Prediction of supercapacitors floating ageing with surface electrode interface based ageing law

Supercapacitors (SC) are power devices used as transitory energy sources for peak power applications such as braking energy recovering in hybrid transports. They are subject to electrochemical ageing processes which affect their performances and reliability. Consequently, the main influence factors on SC ageing kinetic are temperature and voltage. Some ageing law based on experiment results have already been produced (for instance the Eyring law) but are not precisely related to physical considerations. In this article, we propose to use an ageing law which links ageing kinetic with the growth of an interface layer between the electrodes surface and electrolyte, called here SEI (Solid Electrode Interface) layer. In order to have a representative sample, 81 commercial supercapacitors coming from 3 different manufacturers will be tested through floating ageing tests at different voltage and temperature constraints. All presented components are manufactured with the most widespread SC technology (double layer SC using activated carbon for electrode and acetonitrile). The fitting of SC experimental ageing results and SEI ageing law is achieved. Then the effect of temperature and voltage on SEI ageing law parameters is performed.     

DC-bias-voltage dependence of degradation of aluminum electrolytic capacitors

Attention has been paid to reliability-related issues for dc-link capacitors such as monitoring methods, power-loss estimation, and ageing tests. The degradation of the capacitors depends on their operating condition including temperature, ripple current, and dc-bias voltage, which has a strong influence on failures as well. In design stages of power converters, it is desirable to know the relation between the degradation and electrolytic parameters. This paper makes an intensive discussion on the voltage dependence of the degradation of a small aluminum electrolytic capacitor with an ageing test and a leakage-current measurement. The ageing test reveals that a higher dc-bias voltage brings a faster increase in ESR but results in a slower drop in capacitance in a range within the rated voltage. This result implies that either capacitance or ESR cannot be a unique indicator of the lifetime. Attention should be paid both to the ESR and to the capacitance when one monitors the capacitor condition. On the other hand, more than the rated voltage leads a rapid degradation of the capacitor, which can be confirmed by a leakage-current measurement instead of the ageing test.     

Loss-Free Balancing Circuit for Series Connection of Electrolytic Capacitors Using an Auxiliary Switch-Mode Power Supply

Most of today's power converters such as three-phase variable-speed drives, uninterruptible power systems, welding converters, and telecom and server power supplies are based on voltage-source converters equipped with bulky dc-link electrolytic capacitors. To be able to handle full dc bus voltage, the dc bus capacitor is arranged as series-connected electrolytic capacitors rated at lower voltage. An electrolytic capacitor, however, is not an ideal capacitor. It has significant leakage current that strongly depends on the capacitor temperature, voltage, and ageing conditions. To compensate large dispersion of the leakage current and ensure acceptable sharing of the total dc bus voltage among the series-connected capacitors, a passive balancing circuit is often used. Drawbacks of the ordinary passive balancing circuit, such as size, significant losses, and standby consumption are discussed in this paper. An active loss-free balancing circuit, which utilizes an auxiliary switch-mode power supply (SMPS) to equalize the capacitor voltages, is proposed. The capacitors midpoint (MP) is connected to the SMPS via two devices; namely a current injection device and a compensation device. The current injection device injects current into the capacitors MP, while the compensation device sinks the difference between the capacitor leakage currents and the injected current. As a result, the capacitor voltages are controlled and maintained in the desired ratio. The proposed balancing technique is theoretically analyzed and experimentally verified on a laboratory setup. The results are presented and discussed.      

Failure modes of tantalum capacitors made by different technologies

Tantalum capacitor failure modes have been discussed both for the standard manganese dioxide cathode and the new conductive polymer (CP) type. For standard tantalum in the normal operation mode, an electrical breakdown can be stimulated by an increase of the electrical conductance in channel by an electrical pulse or voltage level. This leads to capacitor destruction followed by thermal breakdown. In the reverse mode, we have reported that thermal breakdown is initiated by an increase of the electrical conductance by Joule heating at a relatively low voltage level. Consequently, a feedback cycle consisting of temperature–conductivity–current–Joule heat–temperature, ending with electrical breakdown was created. Both of these breakdown modes possess a stochastic behavior and can be hardly localized in advance. CP capacitors have shown a slightly different current conductivity mechanism compared to standard tantalum capacitors. The breakdown of CP dielectrics is similar to avalanche and field emission breaks. It is an electromechanical collapse due to the attractive forces between electrodes, electrochemical deterioration, dendrite formation, and so on. However, some self-healing of the cathode film has been reported. This can be attributed to film evaporation, carbonizing or reoxidation. Not all of the breakdowns of CP capacitors can lead to self-healing or an open circuit state. Short circuits can also occur.     

离子液体在片式铝电解电容器中的应用研究

利用离子液体具有的高热稳定性、高离子电导率的特点,选用了几种离子液体用作片式铝电解电容器工作电解液。性能测试结果表明,以马来酸或邻苯二甲酸的1,3-二烷基取代的咪唑盐或四氢吡咯盐的离子液体为电解质,所制成的电容器能通过105℃1000h寿命试验和耐回流焊接热试验。但电解液的闪火电压与传统电解液相比较低,一般只能做50V以下的低压电容器产品。     

金属化薄膜电容器电容量衰减的解决方案

针对抑制电磁干扰和降压用金属化薄膜电容器工作一段时间后容量不正常衰减的问题,通过样品解剖和理论分析,收集不同试验条件下的数据,发现金属化薄膜层间空气和封装方式导致容量不正常衰减.将热聚合温度从85℃提高到120℃,选用高温环氧树脂封装,可使所制金属化薄膜电容器在使用过程中电容量衰减小于1％,保证了电子产品在寿命周期内的...     

Embedded thin film capacitors-theoretical limits

The large physical size of capacitors and/or excessive values of associated lead inductance are two major limitations in the development of novel packaging modules, with high packaging density, high performance and reliability along with low system cost. Embedded capacitor technology in thin film form offers a promising solution to these limitations. A design space with capacitance density and breakdown voltage as performance properties, with material dielectric constant and film thickness as parameters has been explored, focusing on tantalum pentoxide (Ta/sub 2/O/sub 5/) as the dielectric material. An inherent tradeoff is established between breakdown voltage and capacitance density for thin film capacitors. The validity of the proposed design space is illustrated with thin films of Ta/sub 2/O/sub 5/, showing deviation from the "best can achieve" breakdown voltage for films thinner than 0.4 /spl mu/m and films thicker than 1 /spl mu/m.     

Voltage-Testing of Thin-film Capacitors

The influence of proof-test voltage and testing time on the working-life distribution of thin film capacitors is presented. The proof-test not only eliminates capacitors with low breakdown voltage, it decreases the working life of the remaining components. A short proof-test is proposed to avoid degrading the remaining components. The test method for estimating the distribution parameters is presented.     

Voltage-Testing of Thin-film Capacitors

The influence of proof-test voltage and testing time on the working-life distribution of thin film capacitors is presented. The proof-test not only eliminates capacitors with low breakdown voltage, it decreases the working life of the remaining components. A short proof-test is proposed to avoid degrading the remaining components. The test method for estimating the distribution parameters is presented.     

400V系列宽温铝电解电容器

着重探讨了焊针式引出４００Ｖ系列宽温（－４０～＋１０５℃）铝电解电容器研制过程中所遇到的主要难题，提出了高压１０５℃彩电用产品的一些设计思想。经过大量实验，在几乎全部采用国产原材料的基础上，研制成功了性能良好的宽温产品，耐久性试验通过１０００ｈ，高温贮存５００ｈ     

低漏电、高击穿电容的HDPCVD工艺研究

介绍了一种低漏电、高击穿电容的HDPCVD(ICPCVD)工艺,并对制备的电容进行了电性能分析和失效分析。通过优化确定了工艺的最佳反应条件,研制出的电容其击穿场强达到8.7MV/cm,在电压加到200V时其电容漏电小于0.5μA。通过与传统的PECVD工艺进行对比,充分体现了HDPCVD(ICPCVD)工艺生长介质的低温生长、低漏电、较高击穿场强、无H工艺等优点。随后的失效分析表明,电容上下电极金属对电容成品率有着很大影响。     

ESR and capacitance monitoring of a dc-link capacitor used in a three-phase PWM inverter with a front-end diode rectifier

Condition monitoring plays an important role in estimating health condition of capacitors because the ageing of the capacitors is usually accompanied by an increase in equivalent series resistance (ESR) and a decrease in capacitance. Either capacitance or ESR cannot be a unique indicator of the lifetime of capacitors in some cases. This paper presents a condition monitoring method of a dc-link capacitor used in a three-phase PWM inverter with a front-end diode rectifier intended for motor drives. The monitoring method extracts both the ESR and capacitance of a capacitor under test from the actual ripple current and voltage without disconnecting the capacitor nor injecting an additional current. The monitoring method, therefore, can be implemented online. Experimental results verify that the monitoring method independently obtains the ESR and capacitance changes of the capacitor under test. This contributes to accurate lifetime estimation of dc-link capacitors.     

CA型固体钽电容器的老化筛选方法

ＣＡ型固体钽电容器是重要的电子元件，为淘汰早期失效产品，确保高的可靠性水平，采用合适的筛选方法十分必要。介绍了：１．敲击漏电流闪变筛选；２．电参数性能测量筛选；３．温度循环筛选；４．高温电负荷老化筛选；５．高温浪涌电压老化筛选；６．高温漏电流老化筛选；７．密封检验筛选。筛选效果最明显的是４、６两项     

氧化膜强化技术在钽电容器生产中的应用

采用氧化膜强化技术在钽阳极体外表面形成抗机械应力的强化氧化膜,并模拟钽电容器回流焊过程,研究回流焊前后钽电容器漏电流变化以及对击穿电压(BDV)的影响。试验结果显示:在回流焊安装前后,应用氧化膜强化技术的电容器漏电流增幅小于普通产品14%;耐BDV比普通产品高6 V。     

Testing the effects of temperature cycling on tantalum capacitors

This study focused on the reliability testing of tantalum capacitors. The objective was to develop efficient tests to examine the effects of temperature cycling on capacitor maximum voltage. A test according to the standard JESD22-A104D overlooks the fact that temperature changes often occur while the voltage is on. Capacitors were first tested according to the standard without voltage; the test was then repeated with added 15 V and 30 V. Second, short cycling tests were run at different temperatures to detect any changes in capacitor characteristics. After the cycling tests, capacitors were tested for voltage, which was slowly increased from 0 V to 90 V, provided no failure occurred. Results suggest that a temperature cycling effect can be achieved in a much shorter time than in standard tests. Temperature cycling can also be accelerated by adding voltage. Possible reasons are discussed in the paper.     

Time dependent breakdown characteristics of parylene dielectric in metal–insulator–metal capacitors

In this work, we present reliability results of MIM (Metal–Insulator–Metal) capacitors fabricated with parylene as the dielectric, deposited at room temperature. We have evaluated the time dependent dielectric breakdown (TDDB) of parylene-based MIM capacitors as a function of constant DC voltage stress, area and dielectric thickness of the capacitor. Mean-time-to-failure (MTTF) of parylene evaluated at different stress voltages shows a power law distribution over the applied voltage range and device area, with MTTF driven by the number of defects. Defect density in the parylene capacitors is also reported and is calculated to be ～1.2 × 10³ defects/cm².     

Breakdown and reliability of p-MOS devices with stacked RPECVD oxide/nitride gate dielectric under constant voltage stress

In this work, the effects of voltage and temperature on the TDDB characteristics of 2.0 nm stacked oxide/nitride (O/N) dielectric, prepared by remote plasma enhanced CVD (RPECVD), has been investigated. The breakdown characteristics and time-to-breakdown (t_BD) are recorded from p⁺-poly/n-Si capacitors under constant voltage stress (CVS) at different temperatures. The t_BD cumulative distributions exhibit a single Weibull slope β of 1.9 for different applied voltages. The charge-to-breakdown (Q_BD) is integrated from the gate current as a function of stress times, and can be used to extract the defect generation rate. The activation energy of 0.39 eV is determined from the Arrhenius law, and the average temperature acceleration factor is about 45 between 25 and 125 °C for a constant gate voltage. The extrapolation of the TDDB lifetime with low percentile failure rate of 0.01% provides a 10-year projection for a total gate area of 0.1 cm² on a chip at 125 °C with the Poisson area-scaling law and a constant voltage acceleration factor of 14.83 V⁻¹. It is projected that the maximum safe operating voltage is 1.9 V for 2.07 nm O/N gate dielectric.     

Alpha particle radiation effects in RF MEMS capacitive switches

The paper investigates the effect of 5 MeV alpha particle irradiation in RF MEMS capacitive switches with silicon nitride dielectric film. The investigation included MIM capacitors in order to obtain a better insight on the irradiation introduced defects in the dielectric film. The assessment employed the thermally stimulated depolarization currents method for MIM capacitors and the capacitance–voltage characteristic for MEMS switches. Asymmetric charging was monitored in MIM capacitors due different contact electrodes and injected charge interactions.     

高压薄膜脉冲电容器放电性能的研究

高压薄膜脉冲电容器是放电触发电路中的重要储能器件,通常用于产生高功率大电流脉冲.分析高压薄膜电容器性能检测指标及实际放电过程,找出了高压薄膜电容器样本失效原因,采取提高卷绕电容器芯工艺水平措施后,所制高压薄膜电容器常规指标合格,放电触发次数可靠性指标达到系统要求的6 000次以上.     

压扁型低噪声金属化电容器工艺研讨

针对压扁型金属化电容器特别是交流和滤波场合使用的电容器存在较大噪声的问题,通过研究聚丙烯薄膜的热传导规律和热收缩特性,总结出不同厚度电容器的最佳热压时间和热聚合条件。结果表明:选择100～110℃的热压温度和与电容器芯子厚度相适应的热压时间,在115～125℃条件下对芯子进行热聚合处理,保温2 h,可使电容器的噪声达到35dB以下。