds, any substance may be used as long as it has an electrically insulating property.

Further, the internal electrode 3 shown in the first and second embodiments.
The a, 3b and the external electrode 4 may be not only a noble metal such as Pd or Ag, but also a base metal such as Cu, Ni or Cr, an oxide of a base metal, or a mixture thereof.

[0025]

As described above, according to the present invention, the ceramic layers and the internal electrode layers of the monolithic ceramic passive element are alternately laminated, and only one ceramic layer is sandwiched between the internal electrode layers. By forming an electrically insulative coating on, the interelectrode distance can be maximized and the capacitance can be reduced.

Also, by making the total thickness of the uppermost and lowermost ceramic layers of the monolithic ceramic passive element smaller than the thickness of the ceramic layers sandwiched by the internal electrode layers, the voltage applied across the electrodes is Although it will be applied between the external electrodes facing the internal electrodes, the resistance of the element surface is increased by forming an insulating coating on the entire surface of the element excluding the external electrodes, so that the multilayer ceramic passive element The device can function between the internal electrodes facing each other.

Further, the effective electrode area can be easily changed according to the purpose of use by variously changing the shape of the internal electrode layer, and the electrostatic capacitance can be reduced by increasing the distance between the electrodes and decreasing the effective electrode area. can do.

As a result, it is possible to increase the resonance frequency at which the noise attenuation rate is maximized as the electrostatic capacitance becomes smaller, and it is possible to absorb and suppress the high frequency noise riding on the signal line. Further, by varying the shape of the effective electrode surface, the amount of noise energy that can be absorbed can be adjusted without changing the electrostatic capacitance.

Further, the main component of the ceramic layer is SrTi.
O ₃ or part of Sr of the SrTiO ₃ is replaced with Ca, Mg,
By using a material in which at least one element of Ba is substituted, both characteristics of the capacitor and the varistor can be provided. This prevents the element from being destroyed even when an abnormal voltage such as an electrostatic pulse having a sharp rise is applied. Further, by decreasing the effective electrode area, the current density is increased, so that α can be increased, and tan α can be decreased to reduce the limiting voltage, and at the same time, the surge resistance and energy resistance can be increased.

[Brief description of the drawings]

FIG. 1 is a sectional view showing the structure of a monolithic ceramic passive element according to Embodiment 1 of the present invention.

FIG. 2 is a plan view showing the shape of internal electrodes according to the first embodiment.

FIG. 3 is a sectional view showing the structure of a monolithic ceramic passive element according to Embodiment 2 of the present invention.

FIG. 4 is a plan view showing the shape of internal electrodes according to the second embodiment.

[Explanation of symbols]

 1 Green Sheet 1a Top Ineffective Layer 1b Bottom Ineffective Layer 2 Effective Layer 3a Internal Electrode 3b Internal Electrode 4 External Electrode 5 Insulating Film

Claims (11)

[Claims] 1. Two internal electrode layers are provided so that ceramic layers and internal electrode layers are alternately laminated, and one end of each of the two internal electrode layers is connected to an opposing external electrode,
The total thickness of the uppermost and lowermost ceramic layers is configured to be smaller than the thickness of the ceramic layers sandwiched by the internal electrode layers, and an insulating coating is formed on the entire surface of the element excluding the external electrodes. A monolithic ceramic passive element. 2. The internal electrode layer has a shape of a rectangle in which one electrode is connected to an external electrode at one end, and a triangle whose base is a portion where the other electrode is connected to the external electrode facing the external electrode. The monolithic ceramic passive device according to claim 1, wherein 3. The shape of the internal electrode layer is a rectangle in which one electrode is connected to the external electrode at one end, and the other electrode is connected to the external electrode opposite to the external electrode with the bottom as the base. The monolithic ceramic passive element according to claim 1, wherein the two sides are substantially triangular and each has a curved line inward. 4. The shape of the internal electrode layer is a rectangle in which one electrode is connected to an external electrode at one end, and the other electrode is connected to the external electrode opposite to the external electrode with the base being the other portion. The monolithic ceramic passive element according to claim 1, wherein the two sides are substantially triangular and each has a curved line that curves outward. 5. The monolithic ceramic passive element according to claim 1, wherein the shape of the internal electrode layer is a triangle whose base is a portion where both internal electrodes are connected to respective external electrodes facing each other. 6. The shape of the internal electrode layer is a substantially triangular shape in which a portion where both internal electrodes are connected to respective external electrodes facing each other is a base and the other two sides are curved curves inward. A laminated ceramic passive device as described. 7. The shape of the internal electrode layer is a substantially triangular shape in which a portion where both internal electrodes are connected to respective external electrodes facing each other is a base and the other two sides are curved lines that curve outward. A laminated ceramic passive device as described. 8. The shape of the internal electrode layer is a triangle whose base is a portion where one electrode is connected to the external electrode, and the other two sides are internal when the portion where the other electrode is connected to the external electrode is a base. The monolithic ceramic passive element according to claim 1, wherein the monolithic ceramic passive element has a substantially triangular shape with a curved line. 9. The shape of the internal electrode layer is a triangle whose base is a portion where one electrode is connected to the external electrode, and the other side is an external portion where the base is a portion where the other electrode is connected to the external electrode. The monolithic ceramic passive element according to claim 1, wherein the monolithic ceramic passive element has a substantially triangular shape with a curved line. 10. The shape of the internal electrode layer is a substantially triangular shape having a curve in which one electrode is connected to the external electrode as a base and the other two sides are curved inward, and the other electrode is connected to the external electrode. 2. The monolithic ceramic passive device according to claim 1, wherein the laminated ceramic passive element has a substantially triangular shape with the curved portion being the outer side and the other two sides being curved outward. 11. The main component of the ceramic layer is SrTiO ₃
Alternatively, a part of Sr of this SrTiO ₃ is replaced by Ca, Mg, B
11. The monolithic ceramic passive element according to claim 1, wherein the monolithic ceramic passive element is substituted with at least one element of a and has characteristics of both a capacitor and a varistor.