JP4062764B2 - Capacitor judgment method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for determining the quality of a capacitor, and more particularly to a method for determining the quality of a capacitor from the charging characteristics when a DC voltage is applied to the capacitor.
[0002]
[Prior art]
In general, in order to determine the quality of a capacitor, a method of measuring the insulation resistance of a capacitor by applying a measurement DC voltage to the capacitor and measuring the leakage current (charging current) of the capacitor after it is fully charged It has been known. Of course, good products have less leakage current.
[0003]
Conventionally, a measurement method defined in JIS-C 5102 is known as this type of charging current measurement method. In this method, since it is necessary to measure a current value in a state where the capacitor is sufficiently charged, a measurement time of about 60 seconds is required. However, along with demands for cost reduction and reliability improvement of electronic devices, there is a demand for improvement in the production capacity and quality of electronic components such as capacitors, and the conventional measurement which requires such a long measurement time per capacitor is required. Measurement methods cannot meet such demands.
[0004]
[Problems to be solved by the invention]
Therefore, in the past, as a simple pass / fail judgment method, the voltage value is applied to the capacitor, the current value is measured several seconds later, and the pass / fail value is determined by comparing the measured current value with a predetermined threshold value. It was. However, even with such a quality determination method, it takes at least a few seconds until a clear difference between a non-defective product and a defective product appears, so it is not always effective time reduction. Further, since the conventional method is a point data comparison for determining whether the threshold value is above or below a predetermined time, it cannot be said to be a highly accurate determination method.
[0005]
SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a capacitor quality determination method capable of accurately determining the quality of a capacitor in a short time.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, the invention described in claim 1 includes a step of applying a DC voltage to the capacitor to be measured, and a plurality of times t ₁ , t ₂ ,. ..., And determining slopes α ₁ , α ₂ ,... Of charging current characteristics and comparing the slopes α ₁ , α ₂ ,. , And the step of determining the quality is a charging current characteristic slope α _{1 at} two points in time t ₁ and t ₂ (t ₁ <t ₂ ) in the charging region of the dielectric polarization component of the capacitor to be measured. , Α ₂ , the slope difference α ₁ -α ₂ is obtained, and whether the slope difference α ₁ -α ₂ is between set values A ₁ and A ₂ (A ₁ > A ₂ ). Provided is a method for determining the quality of a capacitor, wherein the quality of the capacitor to be measured is determined.
The invention according to claim 2 is characterized in that a charging current characteristic is applied at a plurality of times t ₁ , t ₂ ,... In a step of applying a DC voltage to the capacitor to be measured and a charging region of a dielectric polarization component of the capacitor to be measured. inclination alpha _1, alpha _2, the ... request of inclination alpha _1, alpha _2, by comparing ... to each other and a step of determining the quality of the measured capacitor, the quality Is determined at time t ₁ , t ₂ , t ₃ ,... (T ₁ <t ₂ <t ₃ <...) At _three or more points in the charging region of the dielectric polarization component of the capacitor to be measured. , Charging current characteristic slopes α ₁ , α ₂ , α ₃ ,..., And slope differences α ₁ −α ₂ , α ₂ −α ₃ ,. _{α 1 -α 2, α 2 -α} 3, ··· set value _{A 1, A 2, B 1} , B 2, ··· (A 1> A 2, B 1> B 2 If there between..), Said a quality decision method of the capacitor, characterized in that to determine the measured capacitor is good.
According to a third aspect of the present invention, there is provided a charging current characteristic at a plurality of times t ₁ , t ₂ ,... In the step of applying a DC voltage to the capacitor to be measured and the charging region of the dielectric polarization component of the capacitor to be measured. inclination alpha _1, alpha _2, the ... request of inclination alpha _1, alpha _2, by comparing ... to each other and a step of determining the quality of the measured capacitor, the quality Determining the charging current characteristic slopes α ₁ and α ₂ at two points in time t ₁ and t ₂ (t ₁ <t ₂ ) in the charging region of the dielectric polarization component of the capacitor to be measured, calculated slope of the change rate _{(α 1 -α 2) / α} 1, to determine the acceptability of the device under test capacitors by comparing the slope of the change rate _{(α 1 -α 2) / α} 1 and the set value K This is a method for determining whether a capacitor is good or bad.
According to a fourth aspect of the present invention, there is provided a charging current characteristic at a plurality of times t ₁ , t ₂ ,... In a step of applying a DC voltage to the capacitor to be measured and a charging region of a dielectric polarization component of the capacitor to be measured. inclination alpha _1, alpha _2, the ... request of inclination alpha _1, alpha _2, by comparing ... to each other and a step of determining the quality of the measured capacitor, the quality Is determined at time t ₁ , t ₂ , t ₃ ,... (T ₁ <t ₂ <t ₃ <...) At _three or more points in the charging region of the dielectric polarization component of the capacitor to be measured. , Charging current characteristic slopes α ₁ , α ₂ , α ₃ ,... Are obtained, and the rate of change in slope at the adjacent time (α ₁ −α ₂ ) / α ₁ , (α ₂ −α ₃ ) / α ₂ obtains a ..., rate of change of the slope _{(α 1 -α 2) / α} 1, (α 2 -α 3) / α 2, sets the ... values K _1, K ₂ ,..., To determine the quality of the capacitor to be measured.
[0007]
Here, the background to the completion of the present invention will be described.
The inventor accurately measured the change in the current value during charging of the ceramic capacitor, and plotted the current value and time on the logarithmic current-logarithmic time coordinates. As shown in FIG. Found that there is. In other words, an almost constant large current flows during a very short period (1) at the initial stage of charging, but the current value suddenly decreases during the subsequent transition period (2), and then linear charging characteristics with a certain slope (3) The current decreased. This linear charging characteristic (3) was maintained from 1 minute to 2 minutes after the start of charging.
[0008]
Further examination of the above characteristics revealed the following facts. That is, the equivalent circuit of the capacitor is composed of a capacitance C ₀ , an internal resistance r, an insulation resistance R ₀ and a dielectric polarization component D as shown in FIG. 2, but the initial charging characteristic {circle around (1)} is the charging region of the capacitance C ₀ . On the other hand, the linear charge characteristic (3) is the fact that it is the charge region of the dielectric polarization component D.
[0009]
In the case of a non-defective capacitor, the charge characteristic naturally has a characteristic substantially in line with the linear charge characteristic (3) in FIG. On the other hand, in the case of a defective capacitor, as shown by the broken line in FIG. 1, the linear charging characteristic (3) is substantially satisfied in the initial stage of charging, but the current value decreasing rate decreases with time. . In general, the difference between a good product and a defective product clearly appears after a few seconds have passed since the voltage was applied. However, the sign has already appeared at the time of several tens of milliseconds after the voltage application. That is, when the difference between the measured current value of the defective product and the measured current value of the non-defective product is taken, it tends to gradually increase in the positive direction with time.
[0010]
Therefore, the present invention determines whether a capacitor is good or not by paying attention to the difference in slope of charging characteristics between a good product and a defective product.
As is clear from FIG. 1, the non-defective product and the defective product have the same slope α ₁ at time t ₁ , but at time t ₂ after a predetermined time, the slope between the slopes α ₂ and α ₂ ′ is clear. There is a big difference. Therefore, in the present invention, for example, the quality is determined by comparing the inclinations α ₁ and α ₂ at times t ₁ and t ₂ . In this way, it is possible to accurately determine whether the product is good or not in a relatively short time.
[0011]
The number of times of measuring the inclination may be two times or three or more times. However, in order to determine whether the inclination is good or not in a short time, a time t immediately after the voltage application (for example, 1 msec to 100 msec). _It is desirable to obtain the inclinations α ₁ , α ₂ ,... At ₁ , t ₂ ,.
[0012]
For example, when performing two measurements of the time t ₁ and t _2, as claimed in claim 1, while the difference in inclination alpha _{1-.alpha. 2} is setting _{A 1, A 2 (A 1} > A 2) It is easy to determine whether a capacitor is good or bad based on the presence or absence. The reason why the comparison is made with such a width is to reduce the influence of noise and the like.
A ₁ > α ₁ −α ₂ > A ₂
In this case, the slopes α ₁ , α ₂ ,... Are both negative values, but the difference may be positive or negative depending on the charging characteristics. Therefore, the set values A ₁ and A ₂ may be either positive or negative.
[0013]
Also, if the measurements were made three times or more, as in claim 2, the difference between alpha _{1-.alpha. 2} gradient in adjacent time, alpha _{2-.alpha. 3,} seek ..., difference alpha ₁ of the slope -Α ₂ , α ₂ -α ₃ ,... Are between set values A ₁ , A ₂ , B ₁ , B ₂ ,... (A ₁ > A ₂ , B ₁ > B ₂ ,...). It is desirable to determine whether the capacitor is good or bad based on whether or not it is present. That is,
A ₁ > α ₁ −α ₂ > A ₂
And B ₁ > α ₂ −α ₃ > B ₂
In this case, it is determined that the product is non-defective only when all of the plurality of conditions are satisfied.
In addition, when performing the measurement 3 times or more, it is not always necessary to determine the quality based on the difference in inclination at adjacent times.
[0014]
In the first and second aspects, the difference between the inclinations α ₁ , α ₂ ,... Is compared with the set value, but as described in the third and fourth aspects, the rate of change in inclination (α ₁ −α ₂ ) / Α ₁ may be compared with the set value K to determine whether the capacitor is good or bad.
[0015]
Preferably, at a time t ₀ in the charging region of the dielectric polarization component of the capacitor, a step of obtaining a reference charge current characteristic slope α ₀ in advance, a step of applying a DC voltage to the capacitor to be measured, A step of obtaining a charging current characteristic slope α ₀ ′ at the time t ₀ in the charging region of the dielectric polarization component, and a step of determining pass / fail of the capacitor to be measured by comparing α ₀ and α ₀ ′. , May be included.
That is, in the inventions of claims 1 to 4, the quality is determined by the change in the slope at a plurality of times in the charging current characteristics of the capacitor to be measured. Here, the slope that serves as a reference at a predetermined time is obtained in advance. In addition, the quality is determined by comparing the inclination with the inclination of the capacitor to be measured at the same time.
[0016]
The time t ₀ is a time in the charging region of the dielectric polarization component, and is a time when a good product and a defective product can be distinguished. Further, as a method for obtaining the reference charge current characteristic slope α ₀ , for example, a plurality of sample capacitors having good charge characteristics are prepared, the individual slopes at time t ₀ are obtained, and the slope α ₀ is obtained from the average value. ₀ may be determined.
[0017]
The step of obtaining the reference charge current characteristic slope α ₀ is performed as a preparatory step separately from the step of obtaining the slope α ₀ ′ of the capacitor to be measured at time t ₀ . Therefore, after determining the reference inclination α ₀ , the measurement of the inclination α ₀ ′ of the capacitor to be measured at time t ₀ and the comparison between the inclinations α ₀ and α ₀ ′ may be repeated. As the quality determination method, as in the inventions of claims 1 to 4 , the difference between the slopes α ₀ and α ₀ ′, or whether the ratio is within a predetermined range, may be determined. You may discriminate | determine by the magnitude relationship of the absolute value of (alpha) ₀ and (alpha) ₀ '.
[0018]
Preferably , a slope α ₀ ,... Of the reference charging current characteristic is obtained in advance at a plurality of times t ₀ ,..., And each slope α ₀ ,. The quality of the capacitor to be measured may be determined by comparing with the inclination α ₀ ′ at each time t ₀ ,. In this case, if all the comparison conditions are satisfied and the product is determined to be a non-defective product, it is possible to determine the quality of the product with extremely high accuracy.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 3 shows an example of a current measuring device for carrying out the method of the present invention. This measuring apparatus has been proposed by the present applicant in Japanese Patent Laid-Open No. 9-113545.
This measuring apparatus includes a DC measurement power supply 10, a switch 11, a capacitor 12 as a measurement object, a limiting resistor 13, a logarithmic amplifier 14, a measurement amplifier 15, A / D converters 16 and 18, and an arithmetic processing circuit (CPU) 17. It has. At the initial stage of charging, the current value is measured by the measurement amplifier 15 and switched to the logarithmic amplifier 14 at a predetermined threshold, and thereafter, the current value is measured by the logarithmic amplifier 14. Since this measuring device can accurately measure the charging current of the capacitor 12 in a wide range, it continuously measures the current value from the initial charging to the end of charging, which was difficult to measure with the conventional measuring device. It has the feature that it can be measured.
Note that the method of the present invention is not limited to using the measuring device shown in FIG. 3, and any other measuring device can be used as long as it can accurately measure the charging current characteristic of the dielectric polarization component of the capacitor. May be.
[0020]
Now, a first embodiment of the quality determination method according to the present invention will be described with reference to FIG.
First, the switch 11 is turned on and a DC voltage is applied to the measured capacitor 12 (step S1).
Next, a gradient alpha ₂ at time t ₂ after inclination alpha ₁ and the predetermined time at time t _1, for example, determined by differential processing of CPU 17 (step S2).
Next, it is determined whether or not the inclination difference α ₁ −α ₂ is between the set values A ₁ and A ₂ (A ₁ > A ₂ ) (step S3). That is,
A ₁ > α ₁ −α ₂ > A ₂
Is determined to be a non-defective product (step S4), and if the above inequality is not satisfied, it is determined to be a defective product (step S5).
[0021]
For example, the slope α ₁ = −0.985 when the time t ₁ = 0.01 sec (the unit is log ampere / log second, the same applies hereinafter), the slope α ₂ when the time t ₂ = 0.1 sec = −0. Assuming 982, the difference between the two is α ₁ −α ₂ = −0.003, which is very close to 0, so it is determined as a non-defective product.
On the other hand, the time t ₁ = slope α ₁ = -0.985 when the 0.01 sec, a time t ₂ = When the inclination α ₂ = -0.878 when the 0.1 sec, the difference therebetween alpha _{1-.alpha. 2} Since = -0.107 is far from 0, it is determined as a defective product.
Judgment criteria for non-defective products and defective products, that is, the values of A ₁ and A ₂ differ depending on the type of capacitor. In the case of having a linear charging current characteristic as shown in FIG. 1, it is desirable that A ₁ is about −0.0001 and A ₂ is about −0.01.
The unit of inclination is not limited to log current (ampere) / log time (seconds), and may be current / time.
[0022]
As a pass / fail judgment method, in addition to the method of comparing the slope difference α ₁ −α ₂ with a predetermined value as described above, the slope change rate may be compared with a set value.
For example, (α ₁ −α ₂ ) / α ₁ may be obtained, and this may be compared with the set value K (for example, 0.01). If the values of the above specific examples are used, (α ₁ −α ₂ ) / α ₁ = 0.003 for the non-defective product, whereas (α ₁ −α ₂ ) / α for the defective product. _{Since 1} = 0.109, pass / fail can be easily determined.
[0023]
FIG. 5 shows a second embodiment of the quality determination method according to the present invention.
First, a DC voltage is applied to the capacitor 12 to be measured (step S10).
Next, inclinations α ₁ , α ₂ , and α ₃ at three points of time t ₁ , t ₂ , and t ₃ (t ₁ <t ₂ <t ₃ ) are obtained (step S11).
Next, whether the slope differences α ₁ −α ₂ and α ₂ −α ₃ are between the set values A ₁ and A ₂ (A ₁ > A ₂ ), B ₁ and B ₂ (B ₁ > B ₂ ). It is determined whether or not (step S12). That is,
A ₁ > α ₁ −α ₂ > A ₂
And B ₁ > α ₂ −α ₃ > B ₂
Is determined to be a non-defective product (step S13), and if any one of the above inequalities is not met, it is determined to be a defective product (step S14).
In the case of this determination method, since the change in inclination at three times is obtained, it is possible to perform the pass / fail determination with higher accuracy than the method of FIG.
It should be noted that the determination is not limited to the three points of time t ₁ , t ₂ , and t _3, and it is needless to say that the inclination at the time of four or more points may be obtained and determined.
[0024]
Also in this case, as a pass / fail determination method, the rate of change in inclination may be used instead of the difference in inclination.
That is, (α ₁ −α ₂ ) / α ₁ , (α ₂ −α ₃ ) / α ₂ is obtained, and the magnitudes of these values and the set values K ₁ and K ₂ may be compared.
[0025]
FIG. 6 shows a third embodiment of the quality determination method according to the present invention.
In the embodiment of FIGS. 4 and 5, the quality is determined by the change in the slope at a plurality of times in the charging current characteristics of the capacitor 12 to be measured. In this embodiment, the charging current characteristics of the reference capacitor are preliminarily determined. The inclination at a predetermined time is obtained, and the quality is determined by comparing this inclination with the inclination at the same time of the capacitor to be measured.
[0026]
First, step S20 and step S21 are performed as a preparatory process. That is, a DC voltage is applied to a sample capacitor that is known to be a good product in advance (step S20), and a slope α ₀ of the charging current characteristic at a predetermined time t ₀ is obtained (step S21). Specifically, the slope at time t ₀ is obtained from a plurality of sample capacitors, and a value slightly smaller than the average value is preferably set as the slope α ₀ . The time t ₀ and the inclination α ₀ may be stored in a memory.
After the preparatory process is completed, the process proceeds to the measurement / discrimination process. First, a DC voltage is applied to the capacitor to be measured (step S22). This voltage is naturally the same as the voltage applied to the sample capacitor.
Next, the slope α ₀ ′ of the charging current characteristic of the capacitor to be measured at time t ₀ is obtained (step S23).
Next, the reference inclination α ₀ is compared with the inclination α ₀ ′ of the capacitor to be measured (step S24). For example, the magnitudes of | α ₀ | and | α ₀ '| may be compared.
If | α ₀ | ≦ | α ₀ ′ |, it is determined as a non-defective product (step S 25), and if | α ₀ |> | α ₀ ′ |, it is determined as a defective product (step S 26).
Thereafter, the quality of the capacitor to be measured is determined by repeating the measurement / discrimination step (steps S22 to S26).
[0027]
In the case of the method of FIG. 6, even if the charging current characteristic of the capacitor to be measured has a linear characteristic (the inclination is almost constant), it can be clearly determined that the product is defective when the inclination itself is small. .
[0028]
FIG. 7 shows a fourth embodiment of the quality determination method according to the present invention. This embodiment is a modification of the method of FIG.
First, as a preparatory step, a DC voltage is applied to a sample capacitor known to be a good product in advance (step S30), and the slopes α ₀ ,... Of charging current characteristics at a plurality of times t ₀ ,. Is obtained (step S31). The setting method of each inclination α ₀ ,... Is the same as that in the embodiment of FIG.
Next, a DC voltage is applied to the capacitor to be measured (step S32).
Next, slopes α ₀ ′,... Of charging current characteristics of the measured capacitors at the plurality of times t ₀ ,... Are obtained (step S33).
Next, the reference inclination | α ₀ |,... Is compared with the inclination | α ₀ ′ |,... Of the capacitor to be measured (step S34).
When the inclination | α ₀ ′,... Of the measured capacitor is larger than the reference inclination | α ₀ |,..., The product is determined to be non-defective (step S35). When the inclination becomes large, it is determined as a defective product (step S36).
With this method, it is possible to make a pass / fail judgment with higher accuracy than in FIG.
[0029]
The present invention is not limited to a ceramic capacitor, and any capacitor can be used as long as it has a dielectric polarization component, such as an electrolytic capacitor or a film capacitor.
[0030]
【The invention's effect】
As is clear from the above description, according to the present invention , the slope of the charging current characteristic at a plurality of times of the dielectric polarization component of the capacitor to be measured is obtained, and these slopes are compared with each other to determine whether the capacitor to be measured is good or bad. Therefore, it is possible to know the tendency of the charging current characteristic more accurately than the comparison with the threshold value as in the prior art, and to perform the pass / fail judgment with high accuracy.
Moreover, since the quality can be determined by the initial inclination of the dielectric polarization component, the quality can be determined in a very short period of less than 1 second without waiting for several seconds from the voltage application.
[Brief description of the drawings]
FIG. 1 is a diagram showing a change in charging current in a non-defective capacitor and a defective capacitor.
FIG. 2 is a circuit diagram showing an equivalent circuit of a capacitor.
FIG. 3 is a circuit diagram of an example of a current measuring device.
FIG. 4 is a flowchart of the first embodiment of the quality determination method according to the present invention.
FIG. 5 is a flowchart of a second embodiment of the quality determination method according to the present invention.
FIG. 6 is a flowchart of a third embodiment of the quality determination method according to the present invention.
FIG. 7 is a flowchart of a fourth embodiment of the quality determination method according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 DC measuring power supply 12 Measured capacitor 13 Resistance 14 Logarithmic amplifier 15 Measuring amplifier 16, 18 A / D converter 17 CPU

Claims (4)

At a plurality of times t ₁ , t ₂ ,... In the step of applying a DC voltage to the capacitor to be measured and the charging region of the dielectric polarization component of the capacitor to be measured, the charging current characteristic gradients α ₁ , α ₂ ,. Determining the quality of the capacitor to be measured by comparing the slopes α ₁ , α ₂ ,... With each other, and
The step of determining the quality is:
At two points in time t ₁ and t ₂ (t ₁ <t ₂ ) in the charging region of the dielectric polarization component of the capacitor to be measured, slopes α ₁ and α ₂ of charging current characteristics are obtained,
Find the slope difference α ₁ −α ₂ ,
Whether or not the capacitor to be measured is good or bad is determined based on whether or not the slope difference α ₁ −α ₂ is between set values A ₁ and A ₂ (A ₁ > A ₂ ). Method. At a plurality of times t ₁ , t ₂ ,... In the step of applying a DC voltage to the capacitor to be measured and the charging region of the dielectric polarization component of the capacitor to be measured, the charging current characteristic gradients α ₁ , α ₂ ,. Determining the quality of the capacitor to be measured by comparing the slopes α ₁ , α ₂ ,... With each other, and
The step of determining the quality is:
The slope of the charging current characteristic at times t ₁ , t ₂ , t ₃ ,... (T ₁ <t ₂ <t ₃ <...) At _three or more points in the charging region of the dielectric polarization component of the measured capacitor. Find α ₁ , α ₂ , α ₃ , ...
Find the slope differences α ₁ −α ₂ , α ₂ −α ₃ ,...
Differences α ₁ −α ₂ , α ₂ −α ₃ ,... Are set values A ₁ , A ₂ , B ₁ , B ₂ ,... (A ₁ > A ₂ , B ₁ > B ₂ ,. )), It is determined that the capacitor to be measured is a non-defective product. At a plurality of times t ₁ , t ₂ ,... In the step of applying a DC voltage to the capacitor to be measured and the charging region of the dielectric polarization component of the capacitor to be measured, the charging current characteristic gradients α ₁ , α ₂ ,. Determining the quality of the capacitor to be measured by comparing the slopes α ₁ , α ₂ ,... With each other, and
The step of determining the quality is:
At two points in time t ₁ and t ₂ (t ₁ <t ₂ ) in the charging region of the dielectric polarization component of the capacitor to be measured, slopes α ₁ and α ₂ of charging current characteristics are obtained,
Obtain the rate of change of the slope (α ₁ −α ₂ ) / α ₁ ,
A method for determining the quality of a capacitor, characterized in that the quality of the capacitor to be measured is determined by comparing a rate of change in inclination (α ₁ −α ₂ ) / α ₁ with a set value K. At a plurality of times t ₁ , t ₂ ,... In the step of applying a DC voltage to the capacitor to be measured and the charging region of the dielectric polarization component of the capacitor to be measured, the charging current characteristic gradients α ₁ , α ₂ ,. Determining the quality of the capacitor to be measured by comparing the slopes α ₁ , α ₂ ,... With each other, and
The step of determining the quality is:
The slope of the charging current characteristic at times t ₁ , t ₂ , t ₃ ,... (T ₁ <t ₂ <t ₃ <...) At _three or more points in the charging region of the dielectric polarization component of the measured capacitor. Find α ₁ , α ₂ , α ₃ , ...
Find the rate of change in slope (α ₁ −α ₂ ) / α ₁ , (α ₂ −α ₃ ) / α ₂ ,...
The change rate of each slope (α ₁ −α ₂ ) / α ₁ , (α ₂ −α ₃ ) / α ₂ ,... Is compared with the set values K ₁ , K ₂ ,. A method for determining whether or not a capacitor is good, wherein the quality is determined.

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