JPH04317311A - Laminated ceramic capacitor - Google Patents

Abstract

PURPOSE:To provide a copper group inside electrode material for a plumbum group composite perovskite type laminated ceramic capacitor which is so improved as to provide an excellent quality laminated capacitor in which electrode cutting is not produced at a high coating rate and electrostatic capacitance is greater due to a greater occupation area and the like, and the plumbum group composite perovskite type laminated ceramic capacitor with employment thereof. CONSTITUTION:An electrode material includes an alkali earth metal oxide or a compound producing the alkali earth metal oxide at 0.01 to 10wt.% with respect to copper of a main component in terms of the alkali earth metal oxide. Further, a laminated ceramic capacitor has an inside electrode comprising the electrode material and plumbum group composite perovskite is used as a dielectric.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention is a lead-based composite perovskite that has been improved to provide a multilayer capacitor of excellent quality, such as high coverage, no electrode breakage, and large capacitance due to a large footprint. The present invention relates to a copper-based internal electrode for a multilayer ceramic capacitor and a lead-based composite perovskite multilayer ceramic capacitor having the same.

0002

[Prior Art] Lead-based composite perovskites, such as Pb(
Sintered bodies of Mg1/3Nb2/3)O3-PbTiO3 have excellent electrical properties such as bias characteristics and high dielectric properties, so they are used as materials for electronic components such as piezoelectric element materials and capacitor materials. (Unexamined Japanese Patent Publication No. 2-9756
Among them, many multilayer ceramic capacitors using lead-based composite perovskite as a dielectric material are known to use copper-based materials for internal electrodes. Examples of this copper-based material include copper or copper alloy (Japanese Unexamined Patent Publication No. 62-11
5817, JP-A-62-128513),
A copper internal electrode containing a lead oxide, at least one oxide selected from Nb, Ta, and W, and a copper oxide (Japanese Patent Application Laid-Open No. 115817/1983) is known. ing.

By the way, when manufacturing a multilayer capacitor using this lead-based composite perovskite as a dielectric and a copper-based material as an internal electrode, prior to the firing process, a removal process is performed to burn out the binder added during ceramic molding. Binder processing is required. At that time, when general copper is used for the internal electrodes, an oxidizing atmosphere is effective if only the binder is removed, but copper is extremely easy to oxidize in this oxidizing atmosphere, so during burnout, copper oxide , which diffuses into the dielectric material and causes quality deterioration.
Furthermore, in order to avoid such inconveniences, if burnout is performed in a reducing atmosphere that does not oxidize copper, the decomposition of the binder will be insufficient, resulting in generation of residual carbon. Furthermore, during firing, a reducing atmosphere is used to prevent copper from oxidizing, but at this time, the lead oxide that volatilizes due to the influence of residual carbon is reduced to metallic lead, which furthermore has a low melting point in coexistence with copper. As a result, the internal electrode melts during firing, causing some electrode breakage, resulting in a reduction in the coverage of the dielectric material of the electrode, and many other problems.

In order to solve these problems, many methods have been proposed in which copper oxide is used instead of copper as a raw material for internal electrodes, burnout is performed in air, and then reduction treatment is performed to form copper electrodes. (Japanese Unexamined Patent Application Publication No. 62-2033)
No. 21, JP-A-63-15407, JP-A-6
3-15408, JP 63-250809, JP 63-254714, JP 63-2
65411, JP-A-64-89311).

Although these methods are extremely effective in achieving complete burnout, they are accompanied by shrinkage of the internal electrodes during the reduction process, resulting in poor contact with the dielectric material, which leads to static electricity This has the disadvantage of causing variations in capacity.

On the other hand, a method has also been proposed in which copper alloy is used for the internal electrodes to reduce the oxidation of copper oxide (Japanese Unexamined Patent Application Publication No. 1983-1982).
210611), copper alloys have a large specific resistance, which impairs copper's desirable characteristic of low specific resistance, and also has the disadvantage of inevitably increasing costs.

[0007] Furthermore, in order to prevent copper oxide from diffusing into the dielectric as described above, a method has been proposed in which a lead-based dielectric material is contained in the internal electrode to selectively trap copper oxide. (Japanese Unexamined Patent Publication No. 2-62023), this is because if the atmosphere during firing is properly controlled, copper oxide will not be generated, and therefore the diffusion of copper oxide into the dielectric can be prevented. There's no need to do it.

[0008]

Problems to be Solved by the Invention The present invention provides a method for manufacturing a multilayer ceramic capacitor using a lead-based composite perovskite as a dielectric and copper as an internal electrode.
It overcomes the drawbacks such as a decrease in dielectric constant due to residual carbon, a short life due to diffusion of copper oxide, and variations in capacitance due to shrinkage of internal electrodes, and also has a high coverage ratio without causing electrode breakage, allowing for a large occupancy. This was done with the aim of obtaining a copper-based internal electrode material that can provide a multilayer capacitor of excellent quality such as a large capacitance due to area, and a lead-based composite perovskite multilayer ceramic capacitor having the internal electrode. .

[0009]

[Means for Solving the Problems] In order to develop a multilayer ceramic capacitor having the above-mentioned preferable characteristics, the present inventors have conducted various studies on improving the physical properties of the copper-based internal electrodes, and as a result, they have found that Focusing on the fact that lead oxide can be stabilized by including a compound with a low standard free energy of formation, that is, a stable compound in the form of an oxide, or the oxide itself in the internal electrode, after various studies, the dielectric material When a copper-based internal electrode containing a predetermined amount of alkaline earth metal oxide is incorporated into a predetermined capacitor, no copper oxide remains in the electrode, even if the carbon contains about 300 ppm of residual carbon, and It was discovered that volatilized lead oxide was not reduced to metallic lead, and the present invention was developed based on this finding.

[0010] That is, in the present invention, for copper as the main component,
An alkaline earth metal oxide or a compound capable of producing an alkaline earth metal oxide has an alkaline earth metal oxide equivalent of 0.
A copper-based internal electrode material for a lead-based composite perovskite type multilayer ceramic capacitor characterized by containing 01 to 10% by weight, and a copper-based internal electrode made of this material,
The present invention provides a multilayer ceramic capacitor characterized by using a lead-based composite perovskite as a dielectric.

In the internal electrode material of the present invention, copper is the main component, and an alkaline earth metal oxide or a compound capable of producing it (hereinafter referred to as an alkaline earth oxide, etc.) is contained within the above-mentioned range. It is necessary to contain it.

If the ratio of alkaline earth oxides, etc. to copper is less than 0.01%, the desired effect cannot be obtained sufficiently, and if it exceeds 10%, the resistance value of the internal electrode increases, and copper This may cause damage to the excellent characteristics of low resistivity that the metal has.

The present invention also includes a multilayer ceramic capacitor having internal electrodes made of the above-mentioned electrode material and using a lead-based composite perovskite as a dielectric.

[0014] The lead-based composite perovskite used as the dielectric for the multilayer ceramic capacitor basically has the composition of the formula Pb(Mg1/3Nb2/3)O3-PbTiO3, but other than this, In the composition, Ca atoms are introduced into some of the Pb atoms in the A site component, Ni, W, Fe, etc. in the B site component,
A combination of Mg, Nb, and Mn so that the average valence is tetravalent, etc., or a material containing an alkaline earth metal oxide, copper oxide, lead silicate, etc. in addition to these may also be used. Can be done.

To manufacture the multilayer ceramic capacitor of the present invention, metal oxides such as PbO, MgO,
Necessary oxides such as Nb2O3, TiO2, CaO, and PbSiO3, or compounds that can produce these oxides when fired, are mixed in powder or granule form at a ratio that will give the final desired composition, and calcined. After pulverizing the calcined product, it is molded into the desired shape, dried, burnout is performed in a non-oxidizing atmosphere to remove the binder, and then finally fired in a non-oxidizing atmosphere with controlled oxygen partial pressure. Manufactured by. During this firing, it is also possible to coat the fired body with a commercially available copper paste as an external electrode and bake it in an inert atmosphere such as nitrogen, or to simultaneously fire the external electrode.

The above molding is carried out by adding a binder such as an acrylic acid (ester) binder, and the non-oxidizing atmosphere is an inert atmosphere such as nitrogen or argon, or carbon monoxide, A reducing atmosphere containing a gas having a reducing action such as hydrogen is used, and a hydrogen-containing atmosphere is preferred. In the final firing treatment, the oxygen partial pressure is controlled within the range of 10-4 to 10-12 atm, preferably 10-6 to 10-10 atm. The firing temperature is usually 900-1000°C, preferably 920-900°C.
The temperature is selected within the range of 50°C.

[0017] When firing at a temperature higher than 900°C under conditions where the oxygen partial pressure is lower than 10-12 atmospheres, a large amount of oxygen is released and oxygen vacancies are created in the resulting ceramic capacitor, resulting in a decrease in insulation resistance over time. cause a decline in
Sufficient reliability cannot be ensured.

The non-oxidizing atmosphere is used because it is necessary to perform burnout without oxidizing copper, which is the main component of the internal electrodes. In addition to hydrogen, carbon monoxide and hydrocarbons are also known as gases that have a reducing effect, but since these are the same gases that are generated when organic matter is burned, an atmosphere containing them is Under these conditions, the decomposition reaction of the binder is inhibited and residual carbon increases.

The hydrogen-containing atmosphere usually contains an inert gas such as nitrogen and water vapor, so that the hydrogen concentration is appropriately diluted, usually 0.01 to 1000 ppm, preferably 5.
The concentration is adjusted to 0 to 200 ppm. If this is done, the hydrogen concentration will become too low and the reducing action will be significantly reduced, making the prevention of copper oxidation incomplete, causing some oxidation of the copper, and as a result of the progress of diffusion of copper oxide during firing, the electrode Partially disappears, resulting in a lack of capacitance, or hydrogen concentration becomes too high, reducing the lead-based dielectric material to lead, reducing insulation resistance and no longer functioning as a capacitor. There is nothing to do.

[0020] The water vapor suppresses the change in oxygen partial pressure when the hydrogen concentration increases due to the chemical equilibrium between hydrogen and water, and suppresses the change in oxygen partial pressure when the hydrogen concentration increases, and also suppresses the residual carbon generated by hydrocarbons contained in the binder and burnout. It has the effect of promoting the removal of. For example, hydrocarbons and carbon react with water vapor according to the reaction formula shown below, become a gas, and diffuse out of the system.

[Chemical formula 1]

By the way, regarding lead-based perovskite,
Observing its thermal behavior using a thermobalance, it shows that it loses weight in the presence of hydrogen and precipitates metallic lead, but this phenomenon is
It is recognized only when the weight decreases by 2% by weight or more, and not when the weight decrease is less than that. and,
This weight loss is reversible, returning to the original weight increasing the oxygen partial pressure, and with significantly less carbon remaining in the reduced weight state.

[0022] Such a phenomenon is not observed in oxides such as alumina and barium titanate, and is completely unique to lead-based composite perovskites, but reduction occurs easily in the presence of residual carbon. Therefore, when using copper as the internal electrode, it was necessary to suppress the amount to 100 ppm or less, but when using the copper-based internal electrode of the present invention, even if this amount increases to 300 ppm, such inconvenience does not occur. There wasn't.

[0023]

Effects of the Invention According to the present invention, there is provided an electrode material that has a high coverage rate, does not cause electrode breakage, and enables a large capacitance due to a large occupied area, and an excellent quality multilayer capacitor using the material as an internal electrode. is provided.

[0024]

[Examples] Next, the present invention will be explained in more detail with reference to Examples. Examples 1 to 16, Comparative Examples 1 to 5 Sheets were formed using a methacrylic acid binder from a lead-based dielectric material, and had dimensions of 3.2 x 1.6 x 1.0 mm.
Multilayer ceramic capacitors having a thickness of 15 μm and various copper-based internal electrodes having 10 dielectric layers were manufactured. This manufacturing method was performed as follows.

A paste prepared by adding the required amounts of various alkaline earth metal oxides shown in Table 1 to metallic copper powder was printed on the above sheet to form various internal electrodes. The various molded bodies obtained were burned out at 600°C in a nitrogen stream, and then under a nitrogen-hydrogen-water atmosphere (oxygen partial pressure log PO
2=-8.5) and baked at 950°C for 2 hours. The sintered body thus obtained was barrel-polished to expose the internal electrodes at the ends, and then external electrodes were attached thereto. The electrical property test of the sample thus obtained was performed using capacitance (20°C, m
F) and tan δ (20°C x 10-4), 1V
The measurement was carried out by applying an alternating current voltage of 1 KHz and measuring at a frequency of 1 KHz. The results are shown in Table 1.

[Table 1]

Claims (2)

[Claims] Claim 1: 0.01 to 10% by weight of an alkaline earth metal oxide or a compound capable of producing an alkaline earth metal oxide based on the main component copper, calculated as an alkaline earth metal oxide.
A copper-based internal electrode material for a lead-based composite perovskite type multilayer ceramic capacitor, characterized by containing: 2. A multilayer ceramic capacitor comprising a lead-based composite perovskite as a dielectric and copper-based internal electrodes made of the material according to claim 1.