JP7449581B2 - Capacitor measuring device and capacitor measuring method - Google Patents

Description

Embodiments according to the present disclosure relate to a capacitor measuring device and a capacitor measuring method.

One of the electrical characteristics of a capacitor is leakage current. Generally, in order to measure the leakage current of a capacitor, the charge stored in the capacitor is saturated in advance by charging, and the current that still flows is measured as the leakage current. Therefore, the larger the capacity, the longer time is required to saturate the charge. Therefore, a long time is required to measure leakage current.

To measure leakage current, for example, a method is known in which the battery is charged for a certain period of time and then the current is measured. On the other hand, there are individual differences in actual capacitors, with some capacitors charging quickly and capacitors charging slowly. If you are testing multiple capacitors, you will want to set the charging time to match the slower capacitors. This is a time loss for capacitors that charge quickly. If a capacitor that charges quickly is used, a capacitor that charges slowly will measure a large current because it is still being charged, and even if it is a good product, it will be judged as a defective product, resulting in a production loss. In other words, if production time loss is prioritized, the yield will deteriorate, and if yield is taken into account, production time will be lost.

Even if conditions are found that take both into account, the optimal conditions will change if the lot changes, and the derivation of the conditions must be repeated. This individual difference in charging time is at a level that does not pose a problem when the capacitance is relatively small, for example, 10 μF or less. In recent years, for example, MLCCs (Multilayer Ceramic Capacitors) with a capacitance exceeding 300 μF have been commercialized, and problems have become apparent in products with a capacitance exceeding 10 μF because the absolute values of individual differences and lot differences become large.

In Patent Document 1, as a method for efficiently determining leakage current, current values are measured at two points in a certain elapsed time, and a state in which charging has progressed sufficiently is calculated using an approximate formula from the two current values and the elapsed time. It has been proposed to make predictions based on However, since this method is only a prediction, it cannot be said to be a highly reliable measurement method. It is difficult to apply in applications that require high reliability, such as in-vehicle and infrastructure applications.

Patent Document 2 proposes a method of increasing overall efficiency by using part of the charging time for transportation time. However, this method is effective only when the capacitance is, for example, approximately 10 μF. Even if it is applied to a capacitor exceeding 10 μF, no effect will be obtained. In recent years, for example, MLCCs exceeding 300 μF have been commercialized, and this is not a solution to the problem.

Patent No. 3293540 Patent No. 3156658

Capacitor manufacturers conduct characteristic tests on all electronic components they produce, and only good products are shipped. For example, approximately 2 trillion MLCCs are produced annually. In order to completely inspect such a large number of capacitors, a highly efficient measuring device is desired. Capacitor measurement equipment often consists of capacitance measurement and leakage current measurement.

In recent years, the capacitance of capacitors has been increasing, and therefore the time required to measure leakage current is becoming longer. In order to realize a highly efficient measuring device, it is necessary to maximize the efficiency of leakage current measurement.

Therefore, the present disclosure provides a capacitor measuring device and a capacitor measuring method that can measure leakage current at more appropriate timing.

According to the present disclosure, a current detection unit sequentially detects a current value of an inflow current flowing into the capacitor while the capacitor is being charged;
A capacitor measuring device is provided, comprising: a current acquisition unit that acquires a current value of the inflow current as a current value of a leakage current of the capacitor at a timing based on a time change in the current value of the inflow current. .

further comprising a calculation unit that sequentially calculates a time difference value of the current value of the inflow current that is sequentially detected,
The current acquisition unit may acquire, as the current value of the leakage current, a current value of the inflow current at the timing based on a comparison between the time difference value and a first predetermined value.

The current acquisition unit may acquire the current value of the inflow current at the timing when the absolute value of the time difference value becomes less than the first predetermined value as the current value of the leakage current.

The current detection unit sequentially detects the current value of the inflow current flowing through each of the plurality of capacitors in parallel while charging the plurality of capacitors,
The current acquisition unit may sequentially acquire the current value of the inflow current from the capacitor that has reached the timing as the current value of the leakage current.

The capacitor may further include a determination unit that determines whether the capacitor is good or bad based on a comparison between the current value of the leakage current and a second predetermined value.

The current detection unit sequentially detects the current value of the inflow current flowing through each of the plurality of capacitors in parallel while charging the plurality of capacitors,
The determination unit may determine the quality of the capacitors sequentially starting from the capacitors for which the current values of the leakage currents have been acquired.

The battery may further include a control unit that controls a charging unit that charges the capacitor so as to stop charging the capacitor at the timing.

The current detection unit sequentially detects the current value of the inflow current flowing through each of the plurality of capacitors in parallel while charging the plurality of capacitors,
The control unit may control the charging unit to sequentially stop charging the capacitors starting from the capacitor that has reached the timing.

The apparatus may further include a noise processing section that processes the current value of the inflow current detected by the current detection section so as to remove noise.

According to the present disclosure, the current value of the inflow current flowing into the capacitor is sequentially detected while the capacitor is being charged;
A method for measuring a capacitor is provided, which comprises acquiring a current value of the inflow current as a current value of a leakage current of the capacitor at a timing based on a time change in the current value of the inflow current.

FIG. 1 is a diagram showing an example of the configuration of a capacitor measuring device according to a first embodiment. FIG. 2 is an equivalent circuit diagram of a general capacitor related to leakage current measurement. FIG. 3 is a diagram showing a change in current flowing through a capacitor over time when charging is performed by applying a specified voltage to the capacitor. FIG. 1 is a plan view showing an example of the configuration of a capacitor measuring device according to a first embodiment. FIG. 3 is a flow diagram showing an example of the operation of the capacitor measuring device according to the first embodiment. It is a figure showing an example of measurement of leakage current by a 1st embodiment. It is a figure showing an example of quality judgment of a capacitor by a 1st embodiment. FIG. 7 is a diagram showing an example of the configuration of a capacitor measuring device according to a second embodiment. FIG. 7 is a diagram illustrating an example of the configuration of a capacitor measuring device according to a third embodiment. FIG. 7 is a diagram illustrating an example of the configuration of a capacitor measuring device according to a fourth embodiment.

Embodiments of the present invention will be described below with reference to the drawings.

(First embodiment)
FIG. 1 is a diagram showing an example of the configuration of a capacitor measuring device 100 according to the first embodiment. The capacitor measuring device 100 determines whether the capacitor C0 to be measured is a non-defective product. The capacitor measuring device 100 measures, for example, the leakage current of the capacitor C0.

FIG. 2 is an equivalent circuit diagram of a general capacitor C0 involved in leakage current measurement. As shown in FIG. 2, the capacitor C0 is equivalently configured by connecting a main capacitance C, an insulation resistance R1, and a dielectric absorption factor D in parallel. The dielectric absorption factor D is the dielectric polarization formed by the electric field generated internally when a voltage is applied to the capacitor C0, expressed by the internal resistance and capacitance (hereinafter referred to as dielectric polarization capacitance) connected in series. . The dielectric polarization becomes stable after a certain period of time has elapsed since charging of the capacitor C0 starts, but until the dielectric polarization stabilizes, the dielectric polarization capacitance is charged via the internal resistance.

The dielectric absorption factor D is not necessarily expressed equivalently by just one set of internal resistance and dielectric polarization capacitance connected in series as shown in Figure 2, but rather by a set of internal resistance and dielectric polarization capacitance connected in series. It may also be represented by an equivalent circuit with multiple sets connected in parallel. Even in this case, the time change in the current flowing through capacitor C0 when charging capacitor C0 does not depend on the internal configuration of dielectric absorption factor D. The set alone equivalently represents the dielectric absorption factor D.

The current flowing through capacitor C0 after the dielectric polarization is stabilized is actually leakage current flowing through insulation resistor R1. Therefore, in order to accurately measure the leakage current of the capacitor C0, it is necessary to measure the leakage current after the dielectric polarization is stabilized, and by measuring this leakage current, the insulation resistance R1 can also be determined.

FIG. 3 is a diagram showing changes over time in the current flowing through the capacitor C0 when a specified voltage is applied to the capacitor C0 to charge the capacitor C0, with the horizontal axis representing time and the vertical axis representing the current flowing through the capacitor C0. Region X in FIG. 3 is a charging current region, where main capacitance C is mainly charged. Region Y is a dielectric absorption region and is charged with dielectric absorption factor D. The region Z is a leakage current region after the dielectric absorption factor D is sufficiently charged, and the leakage current is measured in this region.

Since it takes a certain amount of time to charge the dielectric absorption factor D in the dielectric absorption region Y, the time from applying the specified voltage to the capacitor C0 to reaching the leakage current region Z also becomes long. Unless the leakage current is measured after the dielectric absorption factor D is charged and the leakage current region Z is reached, an accurate current value cannot be measured.

In addition, there are individual differences in the actual capacitor C0, and there are capacitors that charge quickly and capacitors that charge slowly. This individual difference in charging time is at a level that does not pose a problem when the capacitance is relatively small, for example, 10 μF or less. In recent years, for example, MLCCs (Multilayer Ceramic Capacitors) with a capacitance exceeding 300 μF have been commercialized, and problems have become apparent in products with a capacitance exceeding 10 μF because the absolute values of individual differences or lot differences become large.

Here, whether or not charging has progressed sufficiently can be confirmed by checking that the change in current value over time has become sufficiently small. If the current can be continuously measured, changes in the current value indicate that charging has progressed sufficiently, and the optimal timing for measuring leakage current can be determined. This makes it possible to measure leakage current at more appropriate timing, regardless of individual differences or lot differences, in response to demands for larger capacitance and improved reliability of capacitors.

The capacitor measuring device 100 shown in FIG. ) 60.

The charging/discharging unit 10 charges and discharges the capacitor C0. The charging/discharging unit 10 includes a power source 11 and a switch 12.

The power supply 11 supplies a DC power supply voltage E to the capacitor C0. Power supply voltage E is, for example, 10V.

The switch 12 is a switch that can change the connection between the capacitor C0 and the power supply 11. The switch 12 electrically connects the capacitor C0 and the power supply 11 when charging the capacitor C0. The switch 12 electrically disconnects the capacitor C0 from the power source 11 when stopping charging the capacitor C0. The switch 12 electrically connects the capacitor C0 and the ground node GND when discharging the capacitor C0. The switch 12 is controlled by a PC 60, for example.

As shown in FIG. 1, a current limiting circuit 20 and a current measuring circuit 30 are connected between the capacitor C0 and the charging/discharging section 10.

The current limiting circuit 20 limits the current (inflow current) flowing into the capacitor C0. The current limiting circuit 20 limits the current flowing through the capacitor C0 to 50 mA, for example. Current limiting circuit 20 is, for example, a resistor. The resistance value is determined depending on the magnitude of the inflow current. Note that the current limiting circuit 20 may be included in the charging/discharging section 10.

Current measurement circuit 30 measures the current flowing through capacitor C0. For example, in order to stably measure a minute current of 1 μA or less, a low-noise current measurement circuit 30 is used. The current measurement circuit 30 has a current-voltage conversion circuit. The current-voltage conversion circuit has, for example, a 100Ω shunt resistor 31, and a voltage drop across this shunt resistor 31 is detected.

The voltage amplification circuit 40 amplifies the measurement result of the current measurement circuit 30. More specifically, the voltage amplification circuit 40 amplifies the voltage across the shunt resistor 31 and outputs the amplified voltage. For example, in order to stably measure a minute current of 1 μA or less, a low-noise voltage amplification circuit 40 is used. The voltage amplification circuit 40 includes, for example, an operational amplifier, and amplifies the voltage 500 times. For example, a low ripple dropper type power supply is used as the power supply for the operational amplifier.

The AD conversion card 50 performs AD conversion on the measurement result of the current measurement circuit 30 that has been amplified by the voltage amplification circuit 40. The AD conversion card 50 has an AD converter 51. As the AD converter 51, for example, an AD converter with 16-bit resolution, ±15 V withstand voltage, and ±10 V input is used. The sampling frequency of the AD converter 51 is, for example, 100 kHz.

Further, the AD conversion card 50 (hereinafter also referred to as a current detection section) sequentially detects the current value of the inflow current flowing into the capacitor C0 while the capacitor C0 is being charged. The voltage amplified by the voltage amplification circuit 40 is input to the input section of the AD conversion card 50 . The AD conversion card 50 continuously detects the current value of the inflow current at a predetermined period, such as a 1 millisecond period, for example.

Note that the current limiting circuit 20, the current measuring circuit 30, and the voltage amplifying circuit 40 are arranged on the substrate S, for example. The AD conversion card 50 is connected to the board S by a shielded cable. Thereby, noise can be suppressed.

The PC 60 receives a digital signal of the current value of the inflow current output from the AD conversion card 50. Further, the PC 60 performs various calculations, processes, and controls based on the current value of the inflow current. The PC 60 includes an arithmetic processing section 61 and a storage section 62.

The arithmetic processing section 61 includes a storage control section, a noise processing section, a calculation section, a current acquisition section, a control section, and a determination section. The arithmetic processing unit 61 is, for example, a CPU (Central Processing Unit). Note that the storage control section, noise processing section, calculation section, current acquisition section, control section, and determination section may be realized by one CPU, or may be realized by separate CPUs.

The storage control section causes the storage section 62 to store data such as the current value detected by the current detection section (AD conversion card 50).

The noise processing section processes the current value of the inflow current detected by the current detection section so as to remove noise. The noise processing is, for example, interval averaging processing (this is the processing in the embodiment) and averaging processing. However, the present invention is not limited to this, and other noise processing may be used.

The calculation unit sequentially calculates the time difference value of the current value of the inflow current that is sequentially detected. More specifically, the calculation unit sequentially calculates time difference values of the noise-processed current values.

The current acquisition unit measures leakage current. More specifically, the current acquisition unit acquires the current value of the inflow current at the acquisition timing based on the time change in the current value of the inflow current as the current value of the leakage current of the capacitor C0. The "acquisition timing" is the timing at which the capacitor C0 is sufficiently charged and the leakage current can be measured. Further, the acquisition timing is also the timing at which the leakage current region Z in FIG. 3 is reached. Thereby, the leakage current can be measured at a more appropriate timing regardless of individual differences or lot differences in the capacitor C0.

Note that details of the leakage current measurement will be explained later with reference to FIG. 6.

The control section controls the charging/discharging section 10. The control unit controls the charging/discharging unit 10 (switch 12) to stop charging the capacitor C0 at the acquisition timing. Thereby, charging of the capacitor C0 can be stopped at the timing when the leakage current measurement is completed.

The determination unit determines whether the capacitor C0 is good or bad based on the current value of the leakage current.

Note that details of the pass/fail determination will be explained later with reference to FIG.

The storage unit 62 stores data obtained by the storage control unit, noise processing unit, calculation unit, and current acquisition unit, and determination results obtained by the determination unit. The storage unit 62 stores in advance threshold values TV1 and TV2 used for leakage current measurement and quality determination, which will be described later. The storage unit 62 is, for example, a memory (RAM (Random Access Memory)).

FIG. 4 is a plan view showing an example of the configuration of the capacitor measuring device 100 according to the first embodiment.

A workpiece, which is a capacitor to be measured C0, is conveyed to a separation supply section 2 by a linear feeder 1. The separation supply unit 2 stores individual works one by one in a plurality of work storage holes 4 arranged at approximately equal intervals around the circular conveyance table 3. The transport table 3 is intermittently rotatable around its central axis 5, for example in the R direction shown in the figure, and a plurality of measurement stages 8 are arranged at intervals along the periphery of the transport table 3. There is.

Two probes (not shown in FIG. 4) are provided on the bottom surfaces of the plurality of measurement stages 8 so as to be movable up and down with respect to electrodes provided at both ends of the workpiece. When the workpiece storage hole 4 comes to the position of the measurement stage 8 as the transport table 3 moves, the two probes come into contact with electrodes at both ends of the workpiece. This connects capacitor C0 to the circuit of FIG.

In the example shown in FIG. 4, the measurement stages 8 are provided at substantially the same intervals as the intervals between the workpiece storage holes 4. When measuring leakage current, the transport table 3 is stopped and the probes of the measurement stage 8 are connected to all capacitors. All capacitors are charged and leakage current measured simultaneously. Note that the number of workpiece storage holes 4 and measurement stages 8 shown in FIG. 4 is an example. Further, the present invention is not limited to the example shown in FIG. 4, and only one measurement stage 8 may be provided. In this case, as the transport table 3 rotates, capacitors are measured one by one.

After measuring the leakage current, the charge charged in the workpiece is discharged, and the workpiece is discharged from the discharge stage 9 toward a storage box (not shown). The next workpiece is stored in the separation supply section 2 again in the workpiece storage hole 4 which has become empty after the workpiece has been discharged.

Next, a method for measuring capacitors will be described with reference to FIGS. 5 to 7.

FIG. 5 is a flow diagram showing an example of the operation of the capacitor measuring device 100 according to the first embodiment. FIG. 6 is a diagram showing an example of leakage current measurement according to the first embodiment. FIG. 6 shows, in order from the top, the voltage value of the voltage supplied to capacitor C0, the current value of the inflow current (with noise), the average current value of the current value of the inflow current (noise reduction), and the current value of the inflow current. It shows the time change of the time difference value of . The times shown on the horizontal axis are common.

In addition, in FIG. 6, the current value, average current value, and time difference value near time t1, that is, in the charging current region X of FIG. 3, are omitted. This is because the leakage current is measured in a region where the current value of the inflow current decreases over time. Moreover, the time difference value in FIG. 6 shows an absolute value.

First, the transport table 3 connects the MLCC (capacitor C0) to the circuit (S10). That is, capacitor C0 is connected to the circuit shown in FIG.

Next, the charge/discharge unit 10 applies a DC voltage to the capacitor C0 (S20). This charges the capacitor C0. For example, a DC voltage of 10V is applied to the capacitor. As a result, the voltage rises as shown at time t1 in FIG. Note that the current flowing through the capacitor C0 is limited to, for example, 50 mA by the current limiting circuit 20.

Next, the current detection unit detects the current value CV1 of the inflow current flowing into the capacitor C0 during voltage application (S30). Data points of the current value CV1 are detected, for example, at a period of 1 millisecond.

Next, the noise processing section averages the current value CV1 (S40). For example, the noise processing unit sequentially calculates an average current value CV2 obtained by averaging the sequentially detected current values CV1. The noise processing unit calculates an average value of current values CV1 included in a section around a data point of a certain current value CV1 as an average current value CV2. The "section" is, for example, 10 milliseconds, that is, the range of 10 data points of the current value CV1. The noise processing unit calculates the average current value CV2 while sequentially shifting the data points of the current value CV1. As a result, as shown in FIG. 6, an average current value CV2 with reduced noise in the current value CV1 is obtained. Note that one section is not limited to 10 data points of current value CV1.

Next, the calculation unit calculates the time difference value TD of the average current value CV2 (S50). The calculation unit sequentially calculates a time difference value TD by subjecting the sequentially calculated average current value CV2 to a time difference. Since the average current value CV2 is discrete data, the calculation unit calculates the difference between successive average current values CV2 as the time difference value TD. For example, the calculation unit extracts the average current value CV2 for every 10 data points, and calculates the value of the difference between the extracted adjacent average current values CV2. Note that the interval between extracted data points is not limited to 10 points.

Next, the current acquisition unit determines whether the time difference value TD is less than the threshold value TV1 (S60). The threshold value TV1 is, for example, 10 (nA/section). In the example shown in FIG. 6, one section is 10 milliseconds (10 data points of current value CV1). The threshold value TV1 is determined, for example, in consideration of the time it takes for the time difference value TD to converge, the yield per unit of time of the device, the accuracy of the measuring meter, and the influence of noise.

If the time difference value TD is equal to or greater than the threshold value TV1 (NO in step S60), charging and current value detection are continued. Therefore, steps S30 to S60 are repeatedly executed until the time difference value TD becomes less than the threshold value TV1.

On the other hand, if the time difference value TD is less than the threshold value TV1 (YES in step S60), the current acquisition unit acquires the current value of the leakage current (S70). That is, the current acquisition unit acquires the current value of the inflow current as the current value of the leakage current at the acquisition timing based on the comparison between the time difference value TD and the threshold value TV1 (first predetermined value). More specifically, the acquisition timing is the timing when the absolute value of the time difference value TD becomes less than the threshold value TV1.

As shown at time t2 in FIG. 6, at the acquisition timing when the time difference value TD falls below the threshold value TV1, it is considered that the charging of the capacitor C0 has sufficiently progressed. The current acquisition unit acquires the average current value CV2 at time t2 as the current value of the leakage current.

Next, the charge/discharge unit 10 releases the voltage application (S80). That is, the control section controls the switch 12 of the charging/discharging section 10 to stop charging the capacitor C0. As shown at time t3 in FIG. 6, the voltage falls.

Next, the charging/discharging unit 10 discharges the capacitor C0 (S90). That is, the control section controls the switch 12 of the charging/discharging section 10 to discharge the capacitor C0. Note that the discharge current is limited to, for example, 50 mA by the current limiting circuit 20.

Next, the determination unit determines the quality of the MLCC based on the current value of the leakage current obtained in step S70 (S100).

Thereafter, the transport table 3 rotates to discharge the capacitor C0. The capacitor C0 is classified as a good product or a defective product depending on the result of the quality determination by the determination unit.

Note that steps S80 and S90 may be executed substantially in parallel with step S70. Step S100 is executed after step S70, and may be executed substantially in parallel with steps S80 and S90. That is, the quality determination may be performed immediately after the current value of the leakage current is acquired.

FIG. 7 is a diagram showing an example of the quality determination of the capacitor C0 according to the first embodiment.

In the example shown in FIG. 7, three works A, B, and C are judged to be good or bad. The leakage currents of the works A, B, and C are measured by simultaneously performing the processing shown in FIG. 6.

The current detection unit successively detects the current value of the inflow current flowing through each of the plurality of capacitors C0 in parallel while charging the plurality of capacitors C0. The current acquisition unit acquires the current value of the inflow current as the current value of the leakage current, starting from the capacitor C0 whose acquisition timing has been reached. The control unit controls the charging/discharging unit 10 to stop charging sequentially starting from the capacitor C0 when the acquisition timing is reached.

The determination unit determines whether the capacitor C0 is good or bad based on a comparison between the current value of the leakage current and a threshold value TV2 (second predetermined value). Good products have small leakage current. Therefore, the determination unit determines that the capacitor C0 is a good product when the current value of the leakage current is less than the threshold value TV2. The determination unit determines that the capacitor C0 is a defective product when the current value of the leakage current is equal to or greater than the threshold value TV2. The threshold value TV2 can be correlated with the present device (capacitor measuring device 100) using, for example, a capacitor measured with a reference measuring device.

Further, the determination unit sequentially determines the quality of the capacitor C0 from which the current value of the leakage current has been acquired.

As shown in FIG. 7, from time t1 to time t21, charging and current value measurement are performed on works A, B, and C simultaneously. At time t21, when the time difference value TDa of work A falls below threshold TV1, the charge is saturated and it is determined that charging is complete. Therefore, charging of work A and measurement of the current value are stopped. The current value of the leakage current of the workpiece A is the average current value CV2a at time t21. The average current value CV2a at time t21 is lower than the threshold value TV2. Therefore, the determination unit determines that work A is a non-defective product.

From time t21 to time t22, charging and current value measurement are performed on works B and C simultaneously. At time t22, when the time difference value TDc of the workpiece C becomes less than the threshold value TV1, the charge is saturated and it is determined that charging is complete. Therefore, charging of the workpiece C and measurement of the current value are stopped. The current value of the leakage current of the work C is the average current value CV2c at time t22. The average current value CV2c at time t22 is higher than the threshold value TV2. Therefore, the determination unit determines that the workpiece C is a defective product.

From time t22 to time t23, work B is charged and the current value is measured. At time t23, when the time difference value TDb of work B falls below threshold TV1, the charge is saturated and it is determined that charging is complete. Therefore, charging of work B and measurement of the current value are stopped. The current value of the leakage current of the work B is the average current value CV2b at time t23. The average current value CV2c at time t23 is lower than the threshold value TV2. Therefore, the determination unit determines that work B is a non-defective product.

After leakage current measurement and pass/fail judgment are performed on all the works, the next process is executed.

Here, both works A and B are good products, but the charging times differ depending on individual differences. In the first embodiment, the leakage current is measured at a timing appropriate for each workpiece, regardless of individual differences.

As described above, according to the first embodiment, the current acquisition unit acquires the current value of the inflow current as the current value of the leakage current at the acquisition timing based on the time change of the inflow current that is sequentially detected. As a result, leakage current can be measured at more appropriate timing, regardless of individual differences in capacitor C0, in response to demands for larger capacity and improved reliability of capacitors. Therefore, leakage current can be measured in a shorter time.

Further, in the first embodiment, as described with reference to FIG. 7, leakage current measurement and pass/fail determination can be continuously performed simultaneously on a plurality of works, that is, on multiple channels.

If a current acquisition unit is not provided, a method of setting charging time conditions that takes into account individual differences among a plurality of workpieces may also be considered. However, setting conditions for capacitors with slow charging times can lead to lost production time. Furthermore, if conditions are set to match a capacitor with a fast charging time, it may lead to a deterioration in yield. Furthermore, even if charging time conditions are found that take into account individual differences, the optimum conditions may change if the lot changes, and the derivation of the conditions may have to be repeated.

In contrast, in the first embodiment, there is no need to set charging time conditions, and the leakage current can be measured and the quality judgment can be performed for each workpiece at an appropriate timing, regardless of individual differences or lot differences. . This makes it possible to suppress time loss and deterioration in yield due to leakage current being measured at inappropriate timing.

(Second embodiment)
FIG. 8 is a diagram showing an example of the configuration of a capacitor measuring device 100 according to the second embodiment. The second embodiment differs from the first embodiment in that one PC 60 is shared by a plurality of measurement circuits.

In the example shown in FIG. 8, a plurality of measuring circuits including a charging/discharging section 10, a current limiting circuit 20, a current measuring circuit 30, a voltage amplifying circuit 40, and an AD conversion card 50 are connected to the PC 60. Thereby, using one PC 60, leakage current measurement and pass/fail determination can be performed on multiple works (multiple channels) in parallel.

For example, according to experiments, when an MLCC with a capacitance of 330 μF is charged at 4V, it becomes fully charged in about 10 seconds and the current value stabilizes. If the current is measured every millisecond, the measured value will be 10,000 pieces of data. If 1,000 channels are simultaneously measured, the total will be 10 million pieces of data. If one piece of data is 8 bytes, the total amount of data is 80 megabytes. Furthermore, calculations such as noise removal and time difference are required for each channel.

The storage unit 62 is, for example, a 1 gigabyte memory. The above 80 megabytes of data can be handled by the PC 60 having 1 gigabyte of memory.

The arithmetic processing unit 61 is, for example, a 2.4 GHz clock, multi-core CPU. Calculations such as time difference after removing high-frequency noise specific to analog signals by averaging processing in 10 ms intervals can be executed in a short time with a 2.4 GHz clock and a multi-core (for example, 4 core) CPU. . In applications where results are required immediately, it is more preferable that the arithmetic processing unit 61 has high computational ability.

As in the second embodiment, one PC 60 may process a plurality of works. Also in this case, the same effects as in the first embodiment can be obtained.

(Third embodiment)
FIG. 9 is a diagram showing an example of the configuration of a capacitor measuring device 100 according to the third embodiment. The third embodiment differs from the first embodiment in the configuration after the AD conversion card 50.

The capacitor measuring device 100 includes an arithmetic processing section 71, a storage section 72, and a control computer 80.

The arithmetic processing section 71 according to the second embodiment has substantially the same function as the arithmetic processing section 61 according to the first embodiment shown in FIG. The arithmetic processing unit 71 is, for example, a logic circuit such as an FPGA (Field-Programmable Gate Array). The arithmetic processing unit 71 sends, for example, the leakage current measurement results and the quality determination results to the control computer 80.

The storage unit 72 according to the second embodiment has substantially the same function as the storage unit 62 according to the first embodiment shown in FIG.

The control computer 80 collects measurement data, sends control commands to the arithmetic processing section 71, and the like, for example. Control computer 80 is, for example, a PC.

The processing is not limited to software processing using the PC 60 or the like, and may be combined with hardware processing as in the third embodiment. Also in this case, the same effects as in the first embodiment can be obtained.

(Fourth embodiment)
FIG. 10 is a diagram showing an example of the configuration of a capacitor measuring device 100 according to the fourth embodiment. The fourth embodiment differs from the third embodiment in that one arithmetic processing section 71 and one storage section 72 are shared by a plurality of measurement circuits. Therefore, the fourth embodiment is a combination of the second embodiment and the third embodiment. Also in this case, effects similar to those of the second embodiment and the third embodiment can be obtained.

Reference Signs List 100 Capacitor Measuring Device, 10 Charging/Discharging Unit, 20 Current Limiting Circuit, 30 Current Measuring Circuit, 40 Voltage Amplifying Circuit, 50 AD Conversion Card, 60 PC, 61 Arithmetic Processing Unit, 62 Storage Unit, 71 Arithmetic Processing Unit, 72 Memory part, C0 capacitor, CV1 current value, CV2 average current value, TD time difference value, TV1 threshold, TV2 threshold

Claims (9)

a current detection unit that sequentially detects a current value of an inflow current flowing into the capacitor while the capacitor is being charged;
a calculation unit that sequentially calculates a time difference value of the current value of the inflow current that is sequentially detected;
A capacitor measuring device, comprising: a current acquisition unit that acquires a current value of the inflow current as a current value of a leakage current of the capacitor at a timing based on a comparison between the time difference value and a first predetermined value . The current acquisition unit acquires the current value of the inflow current as the current value of the leakage current at the timing when the absolute value of the time difference value becomes less than the first predetermined value. Capacitor measuring device. The current detection unit sequentially detects the current value of the inflow current flowing through each of the plurality of capacitors in parallel while charging the plurality of capacitors,
3. The capacitor measuring device according to claim 1, wherein the current acquisition unit sequentially acquires the current value of the inflow current from the capacitor that has reached the timing as the current value of the leakage current. The capacitor measuring device according to any one of claims 1 to 3 , further comprising a determining unit that determines whether the capacitor is good or bad based on a comparison between the current value of the leakage current and a second predetermined value. The current detection unit sequentially detects the current value of the inflow current flowing through each of the plurality of capacitors in parallel while charging the plurality of capacitors,
5. The capacitor measuring device according to claim 4 , wherein the determining unit sequentially determines the quality of the capacitor from which the current value of the leakage current has been acquired. The capacitor measuring device according to any one of claims 1 to 5 , further comprising a control unit that controls a charging unit that charges the capacitor so as to stop charging the capacitor at the timing. The current detection unit sequentially detects the current value of the inflow current flowing through each of the plurality of capacitors in parallel while charging the plurality of capacitors,
7. The capacitor measuring device according to claim 6 , wherein the control section controls the charging section so as to stop charging the capacitors sequentially starting from the capacitor that has reached the timing. The capacitor measuring device according to any one of claims 1 to 7 , further comprising a noise processing unit that processes the current value of the inflow current detected by the current detection unit so as to remove noise. While charging the capacitor, sequentially detecting the current value of the inflow current flowing into the capacitor,
Sequentially calculating the time difference value of the current value of the inflow current detected sequentially,
A method for measuring a capacitor, the method comprising: acquiring a current value of the inflow current as a current value of a leakage current of the capacitor at a timing based on a comparison between the time difference value and a first predetermined value .