JP2000124088A - Method for sorting stacked ceramic capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for sorting moducts having imperfect connections between the inner and outer electrodes of the stacked ceramic capacitors with good accuracy. SOLUTION: A stacked ceramic capacitor to be measured 1 has outer electrodes at both ends of a laminate so as to be electrically connected to inner electrodes. The laminate has dielectric ceramic layers and inner electrodes laminated alternately so that one side ends of the inner electrodes are alternately exposed at the facing opposite different faces sandwiching the dielectric ceramic layers. In the capacitor 1, (2) an a-c voltage is applied by at least two cycles between the outer electrodes and then (3) the outer electrodes are short-circuited to cause discharge of stored electric changes, and a capacitance sort step 4 follows to sort and remove the capacitor as a connection-imperfect product, if it has a low capacitance out of a fixed reference characteristic value range.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of selecting a multilayer ceramic capacitor for selecting a defective connection between an internal electrode and an external electrode of the multilayer ceramic capacitor.

[0002]

2. Description of the Related Art Japanese Patent Laid-Open Publication No. 3-5 / 1990 discloses a method for selecting a defective connection between an internal electrode and an external electrode of a multilayer ceramic capacitor.
No. 2212 and Japanese Patent Application Laid-Open No. 9-330855 are disclosed.

In the sorting method described in the first Japanese Patent Application Laid-Open No. 3-52212, the capacitance of a multilayer ceramic capacitor is measured in two or more different frequency bands, and the ratio of the capacitance in each frequency band is determined. In addition, those which are out of the predetermined reference value range are selectively removed as defective connection between the internal electrode and the external electrode.

In the sorting method described in the second Japanese Patent Application Laid-Open No. 9-330855, a DC voltage is applied between external electrodes of a multilayer ceramic capacitor, a change in the behavior of a leakage current waveform at that time is detected, and the behavior is abnormal. The product is first sorted and removed, and then the capacitance of the first sorted non-defective product is measured.

[0005] In addition, a defective connection between an internal electrode and an external electrode of a multilayer ceramic capacitor is generally selected as a defective connection by using the fact that the capacitance value is smaller than a design value by utilizing the fact that the capacitance value is smaller than a design value. A method of removing it has also been used.

[0006]

However, in the screening method disclosed in Japanese Patent Application Laid-Open No. 3-52212, the same multilayer ceramic capacitor is measured at least twice in different frequency bands, and the capacitance value in the measured frequency band is determined. One-to-one correspondence is required, and the ratio is determined and selected, which is very complicated. Further, in the sorting method disclosed in Japanese Patent Application Laid-Open No. 9-330855, a DC voltage is applied between the external electrodes of the device under test, so that it is not possible to detect abnormalities when a voltage is applied in the opposite direction between the external electrodes.

[0007] In addition, a method of treating a small capacitance value as a defective connection between the internal electrode and the external electrode is such that a defective connection has an unstable measured value of the capacitance, and the capacitance value fluctuates for each measurement. There is a problem that the reproducibility is poor and the defective connection cannot be completely removed even if the characteristic selection is repeated several times.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for selecting a multilayer ceramic capacitor which can eliminate the above-mentioned conventional drawbacks and can accurately select characteristics.

[0009]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a multilayer ceramic capacitor in which positive and negative voltages are alternately applied between the external electrodes, and then the external electrodes are short-circuited to discharge the stored electric charge. Then, a characteristic inspection is performed, and a method of selecting and removing an object that is out of a predetermined reference characteristic range is adopted.

In this way, after the portion where the connection between the internal electrode and the external electrode is incomplete is destroyed by discharge, so-called a state of missing capacitance, a multilayer ceramic capacitor having a small capacitance is surely measured by measuring the capacitance. Can be selectively removed.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS According to the first aspect of the present invention, a dielectric ceramic layer and an internal electrode are alternately laminated in a plurality of layers, and one end of the internal electrode is connected to the dielectric ceramic layer. In a multilayer ceramic capacitor having external electrodes formed so as to be electrically connected to the internal electrodes on both end surfaces of the laminate alternately exposed to different end surfaces opposed to each other with a positive and negative voltage between the external electrodes, This is a method for selecting a multilayer ceramic capacitor in which, after being alternately applied, a short circuit is caused between external electrodes to discharge a stored charge, a characteristic test is performed, and a capacitor out of a predetermined reference characteristic value range is selectively removed. By applying positive and negative voltages alternately between the external electrodes, the incomplete connection between the internal electrode and the external electrode is reliably destroyed by discharge. Since the multilayer ceramic capacitor formed of ceramic layers is not connected to an external electrode, the capacitor is in a so-called capacitance-loss state. It becomes small in capacity and can be selectively removed, and by alternately applying positive and negative voltages between external electrodes,
The dielectric ceramic layer sandwiched between the internal electrodes has a function of deteriorating the insulation resistance, and has a function of being selectively removed in a subsequent insulation resistance test.

According to a second aspect of the present invention, there is provided the method for selecting a multilayer ceramic capacitor according to the first aspect, wherein an AC voltage is applied between external electrodes. When an AC voltage is applied between the external electrodes, a voltage in the forward and reverse directions is applied to a portion where the connection between the internal electrode and the external electrode is incomplete, and the portion where the connection is incomplete is destroyed without fail. This has the effect that the capacitance of the multilayer ceramic capacitor is small in the measurement of the capacitance and the capacitor is reliably selected.

According to a third aspect of the present invention, there is provided the method for selecting a multilayer ceramic capacitor according to the first or second aspect, wherein a sine wave voltage is applied between external electrodes. A voltage can be applied in a forward direction or a reverse direction to a portion where connection between the external electrode and the internal electrode is incomplete, and the discharge can be reliably destroyed.

According to a fourth aspect of the present invention, there is provided the method for selecting a multilayer ceramic capacitor according to the first or second aspect, wherein a rectangular wave voltage is applied between external electrodes. As a result, a rectangular wave voltage that can hold the maximum voltage in the positive and negative directions for a long time is applied to the incomplete connection between the internal electrode and the external electrode, so that the incomplete connection is reliably destroyed. Can be sorted out.

According to a fifth aspect of the present invention, there is provided the method for selecting a multilayer ceramic capacitor according to any one of the first to fourth aspects, wherein a voltage of two cycles or more is applied between the external electrodes. . As a result, a continuous positive and negative voltage is applied twice or more to a portion where connection between the internal electrode and the external electrode is incomplete, so that the incomplete connection portion can be more reliably destroyed. It has.

According to a sixth aspect of the present invention, in the multilayer ceramic capacitor according to any one of the first to fifth aspects, a voltage higher than the rated voltage of the multilayer ceramic capacitor is applied between the external electrodes. It is a sorting method. As a result, a voltage in the positive and negative directions that is higher than the rated voltage of the multilayer ceramic capacitor is applied to the incomplete connection between the internal and external electrodes, so that the incomplete connection is more reliably destroyed and sorted. When a later non-defective product is used at a rated voltage or less, it has an effect that it is possible to prevent capacitance loss due to poor connection between the internal electrode and the external electrode.

According to a seventh aspect of the present invention, the positive or negative voltage is alternately applied between the external electrodes in a constant humidity, and the characteristic inspection is performed in the constant humidity. (1) A method for selecting a multilayer ceramic capacitor according to (1), which prevents a surface leak between external electrodes due to the influence of humidity when a voltage is applied between external electrodes, and ensures a defective connection portion. Voltage is applied to the incomplete portion to reliably destroy the incomplete portion, and the capacitance can be reliably measured without being affected by a temperature change in measuring the capacitance.

According to an eighth aspect of the present invention, after the multilayer ceramic capacitor is alternately held in a high-temperature and low-temperature bath for several cycles for a predetermined time, a voltage is applied between the external electrodes. A method for selecting a multilayer ceramic capacitor according to any one of the above. In this way, repeated stress of thermal expansion and thermal contraction is applied to the imperfect connection between the internal electrode and the external electrode, so that the metal is fatigued at that point, and when a voltage is applied between the external electrodes, it can be easily broken. It has the effect of being able to.

According to a ninth aspect of the present invention, after first measuring the electrostatic capacitance of a multilayer ceramic capacitor and sorting out and removing a primary defective product, an external product within a predetermined reference characteristic value range is externally removed. The method for selecting a multilayer ceramic capacitor according to any one of claims 1 to 8, wherein a voltage is applied between the electrodes. In this way, if the connection between the internal electrode and the external electrode is incomplete and the capacitance does not reach the specified value, it is selected and removed in advance by capacitance measurement. In the case where the voltage has reached, the portion where connection is incomplete is surely destroyed by application of positive and negative voltages, and it can be surely removed by the subsequent capacitance measurement.

FIG. 1 shows a method of selecting a multilayer ceramic capacitor according to an embodiment of the present invention, FIG. 2A is a circuit diagram showing the application of the AC voltage, FIG. 2B is a waveform diagram of the AC voltage, and FIG. Shows a comparison of the sorting effect between the embodiment of the present invention and the conventional sorting method. 1 and 2, reference numeral 1 denotes a multilayer ceramic capacitor as an object to be measured, 2 denotes an AC voltage applying step, 3 denotes a discharging step, 4 denotes a measuring step of capacitance and dielectric loss, 5 denotes an insulating resistance measuring step, and 6 denotes an insulating resistance measuring step. Is a waveform of an AC voltage applied to the multilayer ceramic capacitor 1; 7 is a circuit diagram for applying an AC voltage;
Reference numeral 8 denotes a switch, and 9 denotes an AC voltage power supply.

[0021]

[Table 1]

A method for selecting a multilayer ceramic capacitor in the above process flow will be described.

First, Ni was used for the internal electrode and Cu was used for the external electrode. The length was 2.0 mm, the width was 1.25 mm, and the thickness was 0.65 mm.
400 multilayer ceramic capacitors 1 having an F-characteristic having a capacitance of 10 nF and a rated voltage of 50 V were prepared.
Using the sorting method of the present invention shown in FIG.
The AC rectangular wave voltage having a maximum value of +300 V, a minimum value of -300 V and a cycle of 0.2 seconds between the external electrodes was applied between the external electrodes for 3 cycles, and immediately thereafter, the external electrodes were short-circuited to discharge residual charges. Thereafter, the capacitance, the dielectric loss, and the insulation resistance were measured, and primary non-defective products were selected. The non-defective product selection range is as follows: capacitance = 8 to 18 nF, dielectric loss ≦ 5.0%, insulation resistance ≧ 1 ×
10 ¹⁰ Ω. The capacitance and dielectric loss were measured at a frequency of 1 kHz by applying a voltage of 1 Vrms.
(V) × 1 minute value.

Next, the capacitance, dielectric loss and insulation resistance according to the conventional method were measured for the remaining 200 pieces, and the primary non-defective items were similarly selected. The non-defective range and each measurement condition were the same as those used in the selection of the present invention.

Next, a non-defective product according to the screening method of the present invention,
Secondary screening and tertiary screening were performed under the same conditions, method, and screening range as those of the primary screening, and the effects of each screening were confirmed. The results are shown in Table 1 below.

As shown in Table 1, in the primary screening of the conventional method, eight capacitance defects (small C defects) of 8 nF or less occur, and dielectric loss defects (DNG) and insulation resistance defects (IRN).
G) did not occur. Next, the primary sorting good products 192
When secondary sorting was further performed on the individual pieces, five small C defects occurred, and no DNG or IRNG occurred. Subsequently, tertiary sorting was performed on 187 non-defective products in secondary sorting, and three small C defects occurred, and neither DNG nor IRNG occurred.

The small C defective products of the conventional sorting method were respectively buried in resin and polished from the side so as to be orthogonal to the internal electrodes, and the connection state between the internal electrodes and the external electrodes was confirmed.
Incomplete connection was confirmed in all of the small C defective products.

On the other hand, in the sorting method of the present invention, 21 small C defects of 8 nF or less occurred in the primary sorting after the application of the AC rectangular wave, and DNG and IRNG did not occur.
Next, 179 primary sorted good products were further subjected to secondary sorting, followed by tertiary sorting.
NG and IRNG did not occur at all.

[0029] Twenty-one small C defects in the primary sorting were buried in a resin and polished, and the connection state between the internal electrode and the external electrode was confirmed. From this, in the sorting method of the present invention, the first sorting after applying the AC square wave between the external electrodes for three cycles is performed.
It becomes clear that defective connection between the 21 internal electrodes and the external electrodes can be completely removed by screening. In addition, since no IRNG is generated in the primary, secondary, and tertiary sorting, it is understood that the dielectric ceramic layer does not cause dielectric breakdown by applying an AC rectangular wave.

Next, the selection effect when the AC rectangular wave shown in FIG. 3 is applied between the external electrodes for one cycle will be described with reference to (Table 2).

[0031]

[Table 2]

As shown in Table 2, for 200 samples, the maximum value is +300 V, the minimum value is -300 V, and one cycle is 0.
A 2-second AC rectangular wave voltage is applied between the external electrodes for one cycle. Immediately after that, the external electrodes are short-circuited to discharge residual charges. Then, the capacitance, dielectric loss and insulation resistance are measured, and the primary non-defective product is selected. went. In the primary screening, 10 small defects of 8 nF or less occurred, and neither DNG nor IRNG occurred. Subsequently, when secondary sorting was further performed on 190 primary sorted good products, five small C defects of 8 nF or less occurred, and DNG, I
RNG did not occur.

Further, when the 185 second-ordered non-defective products are tertiary-sorted, two small C defects of 8 nF or less occur, and DN
G and IRNG did not occur. After embedding and polishing 10 pieces, 5 pieces, and 2 pieces of each small C defect in the primary, secondary, and tertiary sorting in resin, and checking the connection state between the internal electrode and the external electrode, all of the incompletely connected portions were found. confirmed. For this reason, it is impossible to completely remove the incomplete connection between the internal electrode and the external electrode by simply applying an AC rectangular wave between the external electrodes for one cycle, and to selectively remove the defective electrode in a state where the capacitance is missing. It becomes clear that there is.

Next, the sorting effect when an AC rectangular wave having a voltage equal to or lower than the rated voltage is applied between the external electrodes will be described with reference to FIG. 4 and (Table 3).

[0035]

[Table 3]

As shown in Table 3, an AC rectangular wave voltage having a maximum value of +25 V, a minimum value of −25 V, and a cycle of 0.2 seconds shown in FIG. Immediately after that, the external electrodes were short-circuited to discharge residual charges, and then the capacitance, dielectric loss, and insulation resistance were measured, and primary non-defective products were selected. In the primary screening, 6 small defects of 8 nF or less occurred, and neither DNG nor IRNG occurred.
Subsequently, when the secondary sorting was further performed on 194 primary sorted good products, four small C defects of 8 nF or less occurred, and DN
G and IRNG did not occur.

Further, when tertiary sorting is performed on 190 good secondary sorting products, three small C defects of 8 nF or less occur, and
NG and IRNG did not occur. The primary, secondary, and tertiary sorting of each of the C small defects of 6, 4, and 3 were buried in resin and polished, and the connection state of the internal and external electrodes was confirmed. confirmed. This is because the rated voltage of 50 V was applied for 1 minute when measuring the insulation resistance in primary, secondary, and tertiary sorting, so that the incomplete connection between the internal electrode and the external electrode was destroyed by discharge. In this state, the capacity was lost, and a small C defect occurred. From this, it is clear that when an AC rectangular wave having a voltage equal to or lower than the rated voltage is applied between the external electrodes, it is impossible to completely remove the defective connection between the internal electrode and the external electrode.

Next, the sorting effect when a high-voltage AC rectangular wave is applied between the external electrodes will be described with reference to FIG. 5 and (Table 4).

[0039]

[Table 4]

As shown in Table 4, 200 samples had a maximum value of +1000 V and a minimum value of -1000 V shown in FIG.
Apply an AC rectangular wave voltage of 0.2 seconds per cycle between the external electrodes for 3 cycles, immediately thereafter, short-circuit the external electrodes to discharge the residual charge, and then change the capacitance, dielectric loss, and insulation resistance. The measurement was performed and the primary non-defective product was selected. In the primary selection, 22 small C defects of 8 nF or less are generated, 3 IRNGs are generated, and D
NG did not occur.

Subsequently, when the secondary sorting was further performed on 175 primary sorting non-defective products, a small C defect of 8 nF or less and DNG did not occur, but one IRNG occurred. Further, when tertiary sorting was performed on 174 second-order non-defective products, a small C defect of 8 nF or less and DNG did not occur, but one IRNG occurred. When 22 pieces of each small C defect in the primary screening were buried in resin and polished, and the connection state between the internal electrode and the external electrode was confirmed, all of them were incompletely connected.
Similarly, three, one, and three IRNGs in primary, secondary, and tertiary sorting
When one of them was buried in a resin and polished to confirm the ceramic dielectric layer, a dielectric breakdown caused by application of a high voltage was confirmed. This is due to the dielectric breakdown of the ceramic dielectric layer due to the application of a high voltage AC rectangular wave of 1000 V between the external electrodes.

From this fact, when a high-voltage AC rectangular wave is applied between the external electrodes, it is possible to selectively remove the defective connection between the internal electrode and the external electrode. Since the body layer causes dielectric breakdown and produces an IR defective product, it is not an appropriate sorting method. In addition, the voltage higher than the rated voltage according to claim 6 is 5 to 5 of the rated voltage.
The voltage is about 6 times, and when a higher voltage is applied, the dielectric breakdown of the ceramic dielectric layer occurs. At a lower voltage, defective connection between the internal and external electrodes cannot be completely removed. It is.

In this embodiment, a rectangular wave voltage is applied between external electrodes in a constant humidity of 60 to 65%.
This prevents surface leakage between the external electrodes due to the influence of humidity, and has the effect of reliably applying a voltage to a portion where the connection between the internal electrode and the external electrode is incomplete and destroying the incomplete portion. Further, the capacitance is measured at a constant temperature of 20 to 22 ° C., which has the effect of reliably measuring the capacitance without being affected by a temperature change.

Next, the screening effect when an AC rectangular wave is applied between the external electrodes after performing the cooling / heating cycle will be described with reference to FIG. 6 and (Table 5).

[0045]

[Table 5]

As shown in (Table 5), 200 samples were subjected to + 20 ° C. → + 80 ° C. → + 25 ° C. → −20 shown in FIG.
After repeating the cooling / heating cycle of 30 ° C. → + 25 ° C. three times, FIG.
The maximum value shown in (b) is + 200V, and the minimum value is -200V.
Apply an AC rectangular wave voltage of 0.2 seconds per cycle between the external electrodes for 3 cycles, immediately thereafter, short-circuit the external electrodes to discharge the residual charge, and then change the capacitance, dielectric loss, and insulation resistance. The measurement was performed and the primary non-defective product was selected. In the primary sorting, 22 small defects of 8 nF or less occurred, and neither DNG nor IRNG occurred. Next, when 178 primary sorting good products were further subjected to secondary sorting, C small defects of 8 nF or less, DNG,
No IRNG occurred. Furthermore, when tertiary sorting is performed on 178 secondary sorting good products, a small C defect of 8 nF or less,
DNG and IRNG did not occur.

When 22 pieces of small C defects in the primary sorting were buried in resin and polished, and the connection state between the internal electrode and the external electrode was confirmed, all of them were incompletely connected. This allows the sample to be subjected to thermal cycling, applying repeated thermal expansion and contraction stresses to the incomplete connection between the internal electrode and the external electrode. Even when an AC rectangular wave voltage of about three times the applied voltage is applied, the incomplete connection between the internal electrode and the external electrode is destroyed by discharge, resulting in a so-called capacitance loss state, and the defective connection can be reliably removed. It becomes possible.

Next, the effect of applying a voltage after the primary sorting will be described with reference to FIG. 7 and (Table 6).

[0049]

[Table 6]

As shown in Table 6, the capacitance, the dielectric loss, and the insulation resistance of 200 samples were measured, and primary non-defective products were selected. In the primary screening, three small defects of 8 nF or less occurred, and neither DNG nor IRNG occurred. Subsequently, the maximum value shown in FIG.
Three cycles of an AC rectangular wave voltage with a minimum value of -300V and a cycle of 0.2 seconds are applied, immediately after that, a short circuit is made between external electrodes to discharge residual charges, and then capacitance, dielectric loss, and insulation are applied. When the resistance was measured and the secondary non-defective product was selected, 17 small C defects of 8 nF or less were generated, and DNG and IRNG were not generated. Further, tertiary sorting of 180 secondary sorting good products did not produce small C defects, DNG and IRNG of 8 nF or less.

In the primary and secondary sorting, three C small defects, 1
Seven were buried in resin and polished, and the connection state between the internal electrode and the external electrode was checked. As a result, incomplete connection was found in all of them. That is, first, the multilayer ceramic capacitor is firstly sorted, and an AC rectangular wave voltage is applied between the external electrodes only for the capacitors having good capacitance. In this way, the connection between the internal electrode and the external electrode is incomplete and the capacitance that does not reach the specified value is removed in advance by primary screening, and then the capacitance reaches the specified value even if the connection is incomplete. In such a case, an AC square wave voltage is applied to completely break a portion where connection is incomplete, and it is possible to surely remove the portion in a subsequent capacitance measurement.

From the above results, in the conventional selection method, since the capacitance is measured while the connection between the internal electrode and the external electrode is in an unstable state, the capacitance fluctuates for each measurement and the reproducibility is poor. In some cases, an incompletely connected product is determined as a non-defective product and a defective product is determined. For this reason, it is impossible to sort out and remove incompletely connected products between the internal electrode and the external electrode. On the other hand, by applying an AC voltage between the external electrodes according to the present invention, the connection between the internal electrode and the external electrode can be prevented. In the selection method of measuring the capacitance after reliably discharging and destroying the incompletely connected portion, the multilayer ceramic capacitor formed by the dielectric ceramic layer in which the connection between the internal electrode and the external electrode is incompletely connected is externally connected. Since the connection with the electrode is cut off, that is, a so-called capacitance loss state occurs, the capacitance is surely reduced in the subsequent measurement of the capacitance, and the defective connection can be surely removed. Therefore, according to the method of the present invention, a highly reliable multilayer ceramic capacitor can be provided.

[0053]

As described above, according to the present invention, positive and negative voltages are alternately applied between the external electrodes of the multilayer ceramic capacitor, and the incomplete connection between the internal electrodes and the external electrodes is discharged and destroyed. It can be in a state of so-called capacitance loss,
Therefore, the incomplete connection between the internal electrode and the external electrode can be reliably selected as having a small capacitance by the subsequent measurement of the capacitance of the multilayer ceramic capacitor.

[Brief description of the drawings]

FIG. 1 is a flowchart showing a method for selecting a multilayer ceramic capacitor according to an embodiment of the present invention.

FIG. 2A is a circuit diagram for applying an AC voltage according to the embodiment; FIG. 2B is a voltage waveform diagram of the AC voltage;

FIG. 3 is a voltage waveform diagram when a rectangular wave is applied for one cycle.

FIG. 4 is a voltage waveform diagram when a rectangular wave of a rated voltage or less is applied.

FIG. 5 is a voltage waveform diagram when a high-voltage rectangular wave is applied.

FIG. 6A is an explanatory diagram showing a cooling / heating cycle. FIG. 6B is a voltage waveform diagram when the rectangular wave is applied.

FIG. 7 is a voltage waveform diagram when a rectangular wave is applied after primary sorting.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 DUT 2 AC voltage application process 3 Discharge process 4 Measurement process of capacitance and dielectric loss 5 Insulation resistance measurement process 6 AC voltage waveform 7 Circuit diagram of applying AC voltage 8 Switch 9 AC voltage power supply

Claims (9)

[Claims] 1. A lamination in which a plurality of dielectric ceramic layers and internal electrodes are alternately laminated, and one end of the internal electrodes is alternately exposed to different end faces opposed to each other with the dielectric ceramic layer interposed therebetween. In a multilayer ceramic capacitor having external electrodes formed on both end surfaces of the body so as to be electrically connected to internal electrodes, after alternately applying positive and negative voltages between the external electrodes, the external electrodes are short-circuited and stored. A method for selecting a multilayer ceramic capacitor in which a characteristic test is performed after discharging discharged electric charges, and those that are out of a predetermined reference characteristic value range are selectively removed. 2. The method according to claim 1, wherein an AC voltage is applied between the external electrodes. 3. The method for selecting a multilayer ceramic capacitor according to claim 1, wherein a sine wave voltage is applied between the external electrodes. 4. The method according to claim 1, wherein a rectangular wave voltage is applied between the external electrodes. 5. The method for selecting a multilayer ceramic capacitor according to claim 1, wherein a voltage of two cycles or more is applied between the external electrodes. 6. The method for selecting a multilayer ceramic capacitor according to claim 1, wherein a voltage higher than the rated voltage of the multilayer ceramic capacitor is applied between the external electrodes. 7. The multi-layer ceramic capacitor according to claim 1, wherein positive and negative voltages are alternately applied between the external electrodes during the constant humidity to perform a characteristic test under the constant humidity. Method. 8. The multilayer ceramic according to claim 1, wherein the multilayer ceramic capacitor is alternately held in a high-temperature and low-temperature bath for several cycles for a predetermined time, and then a voltage is applied between external electrodes. How to sort capacitors. 9. The method according to claim 1, wherein the capacitance of the multilayer ceramic capacitor is measured first to sort out and remove primary defective products, and then a voltage is applied between the external electrodes for those within a certain reference characteristic value range. The method for selecting a multilayer ceramic capacitor according to any one of claims 1 to 8.