Breakdown and Self-healing in MnO2 and Polymer Tantalum Capacitors
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Alexander Teverovsky↗
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A Paradigm Shift in Quality Assurance of COTS Capacitors for Space Applications
Limitations of a traditional approach to screening and qualification of COTS capacitors for space applications that is based on burn-in and life test requirements described in the relevant military specifications are analyzed. An alternative approach that is originated from analysis of highly accelerated life testing (HALT) of capacitors susceptible to wear-out failures and allows for assessments of the risks of failure during the mission is suggested. Examples include results of reliability testing of advanced BME ceramic capacitors, polymer tantalum capacitors and multianode manganese oxide tantalum capacitors.
Alexander A Teverovsky↗
Breakdown in Tantalum Capacitors
Failures in tantalum capacitors can be considered as a time-dependent-breakdown and reliability of all types of capacitors, including wet, MnO2 and polymer cathode parts, depends on the efficiency of self-healing that can mend parts after breakdown. A mechanism of self-healing in MnO2 capacitors is associated with oxygen reduction in the cathode layer and isolation of the breakdown site with high-resistive Mn2O3/Mn3O4 compositions. Although this mechanism is commonly accepted, details of self-healing have not been analyzed sufficiently yet, and the effects of scintillations on behavior of the parts has not been fully understood. There is a lack of data on the self-healing efficiency in different lots of capacitors. Even less is known about self-healing in polymer tantalum capacitors. In this work, different types of polymer and MnO2 capacitors have been tested for scintillation breakdown using a constant current stress (CCS) technique modified to allow detection of the amplitudes and durations of current spikes during breakdown. Characteristics of the parts and in particular leakage currents were measured to assess the efficiency of self-healing and improve screening processes for tantalum capacitors. Damaged sites were localized using infrared camera and their appearance analyzed after deprocessing and crosssectioning. Thermal effects during scintillations have been modeled, self-healing processes in polymer and MnO2 cathode capacitors discussed, and mechanisms of breakdown based on the growth of conductive filaments in the dielectric suggested.
tantalum polymer capacitors↗
Lessons Learned from Screening and Qualification of COTS Capacitors
A traditional approach to screening and qualification of hi-rel COTS capacitors and its limitations are analyzed. Results of testing of four types of COTS capacitors for L2 projects are summarized. The types include DLA drawing tantalum MnO2 capacitors, high-voltage hermetically sealed polymer tantalum capacitors, multianode COTS+ capacitors, and feedthrough BME ceramic capacitors. Lessons learned from this experience might accelerate processes and reduce risks of inclusion of COTS components in space projects.
reliability↗
2014 NEPP Tasks Update for Ceramic and Tantalum Capacitors
Presentation describes recent development in research on MnO2, wet, and polymer tantalum capacitors. Low-voltage failures in multilayer ceramic capacitors and techniques to reveal precious metal electrode (PME) and base metal electrode (BME) capacitors with cracks are discussed. A voltage breakdown technique is suggested to select high quality low-voltage BME ceramic capacitors.
ceramic capacitors↗
Useful Life of Tantalum Capacitors
Currently, the major reliability characteristic of tantalum capacitors is the failure rate, which is a constant used to characterize random failures of electronic components. However, contemporary MnO2 and polymer tantalum capacitors have both infant mortality (IM) and wear-out (WO) failures. This requires assessments of the useful life of the parts that is limited by the time of inception of WO failures that can be determined using an adequate reliability model and results of highly accelerated life testing (HALT). In this presentation, a modified time dependent dielectric breakdown (TDDB) model is used to describe both IM and WO failures during HALT. Specifics of physical processes resulting in degradation and failures in polymer and MnO2 tantalum capacitors are discussed, and the increase of IM failures with the level of stress is explained. The model justifies exponential dependence of the acceleration factors on voltage and predicts higher values of the voltage acceleration constant for IM compared to WO failures.
tantalum capacitors↗
Stress Testing of Chip Aluminum Polymer Capacitors
Layered aluminum polymer capacitors (APC) may be viable replacements to current chip tantalum capacitors due to their lower ESR, weight, and smaller size. So far, there is a lack of information regarding the reliability of these parts. Available technical literature is mostly related to the effect on humidity. Although APCs have a limited moisture resistance, it may be contained to the level sufficient for space applications. In this work, seven types of commercial APCs manufactured by four vendors and rated to voltages from 6.3 to 35 V were used to evaluate reliability of the parts under environmental stresses and highly accelerated life tests. Characteristics of the parts, including breakdown voltages, the level of anomalous charging currents (ACC), capacitance, DF, ESR and leakage currents were measured in the process of storage at high-temperatures (from 100 to 150 °C) and high humidity at 85 °C. Monitored highly accelerated life tests have been carried out at temperatures of 85 °C and 125 °C and voltages varying from 1.2 to 1.9 times the rated voltage. Degradation processes and reliability of APCs have been analyzed and compared to polymer tantalum capacitors.
Alexander Teverovsky↗
Evaluation of Aluminum Polymer Capacitors for Space Applications
Layered aluminum polymer capacitors (APC) may be viable replacements to currently used chip tantalum capacitors due to their lower ESR, weight, and smaller size. So far, there is a lack of information regarding the reliability of these parts. Available technical literature is mostly related to the effect of humidity. Although APCs have a limited moisture resistance, it may be contained to the level sufficient for space applications. This work analyzes construction and characteristics of seven types of commercial APCs manufactured by four vendors and rated to voltages from 6.3 to 35 V were analyzed. Their reliability under environmental stresses and highly accelerated life tests was assessed in the range of temperatures and voltages to determine reliability acceleration factors. For this purpose, characteristics of the parts, including breakdown voltages, the level of anomalous charging currents (ACC), capacitance, DF, ESR and leakage currents were measured in the process of storage at high-temperatures (from 100 to 150 °C) and high humidity at 85 °C. Monitored highly accelerated life tests have been carried out at temperatures of 85 °C and 125 °C and voltages varying from 1.2 to 1.9 times the rated voltage. Degradation processes and reliability of APCs have been compared to polymer tantalum capacitors.
Alexander A Teverovsky↗
Effect of Soldering on Polymer and MnO2 Tantalum Capacitors
Soldering might have a strong effect on performance and reliability of most surface mount technology components, including tantalum capacitors. High quality tantalum capacitors are likely the only type of components where soldering simulation is the first step during screening. Nevertheless, post-soldering failures of tantalum capacitors happen and require additional analysis. Popcorning is a well-known effect in plastic encapsulated microcircuits (PEM) and it occurs also in chip tantalum capacitors. The sensitivity of parts to the presence of moisture during soldering is characterized by the moisture sensitivity level (MSL); however, contrary to PEMs, there is no standard procedure for establishing MSL for tantalum capacitors. The effect of absorbed moisture on soldering related degradation and failures in tantalum capacitors have not been studied properly yet, and there is no sufficient information regarding the difference in the sensitivity to soldering between polymer and MnO2 tantalum capacitors. In this work, 16 types of polymer and 9 types of MnO2 cathodes tantalum capacitors with different moisture content have been tested before and after reflow soldering. The level of moisture release after soldering has been estimated and thermo-mechanical analysis used to assess deformation of capacitors during soldering simulations. Results show that moisture uptake in similar parts is approximately two times greater in polymer than in MnO2 capacitors. Cracking of the case and degradation of parameters can occur in both types of parts, but MnO2 capacitors are much more likely to fail catastrophically with a short circuit and possible ignition during the first power-on cycle. This type of failure in MnO2 capacitors is lot-related, can occur even at derated voltages and relatively low levels of moisture sorption corresponding to room conditions. Baking before soldering is an effective measure to prevent failures even in lots susceptible to popcorning damage. Recommendations for baking and testing to establish MSL are suggested.
Alexander Teverovsky↗
Popcorning Failures in Polymer and MnO2 Tantalum Capacitors
Popcorning is a well-known effect in plastic encapsulated microcircuits (PEM) and it occurs in chip tantalum capacitors. The sensitivity of components to the presence of moisture during soldering is characterized by the moisture sensitivity level (MSL); however, contrary to PEMs, there is no standard procedure for establishing MSL for tantalum capacitors.The effect of absorbed moisture on soldering related degradation and failures in tantalum capacitors have not been studied properly yet, and there is no sufficient information regarding the difference in the sensitivity to soldering between polymer and MnO2 capacitors. In this work, 16 types of polymer and 9 types of MnO2 tantalum capacitors with different moisture content have been tested before and after reflow soldering. The level of moisture release during soldering has been estimated and thermo-mechanical analysis used to assess deformation of capacitorsduring soldering simulations. Results show that moisture uptake in similar parts is approximately two times greater in polymer than in MnO2 capacitors. Cracking of the case and degradation of parameters can occur in both types of parts, but MnO2 capacitors are much more likely to fail catastrophically with a short circuit and possible ignition during the first power-on cycle. This type of failure in MnO2 capacitors is lot-related, can occur even at derated voltages and relatively low levels of moisture sorption that corresponds to room conditions. Baking before soldering is an effective measure to prevent failures even in lots susceptible to popcorning damage.
Capacitor↗
Infant Mortality and Wear-Out Failures in Polymer and MnO2 Tantalum Capacitors
Reliability testing of modern tantalum capacitors shows the presence of both types, infant mortality (IM) and wearout (WO) failures. To assure reliable operation, the probability of IM failures should be reduced to below the specified level, and the time of WO inception should be greater than the required useful life of the parts at operation conditions. In this work, several types of MnO2 and polymer cathode tantalum capacitors have been tested at highly accelerated conditions to assess voltage acceleration factors, determine adequate burn-in conditions, and assess the useful life. A modified time dependent dielectric breakdown (TDDB) model has been suggested to explain both types of failure, and a physical mechanism of degradation that is based on migration and reactions of oxygen vacancies explains increase of the defect related, IM failures with the level of stress.
tantalum capacitors↗
Reliability Issues with Polymer and MnO2 Tantalum Capacitors for Space Applications
This work gives a comparative analysis of degradation processes, failure modes and mechanisms in MnO2 and polymer technology capacitors. Analyzed conditions include effects of vacuum and radiation, soldering (pop-corning), long-term storage and operation at high temperatures, stability at low and high temperatures, and anomalous transients. Screening and qualification procedures to assure space-grade quality of CPTCs are suggested.
tantalum capacitors↗
Reliability Issues with Polymer and MnO2 Tantalum Capacitors for Space Applications
This presentation gives a comparative analysis of degradation processes, failure modes and mechanisms in MnO2 and polymer technology capacitors. Analyzed conditions include effects of vacuum and radiation, soldering (pop-corning), long-term storage, operation at high temperatures, stability at low and high temperatures, and anomalous transients. Screening and qualification procedures to assure space-grade quality of CPTCs are suggested.
capacitor↗
Effect of Preconditioning on Post-Soldering Failures in Tantalum Capacitors
Soldering have a strong effect on performance and reliability of most surface mount technology components, including tantalum capacitors. High quality tantalum capacitors are likely the only type of components where soldering simulation is the first step during screening. Nevertheless, post-soldering failures of tantalum capacitors do happen and require additional analysis. Popcorning is a well-known effect in plastic encapsulated microcircuits (PEM) and it occurs also in chip tantalum capacitors. The sensitivity of parts to the presence of moisture during soldering is characterized by the moisture sensitivity level (MSL); however, contrary to PEMs, there is no standard procedure for establishing MSL for tantalum capacitors, and standard J-STD-020 is applicable partially only. In this work, the effect of absorbed moisture on soldering related degradation and failures in tantalum capacitors have been studied using 22 types of polymer and 11 types of MnO2 cathodes tantalum capacitors including single and multianode parts. The amount of moisture released during soldering has been estimated by measurements of mass and capacitance variations. Results show that moisture uptake in similar parts is approximately two times greater in polymer than in MnO2 capacitors. Cracking of the case and degradation of parameters can occur in both types of parts, but MnO2 capacitors are much more susceptible to catastrophic short circuit failures and their ignition is possible during the first power-on cycle. This type of failure in MnO2 capacitors is lot-related, can occur even at derated voltages and relatively low levels of moisture sorption corresponding to room conditions. Baking before soldering is an effective measure to prevent failures even in lots susceptible to popcorning damage. Recommendations for testing to establish MSL and for baking to reduce the probability of failures are suggested.
tantalum polymer capacitors↗
Parametric Failures in COTS Capacitors
Insertion of COTS components into hi-rel systems require extensive environmental testing of the parts that often results in parametric failures. Based on experience with commercial and hi-rel PME and BME ceramic capacitors and polymer and MnO2 cathode tantalum capacitors, this presentation discusses two major reasons for parametric failures. One is due to the marketing pressure that forces manufacturers to squeeze performance of COTS components thus leaving insufficient margin between the rated and actual characteristics. Another, and probably a more serious reason is degradation of characteristics caused by physico-chemical processes in materials under environmental stresses. Reliability assessment requires development of models to predict behavior of the parts during applications based on accelerated testing that might be outside the specified conditions and target applications. Examples of models developed to simulate and predict wear-out failures are presented. Risks associated with overstressing during HALT are discussed.
Teverovsky, Alexander↗
2017 NEPP Tasks Update for Ceramic and Tantalum Capacitors
This presentation gives an overview of current NEPP tasks on ceramic and tantalum capacitors and plans for the future. It includes tasks on leakage currents, gas generation and case deformation in wet tantalum capacitors; ESR degradation and acceleration factors in MnO2 and polymer cathode capacitors. Preliminary results on the effect of moisture on degradation of reverse currents in MnO2 tantalum capacitors are discussed. Latest results on mechanical characteristics of MLCCs and modeling of degradation of leakage currents in BME capacitors with defects are also presented.
ceramic capacitors↗
Select Electronic Parts Operation at Extreme Low Temperature
The purpose of the study presented in this paper is to extend the test period of a selected set of electronics parts at cryogenic condition to dwell period of about 24 hours to demonstrate extreme cold operational capability of these components. The parts tested are tantalum polymer, BX and P90 type ceramic capacitors, thick film resistors, analog multiplexers, a digital inverter, and a D-flip-flop. These parts were tested to assist identifying candidate components that can be used for development of a cold capable telemetry board. There are several past investigations that have shown that COTS (commercial-off-the-shelf) capacitors and resistors tested at cryogenic temperatures and frequencies up to 10MHz did not exhibit significant changes in capacitance and resistance values. Also, there are several test results for active parts. These past tests collected measurements during a temperature sweep from room temperature down to cryogenic temperature with very short dwell time at cryogenic temperature, and back to room temperature. This study extends the operational dwell time to at least 24 hours and returning to room temperature operation without significant degradation in performance, thus, demonstrating the potential for longer dwell time in actual operation in these extreme cold temperatures and a method for identifying the cold operability.
Ashtijou, Mohammad↗
Breakdown and Self-healing in Tantalum Capacitors
Reliability of tantalum capacitors depends on the efficiency of self-healing that restores parts after breakdown. In this work, different types of polymer and MnO2 cathode capacitors have been tested for scintillation breakdown using a constant current stress (CCS) technique modified to allow detection of amplitudes and duration of current spikes. Monitoring of leakage currents with time under bias is used to assess the effect of scintillations. The appearance and composition of damaged sites have been examined after deprocessing and cross-sectioning. Thermal processes during scintillations have been analyzed, a mechanism of breakdown based on growth of conductive filaments in the dielectric suggested, and self-healing processes in polymer and MnO2 cathode capacitors discussed.
tantalum capacitor↗