JP6292014B2 - Conductive paste and ceramic electronic components - Google Patents

Description

  The present invention relates to a conductive paste and a ceramic electronic component.

  In recent years, miniaturization and high functionality of electronic devices are rapidly progressing, and miniaturization is also required for multilayer ceramic capacitors mounted on electronic devices. For example, in the case of a multilayer ceramic capacitor, a capacitor having a high capacitance that can be substituted for an aluminum electrolytic capacitor has been commercialized due to the progress of thinning technology and multilayering technology.

As such multilayer ceramic capacitors are made thinner and multilayered, Ni powder, which is a metal component for forming internal electrodes, is required to be fine and excellent in dispersibility.
That is, when the dispersibility of the Ni powder contained in the conductive paste is deteriorated, when the conductive paste is printed on a ceramic green sheet and dried at the time of manufacturing the multilayer ceramic capacitor, a lump formed by re-aggregation of the Ni powder on the coating film. As a result, there is a problem that the electrical characteristics such as the withstand voltage characteristics and capacitance of the multilayer ceramic capacitor are significantly deteriorated.
Further, if the dispersibility of the conductive paste is poor, when the conductive paste is left unattended, there arises a problem that it adversely affects the precipitation separation of Ni powder and the viscosity stability of the conductive paste.

  Therefore, for example, as a conductive paste capable of obtaining good dispersibility and viscosity stability, a Ni powder and a conductive paste described in Patent Document 1 have been proposed.

The Ni powder described in Patent Document 1 is a Ni powder characterized in that the surface composition is Ni: 5 to 20 mol%, Ni (OH) ₂ : 25 to 75 mol%, NiO: 15 to 65 mol%. Such Ni powder is contained in the conductive paste.

JP 2004-330247 A

  However, the conductive paste of Patent Document 1 does not include a common material that acts as a sintering inhibitor, and cracks due to shrinkage mismatch may occur at the interface between the dielectric layer and the internal electrode in the sintering process. Had a high problem.

  Therefore, an object of the present invention is to provide a conductive paste that further improves the dispersion state of the co-material added as a sintering inhibitor and the Ni powder while ensuring good dispersibility and viscosity stability. It is.

The conductive paste according to the present invention is a conductive paste containing at least a metal component, an oxide, a dispersant, and a binder resin, and the metal component has a surface composition of Ni: 3 to 22 mol%. Ni (OH) ₂ : 64 to 85 mol%, NiO: 0 to 14 mol% of Ni powder, the acid point amount of the dispersant is 500 to 2000 μmol / g, and the acid point amount of the binder resin is 15 to 15 mol%. The conductive paste is characterized by being 100 μmol / g.
The ceramic electronic component according to the present invention is a ceramic electronic component characterized in that a conductor pattern is produced using the conductive paste described above.

The conductive paste according to the present invention is a conductive paste containing at least a metal component, an oxide, a dispersant, and a binder resin, and the metal component has a surface composition of Ni: 3 to 22 mol%. Ni (OH) ₂ : 64 to 85 mol%, NiO: 0 to 14 mol% of Ni powder, the acid point amount of the dispersant is 500 to 2000 μmol / g, and the acid point amount of the binder resin is 15 to 15 mol%. Since it is 100 μmol / g, the interaction between the Ni powder and the oxide that is a co-material, the dispersant, and the binder resin is optimized, and is added as a sintering inhibitor while ensuring dispersibility and viscosity stability. Good dispersibility of the common material and the Ni powder can be ensured.
Further, in the ceramic electronic component according to the present invention, in the ceramic electronic component in which the internal electrode is embedded in the ceramic body, the internal electrode is formed using the conductive paste of the present invention. Therefore, it is possible to obtain a ceramic electronic component having good electrical characteristics with high efficiency.

  ADVANTAGE OF THE INVENTION According to this invention, the electrically conductive paste which further improved the dispersion state of the co-material added as sintering suppression and Ni powder can be obtained, ensuring favorable dispersibility and viscosity stability.

  The above-described object, other objects, features, and advantages of the present invention will become more apparent from the following description of embodiments for carrying out the invention with reference to the drawings.

It is sectional drawing which shows one Embodiment of the ceramic electronic component concerning this invention.

  An embodiment of a conductive electronic paste according to the present invention and a ceramic electronic component in which a conductor pattern is formed using the conductive paste will be described together with a manufacturing method thereof. The ceramic electronic component is, for example, a passive element such as a multilayer ceramic capacitor or a multilayer ceramic inductor, or a multilayer ceramic substrate on which a wiring conductor that electrically connects the elements is formed. In the present embodiment, a multilayer ceramic capacitor will be described as an example of a ceramic electronic component.

1. Conductive Paste The conductive paste includes Ni powder, perovskite oxide containing Ba and Ti as co-materials, a dispersant, a binder resin, and an organic solvent.

The surface composition of the Ni powder is 3 to 22 mol% Ni, 64 to 85 mol% Ni (OH) _{2, and 0} to 14 mol% NiO.

The surface composition of this Ni powder is measured by X-ray photoelectron spectroscopy (XPS method).
The XPS method is a kind of electron spectroscopy that analyzes the surface composition and chemical state of Ni powder as a sample to be measured. The energy of photoelectrons emitted from atoms by photoelectric effect when the surface of Ni powder is irradiated with X-rays. By measuring the distribution, specifically, the kinetic energy of photoelectrons excited by X-rays, the difference between the X-ray energy and the kinetic energy, that is, the binding energy, is obtained, thereby analyzing the element identification and chemical state. be able to.

  Moreover, as an average particle diameter of Ni powder, it is preferable to use a 0.1-0.4 micrometer thing, and can select suitably among these. The average particle diameter of the perovskite oxide containing Ba and Ti is preferably 1 to 100 nm, and can be appropriately selected between these. This is to meet the demand for thinning and multilayering of internal electrodes of ceramic electronic components.

  The acid point amount of the dispersant is 500 to 2000 μmol / g. This dispersant is, for example, a polycarboxylic acid-based dispersant. Further, as the binder resin, for example, a resin solution in which a resin is dissolved in butyl carbitol is used, and the amount of acid sites is 15 to 100 μmol / g. Examples of the resin dissolved in butyl carbitol include ethyl cellulose and cellulose acetate butyrate. The blending ratio of the binder resin is preferably 2 to 8 parts by weight / Ni part by weight, particularly preferably 3.5 to 6.5 parts by weight / Ni part by weight, and is appropriately selected between these. be able to. And butyl carbitol is contained as the balance.

2. Multilayer Ceramic Capacitor FIG. 1 is a vertical sectional view in the length direction showing a multilayer ceramic capacitor 1 in which internal electrodes are formed using the above-described conductive paste.
The multilayer ceramic capacitor 1 includes a ceramic body 10 and external electrodes 20 and 22 formed on left and right ends of the ceramic body 10.

  The ceramic body 10 is vertically moved so as to sandwich the plurality of inner layer ceramic layers 11, the plurality of inner electrodes 12 and 13 disposed at the interfaces between the plurality of inner layer ceramic layers 11, and the plurality of inner layer ceramic layers 11. The outer layer ceramic layers 15a and 15b are arranged in a rectangular parallelepiped structure.

  The internal electrode 12 and the internal electrode 13 are opposed to each other via the inner ceramic layer 11 in the thickness direction. Capacitance is formed in a portion where the internal electrode 12 and the internal electrode 13 are opposed to each other with the inner ceramic layer 11 interposed therebetween. The internal electrodes 12 and 13 are produced using the conductive paste described above. The internal electrodes 12 and 13 are base metal electrodes made of Ni.

  The left end portion of the internal electrode 12 is drawn out to the left end surface of the ceramic body 10 and is electrically connected to the external electrode 20. The right end of the internal electrode 13 is drawn out to the right end surface of the ceramic body 10 and is electrically connected to the external electrode 22.

  The inner ceramic layer 11 is made of a dielectric material such as a perovskite oxide mainly composed of Ba and Ti. The same dielectric material as that of the inner ceramic layer 11 is used for the outer ceramic layers 15a and 15b disposed above and below, respectively.

  The external electrodes 20 and 22 include an electrode layer containing Cu, a first plating layer containing Ni for preventing solder erosion formed on the surface of the electrode layer, and a surface of the first plating layer. It is comprised by the 3 layer structure comprised by the 2nd plating layer containing Sn formed.

  In the multilayer ceramic capacitor 1 having the above configuration, the internal electrodes 12 and 13 use the Ni powder having the above-described surface composition, the dispersant and the binder resin with the acid point amount adjusted, and thus the Ni ceramic powder and the internal powder 12 and 13 are both used. The interaction between the perovskite-type oxide containing Ba and Ti as materials, the dispersant and the binder resin is optimized, and good viscosity characteristics and coating film characteristics can be obtained. Therefore, it is possible to ensure good dispersibility between the co-material added as a sintering inhibitor and the Ni powder while ensuring dispersibility and viscosity stability. As a result, by using the conductive paste according to the present invention, it becomes possible to ensure the smoothness of the coating film, and to obtain a multilayer ceramic electronic component having good electrical characteristics with high efficiency.

3. Next, a method for manufacturing the above-described multilayer ceramic capacitor 1 will be described.

(Production of ceramic green sheet for inner layer or outer layer)
First, a perovskite oxide having Ba and Ti as main components is prepared as a dielectric material. An organic binder, an organic solvent, a plasticizer, and a dispersing agent are mixed in a predetermined ratio with the dielectric powder obtained from this dielectric material, thereby producing a ceramic slurry. This ceramic slurry is formed on an inner layer or outer layer ceramic green sheet on a resin film, for example, so that the thickness after drying is 3.0 μm.

(Preparation of conductive paste)
Next, Ni powder, a perovskite oxide containing Ba and Ti as co-materials, a polycarboxylic acid-based dispersant, a binder resin, and an organic solvent are prepared.

The surface composition of the Ni powder is 3 to 22 mol% Ni, 64 to 85 mol% Ni (OH) _{2, and 0} to 14 mol% NiO. The average particle diameter of the Ni powder is preferably 0.1 to 0.4 μm, and can be appropriately selected between these. The average particle diameter of the perovskite oxide containing Ba and Ti to be prepared is preferably 1 to 100 nm, and can be appropriately selected between these.

  The acid point amount of the dispersant is 500 to 2000 μmol / g. This dispersant is, for example, a polycarboxylic acid-based dispersant. Further, as the binder resin, for example, a resin solution in which a resin is dissolved in butyl carbitol is used, and the amount of acid sites is 15 to 100 μmol / g. Examples of the resin dissolved in butyl carbitol include ethyl cellulose and cellulose acetate butyrate. The blending ratio of the binder resin is preferably 2 to 8 parts by weight / Ni part by weight, particularly preferably 3.5 to 6.5 parts by weight / Ni part by weight, and is appropriately selected between these. be able to. And butyl carbitol is contained as the balance.

  Ni powder, perovskite oxide containing Ba and Ti as co-materials, polycarboxylic acid-based dispersant, binder resin, and organic solvent are blended so as to achieve the above-mentioned blending ratio, and conductive by a ball mill. A paste is made.

(Production of multilayer ceramic capacitor)
Next, on the ceramic green sheet for the inner layer, for example, the conductive paste according to the present invention is screen-printed so that the thickness after drying becomes 1 ± 0.1 μm, and the conductive paste film that becomes the internal electrodes 12 and 13 (Conductor pattern before firing) is formed.

  Next, a plurality of ceramic green sheets for the inner layer on which the conductive paste film is formed are laminated so that the drawing directions of the ends of the conductive paste film are alternate. Furthermore, the ceramic green sheet layer for outer layers is laminated | stacked up and down so that the laminated | stacked ceramic green sheet for inner layers may be pinched | interposed. In other words, a plurality of outer layer ceramic green sheets made of the same material as the inner layer ceramic green sheet and not having a conductive paste film formed thereon are laminated to have a predetermined thickness and pressed to form a laminate. Is done. And this laminated body is cut | divided into predetermined product size, and the unbaking ceramic main body 10 is obtained.

Next, the cut unfired ceramic body 10 is degreased in a nitrogen atmosphere at 400 ° C. for 10 hours, and then in a nitrogen-hydrogen-water vapor mixed atmosphere in a top temperature of 1200 ° C. and an oxygen partial pressure of 10 ^The sintered ceramic body 10 is fired and sintered under the condition of ⁻⁹ to 10 ⁻¹⁰ MPa.

  The inner layer and outer layer ceramic green sheets and the conductive paste film are fired at the same time, the inner layer ceramic green sheet becomes the inner layer ceramic layer 11, and the outer layer ceramic green sheet becomes the outer layer ceramic layers 15a and 15b. The film becomes the internal electrodes 12 and 13.

  Next, an external electrode paste mainly composed of Cu is applied and baked on both ends of the sintered ceramic body 10 to form electrode layers electrically connected to the internal electrodes 12 and 13. . Furthermore, Ni plating and Sn plating are performed on the surface layer of the electrode layer, and the external electrodes 20 and 22 are formed. In this way, a desired multilayer ceramic capacitor 1 is obtained.

(Experimental example)
1. Experimental Examples Samples of the experimental examples are prepared below, and the characteristics evaluation of the conductive paste (viscosity change rate measurement, coating film smoothness, Ni / co-material dispersion state, withstand voltage failure rate evaluation, occurrence rate of reduced capacity product) It was conducted.

(Production of ceramic green sheet for inner layer or outer layer)
First, the main component of the inner layer and outer layer ceramic layers was a perovskite oxide containing Ba and Ti as a dielectric material. The ceramic dielectric powder was mixed with an organic binder, an organic solvent, a plasticizer, and a dispersant at a predetermined ratio to prepare a ceramic slurry. Then, this ceramic slurry was formed on a resin film so that the thickness after drying was 3.0 μm, and a ceramic green sheet for inner layer or outer layer was produced.

(Preparation of conductive paste)
Next, on the ceramic green sheet for the inner layer, the thickness after drying the conductive paste is 1 ± 0.1 μm in a pattern corresponding to the size of the ceramic element after firing (3.2 mm × 1.6 mm). It was screen printed so that
As the conductive paste, 50 parts by weight of Ni powder having a surface composition as shown in Table 1, 5 parts by weight of perovskite oxide containing Ba and Ti as co-materials, and expressed in butyl carbitol. A resin solution in which 10 parts by weight of each resin having an acid point amount as shown in 1 is dissolved, 1 part by weight of a polycarboxylic acid dispersant having an acid point amount as shown in Table 1, and butyl carbitol as the balance A conductive paste of each sample shown in Table 1 was prepared.

Here, the surface composition of the Ni powder was measured by X-ray photoelectron spectroscopy (XPS method). For the measurement, Quantum 2000 manufactured by ULVAC-PHI is used, and the narrow spectrum (Ni2p3 / 2) is subjected to peak separation in nickel / nickel hydroxide / nickel oxide, and each of Ni, Ni (OH) ₂ and NiO is bonded. The mol% of the state was quantified.

The acid point amount of the polycarboxylic acid dispersant was measured by neutralization titration using potassium methoxide as a titration solvent.
Moreover, the acid point amount with respect to each resin kind shown in Table 1 used as binder resin measured the acid point amount of binder resin by the neutralization titration which used potassium methoxide as the titration solvent.

  The average particle diameter of Ni powder was 0.2 μm. The average particle size of the perovskite oxide containing Ba and Ti was 30 nm. The blending ratio of the binder resin was adjusted to 5.0 parts by weight / Ni parts by weight, and a conductive paste was obtained by a ball mill.

(Preparation of evaluation sample)
Then, after peeling the inner layer ceramic green sheet and the outer layer ceramic green sheet on which the conductive paste is screen-printed from the resin film, 350 sheets are stacked and bonded together to form a laminate. Cut to size and divided into individual green ceramic bodies.

Each ceramic body is degreased in a nitrogen atmosphere at 400 ° C. for 10 hours, and then in a nitrogen-hydrogen-water vapor mixed atmosphere at a top temperature of 1200 ° C. and an oxygen partial pressure of 10 ⁻⁹ to 10 ⁻¹⁰ MPa. It baked on the conditions of this.

Next, a resin solution in which 70 parts by weight of Cu powder, 10 parts by weight of a borosilicate glass frit having a SiO ₂ content of 43%, and 20 parts by weight of ethyl cellulose in butyl carbitol are dissolved in the obtained ceramic body after firing. An external electrode paste containing 20 parts by weight was applied by a dip method so that the side thickness after drying was 50 μm and dried. Thereafter, an electrode layer was formed in a nitrogen-air-water vapor mixed atmosphere or a nitrogen-hydrogen-water vapor mixed atmosphere at a top temperature of 790 to 880 ° C. and an oxygen electromotive force of 220 to 280 mV at the top temperature.

  Thereafter, a first plating layer containing Ni is formed on the surface of the electrode layer, and a second plating layer containing Sn is formed on the surface of the first plating layer, thereby forming an external electrode having a three-layer structure. A multilayer ceramic capacitor as each sample was produced.

2. Method for evaluating characteristics of each sample (Measurement of viscosity change rate)
The viscosity change rate was measured by using an E-type viscometer with the initial viscosity at 20 ° C. and 1 rpm, and the change rate (viscosity change rate) from the initial viscosity after 30 days was calculated according to the following formula.
Rate of change from initial viscosity after 30 days (%) = (viscosity after 30 days−initial viscosity) / initial viscosity × 100

(Coating smoothness)
The coating film smoothness was determined by observing the printed coating film surface with a laser microscope (objective lens × 10, n = 5) and calculating the in-plane surface roughness Sa.

(Ni / common material dispersion state)
The Ni / co-material dispersion state is determined by measuring the surface of the printed coating film using FE-SEM under the conditions of magnification × 10000 and the number of fields of view = 20 fields of view. In the case, it was judged as NG. The measurement location was the center of the electrode coating.

(Withstand voltage failure rate evaluation)
The withstand voltage failure rate was calculated by the following formula by measuring the presence or absence of short circuit failure when a DC voltage of 150 V was applied to 10,000 samples.
Withstand voltage failure rate = number of shorted samples / 10000

(Occurrence rate of reduced capacity products)
The rate of occurrence of reduced capacitance products was determined by measuring the capacitance of 10000 samples, and determining that the sample less than 90% of the design capacity was a reduced product, and calculating the rate of occurrence.

3. Results of characteristic evaluation for each sample Table 2 shows the evaluation results of viscosity change rate measurement, coating film smoothness, Ni / co-material dispersion state, withstand voltage failure rate evaluation, and the rate of occurrence of reduced capacity products.

From Table 2, when using the conductive paste of sample number 1 to sample number 4 within the scope of the present invention, excellent “viscosity change rate”, “coating film smoothness”, “Ni / co-material dispersion state” ”,“ Voltage failure rate evaluation ”, and“ Production rate of reduced capacity product ”. That is, the conductive pastes of Sample No. 1 to Sample No. 4 have viscosity stability and the coating film properties can be appropriately controlled. As a result, the samples using this conductive paste have good electrical properties. It was confirmed that it shows the characteristic.
The conductive pastes of Sample No. 1 to Sample No. 4 include Ni powder, perovskite oxide containing Ba and Ti as co-materials, polycarboxylic acid-based dispersant, binder resin, and organic solvent, The surface composition of the Ni powder is 3-22 mol% Ni, 64-85 mol% Ni (OH) ₂ , 0-14 mol% NiO, and the acid point amount of the polycarboxylic acid dispersant is 500-2000 μmol / As the binder resin, for example, a resin solution obtained by dissolving a resin in butyl carbitol is used, and the acid point amount is 15 to 100 μmol / g.
In this conductive paste, the interaction between the Ni powder, the co-material, the dispersant, and the binder resin is optimized, and as a result, good viscosity stability and coating film characteristics can be obtained. It is considered that a sample using the paste has good electrical characteristics.

  On the other hand, when the conductive paste of Sample No. 5 to Sample No. 11, which is outside the scope of the present invention, is used, the interaction between the Ni powder, the co-material and the binder resin is not appropriate, so that the desired viscosity stability and coating film are obtained. As a result, it is considered that a sample having desired electrical characteristics has not been obtained.

The conductive pastes of Sample No. 5 and Sample No. 7 that are out of the scope of the present invention (the conductive paste in which the amount of Ni and Ni (OH) ₂ is outside the scope of the present invention in the surface composition of Ni powder) were used. In this case, the viscosity stability is low, the coating film smoothness and the Ni / co-material dispersion state are NG, the withstand voltage failure rate is as high as 0.54% and 0.43%, respectively, and the rate of occurrence of reduced capacity products Since they are as high as 0.56% and 0.65%, respectively, they are not suitable for practical use. As for the conductive pastes of Sample No. 5 and Sample No. 7, since the amounts of Ni and Ni (OH) ₂ are not appropriate as the surface composition of the Ni powder, the adsorption state of the dispersant and the binder resin is not appropriate. It is assumed that the viscosity stability is lowered and the Ni powder and the common material are poorly dispersed.

  When the conductive paste of Sample No. 6 that is outside the scope of the present invention (the conductive paste in which the amount of NiO is outside the scope of the present invention in the Ni powder surface composition) is used, the Ni / co-material dispersion state is NG. Since the withstand voltage failure rate is as high as 0.12% and the rate of occurrence of reduced capacity is as high as 0.48%, it is not suitable for practical use. In the conductive paste of sample number 6, since the amount of NiO is not appropriate, the adsorption state of the dispersant is not appropriate, and as a result, it is assumed that poor dispersion of the common material occurs.

  When the conductive paste of Sample No. 8 (conductive paste with a dispersant acid point amount of 100 μmol / g) that is outside the scope of the present invention was used, the coating film smoothness was deteriorated and the withstand voltage failure rate Is as high as 0.48%, and the rate of occurrence of reduced capacity products is as high as 0.23%, which is not suitable for practical application. In addition, when the conductive paste of Sample No. 9 (conductive paste having an acid point amount of the dispersant of 3000 μmol / g) that is outside the scope of the present invention is used, the viscosity stability is low and the Ni / co-material dispersed state Is NG, the withstand voltage failure rate is as high as 0.55%, and the rate of occurrence of reduced capacity is as high as 0.62%. In the conductive pastes of Sample No. 8 and Sample No. 9, since the acid point amount of the dispersant is not appropriate, the adsorption state of the dispersant or the adsorption state of the dispersant and the binder resin is not appropriate. It is assumed that a poor dispersion, a decrease in viscosity stability, and a poor dispersion of the common material have occurred.

  When the conductive pastes of Sample No. 10 and Sample No. 11 outside the scope of the present invention (conductive pastes with binder resin acid point amounts of 200 and 7 μmol / g) are used, the viscosity stability is low and practical. Not suitable. In the conductive pastes of Sample No. 10 and Sample No. 11, since the acid point amount of the binder resin is not appropriate, the adsorption state of the binder resin is not appropriate, so that it is assumed that the viscosity stability is lowered.

  In addition, this invention is not limited to the said embodiment, A various deformation | transformation is carried out within the range of the summary.

1 Ceramic electronic components (multilayer ceramic capacitors)
DESCRIPTION OF SYMBOLS 10 Ceramic main body 11 Ceramic layer for inner layers 12, 13 Internal electrode 15a, 15b Ceramic layer for outer layers 20, 22 External electrode

Claims (2)

A conductive paste containing at least a metal component, an oxide, a dispersant, and a binder resin,
The metal component is a Ni powder having a surface composition of Ni: 3 to 22 mol%, Ni (OH) ₂ : 64 to 85 mol%, NiO: 0 to 14 mol%,
The acid point amount of the dispersant is 500 to 2000 μmol / g,
The acid point amount of the binder resin is 15 to 100 μmol / g,
A conductive paste characterized by.   A ceramic electronic component, wherein a conductive pattern is produced using the conductive paste according to claim 1.

Images