JP2015153991A - Electrolytic capacitor life diagnosis method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To diagnose the life of an electrolytic capacitor in a short period of time.SOLUTION: An electrolytic capacitor life diagnosis method according to an embodiment includes: an acceleration test step S10 of measuring a weight and a characteristic parameter while continuing a state where a predetermined voltage is applied to each of a plurality of acceleration test electrolytic capacitors; a database making step S32 of storing a relationship of the characteristic parameter with respect to the weight into a database on the basis of change over time of the weight and of the characteristic parameter obtained in the acceleration test step S10; and a life estimation step S42 of estimating the life of an evaluation target electrolytic capacitor on the basis of the weight and data stored in the database. In the acceleration test, an electrolytic capacitor with dispersion acceleration holes including dispersion acceleration holes piercing a casing of the acceleration test electrolytic capacitor is used, and an area of the dispersion acceleration holes is an area in proportion to a surface area of the acceleration test electrolytic capacitor.

Description

  Embodiments described herein relate generally to a life diagnosis method for an electrolytic capacitor.

  In an electrolytic capacitor, the internal electrolyte solution gradually diffuses, and the electrical characteristics such as electrostatic capacity, equivalent series resistance (hereinafter referred to as ESR), dielectric loss tangent (tan δ), and leakage current are deteriorated. For this reason, it is necessary to diagnose the lifetime. When estimating the lifetime of electrolytic capacitors, the lifetime is estimated by converting to the temperature in the actual usage environment with reference to the manufacturer's guaranteed lifetime.

  Conventionally, the manufacturer's guaranteed lifetime of electrolytic capacitors has been mainly 1000 hours products and 2000 hours products at 105 ° C. However, in recent years, products with a long lifetime such as a 7000 hour product or a 10,000 hour product under a 105 ° C. environment have been developed. The life diagnosis of such a long-life electrolytic capacitor requires an enormous amount of time and may be substantially difficult.

  Further, as a method for predicting deterioration of an electrolytic capacitor, there is a method of measuring the amount of ESR change of the electrolytic capacitor, obtaining a relational expression with the amount of electrolytic solution, and calculating the remaining rate of the electrolytic solution after a predetermined time (Patent Document) 1). In this method, the deterioration of the electrolytic capacitor can be predicted by estimating the ESR after elapse of a predetermined time based on the remaining rate of the electrolytic solution amount after the predetermined time. However, since it is not a method of accelerating the deterioration of the electrolytic capacitor, it is difficult to predict the lifetime of a new electrolytic capacitor in a short period.

  In addition, as a finite-life electronic component and its life confirmation method, a bar code that records the electrical characteristics and lifetime judgment value at the start of use is affixed to the surface of an electronic component such as an electrolytic capacitor, and the amount of degradation of the electrolytic capacitor in use There is a method of determining (Patent Document 2). In this method, it is possible to know the transition degree of the life due to the characteristic deterioration at the time of use and the remaining life. However, although it is possible to estimate the deterioration amount of the electrolytic capacitor used in the market, it is difficult to predict the lifetime of a new electrolytic capacitor in a short period of time.

  Further, in the technique disclosed in Patent Document 3, since the test is performed using a sample having one pinhole, the electric capacity such as capacitance, ESR, tan δ, and leakage current is varied depending on the size of the pinhole. There was a problem that there was a large change and variation in the physical characteristics.

  In the technique disclosed in Patent Document 4, a test is performed using a sample having a plurality of pinholes. For this reason, an electrolytic capacitor having a large case size has an effect of accelerating the diffusion rate of the electrolytic solution. However, an electrolytic capacitor having a small case size has a diffusion rate of the electrolytic solution that is too fast, such as capacitance, ESR, tan δ, and leakage current There was a problem that it was difficult to capture changes in the electrical characteristics of the.

Japanese Patent No. 4364754 Japanese Patent No. 3646567 JP 2012-32332 A JP 2013-44714 A

  As described above, the conventional accelerated test has a problem that it is difficult to predict the life of a new electrolytic capacitor in a short period of time.

  Therefore, an embodiment of the present invention aims at diagnosing the lifetime of an electrolytic capacitor in a shorter period of time than before.

  In order to achieve the above-described object, the present embodiment includes an element part having an electrolyte solution and a lead part protruding outside, a casing containing and storing the element part, and having an open end on one side and the open end An electrolytic capacitor life diagnosis method for estimating the life of the target electrolytic capacitor due to diffusion of the electrolyte sealed in the casing to the outside as an electrolytic capacitor including a sealing member that seals the part, An acceleration test step for performing an acceleration test for measuring the weight and characteristic parameters of the electrolytic capacitor for acceleration test while maintaining a state in which a predetermined voltage is applied to each of the plurality of electrolytic capacitors for acceleration test, and the acceleration test step. From the time variation of the weight of the electrolytic capacitor for acceleration test and the characteristic parameter obtained, the relationship of the characteristic parameter to the weight is determined. A database storing step for storing in a database, and a life estimating step for estimating the life of the electrolytic capacitor to be evaluated from the weight of the electrolytic capacitor for acceleration test and the data stored in the database, and in the accelerated test, Using an electrolytic capacitor with a diffusion acceleration hole provided with a diffusion acceleration hole penetrating the casing of the electrolytic capacitor for acceleration test, the area of the diffusion acceleration hole is an area proportional to the surface area of the electrolytic capacitor for acceleration test Features.

  According to the embodiment of the present invention, the lifetime of the electrolytic capacitor can be diagnosed in a shorter period than before.

It is sectional drawing which shows the structure of the electrolytic capacitor as a test body used with the acceleration test in the lifetime diagnosis method of the electrolytic capacitor which concerns on 1st Embodiment. It is a perspective view which shows the step which forms a diffusion acceleration hole in the casing of an electrolytic capacitor. It is a flowchart which shows the whole procedure of the lifetime diagnosis method of the electrolytic capacitor concerning 1st Embodiment. It is a flowchart which shows the procedure of the acceleration test of the lifetime diagnosis method of the electrolytic capacitor concerning 1st Embodiment. It is a graph which shows a time-dependent change of the electrostatic capacitance change amount at the time of changing the area ratio of the diffusion acceleration hole provided in a casing. It is a perspective view which shows the position of the diffusion acceleration hole provided in a casing. It is a graph which shows the example of the time-dependent change of the electrostatic capacitance change amount at the time of changing the temperature conditions of an accelerated life test. It is a graph which shows the example of the time-dependent change of an electrostatic capacitance change amount in an accelerated life test, and a lifetime point. It is a characteristic view which shows the example of the correlation of the weight variation | change_quantity of an electrolytic capacitor, and an electrostatic capacitance variation | change_quantity. It is an example of the graph which estimates the lifetime of an electrolytic capacitor based on the time-dependent change characteristic of a weight variation, and an electrostatic capacitance variation. It is a graph which shows the example of the correlation of the weight variation | change_quantity of the electrolytic capacitor and ESR variation | change_quantity for demonstrating 2nd Embodiment. It is a graph which estimates the lifetime of an electrolytic capacitor based on the time-dependent change characteristic of the amount of weight changes, and the amount of ESR changes for demonstrating 2nd Embodiment. It is a graph which shows the example of the correlation of the weight of the electrolytic capacitor for explaining 3rd Embodiment, and an electrostatic capacitance change amount. It is a graph which shows the example of the correlation of the weight actual value of the electrolytic capacitor for explaining 3rd Embodiment, and ESR variation | change_quantity.

  Hereinafter, a life diagnosis method for an electrolytic capacitor according to an embodiment of the present invention will be described with reference to the drawings. Here, the same or similar parts are denoted by common reference numerals, and redundant description is omitted.

[First Embodiment]
FIG. 1 is a cross-sectional view showing a structure of an electrolytic capacitor as a test body used in an accelerated test in the electrolytic capacitor lifetime diagnosis method according to the first embodiment. The lead-type electrolytic capacitor 10 includes an element portion 11 and a casing 14 that houses the element portion 11. The casing 14 has an aluminum case 12 and an insulating coating 13 that covers the outside of the aluminum case 12. The casing 14 has a cylindrical shape that is closed on one side, and has a cylindrical side portion 14a, a flat closed end portion 14b, and an open open end portion 14c.

  The opening member 14 c of the casing 14 is filled with a sealing member 15. The material of the sealing member 15 is an elastic material such as rubber. Lead wires 16 a and 16 b are connected to the element portion 11, penetrating through the lead portions 15 a and 15 b provided in the sealing member 15 and projecting to the outside.

  The element unit 11 uses a metal such as aluminum, tantalum, or niobium as an electrode (anode), uses an oxide film layer obtained by anodizing as a dielectric, and uses an electrolyte as a cathode. Specifically, it is formed by winding an anode foil subjected to etching treatment and oxide film formation treatment and a cathode foil subjected to etching treatment through a separator such as electrolytic paper. The element unit 11 is impregnated with a driving electrolyte.

  The aluminum case 12 that houses the element portion 11 is made of aluminum. After the element part 11 is accommodated in the casing 14, that is, the aluminum case 12 and the insulating coating 13, the opening end part 14 c is drawn and the opening of the casing 14 is opened by the sealing member 15 that is an elastic sealing body. The opening is sealed. In addition, a portion of the casing 14 that includes the sealing member 15 in the opening is subjected to drawing processing from the outside, and a drawn portion 17 is formed.

  Although the lead type electrolytic capacitor has been described, the structure is basically the same even in the surface mount type, only the shape of the lead wires 16a and 16b is changed.

  In the electrolytic capacitor 10 thus configured, the internal electrolyte is sealed, but gradually diffuses over time, and electrical characteristics such as capacitance, ESR, tan δ, and leakage current deteriorate. . The electrolyte solution diffusion path includes three paths between the aluminum case 12 and the sealing member 15, between the lead portions 15a and 15b and the sealing member 15, and within the sealing member 15. Among them, the lead portions 15a and 15b and the sealing member are sealed. The path between the members 15 is most easily diffused.

  In the electrolytic capacitor 10 which is a test body for an acceleration test, a diffusion acceleration hole 21 penetrating the aluminum case 12 and the insulating coating 13 is formed in the closed end portion 14b at the same location in order to accelerate the diffusion of the electrolytic solution. ing. Although there are a plurality of types of electrolytic capacitors 10, the ratio of the area of the diffusion accelerating hole 21 to the surface area of the electrolytic capacitor 10 is a constant value regardless of the size of the electrolytic capacitor 10. Note that there may be a plurality of types of this constant value.

  FIG. 2 is a perspective view showing steps of forming diffusion acceleration holes in the casing of the electrolytic capacitor. In an accelerated test in a high-temperature environment or a high-temperature and high-humidity environment, in order to accelerate the diffusion of the electrolytic solution, the diffusion acceleration hole 21 is formed in the closed end portion 14b of the aluminum case 12 (FIG. 1) of the electrolytic capacitor 10 to be accelerated. Form. The diffusion acceleration hole 21 is operated using a needle-like jig 25. A jig such as a desktop drill or a hand drill may be used as the jig. Moreover, when making a micro-sized hole, it can work using the cutting process by a micro drill, the fine electric discharge machining by a fine electric discharge machine, etc.

  Care is taken to make the diffusion acceleration holes 21 as uniform as possible for the same size. At that time, it is necessary to be careful because a burr generated when a hole is formed in the hole forming jig or the aluminum case 12 may cause a failure and accurate data cannot be obtained. The shape of the diffusion acceleration hole 21 may be circular or polygonal. By forming the diffusion acceleration hole 21, the electrolytic solution easily diffuses from the diffusion acceleration hole 21 provided in the aluminum case 12 of the electrolytic capacitor 10, so that the electrolytic capacitor 10 is deteriorated in a shorter time than the conventional life acceleration test. be able to.

  FIG. 3 is a flowchart showing the entire procedure of the electrolytic capacitor life diagnosis method according to the first embodiment. An acceleration test is performed on the electrolytic capacitor 10 (FIG. 1) to be accelerated (step S10). In parallel with the acceleration test, field data and the like are accumulated (step S20). In other words, for electrolytic capacitors that have not been formed with diffusion accelerating holes and collected from the market, the usage environment such as the atmospheric conditions used, the usage conditions such as voltage, and electrical characteristics data are organized for multiple types. And organize the relationship between the usage conditions and the weight of the electrolytic capacitor. In addition, if there are life test data conducted so far, they are also collected.

  Next, based on the result of the acceleration test, field data, and the like, a correlation characteristic between the capacitance of the electrical characteristics and the weight of the electrolytic capacitor 10 or the equivalent series resistance of the electrical characteristics and the weight of the electrolytic capacitor 10 is obtained. . At this time, if there is life test data carried out so far, the relationship between the weight of the electrolytic capacitor 10 and the electrical characteristics as a result of the acceleration test is the same in view of the relationship between the weight of the electrolytic capacitor and the electrical characteristics. Confirm. In other words, the validity of the accelerated test is confirmed. An approximate expression is determined based on this relationship (step S31). This approximate expression is stored in the database 30 (step S32).

  Next, a confirmation test for the electrolytic capacitor to be evaluated is performed (step S41). From the weight of the electrolytic capacitor obtained in the confirmation test for the electrolytic capacitor to be evaluated, the lifetime of the electrolytic capacitor is estimated using the relational expression stored in the database 30 (step S42).

  FIG. 4 is a flowchart showing an accelerated test procedure of the electrolytic capacitor life diagnosis method according to the first embodiment. A plurality of electrolytic capacitors are used for the acceleration test. First, initial characteristics of the electrolytic capacitor to be subjected to the acceleration test are measured (step S11). The measurement items are electrical characteristics such as capacitance, tan δ, ESR, leakage current, and the weight of the electrolytic capacitor. The electrical characteristics of the electrolytic capacitor are measured using an LCR meter, and the weight of the electrolytic capacitor is measured using an electronic balance.

  Next, it is determined whether or not there is a failure in the electrolytic capacitor to be accelerated (step S12). If any of the various characteristics exceeds the specified value for failure determination in the initial characteristic measurement, it is determined as defective before the accelerated test of the electrolytic capacitor to be accelerated. End the test. The failure judgment value is set in advance based on the standard values of various capacitor characteristics described in the manufacturer catalog and product specifications.

  When it is determined that there is no abnormality in the initial characteristics, processing for forming the diffusion acceleration hole 21 in the electrolytic capacitor to be subjected to the acceleration test is performed as processing of the sample (step S13). The diffusion accelerating hole 21 is a through hole having a predetermined area (for example, 0.010% of the surface area of the aluminum case 12) with respect to the surface area of the aluminum case 12 in the closed end portion 14b of the aluminum case 12 of the electrolytic capacitor. It is formed by. The position where the diffusion acceleration hole 21 is formed is not limited to the closed end portion 14b, but may be the side portion 14a. However, the closed end portion 14b is preferable from the viewpoint of ease of processing using a jig.

  Next, the time course of various characteristics of the electrolytic capacitor 10 in which the diffusion acceleration holes 21 are formed is measured (step S14). We confirm changes in various characteristics after providing diffusion acceleration holes, grasp the effects of providing diffusion acceleration holes, and investigate characteristics before the acceleration test.

  Next, an acceleration test is started. First, the electrolytic capacitor 10 to be subjected to the acceleration test is installed in an acceleration environment (step S15). Specifically, the electrolytic capacitor 10 is installed in a high-temperature environment or a high-temperature and high-humidity environment using an environmental test device such as a thermostatic bath, and the rated voltage is applied. At predetermined time intervals, an intermediate measurement is performed to measure various characteristics of the electrolytic capacitor 10 to be accelerated (step S16). The measurement items are the capacitance or ESR, which is an electrical characteristic, and the weight of the electrolytic capacitor 10 to be accelerated. The electrical characteristics may be tan δ or leakage current instead of the capacitance or ESR.

  Next, based on the intermediate measurement result, it is determined whether or not the electrolytic capacitor 10 to be subjected to the acceleration test has failed, that is, whether or not the amount of change in electrical characteristics exceeds a specified value for failure determination ( Step S17). When it is determined that there is a failure (step S17 YES), the acceleration test of the electric field capacitor 10 is terminated. If it is not determined that there is a failure (NO in step S17), it is installed again in the acceleration environment, and the acceleration test is continued until it is determined that there is a failure.

  Although FIG. 4 shows the procedure for one electrolytic capacitor 10, the acceleration test is performed on a plurality of electrolytic capacitors 10 for acceleration test. Therefore, the acceleration test is continued until there is no electrolytic capacitor 10 that is determined to have no failure.

  FIG. 5 is a graph showing the change over time in the amount of change in capacitance when the area ratio of the diffusion acceleration holes provided in the casing is changed. The horizontal axis of the graph shows the progress in the state of being in an accelerated test environment. The vertical axis represents the time transition of the rate of decrease from the capacitance before the start of the acceleration test. Each curve shows the change under the condition that the area ratio is constant. A value CF corresponding to a two-dot chain line in the graph represents a failure determination reference value of the electrolytic capacitor. In the case of this test, the area of the diffusion acceleration hole 21 formed in the aluminum case 12 is within a range of, for example, 0.005% to 0.015% of the surface area of the aluminum case 12 as an appropriate range.

  When the area of the diffusion accelerating hole 21 formed in the aluminum case 12 is smaller than the appropriate range, it takes time to diffuse the electrolytic solution, the decrease in the electrolytic solution is small, and the electrical characteristics hardly change. It takes time. On the other hand, when the area of the diffusion accelerating hole 21 formed in the aluminum case 12 is larger than the appropriate range, the electrolytic solution diffuses immediately. As a result, the electrical characteristics change rapidly, making it difficult to accurately grasp the deterioration tendency.

  In the acceleration test, the rated voltage is applied to the electrolytic capacitor 10 under the maximum operating temperature condition. When measuring the characteristics of the electrolytic capacitor 10, the temperature condition and the voltage application condition are maintained. It ’s difficult. Furthermore, it takes several hours for the measurement. For this reason, measuring too frequently causes an error. Therefore, it is important to set an appropriate measurement interval. In addition, the whole preparation test period can be shortened by preparing the several test body from which the area of the diffusion acceleration hole 21 formed in the aluminum case 12 differs, and implementing the test of a several test body in parallel. .

  FIG. 6 is a perspective view showing an example of positions different from FIG. 2 of the diffusion acceleration holes provided in the casing. In the case of this example, the position of the diffusion acceleration hole 21 is set at the center of the upper part. A slit 22 as an explosion-proof valve is generally provided at the upper part of the electrolytic capacitor 10. The slit 22 is provided in advance so as to be opened at a low internal pressure in order to minimize the phenomenon that the electrolytic solution evaporates and the internal pressure of the case rises and bursts when the electrolytic capacitor 10 generates heat. The shape of the slit 22 of the explosion-proof valve varies depending on the capacitor, but since the center of the slit 22 of the explosion-proof valve can be easily drilled by a drilling jig, if the diffusion acceleration hole 21 is formed in this portion, diffusion Variation in the position of the acceleration hole 21 can be reduced.

  In addition, since the electrolytic solution easily diffuses from the upper part of the electrolytic capacitor 10 in an accelerated test under a high temperature environment, variation in deterioration tendency can be reduced. The location where the diffusion accelerating hole 21 is formed can be, for example, on the side surface other than the center of the closed end portion 14b. However, in this case, it is difficult to form the hole and the size of the hole is likely to vary. is necessary.

  FIG. 7 is a graph showing an example of the change with time of the capacitance change amount when the temperature condition of the accelerated life test is changed. In the acceleration test, the maximum temperature condition of the electrolytic capacitor 10 is, for example, a temperature condition of 105 ° C. If the temperature condition is set low, the diffusion amount of the electrolyte also decreases. As a result, since the amount of change in electrical characteristics is also reduced, it takes time to reach the failure determination standard CF, and the deterioration tendency cannot be grasped in a short time. Regarding the diffusion of the electrolyte, there is a law that the lifetime is halved when the temperature rises to 10 ° C. based on the Arrhenius law (10 ° C. double rule), and this law can also be used for evaluation. .

  In addition, if the temperature condition of the acceleration test is set higher than the maximum temperature condition of the electrolytic capacitor 10, the acceleration of deterioration is obtained, but the dispersion of characteristic values becomes large and the failure mechanism may be changed. In this case, it becomes difficult to judge superiority.

  The maximum temperature condition is within the manufacturer-guaranteed temperature range. As the temperature condition of the acceleration test, the higher the temperature is within the maximum temperature condition, the faster the acceleration can be obtained, and the superiority or inferiority of the electrolytic capacitor can be determined.

  FIG. 8 is a graph showing an example of the change in capacitance with time and the life point in the accelerated life test. In this case, temperature is the result of an accelerated test under certain conditions. In the present embodiment, diffusion acceleration holes 21 are provided in the aluminum case 12 of the electrolytic capacitor 10 to facilitate the diffusion of the electrolytic solution. As a result, the change in electrical characteristics is large, and the failure determination criterion CF is reached in a short time. During this time, if the measurement interval is long, it becomes difficult to capture the change. Therefore, the measurement interval of the accelerated life test is, for example, at least once within 100 hours, and the measurement should be performed at the shortest possible time interval. By shortening the measurement interval as the acceleration increases, the deterioration tendency can be grasped without any problem in accuracy even when the acceleration test is started and the deterioration occurs in a short time.

  Moreover, when predicting the life of an electrolytic capacitor, it is difficult to increase the prediction accuracy unless a failure actually occurs in the accelerated test. Although an approximate expression can be obtained from the change in electrical characteristics due to the accelerated life test and the subsequent deterioration tendency can be predicted, in order to improve the measurement accuracy, the test time of the accelerated life test reaches the failure criterion CF. It is necessary to ensure that the time is confirmed.

  As a result, an accelerated test can be performed to clearly determine the life point at which the electrolytic capacitor reaches a deterioration failure, so that the life estimation in the actual environment can be accurately performed.

  FIG. 9 is a characteristic diagram showing an example of the correlation between the weight change amount of the electrolytic capacitor and the capacitance change amount. The horizontal axis represents the weight change ΔW with respect to the initial value of the electrolytic capacitor 10. The vertical axis represents the capacitance change amount ΔC. In this case, two items of weight and capacitance of the electrolytic capacitor 10 are selected as measurement items for the acceleration test of the electrolytic capacitor 10 in which the diffusion acceleration holes 21 are formed. From the acceleration test, an approximate expression is obtained from the correlation characteristics of the relationship between the weight change amount ΔW and the capacitance change amount ΔC with respect to the initial value of the electrolytic capacitor 10 measured every specified time. Next, the weight change amount WF at the life point in the failure determination criterion CF of the capacitance change amount ΔC is calculated from the approximate expression. Thereby, it is possible to grasp the weight change amount WF in the failure determination criterion CF. This approximate expression is stored in the database 30.

  Even if the amount of change in capacitance ΔC is likely to vary from sample to sample, it is possible to accurately estimate the life of the electrolytic capacitor 10 because the change with time in the amount of change in weight ΔW has little variation in characteristics.

  FIG. 10 is an example of a graph for estimating the lifetime of the electrolytic capacitor based on the change over time characteristic of the weight change amount and the capacitance change amount. In the horizontal axis, the horizontal axis of the first quadrant is time, and the horizontal axis of the second quadrant is the absolute value | ΔC | of the change in capacitance. The vertical axis represents the absolute value of weight change | ΔW |. When the life test results for an electrolytic capacitor not provided with diffusion acceleration holes are stored in the database, the diffusion acceleration holes 21 are formed based on the change over time characteristic of the weight change amount ΔW and the capacitance change amount in the test. The method of estimating the lifetime of the electrolytic capacitor 10 is shown.

  First, the acceleration test result of the electrolytic capacitor 10 in which no diffusion acceleration hole is provided in advance is stored in a database for a plurality of types. An approximate expression is obtained from the change over time of the weight change amount. Since the weight of the electrolytic capacitor changes linearly with respect to the elapsed time, the weight change amount WF at the life point shows a substantially constant value if the electrolytic capacitors are of the same type.

  Next, from the result of the acceleration test of the electrolytic capacitor 10 provided with the diffusion acceleration holes 21, as shown in FIG. 10, the failure determination reference value CF of the capacitance change amount ΔC is determined. An approximate expression is obtained from the correlation characteristic between the capacitance change amount ΔC and the weight change amount ΔW, and the weight change amount WF in the failure determination reference value CF is calculated.

  Next, the life change TF of the electrolytic capacitor is estimated by substituting the weight change amount WF at the life point into the approximate expression in the time change characteristic of the weight change amount ΔW. As a result, even if the change with time of the capacitance is large or the variation is large, the change with time of the weight change amount changes linearly with respect to time. The weight change amount WF at the life point can be calculated, and the life TF of the electrolytic capacitor can be estimated with high accuracy.

  As described above, according to the present embodiment, by providing the diffusion acceleration hole 21 in the case of the electrolytic capacitor, the electrolyte solution gradually diffuses from the diffusion acceleration hole 21. Therefore, the test required for the conventional acceleration test is performed. It is possible to grasp the deterioration tendency in a shorter time than the time. Therefore, in recent years, the life of electrolytic capacitors can be ascertained by accelerating tests, the reliability of the electrolytic capacitors to be evaluated, which are procured parts, and the manufacturer warranty period can be verified in a short period of time. become. In addition, the lead time for product development can be shortened.

  In addition, since the lifetime of the electrolytic capacitor is estimated based on the time-dependent characteristics of the weight change obtained from the acceleration test, even if the change in capacitance with time is large or the variation is large, Since the temporal change characteristic of the weight change amount changes linearly, the life of the electrolytic capacitor can be estimated with high accuracy.

  Further, since the position of the diffusion acceleration hole 21 provided in the casing 14 is the central portion of the upper part of the case, the variation in the position of the diffusion acceleration hole 21 can be eliminated, and the variation in the deterioration tendency due to the diffusion of the electrolyte is reduced. be able to.

  By performing the accelerated test under the maximum operating temperature condition of the electrolytic capacitor and applying the rated voltage, it is possible to judge the superiority or inferiority of the electrolytic capacitor in the minimum necessary time without increasing the variation of the characteristic value. It becomes.

[Second Embodiment]
FIG. 11 is a graph showing an example of the correlation between the weight change amount of the electrolytic capacitor and the ESR change amount for explaining the second embodiment. In this embodiment, two items of weight W and ESR of the electrolytic capacitor 10 are selected as measurement items in the acceleration test of the electrolytic capacitor 10 in which the diffusion acceleration holes 21 are formed. An acceleration test is performed, and a correlation characteristic between the weight change amount ΔW and the ESR change amount ΔESR with respect to the initial value of the electrolytic capacitor 10 measured every specified time is created as shown in FIG. An approximate expression is obtained from this correlation characteristic. Next, the weight change amount WF at the life point in the failure determination reference value EF of the ESR change amount ΔESR is calculated from the approximate expression.

  Thereby, the weight change amount WF in the failure determination criterion EF can be grasped. As a result, even if the ESR variation ΔESR is likely to vary from sample to sample, the characteristics of the change in weight ΔW over time are less varied, so that the lifetime of the electrolytic capacitor 10 to be evaluated can be accurately estimated. Is possible.

  FIG. 12 is a graph for estimating the lifetime of the electrolytic capacitor based on the time-dependent change characteristic of the weight change amount and the ESR change amount for explaining the second embodiment. When the life test result for the electrolytic capacitor without the diffusion acceleration hole is stored in the database, the diffusion acceleration hole 21 was formed based on the change with time of the weight change amount ΔW and the ESR change amount ΔESR in the test. It shows a method for estimating the lifetime of an electrolytic capacitor.

  First, a life test result of an electrolytic capacitor in which diffusion acceleration holes are not formed in advance is stored in a database for a plurality of types. Further, an approximate expression is obtained from the change with time of the weight change amount ΔW. Since the weight of the electrolytic capacitor changes almost linearly with time, the weight change amount WF at the life point shows a substantially constant value if the electrolytic capacitors are of the same type.

  Next, as shown in FIG. 11, the failure determination reference value EF for the ESR change amount ΔESR is determined from the result of the accelerated life test of the electrolytic capacitor provided with the diffusion acceleration holes 21. An approximate expression is obtained from the correlation characteristic between the ESR change amount ΔESR and the weight change amount ΔW, and the weight change amount WF at that value is calculated. Next, the life change TF of the electrolytic capacitor is estimated by substituting the weight change amount WF at the life point into the approximate expression in the time change characteristic of the weight change amount ΔW.

  Even when the ESR change over time ΔESR is large or the variation is large, the change over time characteristic of the weight change amount ΔW changes linearly with respect to time. For this reason, the weight change amount WF at the life point of the ESR change amount EF, which is a failure determination criterion, can be calculated, and the life TF of the electrolytic capacitor can be accurately estimated.

  As described above, according to the present embodiment, by providing the diffusion acceleration hole 21 in the case of the electrolytic capacitor, the electrolyte solution gradually diffuses from the diffusion acceleration hole 21, which is necessary for the conventional life acceleration test. The deterioration tendency can be grasped in a shorter time than the test time. Therefore, the same effect as in the first embodiment can be obtained.

  Further, in this embodiment, the measurement items of the accelerated life test are two items of the weight of the electrolytic capacitor and the ESR, and an approximate expression can be obtained from the correlation characteristics of the amount of change of each measured value, resulting in deterioration failure. The amount of weight change at the life point can be calculated. Furthermore, in the accelerated life test, an approximate expression is obtained from the correlation characteristics between the ESR change amount and the weight change amount, the weight change amount at the life point leading to the deterioration failure is calculated, and the electrolytic capacitor having no diffusion acceleration hole is calculated. The life of the electrolytic capacitor is estimated based on the time-dependent change in weight change obtained from the acceleration test. Therefore, even when the change in ESR change over time is large or the variation is large, the change over time characteristic of the weight change changes linearly, and it is easy to calculate the weight change at the life point. Can be estimated with high accuracy.

[Third Embodiment]
The present embodiment is a method for performing life diagnosis of electrolytic capacitors in units of lots in consideration of variations in the life of electrolytic capacitors in units of lots. FIG. 13 is a graph showing an example of the correlation between the weight of the electrolytic capacitor and the amount of change in capacitance for explaining the third embodiment. The horizontal axis represents the weight W of the electrolytic capacitor 10, and the vertical axis represents the change ΔC in capacitance. Curve A shows an example of characteristics for lot A, and curve B shows an example of characteristics for lot B. Lot A and lot B have different characteristics.

  Generally, electrolytic capacitors are manufactured by mass production. Electrolytic capacitors in the same lot have the same manufacturing date, manufacturing location, and manufacturing line. Therefore, the variation in quality within a lot is very small compared with products of other lots.

  In this way, when the lots of electrolytic capacitors are different, there is a difference in the distribution when the actual measured value of weight and the amount of change in capacitance are expressed in the correlation characteristics. The weight of the life point leading to the deterioration failure (type A is WFA, type B is WFB) is calculated. Thereby, since the difference in the weight characteristics of different lots can be clarified, it is possible to grasp the variation in quality for each lot.

  FIG. 14 is a graph showing an example of the correlation between the actual measured weight of the electrolytic capacitor and the ESR change amount for explaining the third embodiment. The horizontal axis represents the weight W of the electrolytic capacitor 10, and the vertical axis represents the ESR change rate ΔESR. Curve A shows an example of characteristics for lot A, and curve B shows an example of characteristics for lot B. Also in this case, the characteristics of lot A and lot B are different. As in the case of FIG. 12, when the lots of electrolytic capacitors are different, if the relationship between the actually measured weight value W and the ESR change amount ΔESR is shown in the figure, a difference is seen in the distribution. Therefore, an approximate expression of the distribution for each rod is obtained from the obtained correlation characteristics, and the weight of the life point (type A is WFA and type B is WFB) at which the electrolytic capacitor is deteriorated is calculated. Thereby, since the difference in the weight characteristics of different lots can be clarified, it is possible to grasp the variation in quality for each lot.

  As described above, according to the present embodiment, the same effects as those of the first embodiment can be obtained, and in the accelerated life test, the correlation between the actual measured value of the electrolytic capacitor and the change in capacitance or the actual measured value of weight. By calculating the weight of the life point leading to the deterioration failure for each lot from the correlation characteristics between the ESR change amount and the ESR change amount, the difference in characteristics between lots can be clarified.

[Other Embodiments]
As mentioned above, although some embodiment of this invention was described, these embodiment is shown as an example and is not intending limiting the range of invention. For example, in the embodiment, an example in which the present invention is applied to an aluminum electrolytic capacitor has been described, but the present invention is not limited to this. For example, tantalum or niobium may be used and can be applied to various metal electrolytic capacitors. Further, the area of the diffusion acceleration hole provided in the casing of the electrolytic capacitor is generally set within a range of 0.005% to 0.015% of the case surface area, for example, but can be appropriately changed according to the specification. . Further, in the first embodiment, the interphase characteristic between the capacitance change amount and the weight change amount is measured, and in the second embodiment, the correlation characteristic between the weight and the ESR change amount is measured. May be measured.

  Moreover, you may combine the characteristic of each embodiment. Furthermore, these embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention.

  These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and the equivalents thereof.

  DESCRIPTION OF SYMBOLS 10 ... Electrolytic capacitor, 11 ... Element part, 12 ... Aluminum case, 13 ... Insulation coating, 14 ... Casing, 14a ... Side part, 14b ... Closed end part, 14c ... Open end part, 15 ... Sealing member, 15a, 15b ... Lead part, 16a, 16b ... Lead wire, 17 ... Restriction part, 18 ... Explosion-proof valve slit, 21 ... Diffusion acceleration hole, 22 ... Slit, 25 ... Jig, 30 ... Database

Claims (6)

A life of an electrolytic capacitor comprising an element part having an electrolyte solution and a lead part projecting to the outside, a casing containing and storing the element part and having an open end on one side, and a sealing member for sealing the open end An electrolytic capacitor lifetime diagnostic method for estimating the lifetime of the target electrolytic capacitor due to the diffusion of the electrolytic solution sealed in the casing as a diagnostic target,
An accelerated test step for performing an accelerated test for measuring the weight and characteristic parameters of the accelerated test electrolytic capacitor while continuing a state in which a predetermined voltage is applied to each of the multiple accelerated test electrolytic capacitors;
From the time variation of the weight and characteristic parameter of the electrolytic capacitor for acceleration test obtained in the accelerated test step, a database creation step for storing the relationship of the characteristic parameter with respect to the weight in a database;
A life estimation step for estimating the life of the electrolytic capacitor to be evaluated from the weight of the electrolytic capacitor for acceleration test and the data stored in the database;
Have
In the acceleration test, an electrolytic capacitor with a diffusion acceleration hole provided with a diffusion acceleration hole penetrating the casing of the electrolytic capacitor for acceleration test is used, and the area of the diffusion acceleration hole is proportional to the surface area of the electrolytic capacitor for acceleration test. Area
Electrolytic capacitor life diagnosis method characterized by the above.   2. The electrolytic capacitor life diagnosis method according to claim 1, wherein the characteristic parameter is at least one of a capacitance and an equivalent series resistance of the acceleration test electrolytic capacitor.   3. The database creation step includes the step of collecting field data information and storing a relation of a change in weight of the electrolytic capacitor for acceleration test with time as database data. The electrolytic capacitor life diagnosis method described in 1.   The database creation step includes a step of storing, as database data, a relationship of a change in the weight of the electrolytic capacitor with respect to the passage of time of the electrolytic capacitor not provided with the diffusion acceleration hole used in the conventional life test. The electrolytic capacitor lifetime diagnosis method according to claim 1, wherein the electrolytic capacitor lifetime is determined. The target electrolytic capacitor is cylindrical and has a flat closed end on the side opposite to the open end,
5. The electrolytic capacitor life diagnosis method according to claim 1, wherein the diffusion acceleration hole is provided in a central portion of the closed end portion.   6. The electrolytic capacitor life diagnosis method according to claim 1, wherein the acceleration test is performed for each of a plurality of the electrolytic capacitors for the acceleration test for each of a plurality of lots.

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