Method for determining acceptable quality of dielectric (amorphous oxide layer) of tantalum oxide capacitor
By measuring leakage currents at varying voltages and temperatures, the method addresses the inefficiencies of existing dielectric quality assessment methods, providing a cost-effective and time-efficient means to ensure reliable tantalum oxide capacitors.
Patent Information
- Authority / Receiving Office
- RU · RU
- Patent Type
- Patents
- Current Assignee / Owner
- AKTSIONERNOE OBSHCHESTVO ELEKOND
- Filing Date
- 2025-10-02
- Publication Date
- 2026-06-30
AI Technical Summary
Existing methods for determining the quality of the dielectric layer in tantalum oxide capacitors are costly, time-consuming, and require full manufacturing cycles, making them unsuitable for mass production, and they do not allow for early identification of capacitors with low reliability.
A method involving measuring leakage current values at varying voltages and temperatures to assess dielectric quality early in the production process, eliminating the need for full manufacturing cycles and extensive testing, using a 0.01% orthophosphoric acid solution and specific voltage and temperature conditions to determine acceptable dielectric quality.
Enables efficient and cost-effective assessment of dielectric quality, reducing time and material costs while ensuring capacitors with predictable reliability by identifying unacceptable dielectrics before full manufacturing, thus optimizing production efficiency.
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Abstract
Description
[0001] The invention relates to the field of capacitor manufacturing and can be used in the development and production of tantalum oxide capacitors (with liquid electrolyte of the K52-… series, with solid electrolyte (oxide-semiconductor and polymer) of the K53-… series) for assessing the permissible quality of the dielectric (amorphous oxide layer) of the capacitor at the stage of manufacturing the anode plate (anode). The quality of the dielectric depends on the impurity composition of the tantalum powder, the morphology of the tantalum powder, the permissible voltage of electrochemical oxidation and is determined by the defectiveness at a certain thickness of the dielectric. With an increase in the thickness of the formed dielectric, the likelihood of the appearance of defects in the dielectric increases, having a higher conductivity and reducing the thickness of the dielectric at the site of occurrence. Defects in the dielectric can lead to an increase in leakage currents, local overheating and destruction of capacitors during operation [Y.Freeman, Tantalum and Niobium-Based Capacitors, Springer International Publishing AG 2018 113, DOI 10.1007 / 978-3-319-67870-2, 2 Jennifer D. Sloppy, Anodization mechanism and properties of bi-layer tantalum oxide formed in phosphoric acid. / / A Dissertation in Materials Science and Engineering / / The Pennsylvania State University. The Graduate School College of Earth and Mineral Sciences - 2009].
[0002] The proposed method for determining the acceptable quality of the dielectric of a tantalum oxide capacitor is suitable for use in the technological process of manufacturing tantalum oxide capacitors, which includes: forming an anode plate by pressing a metal powder (for example, tantalum) with a wire current collector made of the same metal, with subsequent high-temperature sintering; forming a dielectric on its surface by electrochemical oxidation; forming a cathode plate of the capacitor (for capacitors with solid electrolyte); forming the electrode system of the capacitor (including the cathode for capacitors with liquid electrolyte) and the housing; measuring electrical parameters; identifying capacitors with a low level of reliability when applying constant voltage and exposure to high temperatures (thermal conditioning);conducting resource tests (for reliability) on a sample of capacitor batches (maximum permissible operating conditions are simulated, including accelerated operating time);
[0003] The proposed method for determining the permissible quality of the dielectric on anodes can be used to solve the following problems: determining the admissibility of using a specific powder (with a certain impurity composition and morphology) for the manufacture of capacitors; determining the maximum permissible operating voltage for the tested batch of powder.
[0004] A method is known for determining the quality of the dielectric (amorphous oxide layer) of a capacitor anode by evaluating the image of the outer surface of the anode with a formed oxide layer, obtained by scanning electron microscopy [Y. Freeman, Tantalum and Niobium-Based Capacitors, Springer International Publishing AG 2018 113, DOI 10.1007 / 978-3-319-67870-2].
[0005] The disadvantage of this method is the high cost of research and its duration (it is not used in mass production).
[0006] A method is also known for determining the acceptable quality of the dielectric (amorphous oxide layer) of the anode of a capacitor by conducting electrical tests of capacitors (accelerated operating time at elevated temperatures) for reliability (Industry standard "Oxide-semiconductor fixed-capacitance capacitors", general specifications, OCT II 0025-84, Research Institute "GIRIKOND", 1985; Industry standard "Oxide-semiconductor fixed-capacitance capacitors", general specifications, OCT II 0026-84, Research Institute "GIRIKOND", 1985).
[0007] The disadvantage of this technical solution is the need to perform a full cycle of capacitor manufacturing, the high cost and duration of testing, and the equipment takes up a large area.
[0008] The proposed method differs from the method of conducting endurance reliability testing of existing capacitors in that testing is performed early in production, eliminating the need for the entire manufacturing cycle and lengthy endurance reliability testing. This reduces time and material costs, and eliminates the need for extensive, expensive endurance testing equipment and space. Furthermore, the proposed method enables the production of capacitors with predictable reliability, provided the manufacturing process is followed.
[0009] The technical result of the invention is to obtain a dielectric (amorphous oxide layer) of a tantalum oxide capacitor of acceptable quality at an early stage of production.
[0010] The objective of the present invention is to create a method for determining the acceptable quality of the dielectric (amorphous oxide layer) of the anode of a tantalum capacitor at the stage of forming the dielectric in the production of capacitors.
[0011] The problem is solved as follows.
[0012] The leakage current values (I УТ ) when applying the measurement voltage (U изм ) from the minimum to the maximum value of U изм (up to the breakdown voltage level, depending on the powder type). The measurement time (holding time at a specific voltage value) is 1 minute, followed by discharge. The measurement is performed in a 0.01% aqueous solution of orthophosphoric acid. The measurement is carried out at two electrolyte temperatures: 25+5°C and 85+5°C. Graphs of the dependence of I are plotted. ут from specific U изм . The measurement voltage at which the value of the ratio I ут , measured at 85°C, to the value of I ут, measured at 25°C, equal to no more than 10, is considered the maximum permissible voltage, and the quality of the dielectric is sufficient for the manufacture of capacitors with a failure rate during operation in the maximum permissible mode of no more than 1*10 -6 During 30,000 hours of operation within a 25-year service life. If the value of the above ratio is greater than 10 at a given voltage, the dielectric quality is unacceptable for capacitor manufacturing.
[0013] Examples of the invention
[0014] Example 1. Determining the acceptable dielectric quality for a given maximum working voltage of a capacitor meeting the required reliability level. Five anodes were tested, followed by capacitor manufacturing to determine the maximum working voltage of the capacitor. The data are presented in Table 1 and Fig. 1.
[0015] Table 1. Anode leakage current and capacitor failures during testing
[0016]
[0017] From Table 1, we can see that if the ratio of leakage current measured at 25°C and 85°C is more than 101 times, the quality of the capacitor dielectric is unacceptable.
[0018] Figure 1 shows the curve of change in leakage current at a temperature of 25°C (blue line) and 85°C (orange line). Point 200 (U изм , B) is the beginning of a critical increase in leakage currents at elevated temperatures with a clear break in the given curve.
[0019] Example 2. Determining which powders from different manufacturers with different morphologies (Fig. 2) and the same impurity composition can be used to produce capacitors with a certain reliability. Selecting powders using different manufacturing technologies.
[0020] Figure 2 shows the morphology of the tested powders. Type 1 powder has a more narrowly fractionated initial particle size and a particle shape close to spherical, while types 2 and 3 powders have a flaky particle shape. Type 3 powder has the greatest particle size dispersion.
[0021] Anodes made from Type 1, Type 2, and Type 3 powders were manufactured using identical modes and conditions. Anode leakage current was measured, and life tests were conducted after the capacitors were manufactured. The data are presented in Table 2.
[0022] Table 2. Anode leakage current and capacitor failures during testing
[0023]
[0024] From Table 2, we see that if the leakage current ratio measured at 25°C and 85°C is greater than 10, the capacitor dielectric quality is unacceptable. The morphology of the tantalum powder affects the dielectric quality.
Claims
A method for determining the acceptable quality of a dielectric, which is a layer of amorphous oxide of a tantalum oxide capacitor, characterized in that the leakage current value (I ут ) anode in a 0.01% aqueous solution of orthophosphoric acid for one minute while applying a specific measurement voltage (U изм ), with a voltage range from minimum to maximum value U изм up to the breakdown voltage level depending on the type of powder with subsequent discharge, at two electrolyte temperatures of 25+5°C and 85+5°C, graphs of the dependence of I are plotted ут from specific U изм , calculate the value of the ratio I ут , measured at 85°C, to I ут , measured at 25°C, at a specific voltage, if the value of the ratio I ут , measured at 85°C, to I ут, measured at 25°C, is no more than 10, then the quality of the dielectric is acceptable for the manufacture of capacitors with a failure rate during operation in the maximum permissible operating mode of no more than 1*10 -6 during 30,000 hours of operation within a service life of 25 years, if the value of the ratio I ут , measured at 85°C, to I ут , measured at 25°C, is greater than 10, then the quality of the dielectric is unacceptable for the manufacture of capacitors at a specific voltage.