JPS6184815A - Ceramic capacitor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a ceramic capacitor, and particularly to a highly reliable ceramic capacitor that prevents deterioration of insulation resistance due to openings at high temperatures.

(Prior Art) In recent years, as electronic components have become smaller and lighter, ceramic capacitors have also been pursued to be smaller and lighter. In particular, with regard to ceramic capacitors, in parallel with the progress in miniaturization, consideration is being given to increasing the population, and 'al19' is being attempted as a means of achieving this.

The following improvement methods can be considered as means for reducing the thickness of ceramic capacitors.

■Vacuum such as sputtering method, vacuum evaporation method, ion blating method, vapor phase evaporation method? A method of forming a thin dielectric ceramic layer using iJ film forming means.

■A method of making the dielectric ceramic layer as thin as possible by microcrystallizing the dielectric ceramic material.

■A method to obtain a grain boundary insulated dielectric ceramic layer by forming an insulating layer at the grain boundaries of a thin semiconductor ceramic layer.

(2) Among the methods (2) to (3) above, there is a method in which internal electrodes are formed between a plurality of dielectric ceramic layers to form a laminated ceramic capacitor to further increase the capacitance.

(Problems to be Solved by the Invention) However, after thinning the dielectric ceramic layer by the above method, electrodes for taking out the capacitance can be formed by sputtering, vacuum evaporation, ion blating, or vapor phase evaporation. Alternatively, when a ceramic capacitor is formed by electroless plating, various troubles occur. Particularly noticeable is insulation 1 when used at high temperatures.
This is a deterioration of self-reliance.

The biggest cause of this trouble is that the dielectric ceramic is made of a metal oxide, and the electric wire is made of a metal.

However, with such a combination, it is conceivable that exchange of oxygen inevitably occurs at the interface where the metal oxide constituting the dielectric ceramic and the metal constituting the electrode are in contact with each other.

Exchange of oxygen is difficult to be observed at room temperature, but as the temperature rises, exchange of V element begins to take place.

For example, to explain a ceramic capacitor in which the dielectric ceramic is TiO2 and the electrodes are Cu, at a high temperature, for example 150"C, Ti○2I-3
and Cu change as follows.

When oxygen exchange occurs between the dielectric ceramic and ?E, ffl in this way, the dielectric constant (ε) of the dielectric ceramic
Of course, the insulation resistance ([R) changes significantly, and its value generally decreases by two orders of magnitude or more.

Such a phenomenon becomes particularly noticeable when the dielectric ceramic layer is made thinner, and applies to the ceramic capacitors obtained by the above-mentioned improvement means (1) to (2) for making the ceramic capacitor thinner.

(Purpose of the Invention) Therefore, the present invention provides a highly reliable ceramic capacitor that does not cause changes in dielectric constant or deterioration of insulation resistance by having a structure in which the dielectric ceramic does not become binary when used at high temperatures. The purpose is to

(Structure of the Invention) In other words, the present invention provides a ceramic capacitor characterized in that a nickel oxide layer is interposed between a dielectric ceramic and an external connection electrode formed on the surface of the dielectric ceramic. It is.

Here, dielectric ceramics include those based on high dielectric constants such as barium titanate and strontium titanate, and those based on titanium oxide, magnesium titanate, magnesium oxide-titanium oxide, and silicon oxide. These include temperature-compensated ceramics such as 9-9, and grain-boundary insulated dielectric ceramics in which the grain boundaries of semiconductor ceramics are made into insulators.

Further, when the thickness of the dielectric ceramic is 50 μm or less, the effect becomes stronger when a nickel oxide layer is interposed between the electrodes for connecting the Wffi body ceramic part. In other words, if the thickness of the dielectric ceramic exceeds 50 μm, even if the dielectric ceramic is reduced by the electrode during high-temperature use, the dielectric ceramic is thick enough to cause changes in the dielectric constant and insulation resistance. Deterioration does not appear significantly -0 Therefore, as the dielectric ceramic according to the present invention, it is particularly effective for dielectric ceramics having a thickness of 50 .mu.n1 or less. However, there is no problem in applying the present invention to a dielectric ceramic having a thickness exceeding 50 μm, and it is optional to interpose a nickel oxide layer between the dielectric ceramic and the external connection electrode.

As a method for forming the nickel oxide pattern, a thin film forming method such as sputtering, ion blating, vacuum evaporation, vapor phase evaporation, or electroless plating is used. When forming the nickel oxide layer by sputtering, for example, metal nickel can be used as a target and the atmosphere during sputtering can be a mixed gas of argon and oxygen. J: When forming a nickel oxide layer using a vacuum evaporation method, the nickel oxide layer can be formed, for example, by heating metal nickel or metal nickel powder and evaporating it in an oxygen-containing atmosphere.

Furthermore, in the case of a vapor phase deposition method or an electroless plating method, after forming a nickel layer, a nickel oxide layer can be formed by thermal oxidation.

The thickness of this nickel oxide layer is preferably 2 μm or less. This is E when it exceeds 2 μm.
This is because S and R become high.

The type of metal used for the external connection electrode is not particularly limited, and commonly used metals such as Aq,
Au, Cr, Zr, V, Ni, Zn, Cu, S
n, Pb-3n, Mn, Mo, W, Ti, P(1, AN
One type or a combination of two or more types such as 1! Moreover, this external connection electrode may have a multilayer structure, examples of which include Cr-Cu, Cr-Ni-Δ9, and the like.

Moreover, the ceramic capacitor according to this invention (, +4
Examples include ceramic capacitors made of a single layer of dielectric ceramic, and multilayer ceramic capacitors. This invention is also applied to the case where the various ceramic capacitors described above are of the grain boundary insulation type.

(Example) This invention will be described in detail below according to Examples.3゜Example 1゜Reramic dielectric raw material (f)) The following composition was prepared as Q@.

Nd2Ti207: 63 mol%, 3a Ti
03: 14 mol%, T'! 02: 23 mol%
This raw material water 5) powder was mixed with polyvinyl alcohol as a binder, a surfactant, a dispersant, and water to create a slurry. Then, using this slurry, a ceramic green sheet with a thickness of 35 μm was created by a doctor blade method.

This ceramic green sheet has a length of 7.0 mm and a width of 5 mm.
．． Cut into 0ml size and place A 0 on this sheet.
A (+-Pd paste) of 70 wt% and 630 wt% of P was printed.

Eleven ceramic green sheets with internal electrodes formed in this manner were stacked so that the internal electrodes were exposed at the end faces of the ftf<FFp body. This laminate is placed in the air,
A sintered unit was obtained by firing at 1250°C. The thickness of each dielectric layer of the obtained laminate was 20 μm.

Next, a nickel oxide layer was first formed by sputtering on the end face of this laminated sintered unit where the internal electrodes were exposed.

This nickel oxide layer was formed under the following conditions.

Sputtering atmosphere: argon containing 0% oxygen Pressure crab 2xlOTorr Target: Nickel plate with a diameter of 5 inches and a thickness of 2 mm. Voltage: 500VD, C.

Current: 2. OA sputtering time = 5 minutes Film thickness of nickel oxide layer: 2000A Subsequently, N i Fj as a solder heat-resistant layer was first formed on the nickel oxide layer as a first layer of external connection electrode by a sputtering method.

This Ni layer was formed under the following conditions.

Sputtering atmosphere: argon =3 Pressure crab 2xlOTorr Target: Straight (¥5 inch, 2mm thick nickel plate) Voltage: 480VD, C.

Current: 2. OA time: 15 minutes Membrane weight: 5000A Furthermore, A was added as a second layer external connection electrode on the Ni layer.
The g layer was formed by sputtering.

This 〇 layer can be soldered (it plays a role as a layer that can be soldered).

The Aq layer was formed for 1j under the following conditions.

Sputtering atmosphere: Argon pressure 2x10 Torr Target: Aq plate with a diameter of 5 inches and a thickness of 5 mm Lightning pressure:
540VD, C.

Current: 2. OA time: 6 minutes Film E: 1 μm A high temperature accelerated load life test was conducted on the multilayer capacitor obtained through the above steps under the following conditions.

That is, this capacitor was placed in a temperature atmosphere of 150° C., a voltage of 300 V, which is six times the rated voltage (<50 V), was applied, and the insulation resistance (IR) after 100 hours was measured to be 10 Ω. By the way, the initial value of this multilayer capacitor's insulation resistance <IR) is 1011Ω.
Met. In addition, when installed in an atmosphere with a temperature of 45°C and a relative humidity of 95%, and applying a rated voltage of 50V, the edge resistance (lR) of the rod after being pulled for 500 hours was measured and was 10 Ω.
No change was observed compared to the initial value.

Comparative Example 1 Without forming a nickel oxide layer on the fIVr sintered unit obtained in Example 1, under the same conditions as Example 1, the N1 layer and the second layer were An ACl layer serving as an electrode for external connection was formed to create a multilayer capacitor.

When this multilayer capacitor was tested in the same manner as in Example 1, the insulation resistance (IR) was 9 for 10 hours.
After ε, it decreased to 10 Ω, and after 25 hours it deteriorated to 10 Ω.

Example 2 SrTiOs: 99.3 mol%, Y2O
Each component was weighed so as to have a composition of n: 0.3 mol%, 5i02: 2 mol%, and A: 0.2 mol%, and 10% of the paid binder was added to the weighed raw materials.
(Added mass % and rotated in a ball mill for 16 hours to thoroughly mix and pulverize. After granulation, 1000 kg/
It was molded at a pressure of cm2 to form a disc-shaped molded product. This molded body was fired at 1350° C. for 2 hours. Metal oxides such as PB and 3I are applied to the surface of the controlled porcelain,
A heat treatment was performed at a temperature of 1000 to 1200°C to convert the grain boundaries of the porcelain into an insulator, thereby creating a grain boundary insulated semiconductor 11ti ceramic body. This semiconductor also uses a U-type element body, and a nickel oxide layer is formed on its surface by the same method as in Example 1.
An electrode for external connection of the layer and an electrode for external connection of the second layer were formed to produce a grain boundary insulated semiconductor ceramic capacitor.

This capacitor was subjected to the high temperature accelerated load life test described in Example 1. As a result, the initial value of insulation resistance (I
While R) was 100, it was +o'oO after 100 hours, confirming that there was almost no deterioration in insulation resistance (IR>).

Comparative Example 2 Using the grain boundary insulated semiconductor porcelain body obtained in Example 2, the first test was conducted under the same conditions as Example 1 without forming a nickel oxide layer on the surface of this VTI device body. The N1 layer is the external connection electrode of the layer and the Aft is the external connection electrode of the second layer.
A grain boundary insulated semiconductor ceramic capacitor was fabricated by forming layers.

When this capacitor was tested in the same manner as in Example 1, the insulation resistance (IR) decreased to 1070 after 10 hours, and deteriorated to 10Ω after 25 hours.
.

Example 3 On an alumina substrate, an Ag layer and an N1 layer were successively formed as a lower electrode in the same manner as in Example 1, and a nickel oxide layer was also formed in the same manner as in Example 1.

Next, a dielectric ceramic 3i02 film was deposited on the nickel oxide layer at 5000A by high-frequency sputtering.
It was formed to a thickness of .

The conditions for forming the SiO2 film by high frequency sputtering are as follows.

Sputtering atmosphere: Argon pressure crab containing 5% oxygen 5x10 Torr Target: quartz plate with a diameter of 5 inches and a thickness of 5 mm 500 W Time: 100 minutes 3i02 film thickness: 5000 yen, then oxidize on the 3i02 film Example 1 of the nickel layer
is formed by the same method as above, and furthermore, an N1 layer and an A layer are formed on it.
Is the C1 layer the same as in Example 1? Sequentially formed by
A thin film capacitor made of iO2 was created.

The high temperature accelerated load life test described in Example 1 was conducted on this capacitor. As a result, the initial (direct insulation resistance (I)
R) was 10 Ω and I was 10 Ω after 100 hours.

Comparative Example 3 In making the i-film capacitor according to Example 3,
By carrying out the method described in Example 3 for the (l!!) without forming a nickel oxide layer, a 1%
Created a capacitor.

When this capacitor was tested in the same manner as in Example 1, the insulation resistance was as high as 108Ω.

(Effect) As mentioned above, this light [! According to No. 11, by interposing a nickel oxide layer between the dielectric ceramic and the external 1&connection electrode, it is possible to prevent the dielectric ceramic from becoming binary due to electrical action during high-temperature use. As a result, the electrical characteristics deteriorate, especially the insulation resistance. This has the effect that there is no such thing.

VIh+ Applicants Murata Manufacturing Co., Ltd.

Claims (6)

[Claims] (1) In a ceramic capacitor including a dielectric ceramic and an external connection electrode formed on a surface of the dielectric ceramic, a nickel oxide layer is formed between the dielectric ceramic and the external connection electrode. A ceramic capacitor characterized by: (2) A first external connection electrode is formed on the substrate, a dielectric ceramic is formed on the first external connection electrode, and a second external connection electrode is formed on the dielectric ceramic. In the ceramic capacitor formed, a nickel oxide layer is formed between the dielectric ceramic and the first external connection electrode and the second external connection electrode, as described in claim (1). ceramic capacitor. (3) A laminated dielectric ceramic element body consisting of multiple layers of dielectric ceramic and multiple layers of internal electrodes that are stacked on top of each other via the dielectric ceramic to form capacitance. In a laminated ceramic capacitor in which a pair of external connection electrodes for taking out capacitance are connected to predetermined ones of the internal electrodes, the dielectric ceramic body and the external connection electrodes are formed. A nickel oxide layer is formed between the
Ceramic capacitor described in section 1). (4) The ceramic capacitor according to claims (1) to (3), wherein the dielectric ceramic has a thickness of 50 μm or less. (5) The ceramic capacitor according to claims (1) to (3), wherein the nickel oxide layer has a thickness of 2 μm or less. (6) Claim (1) wherein the external connection electrode is formed by any one of sputtering, vacuum evaporation, ion plating, vapor phase evaporation, or electroless plating. ~Ceramic capacitor according to item (3).