JP7415322B2 - Capacitor inspection device and capacitor inspection method - Google Patents

Description

The present invention relates to a capacitor testing device and a capacitor testing method for testing a capacitor.

Capacitors have conventionally been used as basic circuit elements. Referring to FIG. 6, a multi-layer ceramic capacitor (MLCC) 100, which is an example of a main capacitor, has terminal electrodes 101 and 102 facing each other, and a comb from terminal electrode 101 to terminal electrode 102. a plurality of plate-shaped internal electrodes 103 extending in the shape of teeth, and plates extending in the shape of comb teeth from the terminal electrode 102 toward the terminal electrode 101 and facing each other so as to mesh with the plurality of internal electrodes 103 alternately. It includes an internal electrode 104 having a shape, and a dielectric 105 filled between the internal electrode 103 and the internal electrode 104.

If the plural internal electrodes 103 and 104 are replaced with one internal electrode 103 and 104, respectively, as shown in FIG. 7, the capacitance C of such a capacitor 100 is calculated by S, the distance between the internal electrodes 103 and 104 is d, the dielectric constant of the dielectric 105 is εr, and the permittivity of vacuum is εo, then C=εo·εr·S/d.

In recent years, there has been a demand for higher capacitance and smaller capacitors. In order to reduce the size of the capacitor 100 while increasing the capacitance C of the capacitor 100, attempts are made to increase the relative permittivity εr of the dielectric 105 and to narrow the distance d between the internal electrodes 103 and 104.

Reducing the distance d means making the dielectric 105 between the electrodes, which is an insulator, thinner. If foreign matter is mixed into the dielectric 105, the thinner the dielectric 105 is, the more likely the foreign matter will cause a short circuit between the internal electrodes 103 and 104. When a short circuit occurs between the internal electrodes 103 and 104 due to a foreign object, a current flows inside the capacitor 100 in a path different from the original current path, resulting in a short circuit failure.

Therefore, a test is performed to check for short circuit defects in the capacitor 100 by applying a constant voltage between the terminal electrodes 101 and 102, measuring the leakage current, and calculating the insulation resistance using Ohm's law from the leakage current and the applied voltage. A method is known (for example, see Non-Patent Document 1).

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By the way, a possible defect in the capacitor 100 is a defect in which the leakage current increases only in a certain voltage range depending on the applied voltage.

For example, when a voltage is applied between the internal electrodes 103 and 104, the dielectric 105 undergoes dielectric polarization. The degree of dielectric polarization depends on the applied voltage. As the relative dielectric constant εr increases with the aim of increasing the capacitance of the capacitor 100, the voltage-dependent dielectric polarization also increases. Furthermore, for example, due to charges injected into the internal electrodes 103 and 104 by the applied voltage, an attractive force acts between the internal electrodes 103 and 104, and between the internal electrodes 103 and the internal electrodes 103 and the internal A repulsive force acts between the electrode 104 and the internal electrode 104. In this way, a physical force corresponding to the applied voltage also acts on the internal electrodes 103 and 104.

As described above, since the capacitor 100 has characteristics that depend on the applied voltage, it is considered that the capacitor 100 has defects that occur only in a certain voltage range depending on the applied voltage. Even in capacitors other than multilayer ceramic capacitors, defects that depend on the applied voltage are thought to exist due to the structure of each capacitor.

However, in the inspection method described in Non-Patent Document 1, since the inspection is performed by applying a constant applied voltage, it is not possible to inspect defects that occur depending on the applied voltage.

An object of the present invention is to provide a capacitor testing device and a capacitor testing method capable of testing capacitors for defects that occur depending on applied voltage.

A capacitor testing device according to an example of the present invention is a capacitor testing device for testing a capacitor provided with a pair of terminals, and the capacitor testing device is a capacitor testing device that applies a voltage that substantially linearly increases the voltage applied between the pair of terminals. a current detection unit that detects a current flowing between the pair of terminals as a detection current; and a current detection unit that determines the quality of the capacitor based on a change in the detection current during a period in which the applied voltage linearly increases. and an inspection unit that executes a determination process.

Further, a capacitor testing method according to an example of the present invention is a capacitor testing method for testing a capacitor having a pair of terminals, the method increasing the voltage applied between the pair of terminals substantially linearly. A voltage application process, a current detection process of detecting the current flowing between the pair of terminals as a detection current, and a change in the detection current during the period in which the applied voltage increases linearly, to determine whether the capacitor is good or not. and an inspection step of executing a determination process to determine.

The capacitor testing device and capacitor testing method having such a configuration can test for defects that occur in capacitors depending on the applied voltage.

1 is a block diagram showing an example of the configuration of a capacitor testing device that executes a capacitor testing method according to an embodiment of the present invention. FIG. 2 is an explanatory diagram for explaining an example of the operation of a capacitor testing method and a capacitor testing device according to an embodiment of the present invention. 2 is a flowchart showing an example of the operation of the capacitor testing device shown in FIG. 1. FIG. 2 is a flowchart showing another example of the operation of the capacitor testing apparatus shown in FIG. 1. FIG. 2 is a block diagram showing another example of the configuration of the capacitor testing device shown in FIG. 1. FIG. FIG. 2 is an explanatory diagram for explaining the structure of a multilayer ceramic capacitor. FIG. 3 is an explanatory diagram for explaining the capacitance of a capacitor.

Hereinafter, embodiments according to the present invention will be described based on the drawings. It should be noted that structures given the same reference numerals in each figure indicate the same structure, and the explanation thereof will be omitted. The capacitor testing device 1 shown in FIG. 1 includes a variable voltage source 2 (voltage application section), a current detection section 3, a voltage detection section 4, an inspection section 5, and connection terminals T1 and T2.

The capacitor testing device 1 is a testing device that performs a short circuit test on a capacitor 100 to be tested. Capacitor 100 is, for example, a multilayer ceramic capacitor. Note that the capacitor to be inspected does not necessarily have to be a multilayer ceramic capacitor, but may be another type of capacitor.

The capacitor 100 has a substantially rectangular parallelepiped shape, and a pair of terminal electrodes 101 and 102 (terminals) are provided at both ends thereof.

The connection terminals T1 and T2 are electrodes, probes, etc., and by bringing the connection terminal T1 into contact with the terminal electrode 101 and the connection terminal T2 into contact with the terminal electrode 102, the capacitor testing device 1 can test the capacitor 100. Become. Variable voltage source 2, current detection section 3, and voltage detection section 4 are electrically connected to capacitor 100 via connection terminals T1 and T2.

Variable voltage source 2 applies a voltage between terminal electrodes 101 and 102 of capacitor 100 in response to a control signal from inspection section 5 . The variable voltage source 2 is a so-called power supply circuit, and increases the applied voltage V applied to the capacitor 100 substantially linearly in response to a control signal from the inspection section 5.

The current detection section 3 is a current detection circuit configured using, for example, a shunt resistor. The current detection section 3 detects the current flowing between the terminal electrodes 101 and 102 as a detection current I, and outputs a signal representing the detection current I to the inspection section 5.

The inspection unit 5 is configured using, for example, a so-called microcomputer, and includes a CPU (Central Processing Unit) that executes predetermined arithmetic processing, a RAM (Random Access Memory) that temporarily stores data, and a nonvolatile HDD. (Hard Disk Drive) or a storage device such as a flash memory, a timer circuit, an analog-to-digital converter, a digital-to-analog converter, and peripheral circuits thereof.

The inspection unit 5 executes the determination process, for example, by executing a predetermined control program stored in a storage device. In the determination process, the quality of the capacitor 100 is determined based on the change in the detected current I during a period in which the applied voltage V is linearly increased.

Next, the capacitor testing method and operation of the capacitor testing apparatus 1 according to an embodiment of the present invention will be described with reference to FIGS. 2 and 3.

First, the variable voltage source 2 substantially linearly increases the voltage V applied to the capacitor 100 at a preset slope of ΔV/Δt based on a control signal from the inspection unit 5 (step S1: stamping process). Thereafter, during the period in which steps S1 to S6 are executed, that is, during the period t3 from timing t1 to t2 in FIG. 2, the increase in the applied voltage V in step S1 continues.

The slope of ΔV/Δt means that the change in applied voltage V over time Δt is ΔV (V). ΔV/Δt may be appropriately set according to the characteristics of the capacitor 100 or the response performance of the capacitor testing device 1.

Note that "substantially linear" means that deviations from the straight line due to voltage control errors by the variable voltage source 2, etc. are allowed and the line is regarded as a straight line.

The inspection unit 5 may control the variable voltage source 2 so that the slope of the voltage increase is ΔV/Δt, and after receiving an instruction from the inspection unit 5 to start voltage supply, the variable voltage source 2 autonomously The applied voltage V may be increased linearly with a slope of ΔV/Δt.

When voltage supply from the variable voltage source 2 is started, a current Ic flows through the capacitor 100, as shown in FIG. The current Ic is obtained by the following equation (1).

Current Ic=C・ΔV/Δt (1)
However, C is the capacitance of the capacitor 100.

In equation (1), since C, ΔV, and Δt are all fixed values, the current Ic is a fixed value. That is, when the applied voltage V is linearly increased with a slope of ΔV/Δt, a constant current Ic flows through the normal capacitor 100.

Next, the current detection unit 3 detects the detected current I (step S2: current detection step).

If the capacitor 100 is normal, the detected current I becomes constant at the current Ic obtained by the above equation (1) during the period t3. However, if the capacitor 100 has a voltage-dependent defect, the detected current I may temporarily change during the process of increasing the applied voltage V, as shown in waveform B shown in FIG. 2(b). As shown in waveforms C and D shown in FIG. 2C, the detected current I may gradually increase or decrease as time passes or as the applied voltage V increases. By detecting such a change in the detection current I, voltage-dependent defects or time-dependent defects can be detected.

Therefore, the inspection unit 5 determines whether the detected current I detected by the current detection unit 3 is within the reference range A (step S3: inspection process (determination process)). The reference range A is obtained by adding tolerance ranges such as variations in the characteristics of the capacitor 100, voltage control errors by the variable voltage source 2, and detection errors by the current detector 3 to the current Ic. As the reference range A, for example, a current range of about 0.9Ic to 1.1Ic can be used.

If the detected current I is outside the reference range A (NO in step S3), the inspection unit 5 determines that the capacitor 100 is defective (step S4), and ends the process. Thereby, voltage-dependent defects in the capacitor 100 can be detected.

On the other hand, if the detected current I is within the reference range A (YES in step S3), the inspection unit 5 compares the preset voltage Ve and the applied voltage V (step S5). The set voltage Ve is preset as a voltage that stops the applied voltage V from increasing. As the set voltage Ve, for example, the rated voltage of the capacitor 100 can be used.

If the applied voltage V is less than the set voltage Ve (NO in step S5), the processes in steps S2 to S5 are repeated again. On the other hand, when the applied voltage V is higher than the set voltage Ve (YES in step S5: timing t2), the detected current I changes beyond the reference range A during the process in which the applied voltage V increases linearly from 0 V to the set voltage Ve. It turns out I didn't. Therefore, the inspection unit 5 determines that the capacitor 100 is a good product (step S6).

Next, the inspection unit 5 fixes the applied voltage V output from the variable voltage source 2 at the set voltage Ve (step S7), and ends the process.

As described above, according to the processes of steps S1 to S7, voltage-dependent defects in the capacitor 100 can be brought to light by applying the applied voltage V that changes linearly to the capacitor 100 during the period t3. As a result, a voltage-dependent defect can be detected as a change in the detected current I as shown in waveform B.

Additionally, defects that cause a temporary change in the detected current I as shown in waveform B during period t3, such as abnormal leakage current that flows only at the beginning of voltage application, are caused by defects that depend on the voltage application time. Defects may occur. Additionally, as shown in waveforms C and D, defects that depend on the voltage application time or applied voltage may occur, such as the detection current I gradually increasing or decreasing as time passes or the applied voltage V increases. be.

Even in the case of such a defect, according to the processing in steps S1 to S7, it can be determined that the detected current I is defective even if the detected current I changes temporarily as shown in waveform B during the period t3. Furthermore, as in waveforms C and D, when the detected current I gradually increases or decreases, it can also be determined to be defective. Therefore, it is easy to inspect even time-dependent defects.

Note that, as shown in FIG. 4, the inspection unit 5 may calculate the index K based on the following equation (2) after step S2 (step S8).

Index K=(ΔV/Δt)/I (2)
Since (ΔV/Δt) is a fixed value, if the capacitor 100 is normal, the index K will be constant, and if the detected current I changes, the index K will also change. Therefore, it is possible to test the capacitor 100 using the index K instead of the detected current I.

Then, instead of step S3, the inspection unit 5 may determine whether the index K is within the reference range A' (step S3a: inspection step (determination process)). The reference range A' is the index K corresponding to the current Ic, to which tolerance ranges such as variations in characteristics of the capacitor 100, voltage control errors by the variable voltage source 2, and detection errors by the current detector 3 are added. As the reference range A', for example, a range of about 0.9 (ΔV/Δt)/Ic to 1.1 (ΔV/Δt)/Ic can be used.

In formula (2), the units of ΔV/Δt and I are V/s and A, respectively. Therefore, the unit of index K is V/s/A=Ω/s.

Therefore, when the capacitor 100 is inspected using the index K as in steps S8 and S3a, a parameter in the unit system (Ω/s) that approximates impedance (Ω), which is the main physical quantity expressing the characteristics of the capacitor 100, Based on this, it is possible to determine whether the capacitor 100 is good or bad.

Note that, for example, a plurality of series circuits of the capacitor 100 and the current detection section 3 may be connected in parallel, as in the capacitor inspection apparatus 1a shown in FIG. 5. The variable voltage source 2 may also be configured to apply the applied voltage V in parallel to a plurality of series circuits of the capacitors 100 and the current detection section 3.

Then, the inspection unit 5a performs steps S2 to S6 in FIG. 3 and FIG. Processing may be executed.

Thereby, a plurality of capacitors 100 can be tested in parallel, so it is easy to shorten the test time for a plurality of capacitors 100.

If a parallel test is to be performed using a plurality of capacitor testing apparatuses 1 shown in FIG. 1, as many variable voltage sources 2 as there are capacitors 100 to be tested will be required. On the other hand, according to the capacitor testing apparatus 1a shown in FIG. 5, a plurality of capacitors 100 can be tested in parallel using a single variable voltage source 2.

That is, a capacitor testing device according to an example of the present invention is a capacitor testing device for testing a capacitor provided with a pair of terminals, and the capacitor testing device increases the voltage applied between the pair of terminals substantially linearly. a voltage application section; a current detection section that detects the current flowing between the pair of terminals as a detection current; and an inspection section that executes a determination process to determine.

Further, a capacitor testing method according to an example of the present invention is a capacitor testing method for testing a capacitor having a pair of terminals, the method increasing the voltage applied between the pair of terminals substantially linearly. A voltage application process, a current detection process of detecting a current flowing between the pair of terminals as a detection current, and a change in the detection current during the period in which the applied voltage increases linearly, to determine whether the capacitor is good or not. and an inspection step of executing a determination process to determine.

According to these configurations, when the voltage applied to the capacitor is increased linearly, the current that flows will be constant if the capacitor is normal. Therefore, the quality of the capacitor can be determined based on the change in the detected current during a period in which the applied voltage increases linearly. Furthermore, since changes in the current flowing in response to a linearly increasing voltage, that is, changes in the detected current that occur depending on the applied voltage, are scanned, defects that occur depending on the applied voltage of the capacitor can be inspected. .

Further, in the determination process, it is preferable that the inspection unit determines that the capacitor is defective when the detected current during the period changes beyond a preset reference range.

According to this configuration, during a period when the applied voltage increases linearly, if the capacitor is normal, the current flowing will be constant, so the detected current during the period will be preset for that constant current value. If the change exceeds the reference range, the capacitor can be determined to be defective.

In addition, in the determination process, the inspection unit determines that the index during the period is based on an index obtained by dividing the increase value per unit time of the applied voltage by the detected current. It is preferable that the capacitor is determined to be defective when the change exceeds a range.

According to this configuration, since the applied voltage is increased linearly, the increase value of the applied voltage per unit time is constant. Further, during a period in which the applied voltage increases linearly, if the capacitor is normal, the current flowing is constant, so the detected current during that period is also constant if the capacitor is normal. Therefore, the index obtained by dividing the increase value of the applied voltage per unit time by the detected current is also constant if the capacitor is normal. Therefore, if the index during the period changes beyond a preset reference range for the certain index, the capacitor can be determined to be defective.

Further, the voltage application section applies the applied voltage in parallel to the plurality of capacitors, and includes a plurality of the current detection sections corresponding to the plurality of capacitors, and the inspection section performs the determination process. Preferably, the process is performed for each of the plurality of capacitors.

According to this configuration, since a plurality of capacitors can be tested in parallel, it is easy to shorten the test time for a plurality of capacitors.

1 Capacitor inspection device 1a Capacitor inspection device 2 Variable voltage source (voltage application section)
3 Current detection section 4 Voltage detection section 5, 5a Inspection section 100 Capacitor 101, 102 Terminal electrode (terminal)
103, 104 Internal electrode 105 Dielectric A Reference range B Waveform C Capacitance d Interval I Detection current Ic Current K Indicators T1, T2 Connection terminals t1, t2 Timing t3 Period V Applied voltage Ve Set voltage

Claims (2)

A capacitor inspection device for inspecting a capacitor equipped with a pair of terminals,
a voltage application unit that substantially linearly increases the voltage applied between the pair of terminals;
a current detection unit that detects the current flowing between the pair of terminals as a detection current;
an inspection unit that executes a determination process to determine whether the capacitor is good or bad based on a change in the detected current during the period in which the applied voltage linearly increases;
The inspection unit determines, in the determination process, that the index during the period falls within a preset reference range based on the index obtained by dividing the increase value per unit time of the applied voltage by the detected current. A capacitor inspection device that determines the capacitor to be defective when the capacitor changes by exceeding the specified value. A capacitor testing method for testing a capacitor having a pair of terminals, the method comprising:
a voltage application step of substantially linearly increasing the voltage applied between the pair of terminals;
a current detection step of detecting a current flowing between the pair of terminals as a detection current;
Based on the change in the detected current during the period in which the applied voltage increases linearly,
an inspection step of executing a determination process to determine whether the capacitor is good or bad;
In the inspection step, in the determination process, the index during the period falls within a preset reference range based on an index obtained by dividing the increase value of the applied voltage per unit time by the detected current. A capacitor inspection method that determines the capacitor to be defective when the capacitor changes by exceeding the above amount.

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