Ni paste and multilayer ceramic capacitors

Abstract

A Ni paste characterized by containing an electroconductive powder (A) mainly comprising Ni, a binder resin (B), an organic solvent (C), and a coexisting material (D), and by furthermore containing a Ti-including additive (E) in the range of 0.05-3.50 parts by mass in terms of TiO2 per 100.0 parts by mass of the electroconductive powder (A) mainly comprising Ni, and / or a Zr-including additive (F) in the range of 0.05-2.80 parts by mass in terms of ZrO2 per 100.0 parts by mass of the electroconductive powder (A) mainly comprising Ni. Through the present invention, it is possible to provide a Ni paste for an internal electrode, whereby high-temperature load service life can be improved without reducing the continuity of an electrode film.

Description

Technical Field

[0001] The present invention relates to a Ni paste for forming an internal electrode for manufacturing a highly reliable multilayer ceramic capacitor, and a multilayer ceramic capacitor manufactured using the same.

Background Art

[0002] With the development of recent electronics technology, the requirements for miniaturization and large capacitance of multilayer ceramic capacitors have been further increasing. In order to meet these requirements, the dielectric layers constituting the multilayer ceramic capacitors have been made thinner. However, when the dielectric layer is thinned, the electric field strength applied to each layer becomes relatively high. Therefore, improvement in reliability during voltage application is required.

[0003] Here, a multilayer ceramic capacitor is generally manufactured as follows. First, a dielectric ceramic raw material powder is dispersed in a resin binder and sheeted to form a ceramic green sheet. A conductive paste for an internal electrode mainly composed of a conductive powder, an inorganic powder such as a ceramic powder if desired, a resin binder, and a solvent is printed on the ceramic green sheet in a predetermined pattern, dried to remove the solvent, and an internal electrode dry film is formed. Next, a plurality of ceramic sheets having the obtained internal electrode dry film are stacked and pressed to form a laminate, cut into a predetermined shape, and then fired at a high temperature to obtain a ceramic body. After that, a conductive paste for an external electrode is applied to both end faces of the ceramic body, and then fired to obtain a multilayer ceramic capacitor. Note that the external electrode may be formed by applying an external electrode paste to an unfired laminate and firing it simultaneously with the ceramic body. And as the internal electrode, those using Ni as the main component are known (for example, Patent Document 1).

[0004] When manufacturing a multilayer ceramic capacitor using Ni as the main component for the internal electrode, it is necessary to perform firing in a reducing atmosphere in order to prevent oxidation of Ni. However, at this time, oxygen vacancies are introduced into the dielectric layer, which causes a problem of reducing the high-temperature load life.

[0005] Therefore, Patent Document 2 describes an invention that aims to achieve high-temperature load life by using an internal electrode in which Sn is solid-solved in Ni, thereby changing the height of the electrical barrier at the interface between the dielectric layer and the electrode layer. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2001-101926 [Patent Document 2] WO2012 / 111592 [Disclosure of the Invention] [Problems that the invention aims to solve]

[0007] However, when Sn is dissolved in Ni, the melting point of Ni decreases and sintering is accelerated. This makes ball-up more likely to occur in various parts of the electrode layer during firing, reducing the continuity of the electrode film. This reduction in electrode film continuity leads to a decrease in the capacitance of the capacitor.

[0008] Therefore, an object of the present invention is to provide a Ni paste for internal electrodes that can improve high-temperature load life without reducing the continuity of the electrode film. Another object of the present invention is to provide a multilayer ceramic capacitor that exhibits excellent reliability even when the dielectric layer is further thinned and a high electric field strength voltage is applied. [Means for solving the problem]

[0009] The above problems are solved by the present invention as described below. In other words, the present invention (1) relates to a multilayer ceramic capacitor having a ceramic laminate in which a plurality of ceramic dielectric layers and a plurality of internal electrode layers containing Ni are alternately stacked, and an external electrode formed on the outer surface of the ceramic laminate, wherein the interface between adjacent internal electrode layers and ceramic dielectric layers From the interface toward the dielectric layer, there is a region up to 1 / 16 of the ceramic dielectric layer thickness, and from that interface toward the internal electrode layer, there is a region up to 1 / 2 of the internal electrode layer thickness. Ti and / or Zr The concentration distribution has a concentration that increases in the direction from the internal electrode layer side toward the ceramic dielectric layer side, reaching a concentration peak, and then decreasing. This is a method for forming a diffusion region. The process includes at least the steps of alternately stacking a predetermined number of ceramic green sheets forming the ceramic dielectric layer and internal electrode paste films forming the internal electrode layer to produce a laminate, and firing it at 900 to 1400°C in a reducing atmosphere, The internal electrode paste film is formed using a Ni paste containing (A) a conductive powder mainly composed of Ni, (B) a binder resin, (C) an organic solvent, and (D) a co-material powder. The Ni paste further contains, separately from the (D) common material powder, (E) an additive containing Ti in an amount of 0.05 to 3.50 parts by mass in terms of TiO2 per 100.0 parts by mass of the (A) Ni-based conductive powder, and / or (F) an additive containing Zr in an amount of 0.05 to 2.80 parts by mass in terms of ZrO2 per 100.0 parts by mass of the (A) Ni-based conductive powder. The additive containing (E)Ti yields TiO2 or TiO2 after the calcination process, and the additive containing (F)Zr yields ZrO2 or ZrO2 after the calcination process. This invention provides a method for forming a diffusion region in a multilayer ceramic capacitor characterized by [specific feature].

[0010] Ma Furthermore, the present invention ( 2 The present invention provides a method for forming a diffusion region in a multilayer ceramic capacitor according to (1) or (2), characterized in that the additive containing (E)Ti is included in an amount of 0.05 to 1.30 parts by mass in terms of TiO2 per 100.0 parts by mass of conductive powder mainly composed of (A)Ni, and / or the additive containing (F)Zr is included in an amount of 0.05 to 1.80 parts by mass in terms of ZrO2 per 100.0 parts by mass of conductive powder mainly composed of (A)Ni.

[0011] Furthermore, the present invention ( 3 ) is a ceramic laminate in which multiple ceramic dielectric layers and multiple internal electrode layers containing Ni are alternately stacked, An external electrode formed on the outer surface of the ceramic laminate, comprising, has a diffusion region of Ti element and / or Zr element at the interface between the adjacent internal electrode layer and the ceramic dielectric layer and in the vicinity thereof, the interface and the vicinity thereof are regions from the interface between the adjacent internal electrode layer and the ceramic dielectric layer to the dielectric layer side up to 1 / 16 of the thickness of the ceramic dielectric layer and regions from the interface to the internal electrode layer side up to 1 / 2 of the thickness of the internal electrode layer, In the diffusion region, the concentration of the Ti element and / or the Zr element has a concentration distribution that increases in the direction from the internal electrode layer side to the ceramic dielectric layer side, reaches a concentration peak, and then decreases, and provides a multilayer ceramic capacitor characterized by this.

Advantages of the Invention

[0013] According to the present invention, it is possible to provide a Ni paste for an internal electrode that can improve the high-temperature load life without reducing the continuity of the electrode film. Further, according to the present invention, it is possible to provide a multilayer ceramic capacitor that exhibits excellent reliability even when the dielectric layer is further thinned and a voltage is applied at a high electric field strength.

Brief Description of the Drawings

[0014] [Figure 1] It is a graph showing the relationship between TiO2 in Table 1 of Example 1 and MTTF (TiO2 added) / MTTF (not added). [Figure 2] It is a graph showing the relationship between ZrO2 in Table 2 of Example 1 and MTTF (ZrO2 added) / MTTF (not added).

Embodiments for Carrying Out the Invention

[0015] The Ni paste of the present invention, (A) Conductive powder mainly composed of Ni, (B) Binder resin, (C) Organic solvent, (D) Co-material powder, containing Furthermore, an additive containing (E) Ti is contained within a range of 0.05 to 3.50 parts by mass in terms of TiO2 per 100.0 parts by mass of the conductive powder mainly composed of (A) Ni and / or an additive containing (F) Zr is contained within a range of 0.05 to 2.80 parts by mass in terms of ZrO2 per 100.0 parts by mass of the conductive powder mainly composed of (A) Ni. It is a Ni paste characterized by the above.

[0016] The Ni paste of the present invention is suitably used for the purpose of forming internal electrodes of multilayer ceramic capacitors, and can also be applied to other ceramic electronic components such as multilayer ceramic actuators.

[0017] The Ni paste of the present invention contains at least (A) a conductive powder mainly composed of Ni, (B) a binder resin, (C) an organic solvent, (D) a co-material powder, and "(E) an additive containing Ti and / or (F) an additive containing Zr". That is, the Ni paste of the present invention contains at least (A) a conductive powder mainly composed of Ni, (B) a binder resin, (C) an organic solvent, (D) a co-material powder, and either one or both of (E) an additive containing Ti and (F) an additive containing Zr.

[0018] The (A)Ni-based conductive powder of the present invention is a powder mainly containing Ni, used as a conductive powder in a Ni paste for forming internal electrodes. Examples of (A)Ni-based conductive powders include powders consisting only of metallic Ni. Other examples of (A)Ni-based conductive powders, insofar as they achieve the effects of the present invention, include composite powders of Ni and other compounds, mixed powders of Ni and other compounds, and alloy powders of Ni and other metals. Examples of composite powders of Ni and other compounds include composite powders in which the surface of the Ni powder is coated with a glassy thin film, composite powders in which the surface of the Ni powder is coated with an oxide, and composite powders in which the surface of the Ni powder is surface-treated with organometallic compounds, surfactants, fatty acids, etc. Furthermore, other metals that can be used in the alloy powder are those that do not easily cause melting point depression when alloyed with Ni, or even if they do cause melting point depression, the amount should be such that the aforementioned ball-up phenomenon does not occur. Examples include Cu, Ag, Pd, Pt, Rh, Ir, Re, Ru, Os, In, Ga, Zn, Bi, Pb, Fe, V, Y, etc. (A) The Ni content in the conductive powder mainly composed of Ni is not particularly limited as long as the effects of the present invention are achieved, but is preferably 60.0% by mass or more, particularly preferably 80.0% by mass or more, and even more preferably 100.0% by mass.

[0019] (A) The average particle size of the conductive powder mainly composed of Ni is not particularly limited, but is preferably 0.05 to 1.0 μm. (A) When the average particle size of the conductive powder mainly composed of Ni is within the above range, it becomes dense, smooth, and easy to form a thin internal electrode layer. In this specification, the symbol "~" indicating a numerical range means a range that includes the numerical values ​​written before and after the symbol "~" unless otherwise specified. That is, for example, the notation "0.05~1.0" is synonymous with "0.05 or more and 1.0 or less" unless otherwise specified.

[0020] The content of conductive powder mainly composed of (A)Ni in the Ni paste of the present invention is not particularly limited and may be appropriately selected in the range of 30.0 to 95.0% by mass, taking into consideration the finished viscosity, printability, storage stability, etc. of the Ni paste.

[0021] The (B) binder resin in the Ni paste of the present invention is not particularly limited as long as it can be used as a conductive paste for forming internal electrodes. Examples of the (B) binder resin include those commonly used as conductive pastes for forming internal electrodes, such as cellulose-based resins such as ethyl cellulose, acrylic resins, methacrylic resins, butyral resins, epoxy resins, phenolic resins, rosin, and the like.

[0022] The content ratio of (B) binder resin in the Ni paste of the present invention is not particularly limited, and is usually 0.1 to 30.0 parts by mass, preferably 1.0 to 15.0 parts by mass, per 100.0 parts by mass of (A) conductive powder mainly composed of Ni.

[0023] The (C) organic solvent in the Ni paste of the present invention is not particularly limited as long as it dissolves the (B) binder resin, and examples include alcohol-based, ether-based, ester-based, hydrocarbon-based solvents, and mixed solvents thereof.

[0024] The (D) co-material powder in the Ni paste of the present invention aims to approximate the sintering shrinkage behavior of the internal electrodes to that of the dielectric layer. The type of co-material powder is not particularly limited, but it is desirable to select it so as to minimize the change in capacitor characteristics due to reaction with the ceramic dielectric. The co-material powder is preferably a ceramic powder represented by the general formula: ABO3 (where A is at least one of Ba, Ca, and Sr, and B is at least one of Ti, Zr, and Hf), such as perovskite-type oxide powders like barium titanate, strontium zirconate, and calcium zirconate, or those to which various additives have been added. Furthermore, the co-material powder is preferably the same as, or has an approximate composition to, the dielectric ceramic raw material powder used as the main component of the dielectric layer. Alternatively, the co-material powder may be attached to the surface of the (A) Ni-based conductive powder beforehand and then mixed with the other components in the Ni paste.

[0025] In the Ni paste of the present invention, the content ratio of the co-material powder is such that, per 100.0 parts by mass of conductive powder mainly composed of (A) Ni, the total amount of the co-material powder is greater than 0.0 parts by mass and 50.0 parts by mass, preferably 1.0 to 40.0 parts by mass, and particularly preferably 5.0 to 30.0 parts by mass. If the co-material powder is included in the Ni paste, the effects of the co-material powder can be obtained. On the other hand, if the content ratio of the co-material powder in the Ni paste exceeds the above range, the electrode layer becomes thicker, making it more prone to structural defects, and the electrode layer becomes a discontinuous film.

[0026] The average particle size of the co-material powder is not particularly limited, but it is preferable that it be 30% or less of the average particle size of the conductive powder mainly composed of (A)Ni, as this exhibits a better sintering suppression effect and a denser texture improvement effect. Furthermore, it is preferable that the total specific surface area of ​​the co-material powder in the paste is larger than the total specific surface area of ​​the conductive powder mainly composed of (A)Ni, as this enhances the effect of improving high-temperature load life. Note that by selecting the average particle size and content of the co-material powder, the total specific surface area of ​​the co-material powder in the paste can be made larger than the total specific surface area of ​​the conductive powder mainly composed of (A)Ni. However, if the average particle size of the co-material powder is too small, the sintering of the powder itself will be too fast due to the increase in surface area, which will reduce the sintering suppression effect of the conductive powder mainly composed of Ni. Therefore, it is preferable that the average particle size of the co-material powder be 0.01 μm or larger.

[0027] Component (E) of the Ni paste of the present invention is a Ti-containing additive. The Ti-containing additive is not particularly limited as long as TiO2 can be obtained after firing the Ni paste, but examples include not only pure metal (Ti) but also a Ti-containing oxide (TiO2). 2-x (wherein the formula, 0.00 ≤ x ≤ 1.00)) may be inorganic compounds such as nitrides (TiN, etc.), halides (TiCl4, TiBr4, etc.), sulfides (TiS2, etc.), borides (TiB2, etc.), hydrides (TiH2, etc.), and oxyacid salts (Ti(SO4)2, etc.), or organometallic compounds such as metal carbonyls, metal alkoxides, and metal resinates. In the present invention, TiO2 is particularly preferred as the Ti-containing additive.

[0028] When the Ni paste of the present invention contains an additive containing (E)Ti, the Ni paste of the present invention contains the Ti-containing additive in a proportion such that, when converted to TiO2, the Ti in the Ti-containing additive is 0.05 to 3.50 parts by mass, preferably 0.05 to 1.30 parts by mass, per 100.0 parts by mass of conductive powder mainly composed of (A)Ni.

[0029] Component (F) of the Ni paste of the present invention is a Zr-containing additive. The Zr-containing additive is not particularly limited as long as ZrO2 can be obtained after firing the Ni paste. For example, in addition to pure metal (Zr), it may be an inorganic compound such as an oxide containing Zr (ZrO2), a halide (ZrCl2, ZrBr4, etc.), a nitride (ZrN, etc.), a hydride (ZrH2, etc.), or an oxyacid (Zr(NO3)4·5H2O, Zr(SO4)2, etc.), or an organometallic compound such as a metal carbonyl, a metal alkoxide, a metal resinate, or an organic acid salt. In the present invention, ZrO2 is particularly preferred as the Zr-containing additive.

[0030] When the Ni paste of the present invention contains an additive containing (F)Zr, the Ni paste of the present invention contains the additive containing Zr in a proportion such that, when converted to ZrO2, the amount of Zr in the additive containing Zr is 0.05 to 2.80 parts by mass, preferably 0.05 to 1.80 parts by mass, per 100.0 parts by mass of conductive powder mainly composed of (A)Ni.

[0031] The Ni paste of the present invention may also contain both an additive containing (E)Ti and an additive containing (F)Zr. In that case, the total amount of Ti in the Ti-containing additive and Zr in the Zr-containing additive, when converted to TiO2 and ZrO2 respectively, is preferably in the range of 0.05 to 3.50 parts by mass per 100.0 parts by mass of conductive powder mainly composed of (A)Ni, and more preferably in the range of 0.05 to 1.80 parts by mass.

[0032] The mechanism by which the Ni paste of the present invention obtains the effects described above by containing an additive containing (E)Ti and / or an additive containing (F)Zr in the above proportions is unclear. However, according to tests and studies by the inventors, it was observed that much of the Ti or Zr component contained in the Ni paste migrates to the dielectric layer side during firing of the paste, and as a result, a diffusion region (diffusion layer) containing a high concentration of Ti or Zr is formed in the dielectric layer after firing, at and near the interface with the electrode layer. This also applies when a co-material powder containing Ti or Zr is used as the Ti or Zr component in the Ni paste, but since the composition of the co-material powder is the same as or similar to that of the dielectric layer, even if it diffuses from the internal electrode layer to the dielectric layer side during firing, it hardly affects the elemental distribution of Ti or Zr in the dielectric layer. Therefore, the formation of the diffusion region (diffusion layer) containing high concentrations of Ti or Zr observed at and near the interface with the electrode layer is considered to be due to an additive containing (E)Ti or (F)Zr present in the Ni paste, separate from the co-material powder. In this invention, "interface and its vicinity" refers to the region from the interface between the ceramic dielectric layer and the internal electrode layer to the dielectric layer side up to 1 / 16 of the thickness of the ceramic dielectric layer, and from the interface to the internal electrode layer side up to 1 / 2 of the thickness of the internal electrode layer. The inventors speculate that the presence of this diffusion region (diffusion layer) reduces the rate at which oxygen vacancies in the dielectric layer move toward the cathode during high-temperature load lifetime testing, thereby improving the lifespan. Furthermore, the inclusion of Ti and Zr components in the electrode layer after firing does not lower the melting point of Ni, and therefore does not adversely affect the continuity of the electrode film. However, if the concentration of Ti or Zr in the above-mentioned diffusion region (diffusion layer) in the dielectric layer becomes too high, the wettability with Ni will decrease, which may adversely affect the continuity of the electrode film. If the content of additives containing (E)Ti or (F)Zr in the Ni paste is below the above range, the effect of improving high-temperature load life will not be obtained. If it exceeds the above range, grain growth will occur due to the Ti or Zr components diffused into the ceramic dielectric layer, reducing the high-temperature load life.

[0033] If the content of additives containing (E)Ti or (F)Zr in the Ni paste is below the above range, the effect of improving high-temperature load life cannot be obtained. If it exceeds the above range, in addition to a decrease in the continuity of the electrode film, grain growth due to the Ti or Zr components diffused into the dielectric layer becomes significant, and improvement in high-temperature load life cannot be expected.

[0034] The Ni paste of the present invention may contain known compounds containing metal elements other than those mentioned above, as long as they do not hinder the effects of the present invention. For example, compounds such as Al2O3, CaO, Co3O4, Fe2O3, La2O3, Li2O, MgO, MoO3, SrO, V2O5, WO3, Y2O3, etc., may be added for various purposes. In particular, many commercially available ZrO2 products contain HfO2 as an unavoidable impurity. The present invention also permits the inclusion of such unavoidable impurities as long as they do not hinder the effects of the present invention.

[0035] It should be noted that the present invention does not exclude the inclusion of Sn components. It is believed that Sn alloys with Ni during firing, lowering the melting point and promoting sintering, which leads to the aforementioned ball-up phenomenon. Therefore, if a Sn compound that does not alloy with Ni is used, or if the Sn content is such that the ball-up phenomenon does not occur even if alloying occurs, it may be used in combination with an additive containing (E)Ti or an additive containing (F)Zr.

[0036] In addition to the above, the Ni paste of the present invention may optionally contain additives such as plasticizers, dispersants, and surfactants that are commonly added to Ni pastes for forming internal electrodes.

[0037] The Ni paste of the present invention is prepared by uniformly mixing and dispersing the above-mentioned (A) conductive powder mainly composed of Ni, (B) binder resin, (C) organic solvent, (D) co-material powder, "(E) additive containing Ti and (F) additive containing Zr, either one or both," and various other additives added as needed, in accordance with conventional methods.

[0038] The multilayer ceramic capacitor of the present invention is manufactured using the Ni paste of the present invention by the following method.

[0039] First, dielectric ceramic raw material powder is dispersed in a resin binder and formed into a sheet using a doctor blade method or die coater method to produce a ceramic green sheet containing dielectric ceramic raw material powder. As the dielectric ceramic raw material powder for forming the dielectric layer, powders mainly composed of ordinary perovskite-type oxides are used, such as barium titanate-based, strontium zirconate-based, calcium strontium zirconate-based, or those in which some of the constituent metal elements are replaced with other metal elements. If necessary, various additives to adjust the capacitor characteristics are blended into these raw material powders. The particle size of the raw material powder is preferably about 0.05 to 0.4 μm on average, for example, when the thickness of the dielectric ceramic layer is 5.0 μm or less. Next, the Ni paste of the present invention is applied to the obtained ceramic green sheet by a conventional method such as screen printing, dried to remove the solvent, and a predetermined pattern of internal electrode paste dried film is formed. Then, a predetermined number of ceramic green sheets with the internal electrode paste film formed on them are stacked and heated and pressed together to produce an unfired laminate. Next, the resulting laminate is cut into a predetermined shape and then fired at a high temperature to simultaneously sinter the dielectric layer and electrode layer, thereby obtaining a multilayer ceramic capacitor base body. Subsequently, terminal electrodes are formed by firing them onto both end faces of the base body to obtain the multilayer ceramic capacitor of the present invention. Note that the terminal electrodes may be attached before firing the laminate and fired simultaneously with the laminate.

[0040] The multilayer ceramic capacitor of the present invention obtained in this manner comprises a ceramic laminate in which a plurality of ceramic dielectric layers and a plurality of internal electrode layers containing Ni are alternately stacked, An external electrode formed on the outer surface of the ceramic laminate, Equipped with, The interface between the adjacent internal electrode layer and the ceramic dielectric layer and its vicinity has a diffusion region of Ti and / or Zi elements. This is a multilayer ceramic capacitor characterized by the following features.

[0041] The ceramic dielectric layer in the multilayer ceramic capacitor of the present invention is formed by using a powder mainly composed of a normal perovskite-type oxide, such as a barium titanate-based, strontium zirconate-based, or calcium strontium zirconate-based perovskite-type oxide, or a powder in which some of the metal elements constituting these oxides are replaced with other metal elements, as the dielectric ceramic raw material powder, forming these dielectric ceramic raw material powders into sheets, and firing them in a reducing atmosphere at 900 to 1400°C, preferably 1100 to 1300°C.

[0042] The multilayer ceramic capacitor of the present invention has an internal electrode layer containing Ni formed using the Ni paste of the present invention; that is, the Ni paste of the present invention is formed on a ceramic green sheet for dielectric layer formation by screen printing or the like, dried, and fired. Much of the co-material powder contained in the Ni paste moves from the internal electrode layer to the dielectric layer during firing, but since the composition of the co-material powder is the same as or similar to that of the dielectric layer, even if it diffuses into the dielectric layer, it hardly affects the elemental distribution in the dielectric layer. On the other hand, much of the Ti or Zr component added to the Ni paste separately from the co-material powder moves from the internal electrode layer to the dielectric layer while being oxidized during firing, as described above, and forms a diffusion region (diffusion layer) containing a high concentration of Ti or Zr at and near the interface between the internal electrode layer and the ceramic dielectric layer. In the diffusion region (diffusion layer), the concentration of Ti or Zr increases in the direction from the internal electrode layer to the dielectric layer, reaches a concentration peak, and then decreases. Based on research results to date, it is presumed that the concentration peak is located near the interface, but its exact location has not yet been determined. In other words, the thickness of the diffusion layer, the shape of the concentration gradient, and the location of the concentration peak differ depending on the firing profile, such as the firing temperature, firing time, and heating rate. For example, in an experiment using an additive containing Ti, when the temperature was rapidly increased and firing was performed for a short time, the Ti component diffused from the internal electrode layer to the dielectric layer, and a diffusion layer was formed with a steep concentration gradient (concentration peak) in which Ti was concentrated only in a position very close to the interface with the internal electrode layer. In another experiment, when firing was performed for a long time, almost no Ti was observed in the internal electrode layer, and a diffusion layer with a relatively broad Ti concentration gradient (concentration peak) was formed in the dielectric layer.

[0043] Therefore, the multilayer ceramic capacitor of the present invention comprises a ceramic laminate in which a plurality of ceramic dielectric layers and a plurality of internal electrode layers containing Ni are alternately stacked, An external electrode formed on the outer surface of the ceramic laminate, Equipped with, The material is characterized by having a diffusion region of Ti and / or Zi elements at and near the interface between the adjacent internal electrode layer and the ceramic dielectric layer. Furthermore, due to the above-mentioned features, the multilayer ceramic capacitor of the present invention exhibits improved high-temperature load life, and therefore demonstrates excellent reliability even when the dielectric layer is further thinned and a high electric field strength voltage is applied.

[0044] Furthermore, the presence of Ti or Zr in the dielectric layer and internal electrode layer can be confirmed by combining SEM (scanning electron microscope) or TEM (transmission electron microscope) with elemental analysis techniques such as EDS (energy-dispersive X-ray spectroscopy), WDS (wavelength-dispersive X-ray spectroscopy), or EELS (electron energy loss spectroscopy).

[0045] The internal electrode layer containing Ni in the multilayer ceramic capacitor of the present invention is formed by firing the Ni paste of the present invention in a reducing atmosphere at 900 to 1400°C, preferably 1100 to 1300°C.

[0046] The external electrodes for the multilayer ceramic capacitor of the present invention are not particularly limited as long as they can be used as external electrodes for the multilayer ceramic capacitor.

[0047] Furthermore, the multilayer ceramic capacitor of the present invention comprises a ceramic laminate in which a plurality of ceramic dielectric layers and a plurality of internal electrode layers containing Ni are alternately stacked, An external electrode formed on the outer surface of the ceramic laminate, Equipped with, The internal electrode layer is formed from a fired product obtained by firing the Ni paste of the present invention at 900 to 1400°C. This is a multilayer ceramic capacitor characterized by the following features.

[0048] In the multilayer ceramic capacitor of the present invention, the internal electrode layer is formed by molding the Ni paste of the present invention on a ceramic green sheet for forming a laminated layer by screen printing or the like, drying it, and firing it. The firing temperature of the Ni paste of the present invention is 900 to 1400 °C, preferably 1100 to 1300 °C, and the firing atmosphere is a reducing atmosphere.

[0049] Hereinafter, the present invention will be described based on specific experimental examples, but the present invention is not limited thereto.

Example

[0050] (Example 1) (Manufacture of Ni paste and multilayer ceramic capacitor) (Preparation of Ni paste) For 100.0 g of spherical nickel powder with an average particle size of 0.3 μm, TiO2 or ZrO2 is added at a ratio of parts by mass shown in Table 1 or Table 2. As a co-material powder, 10.0 g of BaTiO3 powder with an average particle size of 0.05 μm, 6.0 g of ethyl cellulose (binder resin), 2.0 g of surfactant, 1.0 g of plasticizer, and 100.0 g of dihydroterpineol acetate (organic solvent) are mixed, and kneaded using a three-roll mill to prepare a Ni paste.

[0051] (Manufacture of multilayer ceramic capacitor) Next, a polyvinyl butyral-based binder, ethanol, and an additive for adjusting capacitor characteristics are added to BaTiO3 powder with an average particle size of 0.2 μm, which is the main component of the ceramic green sheet, and wet-mixed using a media mill to prepare a ceramic slurry.

[0052] This ceramic slurry is sheet-formed by the die coater method to prepare a ceramic green sheet with a thickness of 5.5 μm.

[0053] Next, Ni paste was printed onto the ceramic green sheet in a 1.5 mm x 3.0 mm rectangular pattern, and then dried to form an internal electrode drying film. The thickness of the internal electrode drying film was 1.5 μm. The ceramic green sheets with the internal electrode drying film were stacked so that there were 50 dielectric effective layers, and dried at 90°C at 1250 kg / cm². 2 An unfired ceramic laminate was obtained by applying pressure to compress and shape the materials.

[0054] This ceramic laminate was heated to 700°C in an atmosphere consisting of N2-0.1%H2-H2O gas, and after burning off the binder, the oxygen partial pressure at 1220°C was 1 × 10⁻¹⁶. -8 In a reducing atmosphere consisting of atm N2-0.1%H2-H2O gas, the material was heated at a rate of 5°C / min and held at 1220°C for 2 hours to sinter and densify. Subsequently, a re-oxidation treatment was performed in an N2-H2O gas atmosphere at 1000°C for 3 hours during the cooling stage to obtain a multilayer ceramic substrate.

[0055] Next, a Cu paste for forming external electrodes, containing Cu powder and BaO-based glass frit, was applied to both ends of the multilayer ceramic body, and the external electrodes were formed by baking them at a temperature of 780°C in an N2 atmosphere to create a multilayer ceramic capacitor.

[0056] By performing this process on all of the aforementioned Ni pastes, the samples shown in Table 1 or Table 2 were obtained. In Table 1 or Table 2, the samples marked with an asterisk (*) are comparative examples that do not meet the requirements of the present invention.

[0057] The obtained multilayer ceramic capacitor had external dimensions of width (W): 1.6 mm, length (L): 3.2 mm, and thickness (T): 0.7 mm. The thickness of the internal electrode layer was 1.2 μm, and the thickness of the ceramic dielectric layer interposed between the internal electrodes was 4.0 μm. The area of ​​the counter electrode per dielectric layer was 3.25 mm². 2 That was the case.

[0058] <Evaluation of characteristics> For each multilayer ceramic capacitor fabricated as described above (samples in Table 1 or Table 2), a high-temperature load test was performed using the method described below. The continuity of the internal electrode layer was evaluated, and the vicinity of the interface between the ceramic dielectric layer and the internal electrode layer was observed. It was confirmed that a diffusion region (diffusion layer) was formed in which the concentration of Ti and / or Zr increased in the direction from the internal electrode layer side toward the ceramic dielectric layer side, reached a concentration peak, and then decreased. The results are shown in Table 1.

[0059] (1) High-temperature load test Fifteen samples were taken from each specimen and subjected to a high-temperature load test at 180°C and 60V. The time required for the insulation resistance to drop by an order of magnitude was defined as the failure time for each multilayer ceramic capacitor. This failure time was then plotted using a Weibull plot to determine the Mean Time To Failure (MTTF). The MTTF evaluation results are shown in Table 1 or Table 2.

[0060] (2) Evaluation of the continuity of the internal electrode layer Each multilayer ceramic capacitor in each sample was cut along a plane perpendicular to the internal electrode layer and observed using a scanning electron microscope (SEM). The observation magnification was 1000x, and 10 internal electrodes were randomly selected from the observation field. The ratio of the portion containing electrodes to the total length was measured and evaluated as continuity. Here, a continuity of 90% or more was marked with ◎, 80-90% with ○, and less than 80% with ×, and these were indicated in Table 1 or Table 2.

[0061] [Table 1]

[0062] [Table 2]

[0063] As shown in Table 1 and Table 2, for samples without TiO2 or ZrO2 mixed (Sample Nos. 1 and 15), the MTTF increased for all samples with TiO2 or ZrO2 mixed (except Sample No. 14, i.e., Sample Nos. 2 - 13 and 16 - 25).

[0064] Also, the continuity of the internal electrodes showed over 90% for Sample Nos. 2 - 9 and 16 - 22, and showed 80 - 90% for Sample Nos. 10 - 13 and 23 - 24.

[0065] On the other hand, in the sample where the mixing of TiO2 exceeded the range specified in the present invention (Sample No. 14), the MTTF became lower than that of the sample without TiO2 mixed (Sample No. 1), and the continuity of the internal electrodes was less than 80%. Also, in the sample where the mixing of ZrO2 exceeded the range specified in the present invention (Sample No. 25), the continuity of the internal electrodes was less than 80%.

[0066] From the above, in order to improve the high - temperature load life, it is advisable to mix 0.05 - 3.50 parts by mass of TiO2 and 0.05 - 2.80 parts by mass of ZrO2 per 100 parts by mass of spherical nickel powder. Further, within the range of 0.05 - 1.30 parts by mass of TiO2 and 0.05 - 1.80 parts by mass of ZrO2, it is possible to further improve the high - load life without impairing the continuity of the internal electrodes.

[0067] (Example 2) (Manufacture of Ni Paste and Multilayer Ceramic Capacitor) (Preparation of Ni Paste) For 100.0 g of spherical nickel powder with an average particle size of 0.3 μm, 0.50 parts by mass of titanium oxide shown in Table 3 in terms of TiO2, 10.0 g of BaTiO3 powder with an average particle size of 0.05 μm as a co - material powder, 6.0 g of ethyl cellulose (binder resin), 2.0 g of surfactant, 1.0 g of plasticizer, and 100.0 g of dihydroterpineol acetate (organic solvent) were mixed in a ratio, and Ni paste was prepared by kneading using a three - roll mill.

[0068] (Manufacturing of multilayer ceramic capacitors) The procedure was the same as in Example 1, except that the above Ni paste was used. By performing this process on all of the previously mentioned Ni pastes, the samples shown in Table 3 were obtained.

[0069] <Characteristic Evaluation> The procedure was the same as in Example 1, except that the sample obtained above was used. The results are shown in Table 3.

[0070] [Table 3]

[0071] The results in Table 3 show that even when using Ti oxides in various oxidation states as Ti-containing additives, it is possible to achieve excellent continuity of the internal electrodes and improve high-temperature load life.

Claims

1. A multilayer ceramic capacitor having a ceramic laminate in which multiple ceramic dielectric layers and multiple internal electrode layers containing Ni are alternately stacked, and external electrodes formed on the outer surface of the ceramic laminate, wherein a diffusion region is formed in which the concentration of Ti and / or Zr elements increases in the direction from the internal electrode layer side toward the ceramic dielectric layer, reaches a concentration peak, and then decreases, in a region from the interface between adjacent internal electrode layers toward the dielectric layer side up to 1 / 16 of the thickness of the ceramic dielectric layer, and in a region from the interface toward the internal electrode layer side up to 1 / 2 of the thickness of the internal electrode layer, and the concentration of Ti and / or Zr elements increases in the direction toward the ceramic dielectric layer side, reaches a concentration peak, and then decreases. The process includes at least the steps of alternately stacking a predetermined number of ceramic green sheets forming the ceramic dielectric layer and internal electrode paste films forming the internal electrode layer to produce a laminate, and firing it at 900 to 1400°C in a reducing atmosphere. The internal electrode paste film is formed using a Ni paste containing (A) a conductive powder mainly composed of Ni, (B) a binder resin, (C) an organic solvent, and (D) a co-material powder. The Ni paste further contains (E) an additive containing Ti, separately from the (D) common material powder, per 100.0 parts by mass of the (A) Ni-based conductive powder, with TiO ２ In terms of conversion, within the range of 0.05 to 3.50 parts by mass, and / or, an additive containing (F)Zr per 100.0 parts by mass of the conductive powder mainly composed of (A)Ni, ZrO ２ It should be contained in an amount ranging from 0.05 to 2.80 parts by mass, The additive containing (E)Ti is TiO ２ Alternatively, TiO ２ The result is obtained, and the additive containing (F)Zr is ZrO ２ Alternatively, after the firing process, ZrO ２ It is something that can be obtained, A method for forming a diffusion region in a multilayer ceramic capacitor characterized by the following.

2. The additive containing (E)Ti is added per 100.0 parts by mass of the conductive powder mainly composed of (A)Ni, with TiO ２ In terms of conversion, the amount is within the range of 0.05 to 1.30 parts by mass, and / or the additive containing (F)Zr is added per 100.0 parts by mass of the conductive powder mainly composed of (A)Ni, with ZrO ２ A method for forming a diffusion region in a multilayer ceramic capacitor according to claim 1, characterized in that it contains in an amount equivalent to 0.05 to 1.80 parts by mass.

3. A ceramic laminate in which multiple ceramic dielectric layers and multiple internal electrode layers containing Ni are alternately stacked, An external electrode formed on the outer surface of the ceramic laminate, Equipped with, The interface between the adjacent internal electrode layer and the ceramic dielectric layer and its vicinity has a diffusion region of Ti and / or Zr elements, The interface and its vicinity are defined as a region extending from the interface between the adjacent internal electrode layer and the ceramic dielectric layer to the dielectric layer side up to 1 / 16 of the thickness of the ceramic dielectric layer, and a region extending from the interface to the internal electrode layer side up to 1 / 2 of the thickness of the internal electrode layer. A multilayer ceramic capacitor characterized in that, in the diffusion region, the concentration of the Ti element and / or the Zr element increases in the direction from the internal electrode layer side toward the ceramic dielectric layer side, reaches a concentration peak, and then decreases thereafter.

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