JP2015050409A - Ceramic powder for laminated ceramic capacitor and method of manufacturing laminated ceramic capacitor using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a laminated ceramic capacitor, capable of improving reliability of a laminated ceramic capacitor, and to provide a ceramic powder for a laminated ceramic capacitor.SOLUTION: The method of manufacturing a laminated ceramic capacitor according to the present invention manufactures a laminated ceramic capacitor which includes: a ceramic element assembly formed by alternately laminating a plurality of dielectric ceramic layers and a plurality of internal electrodes; and external electrodes formed on an outer surface of the ceramic element assembly and electrically connected to the internal electrodes. The dielectric ceramic layers of the laminated ceramic capacitor are produced using the ceramic powder which has a crushing strength of 1854 kPa or less and contains a perovskite type compound containing Ba and Ti.

Description

  The present invention relates to a ceramic powder for a multilayer ceramic capacitor and a method for producing a multilayer ceramic capacitor using the same, for example.

  In recent years, electronic devices such as mobile phones and portable music players have been reduced in size and thickness. Accordingly, for example, miniaturization of a multilayer ceramic electronic component built in an electronic device is required.

  A multilayer ceramic capacitor which is one of such multilayer ceramic electronic components is generally composed of a rectangular parallelepiped ceramic body and external electrodes. The ceramic body includes a dielectric ceramic layer and internal electrodes that are arranged so as to face each other between the dielectric ceramic layers and are drawn to both ends of the ceramic body. The external electrodes are connected to the drawn internal electrodes at both ends of the ceramic body.

  Against this background, for example, in order to reduce the size and increase the capacity of a multilayer ceramic capacitor, it is necessary to make the dielectric ceramic layer thinner or increase the number of layers. If the dielectric ceramic layer constituting the multilayer ceramic capacitor is thinned and the number of laminated layers is increased, the size and capacity can be reduced. In addition, environments where such electronic devices are used are diversified. For example, a highly reliable multilayer ceramic capacitor excellent in insulation and durability at high temperature load is desired.

Therefore, in Patent Document 1, in order to obtain a highly reliable, for example, multilayer ceramic capacitor, a multilayer ceramic capacitor in which dielectric ceramic layers and internal electrode layers are alternately stacked is used as a common material for the internal electrode layer. The ceramic powder to be added has a perovskite crystal structure, and X <2 when the weight ratio Wt / Wc of the tetragonal phase content Wt and the cubic phase content Wc is X. Characteristic ceramic powders have been proposed. At this time, there has been proposed a multilayer ceramic capacitor with improved reliability by setting the specific surface area of the ceramic powder to 10 m ² / g or more.

JP 2007-242525 A

  However, in the ceramic powder used for the production of the multilayer ceramic capacitor described in Patent Document 1, the degree of condensation of the ceramic powder has not been studied with respect to the effects on structural defects such as cracks and delamination that occur in the multilayer ceramic capacitor. In addition, the reliability of the multilayer ceramic capacitor has been evaluated for structural defects such as the above-described cracks and delamination, but the reliability has not been quantitatively evaluated.

  Therefore, a main object of the present invention is to provide a ceramic powder for a multilayer ceramic capacitor capable of improving the reliability of the multilayer ceramic capacitor and a method for producing a multilayer ceramic capacitor using the same.

A method of manufacturing a multilayer ceramic capacitor according to the present invention includes a ceramic body in which a plurality of dielectric ceramic layers and a plurality of internal electrodes are alternately stacked, and formed on the outer surface of the ceramic body. And a ceramic powder containing a perovskite type compound containing Ba and Ti, wherein the dielectric ceramic layer has a crushing strength of 1854 kPa or less. It is produced using this, It is a manufacturing method of a multilayer ceramic capacitor characterized by the above-mentioned.
In addition, the method for producing a multilayer ceramic capacitor according to the present invention includes a value of a specific surface area of a powder obtained when heat treating a ceramic green sheet produced using the ceramic powder and an additive, and the ceramic powder and the additive. The difference from the value of the specific surface area of the powder that has only been mixed is preferably 3 m ² / g or less.
The ceramic powder for a multilayer ceramic capacitor according to the present invention is formed on a ceramic body in which a plurality of dielectric ceramic layers and a plurality of internal electrodes are alternately laminated, and on the outer surface of the ceramic body. Ba and Ti, a ceramic powder for a multilayer ceramic capacitor used for producing a dielectric ceramic layer of a multilayer ceramic capacitor comprising externally connected external electrodes, wherein the crushing strength is 1854 kPa or less. A ceramic powder for multilayer ceramic capacitors, comprising a perovskite type compound.

According to the method for manufacturing a multilayer ceramic capacitor according to the present invention, the ceramic powder used for producing the dielectric ceramic layer of the multilayer ceramic capacitor has a crush strength of 1854 kPa or less, and a perovskite type compound containing Ba and Ti. Therefore, it is possible to obtain a multilayer ceramic capacitor having a high reliability with an average failure time (MTTF) of 30 hours or more of the multilayer ceramic capacitor including the dielectric ceramic layer made of the ceramic powder.
In addition, the method for producing a multilayer ceramic capacitor according to the present invention includes a value of a specific surface area of a powder obtained when heat treating a ceramic green sheet produced using the ceramic powder and an additive, and the ceramic powder and the additive. If the difference between the specific surface area of the powder just mixed is 3 m ² / g or less, the average failure time (MTTF) of the multilayer ceramic capacitor obtained by this manufacturing method is higher than 50 hours. The provided multilayer ceramic capacitor can be obtained.

According to the present invention, a method for manufacturing a multilayer ceramic capacitor capable of improving the reliability of the multilayer ceramic capacitor is provided.
According to the present invention, a ceramic powder for a multilayer ceramic capacitor capable of improving the reliability of the multilayer ceramic capacitor is provided.

  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.

1 is a cross-sectional view showing an example of a multilayer ceramic capacitor according to the present invention.

(Multilayer ceramic capacitor)
FIG. 1 is a cross-sectional view showing an example of a multilayer ceramic capacitor according to the present invention. A multilayer ceramic capacitor 10 shown in FIG. 1 includes a rectangular parallelepiped ceramic body 12. The ceramic body 12 includes a number of dielectric ceramic layers 14, 14,. The dielectric ceramic layers 14, 14,... Are made of dielectric main component powder (ceramic powder). The dielectric main component powder according to the present invention contains a perovskite type compound containing Ba and Ti having a crushing strength of 1854 kPa or less.

  These dielectric ceramic layers 14, 14,... Are laminated, and internal electrodes 16a and 16b made of, for example, Ni are alternately formed between the dielectric ceramic layers 14, 14,. In this case, the internal electrode 16 a is formed with one end extending to one end of the ceramic body 12, and the internal electrode 16 b is formed with one end extending to the other end of the ceramic body 12. The internal electrodes 16 a and 16 b are formed so that the intermediate portion and the other end portion overlap with each other with the dielectric ceramic layer 14 interposed therebetween. Therefore, the ceramic body 12 has a laminated structure in which a plurality of internal electrodes 16 a and 16 b are provided via the dielectric ceramic layer 14.

  On one end face of the ceramic body 12, an external electrode 18a made of, for example, Cu is formed so as to be connected to the internal electrode 16a. Similarly, an external electrode 18b made of, for example, Cu is formed on the other end surface of the ceramic body 12 so as to be connected to the internal electrode 16b.

(Manufacturing method of multilayer ceramic capacitor)
Next, the manufacturing method of the multilayer ceramic capacitor concerning this invention is demonstrated. First, the manufacturing method of the dielectric main component powder used for the dielectric ceramic layer 14 is demonstrated.

(Preparation of dielectric main component powder)
First, high-purity BaCO ₃ and TiO ₂ powders are prepared and mixed as starting materials for BaTiO ₃ which is a dielectric main component powder (ceramic powder). Next, the prepared powder is wet-mixed with water in a ball mill to produce a slurry. Thereafter, the prepared slurry is put in an oven and dried at a predetermined temperature until water is removed by evaporation, thereby obtaining an adjusted powder.

  Next, the obtained adjustment powder is calcined at a predetermined temperature, for example, a temperature of 1050 ° C., and dry pulverized to obtain a dielectric main component powder having an average particle diameter of 150 nm. The cohesive strength of the dielectric main component powder obtained after the calcination can be changed by changing the temperature of the oven when obtaining the adjusted powder.

  Here, the average particle diameter of the dielectric main component powder is calculated from the FE-SEM photograph. The evaluation of the setting strength of the dielectric main component powder uses the crushing strength as an index. The crushing strength of the dielectric main component powder according to the present invention is 1854 kPa or less. This crushing strength is obtained by a crushing test of the dielectric main component powder using a microparticle crushing test apparatus (NS-A100 type (manufactured by Nano Seeds Co., Ltd.)). Moreover, this crushing test uses the method based on JISZ8841-1993.

(Manufacturing method of multilayer ceramic capacitor)
Subsequently, the dielectric main component powder obtained by the above-described manufacturing method and the additive SiO ₂ , MgCO ₃ , MnCO ₃ and Dy ₂ CO ₃ powder were added uniformly, and the powder (hereinafter referred to as “powder”) Powder A) is obtained. To the obtained powder (powder A), a polyvinyl butyral binder, a plasticizer and ethanol as an organic solvent are further added, and these are wet-mixed for a predetermined time by a ball mill to produce a ceramic slurry. . The addition amount of each additive is, for example, 2.0 mol parts of Si, 1.0 mol parts of Mg, 0.25 mol parts of Mn, and 1.0 mol parts of Dy with respect to 100 mol parts of Ti. The specific surface area of each powder is, for example, a powder having SiO ₂ of 100 m ² / g, MgCO ₃ of 50 m ² / g, MnCO ₃ of 50 m ² / g, and Dy ₂ CO ₃ of 30 m ² / g. The time for performing this wet mixing is, for example, 5 hours to 15 hours.

  Next, the produced ceramic slurry is formed into a sheet by a lip method, and for example, a rectangular ceramic green sheet having a thickness of 1.1 μm is obtained.

In the present invention, the binder, the plasticizer and the organic solvent are removed from the ceramic green sheet produced by the above-described method, and the powder is taken out, for example, by heat treatment at 400 ° C. for 2 hours in the air. The value of the difference obtained by subtracting the value of the specific surface area of the powder A from the value of the specific surface area of the obtained powder (hereinafter referred to as the powder B) is 3 m ² / g or less. The specific surface area values of the powder A and the powder B are measured by an N ₂ adsorption specific surface area measuring device. In the heat treatment, powder sintering and grain growth do not proceed.

  A conductive paste containing Ni is, for example, screen-printed on the heat-treated ceramic green sheet, and as a result, a conductive paste film serving as an internal electrode is formed.

  Next, the ceramic green sheet on which the conductive paste film is formed is laminated so that the side where the conductive paste film is drawn is staggered, so that a raw laminate to be a ceramic body of the multilayer ceramic capacitor is obtained. can get.

The obtained raw laminate is heated in a N ₂ atmosphere at a predetermined temperature and for a predetermined time, for example, 350 ° C. for 3 hours. After the binder is burned, for example, an oxygen partial pressure of 10 ⁻ Ceramic body sintered and sintered at a predetermined temperature and a predetermined time, for example, 1200 ° C. for 30 minutes in a reducing atmosphere composed of ⁹ MPa to 10 ⁻¹² MPa of H ₂ —N ₂ —H ₂ O gas Is obtained.

Next, a Cu paste containing, for example, glass frit is applied to both end faces of the obtained ceramic body, and baked at a predetermined temperature, for example, 800 ° C. in an N ₂ atmosphere. And an external electrode electrically connected to each other is formed, and a desired multilayer ceramic capacitor is obtained.

  In the multilayer ceramic capacitor obtained by the method for producing a multilayer ceramic capacitor according to the present invention, the dielectric ceramic layer 14 uses a dielectric main component powder having a crushing strength of 1854 kPa or less, so the average failure time is 30 hours. A highly reliable multilayer ceramic capacitor as described above can be obtained.

In the multilayer ceramic capacitor obtained by the method for manufacturing a multilayer ceramic capacitor according to the present invention, the dielectric ceramic layer 14 has a difference of 3 m ² between the value of the specific surface area of the powder A and the value of the specific surface area of the powder B. By setting it to / g or less, a more reliable multilayer ceramic capacitor having an average failure time of 50 hours or more can be obtained.

(Experimental example)
Next, an evaluation experiment performed on the dielectric main component powder and the multilayer ceramic capacitor obtained by the above-described method will be described. When performing the evaluation experiment, a dielectric main component powder and a multilayer ceramic capacitor, which are samples used in the evaluation experiment, were produced as follows.

First, a dielectric main component powder was prepared by the method described below. That is, high-purity BaCO ₃ and TiO ₂ powders were prepared and prepared as starting materials for BaTiO _{3 as} the main component. Next, this blended powder was wet-mixed with a ball mill using water to produce a slurry. Thereafter, the prepared slurry was placed in an oven and dried until it was depleted with water to obtain a conditioned powder. In addition, the temperature of oven was set to 100 degreeC, 75 degreeC, 50 degreeC, and 25 degreeC, and each sample was obtained with each temperature.

  Next, the adjusted powder obtained at each set temperature of the oven was calcined at 1050 ° C. and dry pulverized to obtain each dielectric main component powder having an average particle diameter of 150 nm. A sample obtained at a set temperature of the oven of 100 ° C. is defined as the main component powder 1, a sample obtained at 75 ° C. is defined as the main component powder 2, and a sample obtained at 50 ° C. is defined as the main component powder 3. A sample obtained at 25 ° C. was used as the main component powder 4. In addition, the average particle diameter of each dielectric main component powder was computed from the FE-SEM photograph.

In addition, a powder (hereinafter referred to as “powder A”) was prepared by uniformly adding an additive to the dielectric main component powder for each sample of the main component powder 1 to the main component powder 4. The additive was a powder of SiO ₂ , MgCO ₃ , MnCO ₃ and Dy ₂ CO ₃ . The addition amount of the additive was 2.0 mol parts of Si, 1.0 mol parts of Mg, 0.25 mol parts of Mn, and 1.0 mol parts of Dy with respect to 100 mol parts of Ti. The specific surface area of each powder, SiO ₂ is 100m ² / g, MgCO ₃ is 50m ² / g, MnCO ₃ there is _{^{50m 2 / g, Dy 2 CO}} 3 was 30 m ² / g. Then, to the powder A for each sample, a polyvinyl butyral binder, a plasticizer, and ethanol as an organic solvent were added, and these were wet mixed by a ball mill to produce a ceramic slurry. In addition, with respect to each sample of the main component powder 1 to the main component powder 4, the mixing time was 3 patterns of 5 hours, 10 hours, and 15 hours, respectively.

  Then, using the ceramic slurry of each sample obtained by the above-described method, a sheet was formed by a lip method, and a rectangular ceramic green sheet having a thickness of 1.1 μm was obtained.

  Next, in order to evaluate the specific surface area of the powder, a ceramic green sheet of each sample obtained by the above-described method is heat-treated in the atmosphere at 400 ° C. for 2 hours to prepare a powder (hereinafter referred to as powder B). did.

  On the other hand, as will be described later, in order to produce a multilayer ceramic capacitor for performing a high temperature load test, a conductive paste containing Ni is screen-printed on a ceramic green sheet for each sample obtained by the above-described method. Then, a conductive paste film to be an internal electrode was formed.

  And the ceramic green sheet with respect to each sample in which the electroconductive paste film was formed was laminated so that the side where the electroconductive paste film was drawn was alternated, and the raw laminated body used as a ceramic body was obtained.

Next, the raw laminate for each sample was heated in a N ₂ atmosphere at a temperature of 350 ° C. for 3 hours to sinter the binder, and then H ₂ —N with an oxygen partial pressure of 1 × 10 ⁻⁹ MPa. _In a reducing atmosphere composed of _2- H ₂ O gas, firing was performed at 1200 ° C. for 30 minutes to obtain a sintered ceramic body for each sample.

Then, Cu paste containing glass frit is applied to both end faces of the ceramic body for each of the obtained samples, and baked at a temperature of 800 ° C. in an N ₂ atmosphere to be electrically connected to the internal electrodes. External electrodes were formed, and a multilayer ceramic capacitor for each sample was obtained.

The outer dimensions of the multilayer ceramic capacitor for each sample thus obtained are 1.0 mm in length, 0.5 mm in width, and 0.5 mm in thickness. The thickness of the dielectric ceramic layer interposed between the internal electrodes is as follows. It was 1 μm. The number of effective dielectric ceramic layers was 250, and the counter electrode area per one dielectric ceramic layer was 0.27 mm ² .

(Characteristic evaluation)
The dielectric main component powder and multilayer ceramic capacitor for each sample obtained by the above-described method were evaluated by the following characteristic evaluation method.

1. Evaluation of the cohesive strength of the dielectric main component powder The cohesive strength of the dielectric main component powder was evaluated by the crushing strength. In order to measure the crushing strength, a crushing test of the dielectric main component powder was performed using a microparticle crushing test apparatus (NS-A100 (manufactured by Nano Seeds Co., Ltd.)). This crushing test is based on JISZ8841-1993.

2. Measurement of specific surface area of powder After the prepared powder A and powder B were processed with an absolute mill (ABS-W) manufactured by Vita-Mix at a rotational speed of 24,000 rpm for 1 minute for 50 g of each powder. The specific surface area was measured with an N ₂ adsorption specific surface area measuring device. The value of the specific surface area of the powder A was subtracted from the value of the specific surface area of the powder B, the difference was calculated, and the value was used for evaluation.

3. Measurement of life characteristics by high-temperature load test A DC current of 10 V was applied to 20 multilayer ceramic capacitors at 125 ° C., and the change in insulation resistance with time was observed. Twenty failure times were analyzed with a wiped plot, with the failure when the insulation resistance value of each multilayer ceramic capacitor was 0.1 MΩ or less, and an average failure time (MTTF) was determined.

  Table 1 shows the oven temperature set for preparing each sample of the main component powder 1 to the main component powder 4, which are dielectric main component powders, and each of the main component powder 1 to the main component powder 4. The measurement result of each crushing strength with respect to a sample is shown.

  Table 2 shows the mixing time for preparing the ceramic slurry using each sample of the main component powder 1 to the main component powder 4, the value of the specific surface area of the powder A of each sample and the ratio of the powder B The difference from the value of the surface area and the evaluation result of the mean time to failure (MTTF) of the multilayer ceramic capacitor produced by each sample are shown. In Table 2, sample numbers 7 to 12 marked with * are outside the scope of the present invention.

  According to Table 1, it can be seen that the crushing strength can be lowered by increasing the oven temperature when producing the dielectric main component powder. The main component powder 1 was when the oven temperature was 100 ° C. and the crushing strength was 543 kPa, and the main component powder 2 was when the oven temperature was 75 ° C. and the crushing strength was 1854. The main component powder 3 was obtained when the oven temperature was 50 ° C. and the crushing strength was 2307 kPa, and the main component powder 4 was obtained when the oven temperature was 25 ° C. and the crushing strength was 3028 kPa.

  According to Table 2, in the samples 1 to 6 in which the crushing strength of the dielectric main component powder is 1854 kPa or less, the average failure time (MTTF) of all the multilayer ceramic capacitors is 30 hours or more, which is highly reliable A multilayer ceramic capacitor was obtained.

Further, according to Table 2, the crushing strength of the dielectric main component is 1854 kPa or less, and the powder (powder obtained when the ceramic green sheet formed using the dielectric main component powder and the additive is heat-treated. The difference between the value of the specific surface area of the body B) and the value of the specific surface area of the powder (powder A) obtained by mixing only the dielectric main component and the additive is 3 m ² / g or less. The average failure time (MTTF) of the multilayer ceramic capacitors of 4 and Sample 5 was 50 hours or more, and a more reliable multilayer ceramic capacitor was obtained.

  On the other hand, according to Table 2, in any of the multilayer ceramics produced by using the main component powder 3 and the main component powder 4 in which the crushing strength of the dielectric main component powder is 2307 kPa and 3028 kPa, The capacitor also had an average failure time (MTTF) of 20 hours or less.

  According to Table 2, when obtaining powder B, if polyvinyl butyral binder, plasticizer and ethanol as an organic solvent are added to powder A, and the time during which these are wet mixed by a ball mill is shortened, Accordingly, it was confirmed that the difference between the specific surface area value of the powder B and the specific surface area value of the powder A can be reduced.

  In addition, this invention is not limited to said embodiment, A various deformation | transformation is possible in the range which does not deviate from a summary.

  The method for manufacturing a multilayer ceramic capacitor according to the present invention is suitably used for obtaining a multilayer ceramic capacitor that is required to be reduced in size and capacity.

DESCRIPTION OF SYMBOLS 10 Multilayer ceramic capacitor 12 Ceramic body 14 Dielectric ceramic layer 16a, 16b Internal electrode 18a, 18b External electrode

Claims (3)

A ceramic body in which a plurality of dielectric ceramic layers and a plurality of internal electrodes are alternately laminated;
An outer electrode formed on the outer surface of the ceramic body and electrically connected to the inner electrode, and a method for producing a multilayer ceramic capacitor comprising:
The method for producing a multilayer ceramic capacitor, wherein the dielectric ceramic layer is produced using a ceramic powder containing a perovskite type compound containing Ba and Ti having a crushing strength of 1854 kPa or less. The value of the specific surface area of the powder obtained when the ceramic green sheet produced using the ceramic powder and the additive is heat-treated, and the value of the specific surface area of the powder only obtained by mixing the ceramic powder and the additive The method for producing a multilayer ceramic capacitor according to claim 1, wherein the difference is 3 m ² / g or less. A ceramic body formed by alternately laminating a plurality of dielectric ceramic layers and a plurality of internal electrodes; an external electrode formed on the outer surface of the ceramic body and electrically connected to the internal electrodes; A ceramic powder for a multilayer ceramic capacitor used for producing the dielectric ceramic layer of a multilayer ceramic capacitor comprising:
A ceramic powder for a multilayer ceramic capacitor, comprising a perovskite type compound containing Ba and Ti having a crushing strength of 1854 kPa or less.

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