CN113358955A - Method for detecting reliability of electrolytic capacitor - Google Patents
Method for detecting reliability of electrolytic capacitor Download PDFInfo
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- CN113358955A CN113358955A CN202110615240.2A CN202110615240A CN113358955A CN 113358955 A CN113358955 A CN 113358955A CN 202110615240 A CN202110615240 A CN 202110615240A CN 113358955 A CN113358955 A CN 113358955A
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- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
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Abstract
The invention discloses a method for detecting the reliability of an electrolytic capacitor, which comprises the following steps of 1, setting the temperature of a detection area of the capacitor to be detected as the upper limit category temperature corresponding to the capacitor to be detected; carrying out a power-on test on the capacitor to be detected; and 2, after the preset time is continued, judging the state of the capacitor to be detected. Executing the scheme of the step 1 as a first scheme; and (2) taking the scheme of introducing chlorine-containing corrosive gas into the detection area in the step (1) as a second scheme, executing the two schemes in any sequence for at least one time for corresponding preset time, and judging the state of the capacitor to be detected. According to the invention, the early failure defect caused by the invasion of chloride ions into the interior due to poor sealing of the electrolytic capacitor can be rapidly and effectively screened by combining different experimental schemes. The screening failure detection rate of the major early failure quality defects of the electrolytic capacitor is improved, and the failure rate of production line package returning and after-sale complaints is reduced. And the phenomenon of poor sealing can be effectively screened, and the reliability of the product can be evaluated in a short time.
Description
Technical Field
The invention relates to the field of detection and test, in particular to a method for detecting the reliability of an electrolytic capacitor.
Background
The aluminum electrolytic capacitor has been widely applied to various electronic circuits due to its advantages of large capacity, small volume, low price, etc., and along with the widespread application of domestic large-screen color televisions and variable frequency household appliances (such as variable frequency air conditioners) and the localization of electronic components, the requirements on the quality and reliability of the aluminum electrolytic capacitor, especially the medium and high voltage aluminum electrolytic capacitors, are increasingly high. In particular, the medium and high voltage (160V-450V) aluminium electrolytic capacitor used in large screen colour TV is mainly used in switch power supply part (note: it is mainly used in power supply circuit, and has the functions of energy storage, filtering, by-pass and decoupling), and can be used for filtering after rectification, and its quality can directly affect the performance of whole machine, so that it is a key element in the circuit. However, the existing electrolytic capacitor detection and screening means has low efficiency.
Disclosure of Invention
The invention provides a method for detecting the reliability of an electrolytic capacitor, aiming at solving the technical problem of low electrolytic capacitor testing efficiency in the prior art.
The technical scheme adopted by the invention is as follows:
the invention provides a method for detecting the reliability of an electrolytic capacitor, which comprises the following steps:
step 1, setting the temperature of a detection area of a capacitor to be detected as a working upper limit temperature corresponding to the capacitor to be detected; carrying out a power-on test on the capacitor to be detected;
and 2, after the preset time is continued, judging the state of the capacitor to be detected.
In a second embodiment, step 1 further comprises introducing a corrosive gas containing chlorine into the detection region.
The specific implementation scheme comprises the following steps: executing the scheme of the step 1 as a first scheme; and (2) taking the scheme of introducing chlorine-containing corrosive gas into the detection area in the step (1) as a second scheme, executing the two schemes in any sequence for at least one time for corresponding preset time, and judging the state of the capacitor to be detected.
The test voltage of the power-on test of the capacitor to be detected is a sine alternating current voltage superposed with a rated direct current voltage, wherein the frequency of the sine alternating current voltage is the same as the rated ripple current frequency.
Preferably, the corrosive gas is dichloromethane gas.
Further, the preset time is less than or equal to 12 hours.
The method for judging the state of the capacitor to be detected comprises the following steps: and testing various parameters of the capacitor to be detected, judging whether the various parameters are within a preset parameter range, and if not, determining that the capacitor to be detected is invalid.
After testing various parameters of the capacitor to be detected, dissecting the capacitor to be detected, measuring the contact resistance and the electrode foil voltage withstanding value between the electrode foil and the lead-out foil of the capacitor to be detected, and judging whether the contact resistance and the electrode foil voltage withstanding value between the electrode foil and the lead-out foil are within the corresponding preset parameter range.
The method for determining the state of the capacitor to be detected in the second embodiment may further include: and judging whether the leakage current value of the capacitor to be detected exceeds a preset standard value, if so, judging that the inside of the capacitor to be detected is corroded, and then dissecting to confirm whether chloride ion corrosion occurs.
The method for testing various parameters of the capacitor to be tested specifically comprises the following steps: capacitance value, leakage current value, and ESR value.
Compared with the prior art, the method can quickly and effectively screen early failure defects caused by the invasion of chloride ions into the interior due to poor sealing of the electrolytic capacitor through different experimental scheme combinations. The screening failure detection rate of the major early failure quality defects of the electrolytic capacitor is improved, and the failure rate of production line package returning and after-sale complaints is reduced.
The method can effectively screen the poor sealing phenomenon, can evaluate the reliability of the product in a short time, and can find the poor product as soon as possible through electrochemical reaction after the aluminum electrolytic capacitor internally containing the chloride ion product is electrified.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the embodiments or the prior art descriptions will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without inventive exercise.
FIG. 1 is a block flow diagram of the present invention.
Detailed Description
In order to make the technical problems, technical solutions and advantageous effects to be solved by the present invention more clearly apparent, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
The principles and construction of the present invention will be described in detail below with reference to the drawings and examples.
Through analysis of a large number of failure main boards, the failure of the main boards caused by the bulge failure of the high-voltage electrolytic capacitor at the front section of the switching power supply is confirmed. The analysis of the failure reason and the failure mechanism of the high-voltage electrolytic capacitor is combined with the analysis of a large number of failed products, and the analysis result shows that: the electrolytic capacitor is characterized in that under a specific use environment, due to the fact that chlorine ions corrode an anode to open a circuit to cause capacitor failure caused by the fact that chlorine ions corrode the anode due to the fact that chlorine ions invade from the outside, superscript chlorine elements are gathered nearby the inner portion of an electrolytic capacitor cover plate to cause corrosion failure, and due to the fact that the chlorine ions invade from the outside, the sealing performance of a capacitor end cover is improved, incoming material experiments are guaranteed, and the whole application reliability of the device is improved through the device and quality control.
The invention provides a method for detecting the reliability of an electrolytic capacitor, which comprises the following steps:
step 1, setting the environmental temperature of a detection area of a capacitor to be detected as a working upper limit temperature (upper limit category temperature) corresponding to the capacitor to be detected, for example, 105 ℃; then carrying out a power-on test on the capacitor to be detected;
step 2; after the preset time lasts, for example, 500 hours, the state of the capacitor to be detected is judged, the reliability of the electrolytic capacitor can be determined, and whether the products of the batch have failure products (manufacturing defects) in the incoming material inspection link is judged, so that the poor screening detection rate of the major hidden quality defects of the electrolytic capacitor is improved.
And (3) after the step (2) is completed, selecting the tested and screened electrolytic capacitors, adding 10PPM chloride ion solution, sealing again, and then performing the high-temperature load test, wherein the test period is 500 hours, and judging whether the leakage current of the electrolytic capacitors is increased or not, if so, the anode foil is corroded, and the anode strip is corroded in a serious mode.
In another embodiment, the corrosive gas containing chlorine is introduced into the detection area in step 1 at the same time, and a corrosive gas intrusion test is performed, so that the reliability level of the finished electrolytic capacitor, including whether the sealing is poor and whether the interior contains chlorine ions, can be comprehensively tested. If the sealing is poor, the failure phenomenon cannot be screened out in a short-term test, and the product failure is inevitably caused in long-term use, so that the method can effectively screen the poor sealing phenomenon and can evaluate the reliability of the product in a short term; after the aluminum electrolytic capacitor internally containing chloride ion products is electrified, the poor products can be found as soon as possible through electrochemical reaction.
The corrosive gas can be dichloromethane gas, and other corrosive gases containing chlorine with the same effect can be adopted, and the invention is within the protection scope.
In this embodiment, the duration of the preset time is 12 hours, which greatly reduces the test time compared to the scheme of the previous embodiment, and the preset time can be further reduced, specifically according to the test condition.
In this embodiment, the method for determining the state of the capacitor to be detected includes: and judging whether the leakage current value of the capacitor to be detected exceeds a preset standard value, if so, judging that the inside of the capacitor to be detected is corroded, and then dissecting to confirm whether chloride ion corrosion occurs.
The scheme of the embodiment is the most rigorous, and can effectively screen and remove the defects of the electrolytic capacitor chloride ion corrosion manufacturing process and the poor sealing of the electrolytic capacitor manufacturing. The method is an innovative scheme for screening and detecting the most effective electrolytic capacitor chloride ion corrosion failure and poor sealing assembly through research and a large number of practical experiments.
In order to further improve the detection efficiency, the invention adopts the scheme of step 1 as a first scheme; and (2) taking the scheme of introducing chlorine-containing corrosive gas into the detection area in the step (1) as a second scheme, executing the two schemes in any sequence for at least one time for corresponding preset time, and judging the state of the capacitor to be detected, wherein the scheme can be specifically selected flexibly according to different batches of products. The early failure caused by the invasion of chloride ions into the interior due to poor sealing of the electrolytic capacitor can be rapidly and effectively screened through the combination of different experimental schemes. The screening failure detection rate of the major early failure quality defects of the electrolytic capacitor is improved, and the failure rate of production line package returning and after-sale complaints is reduced.
In a specific embodiment, a sine alternating current voltage with the same frequency as a rated ripple current is superposed on a rated direct current voltage to be used as a test voltage of a capacitor to be detected in an energization test, the peak value of the superposed voltage does not exceed the rated direct current voltage, and the current value does not exceed the rated ripple current value. The foil of the electrolytic capacitor can be quickly broken down in a stacking mode, and the testing efficiency is improved.
The step 2 of judging the state of the capacitor to be detected specifically comprises the following steps: and testing various parameters of the capacitor to be detected, judging whether the various parameters are within a preset parameter range, and if not, determining that the capacitor to be detected is invalid. The method for testing various parameters of the capacitor to be tested specifically comprises the following steps: capacitance value, leakage current value, and ESR value.
After testing various parameters of the capacitor to be detected, dissecting the capacitor to be detected, measuring the contact resistance and the electrode foil voltage withstanding value between the electrode foil and the lead-out foil of the capacitor to be detected, and judging whether the contact resistance and the electrode foil voltage withstanding value between the electrode foil and the lead-out foil are within the corresponding preset parameter range.
And finally, the chloride ion content of the electrolytic capacitor is detected, the chloride ion content in the finished electrolytic capacitor is very low, and in order to avoid detection errors caused by water pollution, the ultrapure water used in the experiment must be very pure, and the chloride ion content detected by the ultrapure water used in the experiment is required to be less than 0.017 ppm.
Sample requirements: and completely loosening the wound aluminum foil and the electrolytic paper, putting the aluminum foil and the electrolytic paper into a beaker, adding ultrapure water to completely soak the aluminum foil and the electrolytic paper, and testing the content of chloride ions by adopting ion chromatography after ultrasonic extraction for 30 minutes.
Determination request:
the chloride ion concentration calculation formula: chloride ion content = instrument display value x dilution factor/capacitance weight
Standard of chloride ion content: the content of chloride ions in the electrolytic capacitor is required to be less than 0.25ppm (calculated by taking the weight of the finished capacitor as a denominator).
The test principle is as follows:
the primary condition for chlorine ion corrosion is that the chlorine ion must reach a certain concentration, because the Al or other oxide film can only be corroded under the condition of peracid or overbase, because the concentration of the chlorine ion reaches a certain time, the paired H + ion can reach a certain concentration, and the peracid condition is formed. The reason why the chloride ion corrosion often occurs at the cathode, particularly at the lead bar and lead aluminum stem is that a certain concentration condition necessary for chloride ion enrichment is easily achieved at the highest cathode potential. While peracid conditions tend to form near the cathode due to cathodic oxidation. It is of secondary importance to see (it was tested that this concentration is 20-50 ppm) whether the conditions at the site of corrosion favoured the onset of corrosion. Therefore, the generation of chloride ions always has a certain induction period. The length is determined by various factors. If the chloride ion content is not high, only a small amount or part of the product will be corroded. Not all products will corrode.
The corrosion mechanism of chloride ions to aluminum or oxide films:
corrosion of aluminum:
the oxide film is corroded by the additional H2:
due to the fact that
Therefore, the corrosion of the chloride ions is not consumed, and the corrosion action of the chloride ions can be repeated continuously. Their final products are white or greenish (grey yellow) deposits of aluminium hydroxide and water. Water not only provides conditions for chloride ion recovery, but water also corrodes Al and Al2O3 (hydrates)
Since the electrolyte contains a certain amount of moisture, the impregnated core also absorbs moisture from the air. Moisture is therefore one of the conditions under which chloride ion corrosion occurs. But also has the function of promoting wave and wave to the corrosion of chloride ions.
The lead bars are corroded continuously, even broken, and corrosion pits appear on the hard stem parts. A large amount of accumulated precipitates may appear at the corrosion site. Off-white or black or slightly yellowish paste-like corrosives. There are three main types analyzed, one is white flocculent alumina precipitate. Second, white translucent gel-like aluminum hydroxide. And thirdly, black loose alumina spalling layer. Other coloring may be associated with the chloride ion source. For example, chloride ions in the cover plate tend to enter the electrolyte with the colored cellulose. Thereby causing corrosion pitting or the build-up to be colored otherwise.
Aluminum is an amphoteric metal which is alkaline when exposed to acid and acidic when exposed to base; the aluminum oxide film has active chemical properties, and simultaneously has a self-protection function, under normal atmospheric conditions, the surface of aluminum metal can be combined with oxygen to form a layer of natural oxide film, so that the inner layer of aluminum is prevented from being oxidized continuously, and a protection effect is achieved. This protective film acts like a barrier and also like a control valve, so aluminum is again classified as "valve metal". Under natural conditions, the oxide film is very thin and can only withstand a direct current voltage of about 1V. By utilizing the function, aluminum is placed in the formation electrolyte, positive direct current voltage is applied, oxygen is promoted to migrate to the inside of the aluminum, the thickness of an oxide film is increased, and meanwhile, the voltage resistance of the aluminum is improved. Because of its chemical activity, the oxide film is unstable, so when it meets chloride ion and sulfate ion, it is easy to be corroded, and loses the voltage-resistant ability. In addition, alumina is also hydrolyzed when meeting water to generate aluminum hydroxide (acid environment) or aluminum metaaluminate (alkaline environment) which is not pressure-resistant, which is why the leakage current of the aluminum electrolytic capacitor is unstable and is easy to rise.
In the production process, trace harmful impurity ions (chloride ions) pollute the capacitor, and the chloride ions move to the positive electrode leading strip under the action of an electric field in the capacitor and corrode aluminum of the positive electrode leading strip, so that the positive electrode leading strip is corroded and disconnected under the action of a long time.
Poor sealing of the product can cause chlorine ion-containing gas or other substances to infiltrate into the electrolytic capacitor, so that the electrolytic capacitor is corroded, and the service life of the electrolytic capacitor is affected.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.
Claims (10)
1. A method for detecting the reliability of an electrolytic capacitor is characterized by comprising the following steps:
step 1, setting the temperature of a detection area of a capacitor to be detected as a working upper limit temperature corresponding to the capacitor to be detected, and carrying out a power-on test on the capacitor to be detected;
and 2, after the preset time is continued, judging the state of the capacitor to be detected.
2. The method according to claim 1, wherein step 1 further comprises introducing a corrosive gas containing chlorine into the detection region.
3. The method for detecting reliability of electrolytic capacitors as claimed in claim 1, wherein the scheme of step 1 is performed as a first scheme; and (2) taking the scheme of introducing chlorine-containing corrosive gas into the detection area in the step (1) as a second scheme, executing the two schemes in any sequence for at least one time for corresponding preset time, and judging the state of the capacitor to be detected.
4. The method for detecting the reliability of the electrolytic capacitor as claimed in claim 1, wherein the test voltage of the energization test of the capacitor to be detected is a sine alternating voltage with the same frequency as the rated ripple current, and a rated direct voltage is superposed.
5. The method of claim 2, wherein the corrosive gas is dichloromethane gas.
6. The method of claim 2, wherein the predetermined time is less than or equal to 12 hours.
7. The method for detecting the reliability of an electrolytic capacitor as claimed in claim 1 or 2, wherein the method for judging the state of the capacitor to be detected comprises: and testing various parameters of the capacitor to be detected, judging whether the various parameters are within a preset parameter range, and if not, determining that the capacitor to be detected is invalid.
8. The method for detecting the reliability of an electrolytic capacitor as claimed in claim 7, wherein after testing the parameters of the capacitor to be detected, the capacitor to be detected is dissected, the contact resistance between the electrode foil and the lead foil of the capacitor to be detected and the withstand voltage value of the electrode foil are measured, and whether the contact resistance between the electrode foil and the lead foil and the withstand voltage value of the electrode foil are within the corresponding preset parameter ranges is determined.
9. The method for detecting the reliability of an electrolytic capacitor as claimed in claim 2, wherein the method for determining the state of the capacitor to be detected comprises: and judging whether the leakage current value of the capacitor to be detected exceeds a preset standard value, if so, judging that the inside of the capacitor to be detected is corroded, and then dissecting to confirm whether chloride ion corrosion occurs.
10. The method according to claim 7, wherein the step of testing the parameters of the capacitor to be tested specifically comprises: capacitance value, leakage current value, and ESR value.
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Application publication date: 20210907 |