JP2005203213A - Conductive paste and laminated ceramic electronic component using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve problems that although a laminated ceramic component is required to make thin a ceramic layer and an inner electrode to miniaturize the laminated ceramic component, and with proceeding thinning of the inner electrode, a break or unevenness of the film thickness is easily generated, and it leads to deterioration in electric characteristics. <P>SOLUTION: Conductive paste contains 100 mol of metal powder mainly comprising nickel to 0.2-6.0 mol of silicon dioxide, and also contains 1/50-1 times in molar ratio at least one element selected from alkali earth metal elements and rare earth elements or a compound containing this element to silicon dioxide, and by using the conductive paste, the generation of the break of the inner electrode is prevented even if the inner electrode is made thin, and the laminated ceramic electronic component having high electric characteristic can be obtained. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a conductive paste and a multilayer ceramic electronic component using the same.

  A conventional method for manufacturing a multilayer ceramic electronic component will be described by taking a multilayer ceramic capacitor as an example.

  FIG. 1 is a partially cutaway perspective view of a multilayer ceramic capacitor 11, in which ceramic layers 12 and internal electrodes 13 made of barium titanate or the like are alternately stacked to form a multilayer body, and the end surfaces of the internal electrodes 13 are stacked. They are laminated so as to be alternately exposed at opposite end faces of the body, and are alternately connected to a pair of external electrodes 14 formed on both end faces of the laminate.

  In recent years, there is an increasing demand for miniaturization of multilayer ceramic electronic components, and it is necessary to make the internal electrode thinner while making the ceramic layer thinner.

  However, internal electrodes that are sintered at the same time as the ceramic layer generally start firing shrinkage at a lower temperature than the ceramic layer. Therefore, the internal electrode is affected by the difference in shrinkage between the ceramic layer and the internal electrode during the temperature rising process in the firing process. In this case, a discontinuity phenomenon occurs, the effective area of the internal electrode decreases, and the electrostatic capacity decreases.

  Therefore, in order to control the sintering of metal powders such as nickel used as the main component of internal electrodes, the technology used to form a nickel composite conductor for internal electrode formation by integrating titanate with nickel in granular form has been used. It was.

As prior art document information related to the invention of this application, for example, Patent Document 1 is known.
JP 2000-233202 A

  However, in the conventional method, when the nickel composite conductor is pulverized in order to make the internal electrode thinner, for example, 1 μm or less, the internal electrode is easily sintered, and thinning becomes difficult. Yes.

  In order to solve the above-mentioned problems, the present invention controls the sintering of the internal electrode in the firing step, and at the same time maintains the bondability at the interface between the internal electrode made of metallic nickel and the ceramic layer, so that the internal phenomenon does not occur. An object of the present invention is to obtain a conductive paste capable of thinning an electrode and a multilayer ceramic electronic component using the same.

  In order to achieve this object, the present invention has the following configuration.

  According to the first aspect of the present invention, 0.2 to 6.0 moles of silicon dioxide per 100 moles of metal powder mainly composed of nickel powder is present in the alkaline earth metal elements and rare earth elements. It is a conductive paste containing at least one element selected from 1 or a compound containing this element in a molar ratio of 1/50 to 1 time with respect to silicon dioxide, and when used as an internal electrode of a multilayer ceramic electronic component, firing In the temperature rising process in the process, the compound containing silicon dioxide and alkaline earth metal element or rare earth element controls the sintering of the internal electrode and at the same time strengthens the interfacial bond between the internal electrode and the ceramic layer. It can be made thin without generation.

  The invention according to claim 2 of the present invention is the conductive paste according to claim 1, wherein the nickel powder has an average particle size of 0.01 to 0.2 μm, and the nickel powder, silicon dioxide and alkaline earth metal element Alternatively, a conductive paste in which a compound containing a rare earth element is uniformly dispersed can be obtained, and the interfacial bondability between the internal electrode and the ceramic layer can be further strengthened, so that the internal electrode can be made thin without interruption. Can do.

  According to a third aspect of the present invention, the average particle size of silicon dioxide and the average particle size of at least one element selected from an alkaline earth metal element and a rare earth element or a compound containing this element are 2. The conductive paste according to claim 1, which is 0.005 to 0.1 μm, wherein the conductive paste further uniformly disperses nickel powder and silicon dioxide and a compound containing an alkaline earth metal element or a rare earth element. As a result, the interfacial bondability between the internal electrode and the ceramic layer can be further strengthened, so that the internal electrode can be made thin without interruption.

According to the fourth to sixth aspects of the present invention, a conductive paste is used, and the ceramic layer has a perovskite type crystal structure represented by ABO _3, and an A / B element ratio is 0.980 to 1. The multilayer ceramic electronic component is 020, the internal electrode can be thinned without deteriorating the electrical characteristics of the ceramic layer, and a small multilayer ceramic electronic component can be provided.

  In the present invention, 0.2 to 6.0 mol of silicon dioxide with respect to 100 mol of metal powder containing nickel powder as a main component, at least one element selected from alkaline earth metal elements and rare earth elements Alternatively, it is a conductive paste containing a compound containing this element in a molar ratio of 1/50 to 1 time with respect to silicon dioxide, and controls the sintering of the internal electrode and at the same time strengthens the interfacial bonding between the internal electrode and the ceramic layer. Thereby, the conductive paste for electrode formation which can respond to an internal electrode and thickness reduction can be provided.

  Furthermore, in the multilayer ceramic capacitor according to the present invention, the present invention relates to 0.2 to 6.0 moles of silicon dioxide with respect to 100 moles of metal powder mainly composed of nickel powder, and includes alkaline earth metal elements and rare earth elements. The internal electrode is thinned by using a conductive paste containing at least one element selected from the above or a compound containing this element in a molar ratio of 1/50 to 1 times that of silicon dioxide. Therefore, it is possible to obtain a multilayer ceramic electronic component having a smaller size and good electrical characteristics.

(Embodiment 1)
The invention according to the first to sixth aspects of the invention will be described below by taking a multilayer ceramic capacitor as an example, using the first embodiment of the invention.

  FIG. 1 is a partially cutaway perspective view of a multilayer ceramic capacitor 11 according to the present embodiment, in which ceramic layers 12 and internal electrodes 13 are alternately stacked to form a stacked body, and the end surfaces of the internal electrodes 13 are stacked. They are laminated so as to be alternately exposed at opposite end faces of the body, and are alternately connected to a pair of external electrodes 14 formed on both end faces of the laminate.

First, the main component is barium titanate, ceramic powders such as Dy ₂ O ₃ , Ho ₂ O ₃ , Er ₂ O ₃ , MgO, Mn ₃ O ₄ as subcomponents, polyvinyl butyral resin as an organic binder, and n as a solvent. -Mixing butyl acetate and dibutyl phthalate as a plasticizer to obtain a ceramic slurry.

  Then, a ceramic sheet having a thickness of 1.5 μm (a thickness of the sintered dielectric layer is about 1 μm) to be a dielectric layer 12 made of ceramic is produced by a doctor blade method or the like.

  On the other hand, a nickel metal powder and a polyvinyl butyral resin as an organic binder, n-butyl acetate as a solvent, and dibutyl phthalate as a plasticizer are mixed and then kneaded by a roll mill to produce a metal paste that becomes the internal electrode 13.

Next, silicon dioxide (SiO ₂ ), barium carbonate (BaCO ₃ ), and dysprosium oxide (Dy ₂ O ₃ ) are weighed so as to have the ratio shown in (Table 1) with respect to 100 mol of nickel powder, and a medium stirring mill Is then dispersed uniformly in an organic solvent, and then a conductive paste is prepared in addition to the above metal paste.

  Next, a desired internal electrode pattern is formed with the same thickness on the green sheet by screen printing using each of the conductive pastes.

  After the printed internal electrodes are dried, 300 sheets are arranged so that the internal electrodes face each other with a green sheet interposed therebetween, integrated by thermocompression bonding, and then cut into dimensions of 1.9 mm in length and 1.0 mm in width. To obtain a laminate.

  Next, this laminate is put in a zirconia firing mortar (referred to as a sheath), the binder is removed at 350 ° C. in the air, and then sintered at 1300 ° C. in a reducing atmosphere consisting of nitrogen and hydrogen. Get.

  Next, after chamfering the corners of the sintered body by barrel polishing, a copper paste is applied as an external electrode to both exposed end faces of the internal electrode, and baked in a nitrogen atmosphere at 900 ° C. to obtain a multilayer ceramic capacitor. .

  Next, the capacitance of this multilayer ceramic capacitor was measured at 20 ° C. at a frequency of 1 kHz and 1.0 Vrms, and after applying a direct current of 10 V for 1 minute, the insulation resistance was measured.

  Further, 100 of the above multilayer ceramic capacitors were embedded in a resin, polished and observed in cross section, and the number of internal structural defects was counted as the structural defect occurrence rate.

  The internal electrode thickness was measured at 10 points in the cross section, and the average value was defined as the internal electrode thickness.

  Next, the apparent relative dielectric constant of the ceramic dielectric layer was calculated by the following equation.

C = ε ₀ ε _r S / d · n
Where C is the capacitance, ε ₀ is the dielectric constant of vacuum, ε _r is the dielectric constant of the ceramic dielectric layer, S is the effective overlapping area of the internal electrodes, d is the thickness of the ceramic dielectric layer, and n is the number of layers. .

  In addition, the product of the capacitance and the insulation resistance (CR product) was calculated for the evaluation of the insulation resistance.

  These results are shown together with (Table 1).

  Here, the relative dielectric constant was 2000 or more, the product of capacitance and insulation resistance (CR product) was 1000ΩF or more, and the structural defect occurrence rate was 0/100 (no structural defects in 100). .

  As shown in (Table 1), the addition amount of silicon dioxide is 0.2 to 6.0 moles with respect to 100 moles of the metal powder, and at least one kind selected from alkaline earth metal elements and rare earth elements In samples Nos. 3 to 6, 10 to 13, 17 to 20, and 23 to 25 containing 1 to 50 times the molar ratio of the compound containing the element of silicon dioxide, the apparent relative dielectric constant and insulation resistance (electrostatic The product of the capacity defect and the insulation resistance does not decrease, and the structural defect occurrence rate is zero.

  More specifically, as shown in Table 1, in the case of Sample No. 2 in which the content of silicon dioxide is less than 0.2 mol with respect to 100 mol of nickel powder, the interface between the internal electrode and the ceramic dielectric layer In the case where the internal electrode is thin, discontinuity occurs and the occurrence rate of structural defects is 0, but the apparent dielectric constant is decreased, which is preferable. Absent.

  In addition, in the case of sample numbers 1 and 2 having a silicon dioxide content of less than 0.2 mol, there is less interfacial bonding between the internal electrode and the ceramic dielectric layer, and the control effect on the sintering behavior of the internal electrode is also small. Therefore, the relative permittivity is lowered, and in addition to this, the occurrence of structural defects is also seen in Sample No. 1 which does not contain silicon dioxide.

  On the other hand, in the case of sample number 7 in which the content of silicon dioxide exceeds 6.0 mol, silicon dioxide in the internal electrode diffuses into the ceramic dielectric layer, and the relative dielectric constant is at the interface between the internal electrode and the ceramic dielectric layer. Therefore, an apparent dielectric constant is lowered because an oxide layer mainly composed of low silicon is generated.

  Accordingly, the optimum content of silicon dioxide is 0.2 to 6.0 mol, more preferably 0.6 to 2.0 mol, per 100 mol of nickel powder.

  In addition, from Table 1, in the case of sample numbers 8, 9, 15, and 16 in which the content of the alkaline earth metal element or rare earth element is less than 1/50 times the molar ratio with respect to the added amount of silicon dioxide, The CR product, which is the product of capacitance and insulation resistance, is low and does not satisfy the electrical characteristics of a multilayer ceramic capacitor.

This is because the relative dielectric constant of the perovskite type compound expressed as ABO ₃ is closely related to the A / B ratio, which is the ratio of the A site element expressed as A and the B site element expressed as B. It is known that when the A / B ratio deviates from the optimum range, the relative permittivity decreases, and silicon dioxide does not form a solid solution in the perovskite type compound (ABO ₃ ). This is because the A / B, which is the ratio of the A site element to the B site element of the perovskite type compound, decreases because of the selective reaction.

  Therefore, by adding an element capable of compensating or substituting the element at the A site or a compound thereof in advance, the A / B ratio balance is shifted to the lower side due to the reaction with silicon, and the relative permittivity is lowered. This can be suppressed, but this effect does not work sufficiently when the amount of the alkaline earth metal element or rare earth element is small.

  On the other hand, in the case of Sample Nos. 14 and 21, in which the addition amount of alkaline earth metal element or rare earth element exceeds 1 time in terms of molar ratio with respect to the addition amount of silicon dioxide, these elements inhibit the ceramic sintering reaction. Since it works in the direction, it becomes insufficiently sintered and cannot function as a multilayer ceramic capacitor.

  Therefore, the range of the optimum addition amount of the alkaline earth metal element or rare earth element is 1/50 to 1 time, more preferably 3/10 to 1 time in terms of molar ratio with respect to the addition amount of silicon dioxide.

  Further, in the case of sample number 22 in which the A / B ratio of the perovskite type ceramic dielectric layer is less than 0.980 from (Table 1), the A / B ratio by the addition of the above silicon dioxide by the addition of the alkaline earth metal element or the rare earth element Can be compensated for to some extent, but it does not reach a complete perovskite structure, so the relative dielectric constant of the multilayer ceramic capacitor decreases.

  In the case of sample number 26 where the A / B ratio exceeds 1.020, the amount of A site element with which an appropriate amount of silicon dioxide contained in the internal electrode reacts is limited, so that the A site element becomes excessive. , A / B ratio is shifted to a higher balance, and the ceramic dielectric layer becomes insufficiently sintered.

  Therefore, the optimal A / B ratio range is 0.980 to 1.020, more preferably 1.000 to 1.020.

  As described above, when the A / B ratio of the perovskite ceramic dielectric layer is in the range of 0.980 to 1.020, a thin internal electrode is formed using the conductive paste according to claim 1 However, it is possible to prevent silicon dioxide in the conductive paste from diffusing into the ceramic dielectric layer, resulting in a shift in the A / B ratio and a decrease in the relative dielectric constant. An electronic component can be obtained.

(Embodiment 2)
Hereinafter, with reference to the second embodiment, the invention described in claims 2 to 6 will be described by taking a multilayer ceramic capacitor as an example.

  First, a ceramic green sheet having a thickness of 1.5 μm is produced in the same manner as in the first embodiment.

  On the other hand, five types of nickel powders having an average particle size shown in (Table 2) were premixed together with polyvinyl butyral resin as an organic binder, n-butyl acetate as a solvent, dibutyl phthalate as a plasticizer, etc., and then kneaded with a roll mill. A metal paste is prepared.

  Moreover, about the nickel powder whose average particle diameter is 0.05 micrometer or less, in order to improve dispersibility, what was previously disperse | distributed in the organic solvent with the protective resin is used in preliminary mixing.

  Next, 1 mol of silicon dioxide and 0.5 mol of dysprosium oxide are added to the obtained metal paste at a ratio of 1 mol to 100 mol of nickel powder and mixed to prepare a conductive paste for internal electrodes.

  The average particle diameters of nickel powder, silicon dioxide, and dysprosium oxide used here were those shown in (Table 2).

  The average particle diameters of nickel powder, silicon dioxide, and dysprosium oxide are measured using a scanning electron microscope (SEM) and a TEM (transmission electron microscope).

  As for silicon dioxide and dysprosium oxide, those in which these compounds are uniformly dispersed in an organic solvent by a medium stirring mill are used in advance.

  Furthermore, in order to disperse these compounds uniformly in the metal paste, the viscosity of the paste was adjusted as low as 1 Pa · s and mixing was performed.

  The conductive paste thus produced was dispersed as single particles without agglomeration of the powder particles.

  Next, using this conductive paste, an internal electrode having a desired shape is formed on the ceramic sheet with the same thickness by gravure printing, and then dried, and 300 sheets are stacked so that the internal electrodes face each other through the ceramic sheet. After being integrated by thermocompression bonding, the laminate is obtained by cutting into dimensions of 1.9 mm in length and 1.0 mm in width.

  The multilayer body is fired after removing the binder under the same conditions as in the first embodiment to obtain a sintered body, and chamfering and external electrode formation are performed to obtain a multilayer ceramic capacitor.

  With respect to the multilayer ceramic capacitor thus obtained, the internal electrode thickness, capacitance, and insulation resistance were measured in the same manner as in Embodiment 1, and the apparent relative dielectric constant and CR product were calculated.

  About these measurement results, it shows in (Table 2) with the average particle diameter of nickel powder, silicon dioxide, and dysprosium oxide.

  Here, as in the first embodiment, the relative dielectric constant is 2000 or more, the product of the capacitance and the insulation resistance (CR product) is 1000 ΩF or more, and the structural defect occurrence rate is 0/100 (the structural defects in 100). That there is no).

  As shown in (Table 2), sample numbers 28 to 30 in which the average particle diameter of nickel powder is 0.01 to 0.2 μm and the average particle diameters of silicon dioxide and dysprosium oxide are 0.005 to 0.1 μm. In 33 to 35 and 38 to 40, the apparent relative dielectric constant and the insulation resistance (represented by the product of the capacitance and the insulation resistance) are not lowered, and the occurrence rate of structural defects is zero.

  On the other hand, in the case of the sample number 31 in which the average particle diameter of the nickel powder exceeds 0.2 μm, silicon dioxide and dysprosium oxide cannot be uniformly dispersed in the internal electrode, and the internal electrode and the ceramic dielectric layer As a result, the internal electrode is interrupted and the apparent relative permittivity is lowered.

  Furthermore, since the particle diameter of the nickel powder is large compared to the thickness of the internal electrode thinned to 1 μm or less, the thickness becomes uneven when the internal electrode is printed on the ceramic sheet, causing internal electrode interruption after firing, The apparent dielectric constant is reduced.

  On the other hand, in the case of sample number 27 in which the average particle diameter of nickel powder used for the internal electrode is less than 0.01 μm, silicon dioxide and dysprosium oxide are uniformly dispersed in the internal electrode, but the reactivity is low because the nickel powder is very fine. The control of the sintering behavior of the internal electrode is not sufficiently performed.

  For this reason, when the internal electrode is made thin, a discontinuous portion is generated, the apparent relative dielectric constant is lowered, and a structural defect is also generated.

  Therefore, the average particle diameter of the optimum nickel powder is in the range of 0.01 to 0.2 μm.

  Furthermore, from Table 2, in the case of sample numbers 36 and 41 where the average particle diameter of silicon dioxide or dysprosium oxide exceeds 0.1 μm, these compounds that contribute to the interface bonding between the internal electrode and the ceramic dielectric layer are nickel particles. Since the internal electrode cannot be uniformly dispersed, the apparent dielectric constant is reduced as a result of the interruption in the internal electrodes.

  On the other hand, in the case of sample numbers 32 and 37 in which the average particle diameter of silicon dioxide or dysprosium oxide used for the internal electrode is less than 0.005 μm, even if these compounds can be uniformly dispersed among the nickel particles, Since sintering is accelerated, the sintering behavior of the internal electrode cannot be sufficiently controlled, and when the internal electrode is thinned, the apparent relative dielectric constant is reduced due to the occurrence of breaks.

  Therefore, the optimum average particle diameter range of silicon dioxide and dysprosium oxide is 0.005 to 0.1 μm.

  In the first and second embodiments, the multilayer ceramic capacitor has been described as an example. However, the same effect can be obtained with other multilayer ceramic components such as a multilayer chip inductor, a multilayer thermistor, and a ceramic multilayer substrate.

  In the first and second embodiments, barium carbonate is used as the alkaline earth metal element compound. For example, magnesium, calcium, strontium oxide, carbonate, oxalate, chloride, etc. are also used. The effect is obtained.

  Similarly, dysprosium oxide is used as the rare earth element compound, but the same effect can be obtained by using, for example, an oxide, carbonate, oxalate, chloride, or the like of erbium or ytterbium.

  Moreover, when adding the said additive, you may add what added each additive previously, heat-processed into glassy form, and grind | pulverized.

  Further, in the first and second embodiments, carbonates or oxides of alkaline earth metal elements or rare earth elements are used, but instead of adding these compounds, a vacuum deposition method, a sputtering method, or the like can be used on the nickel powder. A method of forming an alkaline earth metal element or rare earth element by a thin film forming method can also be used.

  The conductive paste of the present invention is particularly effective for a ceramic composition having resistance to reduction.

  In addition, rare earth elements, particularly lanthanoid element compounds, have the property of becoming electron donors at high temperatures, and the addition of such elements also has the effect of improving reliability.

  The conductive paste and the multilayer ceramic electronic component according to the present invention provide a continuous thin internal electrode without interruption of the electrode layer even when the thickness of the internal electrode is reduced. It can also be applied to uses such as printed conductors.

1 is a partially cutaway perspective view of a multilayer ceramic capacitor according to a first embodiment of the present invention.

Explanation of symbols

11 Multilayer Ceramic Capacitor 12 Dielectric Layer 13 Internal Electrode 14 External Electrode

Claims (6)

At least one element selected from alkaline earth metal elements and rare earth elements, or this element, from 0.2 to 6.0 mol of silicon dioxide with respect to 100 mol of metal powder containing nickel powder as a main component The electrically conductive paste which contains the compound containing 1 / 50-1 times in the molar ratio with respect to the said silicon dioxide. The conductive paste according to claim 1, wherein the nickel powder has an average particle size of 0.01 to 0.2 μm. The average particle diameter of silicon dioxide, the average particle diameter of at least one element selected from alkaline earth metal elements and rare earth elements or a compound containing this element is 0.005 to 0.1 μm, and nickel The conductive paste according to claim 1, wherein the powder has an average particle size of 0.01 to 0.2 μm. In a multilayer ceramic electronic component in which ceramic layers and internal electrodes are alternately stacked, and external electrodes are provided on the exposed end surfaces of the internal electrodes, the internal electrodes are based on 100 mol of metal powder containing nickel powder as a main component. 0.2 to 6.0 moles of silicon dioxide, at least one element selected from alkaline earth metal elements and rare earth elements, or a compound containing this element in a molar ratio of 1/50 to silicon dioxide A multilayer ceramic having a perovskite crystal structure represented by ABO ₃ and an A / B element ratio of 0.980 to 1.020. Electronic components. The multilayer ceramic electronic component according to claim 4, wherein the nickel powder in the conductive paste has an average particle diameter of 0.01 to 0.2 μm. The average particle diameter of silicon dioxide and the average particle diameter of at least one element selected from alkaline earth metal elements and rare earth elements or a compound containing this element is 0.005 to 0.1 µm. 4. The multilayer ceramic electronic component according to 4.

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