JP7127369B2 - Determination method for quality of multilayer ceramic capacitors - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for judging quality of a laminated ceramic capacitor, and more particularly to a method for judging the quality of a laminated ceramic capacitor based on insulation resistance.

Conventionally, various methods have been proposed for judging non-defective and defective multilayer ceramic capacitors. As one of the methods for judging non-defective products and defective products, there is known a method of measuring the insulation resistance of a multilayer ceramic capacitor to judge non-defective products and defective products.

Patent Literature 1 describes a method for accurately detecting defective products by applying an AC voltage between a pair of external electrodes of a multilayer ceramic capacitor and then measuring the insulation resistance. That is, by applying an AC voltage, the portion where the connection between the internal electrode and the external electrode is incomplete is destroyed, so that it is possible to accurately detect defective products in which the connection between the internal electrode and the external electrode is incomplete. Patent Document 1 describes that it is possible.

Japanese Unexamined Patent Application Publication No. 2000-124088

However, Japanese Patent Laid-Open No. 2002-200001 does not describe the time for which a voltage is applied between a pair of external electrodes when measuring insulation resistance. For this reason, depending on the voltage application time, the insulation resistance cannot be measured with high accuracy, and there is a possibility that defective products may be included in those determined as non-defective products.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for accurately measuring insulation resistance and determining whether a multilayer ceramic capacitor is good or bad.

The quality judgment method of the multilayer ceramic capacitor of the present invention comprises:
a body made of a dielectric ceramic; a plurality of internal electrodes embedded in the body so as to be alternately led out to first and second end faces of the body; preparing a multilayer ceramic capacitor comprising an end face and a pair of external electrodes provided on the second end face and connected to the internal electrode;
a step of applying a predetermined voltage to the pair of external electrodes for a charging time T determined based on the dielectric constant ε of the multilayer ceramic capacitor;
measuring the insulation resistance after applying the predetermined voltage;
a step of determining whether the multilayer ceramic capacitor is good or bad based on the measured insulation resistance;
with
The charging time T is characterized by satisfying the following formula (3) in the relationship between fa represented by the following formula (1) and fb represented by the following formula (2) .
fa=0.95×(6.28×ε-60) (1)
fb=1.05×(6.28×ε−60) (2)
1/(2fb)≤T≤1/(2fa) (3)

The predetermined voltage may be a square-wave voltage with a frequency f=1/(2T) that alternates between positive and negative values every charging time T.

Also, the predetermined voltage may be 300 V or less.

In the step of determining the quality of the laminated ceramic capacitor, the average value K and the variance value σ of the insulation resistance of the plurality of measured laminated ceramic capacitors are obtained, and the measured insulation resistance is (K−4σ) or less. The laminated ceramic capacitor may be determined as a defective product.

According to the method for judging quality of a laminated ceramic capacitor of the present invention, a predetermined voltage is applied for a charging time T determined based on the dielectric constant ε of the laminated ceramic capacitor to measure the insulation resistance. Based on the above, the good product and the defective product are determined . The charging time T satisfies the following formula (3) in the relationship between fa represented by the following formula (1) and fb represented by the following formula (2).
fa=0.95×(6.28×ε-60) (1)
fb=1.05×(6.28×ε−60) (2)
1/(2fb)≤T≤1/(2fa) (3)
As a result , the insulation resistance can be measured with high accuracy, and the quality of the multilayer ceramic capacitor can be determined with high accuracy, so that defective products can be suppressed from being included in the products determined as good products.

1 is a perspective view of a laminated ceramic capacitor; FIG. 2 is a cross-sectional view of the multilayer ceramic capacitor shown in FIG. 1 taken along line II-II. FIG. FIG. 2 is a cross-sectional view along line III-III of the multilayer ceramic capacitor shown in FIG. 1; FIG. 4 is a diagram showing waveforms of rectangular wave voltages applied between a pair of external electrodes of a multilayer ceramic capacitor; 4 is a flow chart showing a procedure for judging quality of a laminated ceramic capacitor;

Embodiments of the present invention will be shown below, and features of the present invention will be specifically described.

First, the configuration of the multilayer ceramic capacitor, which is the target of quality judgment, will be described.

(multilayer ceramic capacitor)
FIG. 1 is a perspective view of a laminated ceramic capacitor 10. FIG. FIG. 2 is a cross-sectional view of the multilayer ceramic capacitor 10 shown in FIG. 1 along line II-II. FIG. 3 is a cross-sectional view of the multilayer ceramic capacitor 10 shown in FIG. 1 along line III-III.

As shown in FIGS. 1 to 3, the multilayer ceramic capacitor 10 is an electronic component having a rectangular parallelepiped shape as a whole, and includes a ceramic body 11 and a pair of external electrodes 14a and 14b. The pair of external electrodes 14a and 14b are arranged to face each other as shown in FIGS.

Here, the direction in which the pair of external electrodes 14a and 14b face each other is defined as the length direction L of the multilayer ceramic capacitor 10, and the stacking direction of the internal electrodes 13a and 13b, which will be described later, is defined as the thickness direction Z, and the length direction L and the thickness direction Z are defined as the width direction W. As shown in FIG.

The ceramic body 11 has a first end face 15a and a second end face 15b facing each other in the length direction L, a first principal face 16a and a second principal face 16b facing each other in the thickness direction Z, and a width direction W It has a first side 17a and a second side 17b facing each other.

The ceramic body 11 preferably has rounded corners and ridges. Here, the corner portion is a portion where three surfaces of the ceramic body 11 intersect, and the ridge portion is a portion where two surfaces of the ceramic body 11 intersect.

As shown in FIGS. 2 and 3, the ceramic body 11 includes a dielectric layer 12, first internal electrodes 13a and second internal electrodes 13b.

The dielectric layer 12 includes an outer dielectric layer 121 located outside the ceramic body 11 in the thickness direction, and an inner dielectric layer 122 located between the first internal electrode 13a and the second internal electrode 13b. include.

The dielectric layer 12 is made of, for example, a material containing dielectric ceramic as a main component. Specific examples of dielectric ceramics include BaTiO ₃ , CaTiO ₃ , SrTiO ₃ and CaZrO ₃ . Subcomponents such as Mn compounds, Mg compounds, Si compounds, Co compounds, Ni compounds, and rare earth compounds may be appropriately added to the dielectric layer 12 .

The first internal electrode 13a is drawn out to the first end surface 15a of the ceramic body 11. As shown in FIG. Also, the second internal electrode 13b is drawn out to the second end surface 15b of the ceramic body 11 . The first internal electrodes 13a and the second internal electrodes 13b are alternately arranged in the thickness direction Z with the inner dielectric layers 122 interposed therebetween.

The first internal electrode 13a has a counter electrode portion which is a portion facing the second internal electrode 13b, and a lead electrode portion which is a portion drawn from the counter electrode portion to the first end surface 15a of the ceramic body 11. It has The second internal electrode 13b consists of a counter electrode portion that faces the first internal electrode 13a and a lead electrode portion that extends from the counter electrode portion to the second end surface 15b of the ceramic body 11. and

A capacitance is formed by the opposing electrode portion of the first internal electrode 13a and the opposing electrode portion of the second internal electrode 13b facing each other with the inner dielectric layer 122 interposed therebetween, thereby functioning as a capacitor.

The first internal electrode 13a and the second internal electrode 13b contain, for example, metals such as Ni, Cu, Ag, Pd, and Au, alloys of Ag and Pd, and the like. The first internal electrode 13 a and the second internal electrode 13 b may further contain dielectric particles having the same composition as the ceramic contained in the dielectric layer 12 .

The first external electrode 14a is formed over the entire first end surface 15a of the ceramic element body 11, and extends from the first end surface 15a to the first main surface 16a, the second main surface 16b, and the first main surface 16b. side 17a and the second side 17b. The first external electrode 14a is electrically connected to the first internal electrode 13a.

The second external electrode 14b is formed over the entire second end surface 15b of the ceramic body 11, and extends from the second end surface 15b to the first main surface 16a, the second main surface 16b, and the first main surface 16b. side 17a and the second side 17b. The second external electrode 14b is electrically connected to the second internal electrode 13b.

The first external electrode 14a and the second external electrode 14b comprise, for example, a sintered metal layer and a plated layer.

The sintered metal layer is a layer containing glass and metal, and may be one layer or multiple layers. Metals included in the sintered metal layer include, for example, at least one of metals such as Cu, Ni, Ag, Pd, and Au, alloys of Ag and Pd, and the like.

The sintered metal layer is formed by applying a conductive paste containing glass and metal to the ceramic body and baking the paste. Baking may be performed simultaneously with firing the ceramic body 11 or may be performed after firing the ceramic body 11 .

The plating layer disposed on the sintered metal layer includes, for example, at least one of metals such as Ni, Cu, Ag, Pd, and Au, alloys of Ag and Pd, and the like. The plated layer may be one layer, or may be multiple layers. However, the plating layer preferably has a two-layer structure of a Ni plating layer and an Sn plating layer. The Ni plating layer functions to prevent the sintered metal layer from being eroded by solder when mounting the multilayer ceramic capacitor 10 . In addition, the Sn plating layer functions to improve the wettability of solder when mounting the multilayer ceramic capacitor 10 .

(Manufacturing method of multilayer ceramic capacitor)
A method for manufacturing the multilayer ceramic capacitor 10 described above will be briefly described.

First, a ceramic slurry is prepared by mixing and dispersing a binder and an organic solvent in dielectric ceramic powder. Dielectric ceramic powders include, for example, BaTiO ₃ or CaZrO ₃ .

Subsequently, a ceramic green sheet is produced by coating the ceramic slurry on the resin film.

Subsequently, an internal electrode pattern is formed by preparing an internal electrode conductive paste and printing the internal electrode conductive paste on a ceramic green sheet. The internal electrode conductive paste contains, for example, Ni powder, an organic solvent, a binder, and the like. A printing method such as screen printing or gravure printing can be used for printing the conductive paste for internal electrodes.

Subsequently, a predetermined number of ceramic green sheets on which internal electrode patterns are not formed are stacked, and ceramic green sheets on which internal electrode patterns are formed are successively stacked thereon, and further internal electrode patterns are formed thereon. A predetermined number of ceramic green sheets are laminated to produce a mother laminate.

Subsequently, the mother laminated body is pressed by a method such as a rigid body press or a hydrostatic press, and then cut into a predetermined size by a cutting method such as press cutting, dicing, or laser. After that, the corners and ridges are rounded by barrel polishing or the like. An unfired laminate is obtained through the above-described steps. In this unfired laminate, internal electrode patterns are exposed on both end faces.

Subsequently, by firing the unfired laminate, a ceramic body is obtained.

Subsequently, a conductive paste for external electrodes is applied to both end faces of the ceramic body. The conductive paste for external electrodes contains, for example, metal particles containing Cu and glass.

Subsequently, after drying the external electrode conductive paste applied to both end surfaces of the ceramic body, baking is performed at a predetermined temperature. As a result, sintered metal layers are formed on both end faces of the ceramic body.

Subsequently, a plated layer is formed on the sintered metal layer. For example, the sintered metal layer is plated with Ni and then plated with Sn.

(Method for Determining Quality of Multilayer Ceramic Capacitor)
A method for judging whether the multilayer ceramic capacitor 10 according to the present embodiment is good or bad will be described with reference to the flowchart shown in FIG.

First, a laminated ceramic capacitor 10 having the structure described above is prepared (step S1). The multilayer ceramic capacitor 10 having the structure described above includes a ceramic element body 11 made of a dielectric ceramic, and a ceramic element body 11 that is alternately led out to the first end surface 15a and the second end surface 15b of the ceramic element body 11. and a pair of external electrodes 14a, 14b provided on the first end surface 15a and the second end surface 15b of the ceramic body 11 and connected to the internal electrodes 13a, 13b. A multilayer ceramic capacitor comprising

Subsequently, a predetermined voltage is applied between the pair of external electrodes 14a and 14b of the multilayer ceramic capacitor 10 for a charging time T determined based on the dielectric constant ε of the multilayer ceramic capacitor 10 (step S2).

In the present embodiment, a rectangular wave voltage with a frequency f=1/(2T), in which positive and negative values alternate every charging time T, is applied. That is, the period of the rectangular wave voltage is 2T.

FIG. 4 is a diagram showing the waveform of the rectangular wave voltage applied between the pair of external electrodes 14a and 14b of the multilayer ceramic capacitor 10. As shown in FIG. The maximum value V1 of the rectangular wave voltage is 300 V or less, and is appropriately determined based on the capacitance of the laminated ceramic capacitor 10, for example.

The charging time T satisfies the following formula (3) in the relationship between fa represented by the following formula (1) and fb represented by the following formula (2).
fa=0.95×(6.28×ε-60) (1)
fb=1.05×(6.28×ε−60) (2)
1/(2fb)≤T≤1/(2fa) (3)

The frequency f of the rectangular wave voltage described above is greater than or equal to fa represented by equation (1) and less than or equal to fb represented by equation (2). That is, the relationship fa≤f≤fb is established.

The inventors of the present application have conducted experiments and the like for fa represented by the formula (1) and fb represented by the formula (2) in order to accurately discriminate between non-defective and defective multilayer ceramic capacitors 10. It was discovered by

After applying a predetermined voltage to the pair of external electrodes 14a and 14b for the charging time T, insulation resistance is measured by a known method, for example, by measuring leakage current (step S3).

Note that the measurement of the insulation resistance may be performed a plurality of times for each charging time T. For example, the insulation resistance may be measured a plurality of times and the average value may be obtained.

Then, the quality of the laminated ceramic capacitor 10 is determined based on the measured insulation resistance (step S4).

Here, the insulation resistance is measured for a plurality of laminated ceramic capacitors 10 to obtain an average value K and a variance value σ, and the laminated ceramic capacitors 10 having an insulation resistance of (K−4σ) or less are determined to be defective.

By the determination method described above, it is possible to accurately discriminate between non-defective and defective multilayer ceramic capacitors 10 . In particular, it is possible to prevent defective products from being included in products determined to be non-defective products.

(Example)
A plurality of types of laminated ceramic capacitors having different dielectric constants were produced by changing the ratio of the materials constituting the dielectric layers of the ceramic body. A plurality of types of laminated ceramic capacitors thus produced were subjected to a known moisture resistance test to confirm the existence of laminated ceramic capacitors with inherent structural defects.

Structural defects include, for example, the proximity of laminated internal electrodes, poor connection between internal electrodes and external electrodes, and the like.

Subsequently, the multilayer ceramic capacitor was dried in a vacuum and high-temperature environment to recover IR (insulation resistance) deterioration.

After that, as described above, the insulation resistance was measured by applying a rectangular wave voltage with a frequency f at the charging time T. Then, based on the measured insulation resistance, the multilayer ceramic capacitors were classified into non-defective products and defective products. Specifically, the insulation resistance is measured for a plurality of laminated ceramic capacitors, the average value K and the variance value σ are obtained, and the laminated ceramic capacitor 10 having an insulation resistance of (K−4σ) or less is determined as a defective product. , and those other than that were judged to be non-defective products. Table 1 shows the determination results.

Table 1 shows 19 determination results with different relationships between the dielectric constant ε and the frequency f (period 2T). The sorting result and structural defect content rate are shown, respectively.

Here, 5,000 multilayer ceramic capacitors of sample numbers 1 to 19 were prepared, and good/defective products were discriminated. The sorting result shows the percentage of 5,000 products that were determined to be non-defective products and the percentage of products that were determined to be defective.

The structural defect content rate represents the content rate of products that actually contain structural defects among those judged to be non-defective products or defective products. For example, regarding the multilayer ceramic capacitor of sample number 15, the percentage of those judged to be non-defective products that actually contained structural defects was 0.3%. The percentage of those containing defects is 31.9%.

The presence or absence of structural defects was examined by the following method. That is, the multilayer ceramic capacitor was polished to expose the cross section, and the cross section was observed with a scanning electron microscope (SEM). However, 1000 pieces were randomly selected from those judged to be non-defective, and the presence or absence of structural defects was examined. .

The dielectric constants ε of the multilayer ceramic capacitors of sample numbers 1 to 19 shown in Table 1 are any of 30, 70, 125, 2500 and 3500. For each dielectric constant ε, the range of frequency f that satisfies the conditions of the present invention is as follows.
Permittivity ε=30: 121.98≦f≦134.82
Permittivity ε=70: 360.62≦f≦398.58
Permittivity ε=125: 688.75≦f≦761.25
Permittivity ε=2500: 14858≦f≦16422
Permittivity ε=3500: 20824≦f≦23016

In Table 1, the frequency f of the AC voltage applied for quality judgment of the laminated ceramic capacitors of sample numbers 10 to 19 does not satisfy the relationship fa≦f≦fb, which is the condition of the present invention. Therefore, the charging time T also does not satisfy the relationship of the above formula (3).

As shown in Table 1, in the pass/fail judgment of the multilayer ceramic capacitors of sample numbers 10 to 19, defective products are included in the non-defective products. For example, in the quality judgment of the multilayer ceramic capacitor of sample number 10, 0.1% of defective products are included in those judged as good products. Also, in the quality judgment of the laminated ceramic capacitor of sample number 19, 0.5% of defective products were included in those judged to be non-defective products.

On the other hand, the frequency f of the AC voltage applied in the quality judgment of the multilayer ceramic capacitors of sample numbers 1 to 9 is slightly lower than fa shown in equation (1) or slightly higher than fb shown in equation (2). did. As shown in Table 1, in the pass/fail judgment of the multilayer ceramic capacitors of sample numbers 1 to 9, none of the non-defective products with structural defects were included.

In addition, in the pass/fail judgment of the multilayer ceramic capacitors of sample numbers 1 to 9, among the pass/fail judgment results of the multilayer ceramic capacitors of sample numbers 10 to 19, when compared with the judgment result of the same dielectric constant ε, it was judged to be a defective product. It can be seen that a high proportion of defective products with actual structural defects are included in the products that have been processed.

Also, although not shown in Table 1, when a rectangular wave voltage having a frequency f satisfying the relationship fa≦f≦fb was applied at the charging time T satisfying the relationship of formula (3), and the pass/fail judgment was performed. Also, it was confirmed that not even one defective product was included in the products judged to be non-defective products. Further, when the rectangular wave voltage of the frequency f is applied for the charging time T satisfying the relationship of the expression (3) and the pass/fail judgment is performed, the relationship of the expression (3) and the relationship of fa≤f≤fb are satisfied. It was confirmed that defective products with actual structural defects were included in a higher proportion of products determined to be defective compared to cases where the criteria were not met.

That is, when a rectangular wave voltage with a frequency f = 1/(2T) is applied at a charging time T that satisfies the relationship of formula (3) to determine whether the multilayer ceramic capacitor is good or bad, defective products are found among the good products. I was able to confirm that there were no non-defective products. Moreover, even if the frequency f is slightly lower than fa or slightly higher than fb and the charging time T slightly deviates from the relationship of the above equation (3), defective products should not be included in the non-defective products. could be confirmed.

For these reasons, as in the method for judging quality of a multilayer ceramic capacitor in this embodiment, a rectangular wave voltage with a frequency f = 1/(2T) is applied at a charging time T that satisfies the relationship of expression (3). By judging the quality of the multilayer ceramic capacitor, it is possible to prevent defective products from being included in those judged to be non-defective products. Therefore, it is possible to suppress the use of a multilayer ceramic capacitor that is determined to be a non-defective product in an electronic device or the like in spite of being a defective product.

In addition, according to the method for judging quality of a multilayer ceramic capacitor according to the present embodiment, it is possible to increase the ratio of defective products that actually have a defective structure among those judged to be defective. Detection accuracy can be improved.

Furthermore, according to the method for judging quality of a multilayer ceramic capacitor in the present embodiment, by setting the charging time T to the minimum value within the range satisfying the relationship of the above formula (3), the multilayer ceramic capacitor can be accurately charged in a short charging time. It is possible to judge whether the product is good or bad. Thereby, the manufacturing efficiency of the laminated ceramic capacitor can be improved.

The present invention is not limited to the above embodiments, and various applications and modifications can be made within the scope of the present invention.

10 Multilayer ceramic capacitor 11 Ceramic element body 12 Dielectric layer 13a First internal electrode 13b Second internal electrode 14a First external electrode 14b Second external electrode 15a First end face 15b Second end face 16a main surface 16b second main surface 17a first side surface 17b second side surface 121 outer dielectric layer 122 inner dielectric layer

Claims (4)

a body made of a dielectric ceramic; a plurality of internal electrodes embedded in the body so as to be alternately led out to first and second end faces of the body; preparing a multilayer ceramic capacitor comprising an end face and a pair of external electrodes provided on the second end face and connected to the internal electrode;
a step of applying a predetermined voltage to the pair of external electrodes for a charging time T determined based on the dielectric constant ε of the multilayer ceramic capacitor;
measuring the insulation resistance after applying the predetermined voltage;
a step of determining whether the multilayer ceramic capacitor is good or bad based on the measured insulation resistance;
with
The charging time T satisfies the following formula (3) in the relationship between fa represented by the following formula (1) and fb represented by the following formula (2). Good/bad judgment method.
fa=0.95×(6.28×ε-60) (1)
fb=1.05×(6.28×ε−60) (2)
1/(2fb)≤T≤1/(2fa) (3) 2. The quality of the multilayer ceramic capacitor according to claim 1 , wherein the predetermined voltage is a rectangular wave voltage with a frequency f=1/(2T) in which positive and negative values are alternated every charging time T. judgment method. 3. The method for judging quality of a multilayer ceramic capacitor according to claim 1, wherein said predetermined voltage is 300 V or less. In the step of determining the quality of the laminated ceramic capacitor, the average value K and the variance value σ of the insulation resistance of the plurality of measured laminated ceramic capacitors are obtained, and the measured insulation resistance is (K−4σ) or less. 4. The method for judging quality of a laminated ceramic capacitor according to claim 1 , wherein said laminated ceramic capacitor is judged to be defective.

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