JP2009295606A - Method for testing multilayer ceramic capacitor and method for manufacturing the multilayer ceramic capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for testing a multilayer ceramic capacitor, capable of evaluating the reliability of a multilayer capacitor with high accuracy, having a dielectric layer of 2 μm or smaller thickness at an initial stage. <P>SOLUTION: A voltage is applied to the multilayer ceramic capacitor to measure a current value I1, then a voltage reverse to this voltage is applied to measure a current value I2, a current ratio of the current value I2 to the current value I1 is obtained, and the obtained current ratio is used as a first current ratio. The current ratios of a plurality of multilayer ceramic capacitors, each having the manufacturing method same as that of the above multilayer ceramic capacitor are calculated, in the same manner as that of the current ratio, and the calculated current ratios are each used as a second current ratio. A multilayer ceramic capacitor having the first current ratio which is not smaller than that of a lower value a-3×σ and not larger than that of an upper value a+3×σ, calculated from a mean value between the second current ratio and the standard deviation value σ is evaluated as not having problems in reliability, in a high-temperature load environment. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for testing a multilayer ceramic capacitor having a dielectric layer and an internal electrode layer, and a method for manufacturing the multilayer ceramic capacitor.

  In recent years, there has been a high demand for downsizing of electronic components accompanying the increase in the density of electronic circuits, and the downsizing and increase in capacity of multilayer ceramic capacitors are rapidly progressing.

  In order to realize this, a method of thinning a dielectric layer of a ferroelectric ceramic made of barium titanate or the like is adopted, and the thickness of one layer of the dielectric layer has become 1 to 3 μm.

  Therefore, the electric field per dielectric layer of the multilayer ceramic capacitor having a predetermined rated voltage becomes very large, and there is a problem that the insulation resistance of the multilayer ceramic capacitor deteriorates in the reliability test.

As a test method for evaluating the reliability of a conventional multilayer ceramic capacitor, for example, in Patent Document 1, each current value when a voltage having the same polarity is continuously applied to the multilayer ceramic capacitor is measured, and the current value is measured. A method has been proposed for evaluating the reliability of ceramic capacitors in a high-temperature load test based on the value of the ratio.
JP-A-10-335174

  However, such a conventional method for testing a multilayer ceramic capacitor is one in which a voltage having the same polarity is continuously applied. When the thickness of the dielectric layer made of a ferroelectric ceramic is 2 μm or less, the first test is performed. The current value of the second time becomes very small compared to the current value of the current, and it becomes impossible to obtain a correlation between the ratio of the current value and the deterioration of the insulation resistance in the high temperature load test, and the reliability of the multilayer ceramic capacitor can be evaluated. There was a problem that it was not possible.

  An object of the present invention is to solve such a conventional problem and to provide a test method capable of accurately evaluating the reliability of a multilayer ceramic capacitor in a high temperature load environment from the initial characteristics of the multilayer ceramic capacitor.

  It is another object of the present invention to provide a method for manufacturing a multilayer ceramic capacitor in which deterioration of insulation resistance is reduced in a high temperature load environment.

  In order to achieve the above object, the present invention provides a method for testing a multilayer ceramic capacitor having an external electrode on a ceramic body in which dielectric layers and internal electrode layers are alternately stacked, wherein a voltage is applied to the multilayer ceramic capacitor. The current value I1 is applied, and then the reverse voltage of the voltage is applied to measure the current value I2. The current ratio of the current value I2 to the current value I1 is determined according to the current ratio of the multilayer ceramic capacitor in a high temperature load environment. This is a test method for the multilayer ceramic capacitor for evaluating reliability.

  Also, a multilayer ceramic capacitor having external electrodes on a ceramic body in which dielectric layers and internal electrode layers are alternately stacked is prepared, a voltage is applied to the multilayer ceramic capacitor, and a current value I1 is measured. Applying a reverse voltage, measuring a current value I2, calculating a current ratio of the current value I2 to the current value I1, and setting the current ratio as a first current ratio; and the same as the multilayer ceramic capacitor A voltage is applied to a plurality of multilayer ceramic capacitors having a manufacturing method to measure a current value I1a, then a reverse voltage of the voltage is applied to measure a current value I2a, and a current of the current value I2a with respect to the current value I1a A step of calculating a ratio and setting this current ratio as a second current ratio; calculating an average value a and a standard deviation value σ of the second current ratio; a lower value a−k × σ; an upper value a + k × σ (k is Positive value) And a selection step of making the multilayer ceramic capacitor having a first current ratio not less than the lower value and not more than the upper value of the second current ratio as non-defective products.

  As described above, a voltage is applied to the multilayer ceramic capacitor to measure the current value I1, and then a reverse voltage of this voltage is applied to measure the current value I2 to obtain a current ratio that is a ratio of the current value I2 to the current value I1. Based on the relationship between the current ratio value and the insulation resistance deterioration in the high temperature load environment, the initial stage determines whether the multilayer ceramic capacitor causes the insulation resistance deterioration in the high temperature load environment based on the current ratio value. Can be evaluated with high accuracy.

  The reason there is a relationship between the value of the current ratio and the deterioration of the insulation resistance in a high-temperature load environment is that the polarity is different if there is an uneven location where the additive is abnormally distributed in the dielectric particles of the dielectric layer When voltage is applied, the behavior of dielectric polarization is different from that of a uniform part, and the value of the current ratio becomes very large or extremely small. In addition, uneven parts in such dielectric particles are insulated in a high temperature load environment. It is considered that resistance is likely to be deteriorated, so that the value of the current ratio is very large or extremely small is likely to cause deterioration of the insulation resistance.

  Further, the lower value a−k × σ and the upper value a + k × σ calculated from the average value a and the standard deviation value σ of the second current ratio of the plurality of multilayer ceramic capacitors having the same manufacturing method as the multilayer ceramic capacitor to be selected are obtained. Obtaining and selecting a multilayer ceramic capacitor with excellent reliability with reduced deterioration of insulation resistance in a high-temperature load environment by making the first current ratio of the multilayer ceramic capacitor to be obtained higher than the lower value and lower than the upper value. The effect which can be produced is produced.

  Hereinafter, the best mode for carrying out the present invention will be described.

(Embodiment)
A test method and a manufacturing method of the multilayer ceramic capacitor in the embodiment of the present invention will be described.

  FIG. 1 is a cross-sectional view of a multilayer ceramic capacitor.

  As shown in FIG. 1, the multilayer ceramic capacitor has an external electrode 4 on a ceramic body 3 in which dielectric layers 1 and internal electrode layers 2 are alternately stacked. Conductive with the internal electrode layer 2 exposed at both end portions is disposed at both end portions of the ceramic body 3.

  First, a manufacturing method until forming the external electrode 4 of the multilayer ceramic capacitor will be described.

  A ceramic raw sheet to be the dielectric layer 1 and a conductive paste film to be the internal electrode layer 2 are prepared.

  The ceramic raw sheet is formed by applying a ceramic slurry on a PET film using a method such as a doctor blade and drying, and the ceramic slurry is a dielectric powder generated from a ceramic raw material powder such as barium titanate, It is a mixture of a binder such as polyvinyl butyral resin or acrylic resin, a plasticizer such as phthalate ester, and a solvent such as butyl acetate.

  The conductive paste film is formed by applying and drying a conductive paste in a pattern on a PET film by a gravure printing method, and the conductive paste is formed of a conductive metal powder mainly composed of nickel or the like and polyvinyl. It is a mixture of a binder such as butyral resin, a plasticizer such as phthalate ester, and a solvent such as butyl acetate.

  Next, a ceramic raw sheet and a conductive paste film are alternately laminated to produce a laminated body, and this laminated body is cut and separated so as to have a predetermined size. I got a chip. These multilayer green chips were fired to form the ceramic body 3.

  Subsequently, external electrodes 4 were formed on both ends of the ceramic body 3. The external electrode 4 is obtained by applying a conductive paste to the ceramic body 3 and firing to form a base electrode 5 and then forming a plating layer 6 on the base electrode 5 by wet plating.

  As described above, a plurality of laminated ceramic capacitors formed in the same lot up to the external electrode 4 were prepared. This is group 1.

  FIG. 2 is a process diagram showing a process of measuring a current value I1 and a current value I2 and calculating a current ratio according to the embodiment of the present invention.

  Next, the current value I1 and the current value I2 of the multilayer ceramic capacitor are measured.

  As shown in FIG. 2, in the process of measuring the current value I1 and the current value I2, the multilayer ceramic capacitor on which the external electrode 4 is formed is heat-treated at a high temperature, and then a voltage equal to or lower than the rated voltage is applied to cause a short circuit. Inspection is performed to remove short-circuited products, and non-defective products are discharged in the short-circuit inspection.

  Next, a voltage is applied to the multilayer ceramic capacitor, the current value I1 is measured and discharged, and then the current value I2 is measured and discharged sequentially.

  The current value I1 is measured by applying a voltage using one of the external electrodes 4 at both ends as a positive electrode and the other as a negative electrode, and the current value I2 is the same voltage value as the applied voltage of the current value I1, The measurement was performed by applying a reverse voltage with one of the electrodes 4 as a negative electrode and the other as a positive electrode.

  The applied voltage is preferably 2 times the rated voltage of the multilayer ceramic capacitor to 0.8 times the breakdown voltage, and the variation in the current ratio, which will be described later, is increased, thereby improving the accuracy of determining the reliability of the multilayer ceramic capacitor. it can.

  Moreover, the application time of the voltage of current value I1 and current value I2 is the same, and the application time is preferably 10 s or less.

  Next, the current ratio of the multilayer ceramic capacitor is calculated. The current ratio is the ratio of the current value I2 to the current value I1, and the current ratio of the multilayer ceramic capacitors of group 1 is the first current ratio.

  On the other hand, a reference value for evaluating and determining the value of the first current ratio is obtained. In order to obtain this reference value, a group of a plurality of multilayer ceramic capacitors having the same manufacturing method as that of group 1 until the formation of the external electrode 4 is prepared. This is group 2.

  In the same manner as in group 1, the voltage of the multilayer ceramic capacitor of group 2 is applied to measure the current value I1, and after discharging, the reverse voltage of this voltage is applied to measure the current value I2, and this current value I1, The current value I2 is defined as a current value I1a and a current value I2a, respectively, a current ratio that is a ratio of the current value I2a to the current value I1a is obtained, this is defined as a second current ratio, and an average that is a statistic of the second current ratio The value a and the standard deviation value σ are calculated.

  Subsequently, a lower value and an upper value as reference values are calculated from the average value a of the second current ratio and the standard deviation value σ. The lower value is a−k × σ, and the upper value is a + k × σ (k is a positive value).

  Group 2 may be all or part of the multilayer ceramic capacitors of Group 1 and may be of a different lot than Group 1, in which case the first current ratio of Group 1 is Prior to the determination, the lower and upper values of the second current ratio of the group 2 can be determined in advance.

  Here, the coefficient k has the same manufacturing method as the group 1 until the formation of the external electrode 4, and a group 3 of multilayer ceramic capacitors of a lot different from the group 1 is prepared. The third current ratio and the high temperature load test of the group 3 are prepared. Is determined in advance based on the relationship with the deterioration of the insulation resistance.

  The third current ratio is obtained by measuring the current value I1 and the current value I2 of the multilayer ceramic capacitor of the group 3 in the same manner as the group 1, and setting the current value I1 and the current value I2 as the current value I1b and the current value I2b, respectively. The current ratio of the current value I2b to the value I1b is used.

  The coefficient k is preferably 2.5 to 3.2 for a multilayer ceramic capacitor having a dielectric layer 1 having a thickness of 2 μm or less, whereby a highly reliable multilayer ceramic capacitor can be selected.

  Next, the first current ratio of the multilayer ceramic capacitor of group 1 is compared with the lower value and the upper value obtained from the second current ratio of the multilayer ceramic capacitor of group 2.

  When used in the test method of the multilayer ceramic capacitor, it is evaluated that there is no problem in reliability in the high temperature load test when the first current ratio is not less than the lower value and not more than the second value of the second current ratio. It is evaluated that there may be a problem in reliability in the high temperature load test, and the reliability of the group 1 multilayer ceramic capacitors is evaluated based on the value of the first current ratio.

  Further, when used in the method for manufacturing a multilayer ceramic capacitor, it is determined that the first current ratio is a non-defective product when the first current ratio is not less than the lower value and not more than the second current ratio, and the first current ratio is the second current ratio. When the value is smaller than the lower value or larger than the upper value, it is judged as a defective product, and the group 1 multilayer ceramic capacitors are selected.

  Hereinafter, specific examples of the testing method of the multilayer ceramic capacitor of the present invention will be described.

(Example 1)
The multilayer ceramic capacitor of Example 1 has an external electrode on a ceramic body in which dielectric layers and internal electrode layers are alternately stacked, and the thickness of the dielectric layer between the internal electrode layers is 2.0 μm. is there.

The ceramic slurry has a dielectric powder with an average particle size of about 0.2 μm. The dielectric powder is mainly composed of barium titanate, and added with rare earth oxides, SiO ₂ , MgO, MnO _2, etc. What mixed the ceramic raw material powder which added about 2 wt% of the thing was calcined and pulverized.

  This ceramic slurry was applied onto PET and a film and dried to prepare a green ceramic sheet.

  The conductive paste film was produced using a conductive paste containing metallic nickel powder.

  Next, the ceramic raw sheet and the conductive paste film are alternately laminated to form a laminate having 300 conductive paste films, and then separated into individual pieces to produce a ceramic body. External electrodes were formed on the element body to obtain a plurality of multilayer ceramic capacitors. The plurality of multilayer ceramic capacitors are set as group 1.

  Next, as shown in FIG. 2, the current values I1 and I2 of the multilayer ceramic capacitor were measured. The current values I1 and I2 were measured by first conducting a short inspection after heat treatment of the multilayer ceramic capacitor at 150 ° C. for 30 minutes, and then discharging by short-circuiting the external electrodes at both ends. Subsequently, the current value I1 was measured and discharged, and then the current value I2 was measured and discharged.

  The current value I1 is a current value obtained by applying a voltage five times the rated voltage, the current value I2 is a current value obtained by applying a voltage five times the rated voltage by reversing the polarity of the voltage, and the current values I1, A first current ratio was obtained from the current value I2.

  Further, the group 2 of the multilayer ceramic capacitors for obtaining the second current ratio described in the embodiment is set as the group 1, and the second current ratio, that is, the average value a of the first current ratio and the standard deviation value σ are set as follows. Asked. The average value a was 1.107, and the standard deviation value σ was 0.023.

  Furthermore, the coefficient k is set to 3 based on the results described later, and the first current ratio is from a lower value of 1.038 (a−3 × σ) to an upper value of 1.176 (a + 3 × σ). It was evaluated that there was a problem with reliability in the high temperature load test for the other current ratios.

  The coefficient k is determined in advance from group 3 based on the relationship between the current ratio and the insulation resistance failure in the high temperature load test as follows.

  Group 3 is a multilayer ceramic capacitor having the same manufacturing method up to formation of external electrodes as in Group 1, and is manufactured in a lot different from Group 1.

  The current values I1 and I2 of the multilayer ceramic capacitors of group 3 were measured in the same manner as in group 1 to obtain a current ratio, and an average value a and a standard deviation value σ of the current ratio were calculated. At this time, the average value a of the current ratio of group 3 was 1.122, and the standard deviation value σ was 0.026.

  Next, the following samples 1 to 4 were extracted from the multilayer ceramic capacitors of group 3.

  Sample 1 has a coefficient k of 3 and a current ratio in the range of a lower value of 1.044 (a−3 × σ) or higher and an upper value of 1.200 (a + 3 × σ) or lower. Extracted.

  Sample 2 had a coefficient k of 3 and a current ratio smaller than the lower value of 1.044 or larger than the upper value of 1.200, and 300 samples were extracted from group 3.

  Sample 3 has a coefficient k of 3.5 and a current ratio in the range of a lower value of 1.031 (a−3.5 × σ) or higher and an upper value of 1.213 (a + 3.5 × σ) or lower. , 1000 pieces were extracted from group 3.

  Sample 4 had a coefficient k of 3.5 and a current ratio smaller than the lower value of 1.031 or larger than the upper value of 1.213, and 50 samples were extracted from group 3.

  The multilayer ceramic capacitors of Samples 1 to 4 were subjected to a high temperature load test in which a rated voltage was applied at a temperature of 85 ° C. for 1000 hours, and the insulation resistance failure rate after the high temperature load test was determined.

  Insulation resistance failure is a resistance value measured by applying a rated voltage for 1 minute and a resistance value of 2 MΩ or less.

  The results are shown in (Table 1).

  As shown in (Table 1), samples 1 to 4 have insulation resistance failure rates of 0.0%, 37.0%, 0.1%, and 64.0% in the high-temperature load test, respectively. When the ratio is in the range of the lower value a-3 × σ to the upper value a + 3 × σ, there is no insulation resistance failure in the high temperature load test, and the current ratio is smaller than the lower value a-3 × σ or higher value a + 3 × σ. If it is larger, an insulation resistance failure has occurred in the high temperature load test.

  Therefore, based on the relationship between the current ratio of group 3 and the insulation resistance failure in the high temperature load test, the coefficient k is set to 3 for group 1 having the same manufacturing method as that of group 3, so that the multilayer ceramic capacitor of group 1 is obtained. If the first current ratio is lower than the lower limit than the first current ratio and lower than the upper limit, it can be evaluated that the insulation resistance does not deteriorate in the high temperature load test.

  Next, specific examples of the manufacturing method of the multilayer ceramic capacitor of the present invention will be described.

(Example 2)
In the second embodiment, 2000 multilayer ceramic capacitors that have been subjected to the formation of external electrodes are extracted from the group 1 of the first embodiment.

  The first current ratio is the same as that of the first embodiment, and the average value “a” before selection of non-defective products is 1.107, and the standard deviation value σ is 0.023.

  Next, based on Example 1, the coefficient k is set to 3, and a multilayer ceramic capacitor having a first current ratio in the range of a lower value of 1.038 or more and an upper value of 1.176 or less is judged as a non-defective product and selected. did.

(Example 3)
In Example 3, 2000 pieces were produced in the same manner as in Example 1 until the formation of the external electrodes, except that the thickness of the dielectric layer of the multilayer ceramic capacitor was 1.25 μm.

  After measuring the current value I1 and the current value I2 as in Example 1, the first current ratio, the average value a of the first current ratio, and the standard deviation value σ were obtained. The average value a of the first current ratio before selection of non-defective products was 1.291, and the standard deviation value σ was 0.090.

  Next, a coefficient k is set to 3, and a multilayer ceramic capacitor having a first current ratio in the range of a lower value of 1.021 (a−3 × σ) or higher and an upper value of 1.561 (a + 3 × σ) or lower is determined as a non-defective product. The multilayer ceramic capacitors were selected.

(Comparative example)
The comparative example was manufactured in the same manner as in Example 1 until the formation of the external electrode, and 2000 multilayer ceramic capacitors formed with this external electrode were extracted from Group 1 of Example 1 and heat-treated at 150 ° C. for 30 minutes. Thereafter, a short inspection and a discharge were sequentially performed.

  Next, 1000 pieces were selected from non-defective products of the multilayer ceramic capacitors of Example 2, Example 3, and Comparative Example, respectively, and a high temperature load test was performed for 1000 hours by applying a rated voltage at a temperature of 85 ° C.

  The results are shown in (Table 2).

  As shown in (Table 2), the insulation resistance defect rates in the high temperature load test of Example 2, Example 3, and Comparative Example are 0.0%, 0.0%, and 0.2%, respectively. 2. In Example 3, no insulation resistance failure occurred.

  As described above, when the thickness of the dielectric layer of the multilayer ceramic capacitor is 2.0 μm or less, the coefficient k is set to 3 and the first current ratio is in the range of the lower value a−3 × σ to the upper value a + 3 × σ. By sorting out certain ones, a highly reliable multilayer ceramic capacitor can be obtained.

  The test method and the manufacturing method of the multilayer ceramic capacitor according to the present invention can accurately evaluate whether or not the multilayer ceramic capacitor causes deterioration of insulation resistance in a high temperature load environment, and can also accurately evaluate the high temperature load environment. Therefore, it is possible to obtain a multilayer ceramic capacitor excellent in reliability with reduced deterioration of insulation resistance, and is useful for electronic circuits and electronic devices that require high density.

Cross section of multilayer ceramic capacitor Process drawing which shows the process of measuring the electric current value I1 and the electric current value I2 of embodiment of this invention, and calculating a current ratio

Explanation of symbols

1 Dielectric layer 2 Internal electrode layer 3 Ceramic body 4 External electrode

Claims (3)

A test method for a multilayer ceramic capacitor having external electrodes on a ceramic body in which dielectric layers and internal electrode layers are alternately stacked, wherein a voltage is applied to the multilayer ceramic capacitor to measure a current value I1, and then A test method for a multilayer ceramic capacitor in which a reverse voltage of the voltage is applied, a current value I2 is measured, and a reliability of the multilayer ceramic capacitor in a high temperature load environment is evaluated based on a current ratio of the current value I2 to the current value I1 . A multilayer ceramic capacitor having an external electrode on a ceramic body in which dielectric layers and internal electrode layers are alternately stacked is prepared, a voltage is applied to the multilayer ceramic capacitor, a current value I1 is measured, and then the voltage Applying a reverse voltage to measure a current value I2, calculating a current ratio of the current value I2 to the current value I1, and setting the current ratio as a first current ratio;
A voltage is applied to a plurality of multilayer ceramic capacitors having the same manufacturing method as the multilayer ceramic capacitor to measure a current value I1a, then a reverse voltage of the voltage is applied to measure a current value I2a, and the current value I1a is measured. Calculating a current ratio of the current value I2a and setting the current ratio as a second current ratio;
Calculating an average value a and a standard deviation value σ of the second current ratio to obtain a−k × σ and an upper value a + k × σ (k is a positive value);
A selection step in which the multilayer ceramic capacitor in which the first current ratio is equal to or higher than the lower value of the second current ratio and equal to or lower than the upper value is a non-defective product;
A method of manufacturing a multilayer ceramic capacitor comprising: 3. The method of manufacturing a multilayer ceramic capacitor according to claim 2, wherein the multilayer ceramic capacitor has a thickness of the dielectric layer of 2 μm or less and the coefficient k is 2.5 to 3.2. 4.

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