JP2003043098A - Method and apparatus for withstand voltage test of capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the accuracy of a withstand voltage test of a capacitor to improve the product quality after delivery. SOLUTION: The withstand voltage test 15 comprises a first test process composed of a step (S151) of applying an AC voltage or an AC voltage superposed on a DC voltage across a capacitor under test to accelerate its deterioration, a step (S152) of starting measuring a leak current after a fixed time lapsed from application of a rated DC voltage as a test voltage and a step (S153) of judging the quality thereof, based on whether a measured value within a specified time exceeds a first leak current reference value, and a second test process composed of a step (S154) of changing the test voltage to a lower DC voltage than the rated voltage, applying it across the capacitor judged to be nondefective under test, and measuring a leak current similarly to the first test process, and a step (S155) of judging the quality thereof, based on whether a second leak current reference value is exceeded.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for testing a dielectric strength voltage of a capacitor and a testing device, and more particularly to a method for testing a dielectric strength voltage of a capacitor, in which a test voltage is applied, a leak current at that time is measured, and the quality is judged from the measured value. And test equipment.

[0002]

2. Description of the Related Art Conventionally, the method for testing the dielectric strength of this type of capacitor has been performed by the method shown in FIG.

Capacitors are generally classified into ceramic capacitors, film capacitors, tantalum, electrolytic capacitors, etc., but the concept of test method standard values regarding withstand voltage may differ depending on this type. Regarding the withstand voltage of the capacitor, there are a breakdown voltage that will be destroyed at a voltage higher than this and a rated voltage that indicates the upper limit voltage that can be stably used due to operating environment conditions or service life. Ratio (breakdown voltage / rated voltage)
Is large for a ceramic capacitor, for example, 3 to 4 for this high breakdown voltage product and 7 to 15 for this low breakdown voltage product. On the other hand, tantalum and electrolytic capacitors are small, for example, 1.
With 5 to 2, there is little margin against the breakdown voltage.

In the withstand voltage test, a set high voltage is applied to the capacitor under test to test whether it breaks down (mainly short circuit failure), and a rated voltage is applied to the capacitor under test. Measure the leakage current at this time, and if the measured value exceeds the set reference value, that is, if the insulation resistance value is low, it is judged as a defective product because there is a risk of breakdown due to insufficient withstand voltage. There is a dielectric strength test.

FIG. 1 is a flow chart showing a conventional general manufacturing and inspection process for a capacitor. In the manufacturing process, the step of firing (S41) is followed by the step of cross-section polishing (S42), and this step is often applied particularly to ceramic capacitors. That is, although a ceramic capacitor has a high breakdown voltage, when a progressive defect exists inside the insulating layer, the defect may occur after a while due to stress such as the usage environment after being put on the market. In order to avoid this, a step of polishing the cross section is carried out. That is, the internal abnormality is detected by polishing the product by lot sampling after firing, and observing the cross section with a microscope to see if there are any micro defects.

Next, the external electrode is plated (S43) to start the test process.

First, in the test process, the above-mentioned breakdown voltage breakdown test (S44) for applying a breakdown voltage is performed, and defective products destroyed by this are excluded. The non-destructive non-defective product is subjected to the following withstand voltage test (S451). This withstand voltage test is strictly carried out especially for tantalum and electrolytic capacitors which cannot afford a sufficient margin against breakdown voltage. In this test, the DC rated voltage is applied and the leakage current at that time is measured. However, since the charging current flows immediately after the DC rated voltage is applied, this charging time elapses, and the leakage occurs after a certain time as a margin. Measure the current. Then, this measured value is compared with a preset reference value (S
452) If it is outside the reference value, it is excluded as a defective product, and if it is within the reference value, it is determined as a good product. Next, the capacitance and tan δ measurement (S46) are performed. Then, the measurement result having no problem is packaged and shipped (S17).

[0008]

Among the processes of the prior art described above, there are the following problems in the dielectric strength test (S45). FIG. 5 is a characteristic diagram showing a measurement example of leakage current in this dielectric strength test. A is a good product, and B is a bad product. The charging current flows immediately after the DC rated voltage is applied, but the charging current decreases with the passage of time, and becomes substantially stable at the point a. Further, the leak current is measured at time point b when a certain time has elapsed. In the good product B, the leakage current is smaller than the reference value, and the fluctuation is small and stable, so there is no problem in the good product determination. However, the defective product A has a leakage current larger than the reference value and is unstable due to a large vertical swing, and if there is a downward swing at the measurement point b as shown in the figure, it is determined as a defective product even if it is a non-defective product. Will be done.

Further, the test voltage is only the rated voltage, and in particular, the characteristics in the actual working voltage of a voltage lower than the normal rated voltage are not reflected, that is, the test condition is a one-point method. There is a problem that is not good.

[0010] Further, there is a problem that no countermeasures against changes in the flatness of the product have been considered, there is a risk that defective products may occur during future use, and sufficient quality assurance is not made.

[0011]

SUMMARY OF THE INVENTION A method of testing a dielectric strength of a capacitor according to the present invention is to measure a leak current by applying a predetermined test voltage to a capacitor under test, and measure this measured value and a preset leak current reference value. In the method of testing the dielectric strength of a capacitor for determining whether the voltage is good or bad, first, an AC voltage or a voltage obtained by superimposing an AC voltage on a DC voltage is applied to a capacitor under test to accelerate deterioration, and then a DC rated voltage as the voltage under test Is applied to the capacitor to be tested, the leakage current measurement is started after a lapse of a certain time, and if the measured value does not exceed the first leakage current reference value within a predetermined time, it is judged as a good product, and if it exceeds, it is determined as a defective product. A first test step to
Leakage current is applied to the capacitor under test determined to be non-defective in the first test step by changing it to a DC low voltage lower than the DC rated voltage as the test voltage and applying the leakage current in the same manner as in the first test step. A second test step is provided in which, when the measured leakage current does not exceed the second leakage current reference value, it is a good product, and when it exceeds the second leakage current reference value, it is determined as a defective product.

The first leakage current reference value was obtained from this evaluation data by previously evaluating variations in leakage current when the DC rated voltage was applied for each type of capacitor, temperature fluctuations, deterioration characteristics and the like. It may be set by multiplying the reference value by a predetermined margin coefficient, and the set value may be variable.

Further, as the second leakage current reference value, in claim 2, the DC rated voltage is set to the DC low voltage, and a margin coefficient obtained by reducing the margin coefficient to 1/2 to 1/3 is used. It may be set by setting.

Further, the number of capacitors to be tested may be plural, and the first and second inspection steps may be executed in parallel to the plurality of capacitors to be tested.

Further, the quality judgment data of each of the capacitors to be tested generated in the first and second test steps may be totalized for each manufacturing lot, stored in a storage medium as a database.

The AC voltage may have the same frequency as the natural vibration frequency of the capacitor under test.

More specifically, the capacitor withstand voltage testing apparatus of the present invention stores a plurality of the capacitors to be tested and selects the AC voltage or the DC voltage multiplied by the AC voltage or each of the test voltages. A test table for sequentially applying each of the capacitors to be tested, a loading mechanism for storing a plurality of the capacitors to be tested, which are packed and conveyed in a cartridge or the like, in the test table, and a loading mechanism stored in the test table. A measuring unit that measures the leakage current for each of the capacitors under test to which each of the test voltages is sequentially applied and converts this measured value into data and outputs the measured data as measurement data.
An ejection mechanism for categorizing and ejecting each of the capacitors under test stored in the test table into a non-defective tray or a non-defective tray according to the pass / fail data after completing the first and second test steps; And a first storage medium for storing a control program for instructing each part to execute the second test process, and a database for storing the first and second leakage current reference values as first and second reference value data. And the above-mentioned measurement data and the above-mentioned first and second reference value data are input, and both are compared and calculated, and the quality of the corresponding capacitor under test is judged, and the quality data indicating the result and the quality data are shown. And a second storage medium for storing the lot-specific pass / fail data.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a flow chart showing an embodiment of a dielectric strength test method of the present invention, and FIG. 2 is a measurement of leakage current in (a) first test step and (b) second test step in FIG. FIG. 3 is a characteristic diagram showing an example, and FIG. 3 is a block diagram showing a test apparatus that executes the dielectric strength test step in FIG.

First, the dielectric strength test method will be described with reference to FIG. The process of the withstand voltage test (S15) in the figure is a target part of the present invention, and each step before and after that, namely, firing (S11), cross-section polishing (S12), and plating treatment (S).
Each step of 13), breakdown voltage test (S14), static electricity, tan δ measurement (S16), packaging, and shipping (S17) is the same as each step with the same name in FIG.

In the withstand voltage test S15, first, an AC voltage or a voltage obtained by superimposing an AC voltage on a DC voltage is applied to a capacitor under test to accelerate deterioration (S151). After that, the DC rated voltage is applied to the capacitor under test, and the measurement of the leakage current is started after a certain time has passed (S152). Then, if the measured value does not exceed the first leakage current reference value within a predetermined time, it is determined to be a good product, and if it exceeds the first leakage current reference value, it is determined to be a defective product (S153). A voltage lower than a DC rated voltage as a test voltage, for example, a low voltage of a general working voltage, is applied to a first test process including the above steps and a capacitor under test determined to be a non-defective product in the first test process. Is applied to measure the leak current in the same manner as in the first test step (S154). If the leak current does not exceed the second leak current reference value, it is determined as a good product, and if it exceeds the second leak current reference value, it is determined as a defective product (S155). ) A second test process consisting of steps.

The details of each test process will be described below. In the first test process, in step S151, an AC voltage is applied when the capacitor under test is non-polar, and a voltage obtained by superimposing the AC voltage on the DC voltage is applied when the capacitor is polarized, and repeated stress is applied by the AC voltage. Accelerates deterioration.
That is, when a minute defect or the like is present inside the capacitor, the defect is made visible by applying an AC voltage, and in the next steps S152 and S153, this type of defective product can be detected to improve the product quality after shipping. Stabilize.

The AC voltage at this time may be set to have the same frequency as the natural vibration frequency of the capacitor under test so as to accelerate the acceleration of deterioration. By doing so, the application time can be shortened. .

In steps S152 and S153,
This will be described with reference to FIG. A is a defective product and B is a non-defective capacitor, and the charging current flows immediately after the DC rated voltage is applied, so the leakage current is large but it decreases with the passage of time, and a further margin is taken into consideration. Stabilize at point a. The leakage current is monitored up to a point b after a lapse of a predetermined time, for example, 60 seconds from the point a, and the peak value at the point c in A exceeds the first reference value. judge. Since B does not exceed the first reference value during monitoring, it is determined as a good product. Since the measurement is continuously performed during the monitoring period in this way, a reliable determination can be made without leaving an instantaneous peak.

The first reference value is predetermined to the reference value obtained from this evaluation data by previously evaluating variations in leakage current when a DC rated voltage is applied for each type of capacitor, temperature fluctuations, deterioration characteristics, and the like. It is set by multiplying the margin coefficient of and the set value can be changed. By making this variable, the reference value can be corrected to the optimum value at any time.

Next, in the second test step, in the main test step, instead of the DC rated voltage in the first test step, a low voltage,
For example, a commonly used voltage is applied and the waveform of the leakage current value is continuously monitored. When the applied voltage is lowered, the leakage current value becomes smaller and the waveform has a relatively small fluctuation. Therefore, when the leakage current fluctuates due to the internal defect, this is shown in FIG. 2 (b). It can be observed as a distinct peak waveform. That is, it is possible to easily detect the fluctuation of the leakage current due to the minute defect existing inside the insulating layer based on this peak value. By comparing this peak value with the optimum reference value, it is possible to judge whether the first pass or fail. It is possible to detect defective products that could not be detected in the test process.

That is, in step S154, a DC low voltage is applied to the capacitor to be tested which has been determined to be non-defective in the first test step, and the leakage current is measured. DC at this time
The low voltage is a voltage value considering the derating recommended by the manufacturer, that is, a working voltage with allowance, for example, 50 to 80% for a ceramic capacitor, 30 to 50% for a tantalum capacitor, and about 50% for a film capacitor.

Next, in step S155, it is determined whether the measured value of the leakage current is within the second reference value.
This will be described with reference to (b). As in the case of FIG. 2A, when a DC low voltage is applied, a charging current flows, so that it is large, and this gradually decreases and stabilizes at time point d with a margin. The measurement is started at this point d, and the leakage current is continuously monitored for a predetermined time, for example, point e after a lapse of 60 seconds. Figure 2
Compared to (a), the leakage current is small and the shake is stable, but the peak is remarkable. Defective product A is determined to be defective because the peak value at point c exceeds the second reference value.
B of the non-defective product has a peak but does not exceed the reference value, and is therefore determined to be the non-defective product.

The second reference value is set in the same manner as the setting of the first reference value, but it is used as the evaluation data when the applied voltage is a DC low voltage, and the margin coefficient is 1 when the first reference value is set. / 2
Set it down to 1/3. The reason for reducing the margin factor is to make the detection of the peak value more strict because the leakage current when the DC low voltage is applied is stable as described above.

It is not necessary to perform both the first and second test steps depending on the type of capacitor. For example, tantalum and electrolytic capacitors have a self-repairing function, so that a small peak in the second test step is required. Since the value does not matter so much, the second test step is omitted or simplified and the first test step is focused on. Also, in the case of the ceramic type capacitor, on the contrary, the minute peak value is a problem, so
Be sure to carry out the test process of.

Since it takes time to carry out through the first and second test steps described above, in an actual test apparatus, a plurality of capacitors under test are automatically tested in parallel and automatically. go. FIG. 3 shows an example of this test apparatus.

First, the configuration will be described with reference to FIG. This device is composed of an H / W (hardware) unit 1 and an S / W (software) unit 2.

The H / W unit 1 stores a plurality of capacitors to be tested, and AC voltage or a voltage obtained by superposing AC voltage and AC voltage or a test voltage in the first and second test steps, that is, DC rated voltage, DC. The test table 12 that selects one of the low voltages and sequentially applies it to each capacitor to be tested, and the plurality of capacitors to be tested that are transported by being packed in a cartridge (not shown) are stored in the front test table 12. Leakage current is measured for each of the carrying-in mechanism 11 and the capacitors under test that are stored in the test stand 12 and sequentially applied with the test voltage, and the continuous measurement values are converted into data and output as measurement data 102. The measuring unit 14 and the first or second
After the completion of the test process of 1., the discharging mechanism 13 for classifying and discharging each capacitor to be tested stored in the test table 12 according to the pass / fail data 101 to a non-defective tray (not shown) or a defective tray (not shown). It consists of

The S / W unit 2 also stores a memory 21 for storing a control program for sequentially instructing each unit to execute the first and second test processes, and a first and a second leakage current reference value. The database 23 stored as the 1st and 2nd reference value data 105 and the measurement data 102 and the 1st and 2nd reference value data 105 are input, and both are compared and calculated to determine the quality of the corresponding capacitor under test. A good / bad data 101 indicating the result and a calculation unit 22 for generating and outputting lot-based non-defective product data 104 in which the pass / fail data 101 is associated with a manufacturing lot, and a memory 2 for storing the lot-specific good / bad data 104.
4 and 4.

Next, the operation of the test apparatus will be described. The withstand voltage test 15 described with reference to FIGS. 1 and 2 is automatically executed by the control program 103 stored in the memory 1 as each part operates.

First, a plurality of capacitors to be tested, which are contained in a cartridge or the like and conveyed, for example, in units of 200, are sequentially stored by the carry-in mechanism 11 at predetermined locations on the test stand 12. On the test stand 12, the AC voltage is selected at the time when the storage is completed and is simultaneously applied to the capacitors under test (S151 in FIG. 1). After application for a predetermined time, a DC rated voltage is then selected as a test voltage and applied simultaneously to the capacitors under test. During this application,
The leakage current value of each capacitor under test is sequentially measured by the measuring unit 14 at the timing described in (a), and the measured data 1
Is output as 02 (S152). This measurement data 1
02 is compared with the reference value data 105 by the calculation unit 22, and the quality of each capacitor to be tested is determined, and the quality data 101 is output (S153). The discharging mechanism 13 sets the capacitor under test of the test table 12 to the pass / fail data 101.
By the above, the non-defective product is classified into the non-defective product tray, and the defective product is classified into the defective product tray and discharged.

After the completion of this first test step, a DC low voltage is selected as the test voltage, which is simultaneously applied to each capacitor under test, and the measuring unit 12 sequentially measures the leakage current and outputs the measurement data 102. (S154). With respect to this measurement data 102 as well, the quality determination is performed by the calculation unit 22, and the quality data 101 is output (S155). The ejection mechanism 13 classifies the non-defective and defective products based on the pass / fail data 101 and ejects them to the respective trays.

Further, the calculation unit 22 generates and outputs lot-specific pass / fail data 104 in which the pass / fail data 101 is tabulated for each manufacturing lot. Since the memory 24 stores and stores this, it is read out at any time and used for the following analysis. That is, by comparing the data between lots, the variation between lots can be verified. If there is a specific tendency in this variation, it means that the raw materials used are abnormal,
It is possible to notice the existence of an abnormality of the device or a problem caused by the person in charge of manufacturing, and feed the information back to the previous process. In this way, it is possible to detect anomalies across different lots where it is difficult to find differences among individual products.

Incidentally, each test voltage or reference value data is
Set and set in advance according to the type of capacitor under test.

[0040]

As described above, the method for testing the withstand voltage of the capacitor of the present invention and the test apparatus measure the leakage current by applying the DC rated voltage as the test voltage after applying the AC voltage to accelerate the deterioration. There is a two-stage test process including a first test process for determining pass / fail and a second test process for subsequently measuring a leak current by applying a DC low voltage as a test voltage. By continuously measuring the leakage current for a predetermined period, it is possible to make a reliable pass / fail judgment and improve the product quality after shipment.

A plurality of capacitors to be tested are connected in parallel,
In addition, there is an effect that the test can be performed efficiently and accurately by the test equipment that automatically processes all the test processes.Furthermore, by feeding back the quality data generated during this test to the previous process, the quality in the product process can be improved. There is an effect that can improve.

[Brief description of drawings]

FIG. 1 is a flowchart showing an example of an embodiment of a dielectric strength test method of the present invention.

FIG. 2 is a characteristic diagram showing an example of measurement of leakage current in (a) first test step and (b) second test step in FIG.

FIG. 3 is a block diagram showing a test apparatus that realizes the dielectric strength test method of FIG.

FIG. 4 is a flowchart showing manufacturing and inspection steps of a conventional dielectric strength test method.

FIG. 5 is a characteristic diagram showing an example of measurement of leakage current in FIG.

[Explanation of symbols]

1 H / W part 11 Carry-in mechanism 12 test bench 13 Discharge mechanism 14 Measuring section 2 S / W section 21, 24 memory 22 Operation part 23 Database

Claims (7)

[Claims] 1. A dielectric strength test method for a capacitor, which comprises applying a predetermined test voltage to a capacitor under test to measure a leakage current, and comparing the measured value with a preset reference value of the leakage current to judge acceptability. First, an AC voltage or a voltage obtained by superimposing an AC voltage on a DC voltage is applied to a capacitor under test to accelerate deterioration, and then a DC rated voltage is applied to the capacitor under test as the voltage under test. In the first test step, in which the measurement is started and the measured value does not exceed the first leakage current reference value within a predetermined time The test voltage determined to be non-defective is changed to a low DC voltage lower than the DC rated voltage and applied as the test voltage, and the leakage current is measured in the same manner as in the first test step. And a second test step of determining that the leakage current is a good product if the leakage current does not exceed the second leakage current reference value and a defective product if the leakage current exceeds the second leakage current reference value. 2. The first leakage current reference value is obtained from the evaluation data by previously evaluating variations in leakage current when the DC rated voltage is applied for each type of capacitor, temperature fluctuations, deterioration characteristics, and the like. 2. The method of testing a dielectric strength of a capacitor according to claim 1, wherein the reference value is set by multiplying the reference value by a predetermined allowance coefficient, and the set value can be varied. 3. The second leakage current reference value is set according to claim 2.
3. The insulation withstand voltage of the capacitor according to claim 2, wherein the DC rated voltage is set to the DC low voltage, and a margin coefficient obtained by reducing the margin coefficient to 1/2 to 1/3 is used. Test method. 4. The number of the capacitors to be tested is plural, and the first and second inspection steps are executed in parallel to the plurality of the capacitors to be tested. Alternatively, the method of testing the dielectric strength of the capacitor according to the item 3. 5. The quality judgment data of each of the capacitors to be tested generated in the first and second test steps is aggregated for each manufacturing lot, stored as a database, and stored in a storage medium. 2. A method for testing dielectric strength of a capacitor according to 2, 3, or 4. 6. A test stand in which a plurality of capacitors to be tested are stored and a voltage obtained by weighting the AC voltage to the AC voltage or a DC voltage or each of the test voltages is selected and sequentially applied to each of the capacitors to be tested. A loading mechanism for storing a plurality of the capacitors under test packed in a cartridge or the like and transported in the test table, and each of the capacitors under test stored in the test table and to which the test voltages are sequentially applied. A measuring unit for measuring the leakage current and converting the measured value into data and outputting it as measured data, and each of the test objects stored in the test table according to the pass / fail data after the first or second test process is completed. A discharge mechanism for classifying and discharging the test capacitors into a non-defective tray or a defective tray, and a control for instructing each part to execute the first and second test steps A first storage medium for storing a program, a database for storing the first and second leakage current reference values as first and second reference value data, the measurement data, and the first and second reference values Value data is input, and both are compared and calculated to determine whether the corresponding capacitor under test is good or bad, and good or bad data indicating the result and good or bad data for each lot in which the good or bad data is associated with a manufacturing lot are generated and output. 6. A capacitor withstand voltage test apparatus according to claim 5, further comprising a unit and a second storage medium for storing the lot-specific quality data. 7. The method for testing the withstand voltage of a capacitor according to claim 1, wherein the frequency of the AC voltage is the same as the natural vibration frequency of the capacitor under test. .