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The capacitor is a passive electrical device, used to collect electrical energy by generating a potential difference. It is generally consisting of combination of two conductors placed next to each other separated by dielectric medium. The performance of a capacitor expressed in terms of the capacitance (C) depends on the dimension/geometry of the plate/electrode and the dielectric constant of the material, where the dielectric can be defined by insulating medium having permittivity, with no AC power losses or DC leakage. The capacitor shows different response to AC and DC sources. These are mainly used to supply power in several electronic and electrical systems. Therefore, this chapter provides the fundamental aspects of the capacitors and their basic properties. It emphasizes on the parallel plate model, the basic terminologies associated with the capacitors along with the equivalent circuits of the capacitor and its response to the externally applied AC and DC sources. It also describes about different types of capacitors that are being fabricated using different materials and different construction techniques. These different types of capacitors provide some unique properties.

Electrochemical capacitors are becoming promising energy conversion/storage and power output devices. However, high cost and low energy density are two serious disadvantages. By integrating the advantages of Li-/Na-ion batteries and electrochemical capacitors, Li-/Na-ion capacitors have been explored recently. Al is very cheap and is the most abundant metal element on the earth. There are few reports on Al-ion capacitors due to the challenges in finding a suitable anode with large capacitance and good rate performance. Here, the feasibility of assembling an Al-ion capacitor with good electrochemical performance is demonstrated. The Al-ion capacitor is assembled by using a composite of MoO3 nanotubes coated by a conductive polypyrrole (PPy@MoO3) as an anode, which functions via a redox intercalation/deintercalation of Al3+ ions in aqueous solution. It delivers a capacitance of 693 F g−1, about 3 times higher than that of electrode materials for sodium-ion capacitors in aqueous solution. Combined with an activated carbon (AC) cathode, the Al-ion capacitor presents an energy density of 30 W h kg−1 and an excellent cycling life with 93% capacitance retention after 1800 cycles. This finding provides another energy storage device with low cost and promotes the application of capacitors.

Emerging power electronics in a broad range of military, aerospace, hybrid vehicle, renewable energy and drilling applications rely on advances in dielectric materials for capacitors. Compact capacitors possessing low dielectric loss and high operating temperature capability are needed for power conditioning in advanced converter and inverter designs for these applications. Wound film capacitors represent the preferred capacitor technology but are limited by low operating temperature capabilities, < 150°C, and low volumetric efficiency, capacitance per unit volume less than 1.0 μF/cc. TPL is developing processes and manufacturing techniques for fabrication of advanced capacitor films comprised of high temperature polymers modified with ceramic nanoparticles. The selected polymers enable high temperature operation and the ceramic nanoparticles enhance volumetric efficiency by increasing the dielectric constant. The fabricated films are adaptable to conventional wound film capacitor construction methodologies. This paper provides an overview of TPL's experience to-date with a film dielectric material system comprised of fluorenone polyester polymer and titanate nanoparticle filler. The fluorenone polyester polymer was selected to provide a stable operating temperature of at least 200°C, while the addition of the titanate powder increases the dielectric constant and, in turn, the volumetric efficiency of wound film capacitors constructed with this film system. Status and ongoing capacitor development issues are provided relative to the intended high temperature power conditioning applications.

High energy density capacitor is a key device in pulse power system such as Electromagnetic Gun system and Laser Fusion system. The increase of energy density of capacitor is beneficial from emerge of metallized technology in electrode and advancement in manufacturing. In this paper, first, the influences of different temperature, electric field strength and Ω/square on the insulation resistance and voltage drop are compared for proper use of capacitor and for manufacture improvement purpose. Then, influences of different charging rate and temperature on capacitor are compared for selecting a reasonable charging method. A capacitor is united by several metallized capacitors with series or parallel connection. The arrangement method and the difference of circumstance result in the temperature difference among the capacitors and influence the characteristics of capacitor. The test with two series capacitor be charged under different temperature indicates that the difference of temperature results in the difference of the voltage distribution. The difference is greater as the temperature increase. The results of the test also show that the time of charge is an important factor which influences the voltage of the capacitor obviously.

A high-energy-density capacitor is a key device in power supply source in an electromagnetic-gun system. In order to increase the reliability of the power source equipment, the lifetime of the capacitor must be extended. The increasing of the lifetime is mainly beneficial from the self-healing characteristic of the capacitor. First, this paper verifies the effects of sheet resistance (Rs>;30Ω/□) and pressure between layers on the self-healing characteristic through experiments. The experimental results show that the self-healing energy is approximately inversely proportional to the square of sheet resistance. When the sheet resistance is reasonable, the self-healing energy can be limited to less than 40 mJ. In addition, the self-healing energy decreases with the increase of the pressure. When the pressure is greater than 200 kPa, the self-healing energy can be limited to less than 10 mJ. Then, the effect of interlayer air on the discharge arc in the self-healing process is analyzed. Meanwhile, this paper presents that the lifetime of the capacitors can be extended through excluding or decreasing the interlayer air. At last, two methods are provided: wrap strengthening and impregnation in vacuum. The experimental results show that the lifetime of the capacitors can be increased up to 1.6 times and 4-5 times through these two methods, respectively.

In this study, large-current (75 - 400 A), high-voltage (500 - 1000 V rms ), reliable capacitors with capacitances (C) of 100 - 1000 nF were developed for energy storage facility applications. Mica was used as the dielectric of the capacitors. In order to form a parallel stack of a capacitor element, 50 ㎛ thick mica sheets with a size of 30mm×35mm were used with lead foils for the plate lead type of mica capacitors (HCM-L), while the same sizes of mica sheets coated by Ag paste were employed with lead foils for the parallel plate terminal type (HCM-C). The developed capacitors exhibited well behaviored device characteristics which meet the requirements of the capacitors. The developed capacitors also showed excellent characteristics for thermal shock test. The stability characteristics of developed capacitors for large current stress was superior to those measured for the capacitors prepared recently by CDE Tm .Key Words : Large-current, Mica capacitor, High-voltage, Energy storage*비 회 원 : 안양대 공대 디지털미디어학과 교수†교신저자, 정회원 : 호서대 공대 시스템제어공학과 교수E-mail : ejyun@hoseo.edu 접수일자 : 2011년 8월 4일 최종완료 : 2011년 9월 1일

Film capacitors that perform well at temperatures exceeding 150°C and have energy densities in excess of 1 J/cm3 are an enabling technology for many applications in automotive, geophysical exploration, aerospace, and the military. To address this need Faradox Energy Storage, Inc. has produced and is testing high temperature film capacitors fabricated using amorphous oxides (OxFilm™) as the dielectric material. The capacitors are made by depositing thin films of an oxide dielectric on both sides of a double metalized polyimide substrate to form dielectric-coated electrodes. Currently Faradox is producing 2″ long, 1/4″ diameter 2 uF, 100 VDC capacitors using silicon dioxide as the dielectric material. In this paper we present test data demonstrating that OxFilm capacitors have relatively stable properties over a wide temperature range. Measurements include capacitor testing at different 3rd Party test facilities and internal testing using a variety of test conditions including:Life testing at 200 and 250°C for over 1000 hours with measurements of capacitance, leakage, dF and ESR.Capacitance versus voltage, temperature and frequencyImpedance, ESR, and dF versus frequency and temperature and voltageData will also be presented that show these capacitors can be cycled between 0°C and 200°C without degrading their performance. Work is ongoing to obtain additional test data with more statistically significant numbers of capacitors.

Conventional electric double layer capacitors (EDLC) designed with two symmetrical activated carbon electrodes can deliver substantially more power than similar size Li-ion batteries. There is presently a major effort to increase the energy density of EDLC s up to a target value in the vicinity of 20-30 Wh kg–1.The present review article deals with the recent contributions to get this high energy density and new approaches that have been made to increase the withstanding voltage of the EDLCs. Important alternative approach to meet this goal that is under serious investigation is to develop an asymmetric (hybrid) capacitors. Hybrid capacitor systems are the promising approach to meet the goal to effectively increase the energy density. The investigation is to develop hybrid capacitors has been initiated by Li-ion capacitors. And, now Nanohybrid capacitor certainly achieves as high energy density as Li-ion capacitors with higher stability, higher safety and higher productivity. This is the new lithium-ion based hybrid capacitor using the lithium titanate (Li4Ti5O12) negative intercalation electrode that can operate at unusually high current densities. The high-rate Li4Ti5O12 negative electrode has a unique nano-structure consisting of unusually small nano-crystalline Li4Ti5O12 nucleated and grafted onto carbon nano-fiber anchors (nc-Li4Ti5O12/CNF).

The on-wafer serial connection of two capacitors (stacked capacitors) is attractive for two reasons: on one hand the intrinsic reliability and especially the immunity against high voltage pulses increases and on the other hand the early fail risk decreases tremendously. The intrinsic and extrinsic reliability of stacked capacitors are demonstrated using the example of a metal insulator metal capacitor (MIMCAP) with Al2O3 dielectric. The intrinsic reliability of a stacked capacitor, where each of the capacitors uses a dielectric of thickness thk, is equal to the intrinsic reliability of a single capacitor with twice the dielectric thickness 2 * thk. The reduction of early fails for a stacked capacitor is a probability effect: if a single capacitor has the probability p to fail early and an early fail of the stacked capacitor is the combination of two single capacitors each of which contains an early fail, then the stacked capacitor fails early with a probability of p2. This basic idea is checked by voltage ramp experiments on single and stacked MIM capacitors, where the single MIM capacitors show besides the intrinsic branch a prominent extrinsic branch.

An important trend is the use of plug and play microinverters attached to the PV panel, allowing the so called AC module. However, these converters are subjected to high temperature and humidity. Thus, in order to improve reliability and achieve long lifetime, this work proposes a new topology that provides inductive power decoupling and eliminates electrolytic and even film capacitors, using a single ceramic or mica capacitor. The topology also provides inductor miniaturization and efficiency improvements.

An important trend in photovoltaic lines of research is the use of plug and play microinverters attached to the panel, allowing the so called AC module. However, these converters are subjected to high temperature and humidity. In order to improve reliability and achieve long lifetime, this work proposes a new topology, which provides inductive power decoupling and eliminates electrolytic and even film capacitors, using a single ceramic or mica capacitor. A thorough theoretical analysis of the topology is provided and simulation results prove its feasibility and advantages.

Electric double-layer capacitors based on charge storage at the interface between a high surface area activated carbon electrode and an electrolyte solution are characterized by their long cycle-life and high power density in comparison with batteries. However, energy density of electric double-layer capacitors obtained at present is about 6 Wh/kg at a power density of 500W/kg which is smaller as compared with that of batteries and limits the wide spread use of the capacitors. Therefore, a new capacitor that shows larger energy density than that of electric double-layer capacitors is proposed. The new capacitor is the hybrid capacitor consisting of activated carbon cathode, carbonaceous anode and an organic electrolyte. Maximum voltage applicable to the cell is over 4.2V that is larger than that of the electric double-layer capacitor. As a result, discharged energy density on the basis of stacked volume of electrode, current collector and separator is more than 18Wh/l at a power density of 500W/l.

International audience; In this paper, we use an analytic model to calculate the losses in the metallized polypropylene film capacitors. The model is validated experimentally for capacitors having the same capacitance but different geometry. For each group of capacitors a temperature distribution in the roll is assumed with the aim of optimizing its thermal performance. It appears that the heating of a long capacitor is higher than that of an equivalent flat capacitor subjected to the same electric stresses.

The provision of adequate decoupling capacitance in the power distribution system for integrated circuits (ICs) is an increasing concern. As clock rates and the IC gate density increase, discrete chip capacitors do not satisfy the decoupling requirements for high current switching at very high frequencies. Thin film capacitors not only exhibit better high frequency performance than discrete ceramic capacitors, but also provide the possibility for passive component integration. In this work, the high frequency performance of thin film capacitors was investigated using Maxwell Eminence, a high frequency structure simulator based on the finite element method. Good agreement between the calculated impedance and experimental results was obtained. At high frequencies, the performance of thin film capacitors is related to contact configurations, dielectric and metal layer thicknesses, and capacitor shapes. The influence of these factors on the impedance behavior was examined. Equivalent circuits of a thin film capacitor for use in a circuit simulator at high frequencies are discussed.

The failure mode analysis is conducted for the Oil-free (dry) Can-less pulse capacitors of 6kV working voltage. Pulse capacitor stability directly influences the dependability of the pulse power system, in which, capacitor located in. This capacitor is discharged in a low inductive circuit with sub-microsecond rise time of kA current peak pulse. Oil impregnated metal can capacitor delivers high power to the load. But use of these capacitors is limited due to high self inductance, higher weight, volume and oil leakage problems. Bi-axially oriented polypropylene (BOPP) film and aluminum foil with extended foil compact design oil-free capacitor delivers moderately high power, which comes closest to fulfilling the need. This paper describes the work done at High Voltage Laboratory in the field of oil-free pulse capacitors development and the analysis carried during development and testing of these capacitors. Which helps to improve the material, design, process, testing methods etc to develop an oil-free. Failure mode of the capacitors and some of the failed capacitors photographs are also presented.

Self-healing capacitors fabricated of metalized polypropylene film as the dielectric material are widely used in power electronics. Self-healing process makes elimination of local defects in these capacitors possible and extends the life-time of them. It was shown that the measuring of capacitor V/A characteristic nonlinearity is usable and effective tool for monitoring of capacitor quality. Six capacitors of this type were aged in an oven at the temperature of 90 °C for 1000 hours under normal ambient conditions and changes caused by ageing were monitored with the nonlinearity measurement. It was found that nonlinearity of capacitor grows with the time of ageing.

High energy (>5kJ) capacitors based on a number of different dielectric and electrode technologies are available for use in pulse power systems. Discrete foil electrode capacitors are appropriate for higher voltage, lower capacitance, and faster discharge. Discrete foil capacitors offer the highest peak power and average power capabilities and elements can be connected in series to achieve extremely high voltages, up to a few megavolts. Both metallic and insulating plastic cases can be combined with different dielectric/electrode winding types to provide optimized capacitors. This work will compare the capabilities of different capacitor technologies for a wide range of operating conditions and provide guidance in selection of high energy capacitors for future applications.

Summary form only given. High energy (>5kJ) capacitors based on a number of different dielectric and electrode technologies are available for use in pulse power systems. Metalized electrode technologies allow higher energy densities to be achieved (up to 3 J/cc) at lower voltages, higher capacitances, and longer discharge timescales. Self-healing is a key feature of metalized film capacitors, allowing polymer film or paper dielectrics either to be used close to their intrinsic breakdown strengths, or providing greatly enhanced reliability and lifetime. Both metallic and insulating plastic cases can be combined with different dielectric/electrode winding types to provide optimized capacitors. While oil-filled capacitors still provide enhanced performance in high voltage applications, dry type capacitors are becoming popular. This work will compare the capabilities of different capacitor technologies for a wide range of operating conditions and provide guidance in selection of high energy capacitors for future applications.

Summary form only given. There is a significant need for high temperature capacitors for a variety of operating conditions including pulse power, and high frequency power conditioning applications at temperatures between 125°C and 200°C. Here we cover several new developments in high temperature capacitor technologies presenting results on thin film capacitors useful for long life, high energy density, and high reliability. Additionally, results are presented on an improved very-high temperature film (200°C and higher) with more reliable self-healing, longer lifetime, and higher energy densities. Results from metallized film capacitors with improved termination demonstrating drastic improvements in current carrying capabilities in both CW RMS current and peak pulse current regimes are also presented. Finally, a theoretical high temperature capacitor utilizing a combination of these technologies is discussed and compared to existing COTS and SOTA capacitors.

Now a day's Low Tension (L.T.) & High Tension (H.T.) capacitors are manufactured by using All Polypropylene Film (APP) and L.T. capacitors. All Polypropylene Film has very less dielectric losses, long life, high voltage stress. So it is widely used in H.T. as well as L.T. capacitor. However, the cost of L.T. capacitor is increased due to use of APP in L.T. capacitor. As more costing, the use of APP in L.T. capacitor is limited. The main disadvantage of APP is non-self-healing property. On the other hand, Metallized Polypropylene Film has self-healing property. There are many advantages due to use of MPP film in capacitor - the size of capacitor is reduced, losses are less and cost of capacitor is decreased. So, it is an optimal technique to use MPP in manufacturing of H. T. capacitors.

Electric double-layer capacitors (EDLCs) based on charge storage at the interface between a high surface area carbon electrode and a propylene carbonate solution are widely used as maintenance-free power sources for 1C memories and microcomputers. New applications for electric double-layer capacitors have been recently proposed. The popularity of these devices is derived from their high energy density relative to conventional capacitors and their long cycle life and high power density relative to batteries. The performance of the capacitor depends not only on the material used but also on the construction of the cells. The material, construction and performance of coin-type capacitors for memory protection and power capacitors for large power sources are described.

Electronic devices like notebooks, smart phones, GPS units, LED TVs and other daily life applications are produced with increased functionality and complexity from year to year. Today’s electronic devices must be equipped with new smart electronic circuitry designs to add more functionality within a single device, while not making them larger in size. As the electronic circuits are made of various components, active semiconducting chips and passive components, like resistors, capacitors and inductors, more and more components are needed per single unit. While the number of components increases all components are subject to miniaturization to increase the volume efficiency. As capacitors are one of the more important passive components and every device consists of more than one hundred capacitors, a lot of effort is put on developing smaller sized capacitors. Capacitors can be made from a wide variety of dielectrics and the components can have various shapes. The majority are surface mount capacitors and especially multilayer ceramic capacitors are one of the more popular types. These multilayer ceramic capacitors are mainly used in today’s electronic devices and these types of capacitors are discussed in this thesis. As the name multilayer ceramic capacitor already suggests the components are made up of a body, in which alternating layers of dielectrics and conducting metal electrodes are embedded. In Chapter 2 the manufacturing of multilayer ceramic capacitors is explained in more detail. In the 1980s and 1990s the majority of multilayer capacitors were made with expensive noble metals like palladium or platinum. Due to the price increase of these noble metals at the end of the 20th century, the passive component industry started to develop new dielectric materials suitable for co-firing with less expensive noble metals like pure silver or silverpalladium alloys. Another way to decrease metal costs is to implement base metals like nickel and copper as electrode material. Therefore new types of dielectric materials had to be developed in order to be co-fired with nickel or copper in a reducing atmosphere to prevent the metals from oxidizing. Multilayer ceramic capacitors can be made of a wide variety of materials and depending on the electrical characteristics they are employed in different applications. This thesis describes dielectrics, personally developed for use in commercial multilayer capacitors, which show high stability towards temperature, frequency and voltage in Chapter 3. These dielectrics have low or moderate permittivity values and they are primarily used for filtering, smoothing and temperature control applications. Chapter 3 also describes multilayer capacitors having relatively high permittivities. These are based on barium-neodymiumtitanates and zinc-magnesium-titanates. These materials are suitable for co-firing with pure silver or silver-palladium alloys. It is described how to modify the dielectric composition in order to co-fire with high silver content electrodes and which strategy has to be followed in order to get reliable multilayer capacitors. Furthermore, it is described how high-permittivity temperature stable capacitors having copper electrodes can be produced. These types of dielectrics have very low equivalent series resistance characteristics. Such capacitors can be used in high frequency applications especially. Various multilayer capacitors with electrodes of silver-palladium alloys, copper and nickel electrodes were made. The equivalent series resistance characteristics were determined to compare these capacitors with respect to their performance at high frequencies. Multilayer capacitors with the lowest equivalent series resistances are obtained when metals having the lowest possible bulk resistivity, like copper or silver, are selected. The second part, Chapter 4, describes multilayer capacitors that are used for decoupling and bypassing purposes in electronic circuitry. These capacitors consist of dielectrics which are based on modified ferroelectric barium titanates. Typically they have very high permittivity values. They are less stable towards temperature changes, but they are important for their high capacitive volume efficiency. The multilayer ceramic capacitors are already produced with low cost metals, in particular nickel electrodes. Development is mainly focused on increasing the capacitive volume efficiency by decreasing the dielectric layer thickness and by maximizing the number of electrodes layers. Various strategies are described to make high capacitance multilayer capacitors. The dielectrics layers of these high capacitance multilayer capacitors were already decreased down to 1 μm thickness in recent years. The grain size of the ceramics is typically 200–250 nm and efforts are made to decrease the grain size further, while maintaining reliable capacitor characteristics. The influence of the applied electrical field on the dielectric layers is explained in this chapter, and a strategy is presented how to develop new high permittivity dielectrics effectively. The influence of raw materials properties, particle size distribution of raw materials, and formulation on electrical properties and microstructures of the ceramics is described, while a conventional production method is used. With an alternative method it is possible to make ceramics having high permittivity values as well. In that process raw materials are used, which have high concentrations of yttrium oxide and copper oxide in the barium titanate lattice. These doped barium titanate powders are then mixed with pure barium titanate powders, together with extra dopant elements, to produce a new type of dielectrics.

The article relates to the fabrication of embedded P-N junction capacitors, using System-in-Package (SiP) technology, on a silicon interposer wafer with Through-Silicon-Via (TSV). The P-N junction capacitors are fabricated using current micromachining technologies, including etching high aspect-ratio, three-dimensional honeycomb structure and thermal oxidation, thermal dopant diffusion, sputtering, and metallization and so on. The fabricated capacitor displays high capacitance density compared with common two-dimensional (2D) P-N junction capacitors. Tests at high frequency (10 Mhz–40 GHz) were conducted to evaluate the properties of these capacitors. Test results show that the capacitors have a high capacitance density up to 12nF/mm2 of wafer area, with reverse bias voltage of 1V, which is about 10–12 times that of 2D semiconductor capacitors, and is attributed to the increased junction area inherent in the three-dimensional via structure. These capacitors can be used for decoupling under a wide frequency range from 300 MHz to 3.2 GHz. they show a low parasitic inductance by measuring. Capacitor has a characteristic that capacitance value also keeps up constant with the increase of frequency.

Embedded capacitor technology is one of the methods to miniaturize and to obtain higher performance of electronic package systems. High dielectric constant epoxy/ceramic composites have been of great interest as embedded capacitor materials for packaging applications, because they have good processability and compatibility with printed circuit boards (PCB), in addition to high dielectric constant. In this study, we have demonstrated the fabrication of prototype-scale embedded capacitors in manufacturing scale PCBs using multi-layer PCB build-up process. Specially formulated B-stage epoxy/BaTiO3 embedded capacitor films (ECFs) were used as not only an adhesive between two copper clad laminates (CCLs) but also capacitor dielectrics for embedded capacitors. The total thickness of PCB included embedded capacitor was below 250 mum. Dielectric properties of epoxy/BaTiO3 ECFs were measured at 100 kHz using a LCR meter, and the dielectric properties at high frequency were measured using devices specially designed for correcting stray effect around capacitors. High temperature storage test at 150degC, high temperature /humidity test with 60degC/60RH% condition, and reflow process at 260degC were performed to evaluate the reliability of prototype-size embedded capacitors. In summary, fabrication of B-stage epoxy/BaTiO3 composite embedded capacitors in prototype-scale 405 times 508 mm PCBs using CCL was successfully demonstrated using conventional PCB manufacturing processes, and their dielectric properties and reliability were evaluated.

A compact low-inductance capacitors PC 200-1.5 with a 1.5-nF capacitance and with pulsed charging up to 200 kV has been designed. The PC 200-1.5 capacitor uses combined paper-film insulation with castor oil impregnation. To decrease edge effects in the capacitor, the insulation in the region of the sharp edge was divided into thin layers by means of capacitor plates displaced with respect to each other to a given value. The PC 200- 1.5 capacitors have been tested as peak capacitors in a stage of the high-power pulse transformer LTD-100 R [1] that provided an increase in its output power by ~25%. The lifetime of the capacitors is longer than 2- 103 pulses.

In this work, we compare silicon nitride MIM capacitors to metal finger capacitors and clarify the performance and cost trade-offs. Our measurements show that MIM capacitors are superior to metal finger capacitors in terms of matching and process tolerance, but equivalent metal finger capacitors have higher Q, lower voltage coefficient and lower temperature coefficient.

This chapter describes various types of capacitors that are suitable for switchmode power supplies. The main characteristic of a capacitor is that it stores charge when presented with a voltage. A real capacitor is a combination of resistance, capacitance, and inductance. The chapter presents equivalent circuits for a real polar and nonpolar capacitor. The polar capacitors also include a parasitic diode that allows current to flow if the capacitor is reverse biased. This diode is an actual physical diode formed by the metal and oxides used for the plates and the dielectric. The polar capacitors are formed from metals that are called “valve metals” because of the characteristics of the metal and the oxide dielectric. The valve metals used for capacitors are aluminum, tantalum, and niobium. Aluminum electrolytic capacitors are the oldest bulk capacitor technology. They are the composition of choice for the input power supply in an off-line power supply. All aluminum electrolytic capacitors are made of a sandwich of an aluminum anode foil, a paper separator, an aluminum cathode foil, and another paper layer. Solid tantalum capacitors are used in applications where their volumetric efficiency is an advantage. Tantalum capacitors have significantly lower maximum voltage than aluminum electrolytics.

The DC-link bus capacitors after the input rectifier in inverter-powered systems are often chosen to meet the high ripple current requirements, and consequently, larger, more expensive capacitors with more capacitance than needed get designed into systems. This paper shows how a new electrolyte for the aluminum electrolytic bus capacitors can eliminate the need for extra capacitance and reduce the capacitor count by 50%.

Many DC-to-DC converters are under-filtered when it comes to RFI control and must be decoupled externally. Because the input filter section sees a moderate to low series current, normally one or two amps at 48 volts, a small valued capacitor can be used on the input, provided the dissipation factor is low enough to efficiently sink the ripple current, and the high frequency impedance is low enough to bypass reflected RFI. These capacitors can be either X7R ceramic or special multilayer polymer film (MLP) capacitors. Both types are built on a "stacked" layer construction that features very low impedance and ESR extending well beyond the switching frequency of high-density converters. Developments to provide higher capacitance values in small package sizes have now led to the use of these low ESR capacitors in output filters where the load currents are at least ten times higher than on the higher voltage input bus. The selection of an electrostatic capacitor (ceramic or film) can improve the reliability of the power system to a level where the tantalum electrolytic capacitors typically used can either be reduced in number or eliminated from the output filter. MLP capacitors represent the next generation of capacitor technology. While its mechanical structure is next generation technology, it is still based on proven film capacitor fundamentals with their established track record of both durability and reliability.

A description is given of a multilayer ceramic capacitor developed for AC voltage operation by using a dielectric characterized by very low loss, even at large signal amplitudes. The result is a new class of ceramic capacitors useful in many medium power AC application such as line isolation and bypass to ground, small motor controls, etc. The dF of these ceramic capacitors compares favorably with that of small aluminium electrolyte capacitors. Comparable films are much larger, and the ceramic devices can be rated for much higher ambient temperature operation. Novel approaches to large-signal capacitor measurement, under conditions closely approximating use conditions, are presented for a range of low frequencies up to at least 10 kHz. It is demonstrated that at high frequencies, high resonant frequency and low series resistance are good figures of merit for capacitors. >

The authors present a novel metal-to-silicide-polysilicon capacitor and compare it with metal-to-polysilicon capacitors and conventional polysilicon-to-polysilicon capacitors. Voltage coefficient data for these capacitor structures with oxide, oxide/nitride, oxide/nitride/oxide, and nitride dielectrics are also discussed. It is shown that when metal-to-silicided polysilicon capacitors are used, voltage coefficients of less than 4 p.p.m./V can be attained, which is considerably less than that obtained when metal-to-poly or conventional poly-to-poly capacitors are used. For high-precision A/D converters, this value will make possible accuracies of up to 18 bits through self-calibration. >

The authors describe and analyze two capacitors which are incorporated in a baseline BiCMOS technology without added process complexity. The first capacitor is formed between degenerated doped polysilicon and silicon. The second is formed between two degenerately doped polysilicon layers. In both structures, the insulator is a deposited or grown oxide. The sensitivity of the capacitor voltage coefficient to oxide thickness and surface dopant concentration is discussed theoretically and compared to measured data. The two capacitors are optimized to exhibit very low voltage coefficients. >

Digitalization in electronic systems is required with capacitors which are large capacitance with small size, low impedance at high frequency, and high reliability. The fabrication and properties of aluminium solid electrolytic capacitors are investigated. Employing a conducting polymer film such as, polypyrrole as solid electrolyte, solid type aluminium electrolytic capacitors were made. The surface of insulating oxide is covered with conducting polymer layer prepared by chemical oxidative polymerization. Thereafter this conducting layer is covered with conducting polymer prepared by electrochemical polymerization. The dielectric properties of these capacitors were also measured and discussed. Regarding the frequency characteristics of the trial capacitor, impedance and ESR at high frequency is lower than those of the stacked type film capacitor. It is also confirmed that the temperature coefficient of capacitance and dissipation factor of the capacitor is lower than that of the film capacitor and liquid type aluminium electrolytic capacitor. >

Proper component selection is the first step in building reliable equipment. To select the correct capacitor to be used, the design must know as much as possible about the different types. The designer should know the advantages and disadvantage; the behavior under various environmental conditions; the construction; the effect of circuits on capacitors; and what makes capacitors fail. This paper addresses the different types of capacitors and gives some guidance in their applications. The following types of capacitor are discussed: ceramic, plastic film, aluminium electrolytic, tantalum, glass, and mica.

The double-layer capacitor is a recent innovation that combines high surface area electrode materials with the high capacitance per unit area of the chemical double layer. Commercially available devices with a capacitance of 1500 F are now available (Matsushita, 1992). This improvement in rated capacitance has presented opportunities for the use of double layer capacitors in high power and/or high energy storage applications (Burke, 1995 and Hall, 1995). This paper examines the discharge performance characteristics of several capacitors, including both aqueous and organic electrolyte devices. A useful simplified model is assumed for the double layer capacitor, consisting of an equivalent series resistance (ESR) and a capacitor in series. Values for these two parameters are determined in this investigation under various discharge conditions, along with peak current during short circuit conditions.

Power-distribution networks need to provide flat low impedance over a wide band. Bypass capacitors with different values, and capacitors and planes create resonance peaks, unless the capacitor parameters are selected properly. Distributed matched bypassing is used to create a smooth impedance profile. The ESR of ceramic capacitors is increased by adding embedded annular resistors in series to the capacitors.

This chapter provides an overview of capacitors. A capacitor is an arrangement of conductors that are insulated from each other so that charge can be stored. When Direct Current (DC) or pulse waveforms are applied to capacitors, the charge and discharge behavior is important. The simplest type of capacitor is the parallel-plate type, using air as its insulation between the plates. If any solid or liquid insulator is placed between the plates, the capacitance of the arrangement is increased, and the factor by which the capacitance is increased is called the relative permittivity of the material between the plates. The chapter describes several capacitors, one of them is electrolytic capacitor. The principle is that several metals, notably aluminum and tantalum, can have very thin films of their respective oxides formed on the surface when a voltage is applied in the correct polarity between the metal and a slightly acidic liquid. These very thin films then insulate the metal from the conducting liquid, the electrolyte, forming a capacitor, an electrolytic capacitor. Another capacitors are variable capacitors, such capacitors, once used in radio receivers, are now available only for replacement purposes and can be quite difficult to find.

Gas-dielectric capacitors of 5 and 10-pF are described. With Zerodur as the structural material, the capacitors are stable with time, have small temperature and voltage coefficients, and have been used successfully as traveling standards. A relatively large sensitivity to ionizing radiation is observed in these capacitors. >

The steady increase in the severity of operating conditions for capacitors and the need for more diverse characteristics has spurred the search for new and better capacitor dielectrics. The synthetic plastics industry, which is the source of a number of useful dielectric materials, has recently produced a new and promising dielectric in film form known as polyethylene terephthalate or ?Mylar.? This material is unusually strong, has a high softening point, and is available in very thin films which makes it especially suitable for capacitor insulation. The electrical characteristics of capacitors wound with Mylar film are likewise promising. As compared to mineral-oil-impregnated paper capacitors, unimpregnated Mylar capacitors exhibit higher dielectric strength, higher insulation resistance, and can be operated at higher ambient temperatures. Their loss characteristics are comparable with those of impregnated paper and the capacitance stability over the usual range of ambient temperatures approaches that of mica capacitors. Mylar is relatively nonhygroscopic and tests indicate that for moderate atmospheric conditions capacitors made from it do not require additional moisture protection. The film can be metallized readily by current techniques and, when used in metallized capacitors, appears to possess advantages over metallized paper in several respects.

The use of thin layers of organic material as capacitor dielectric is of considerable interest in connection with miniaturization techniques. A technique has been established for the manufacture of capacitors, employing aluminium foil coated with lacquer on both sides; edge insulation is achieved by etching away the exposed metal at one edge, and the second electrode is of evaporated metal. Using a 3?m coating of polyisocyanate lacquer, miniature capacitors, having a performance at 50 V and 50° C equal to that of paper capacitors, can be manufactured with an improvement in space factor of at least six. The etching technique is shown to have no adverse effect on life characteristic and enables small capacitors to be made with good high-frequency characteristics.

A capacitor has been developed which is superior to previously reported duplex capacitors. The dielectric consists of anodic tantalum oxide overlaid with silicon dioxide deposited by RF sputtering. This capacitor proved usefuI as a low-valued capacitor Of capacitance density ranging from 150 pF/mm2to 20 pF/mm2, corresponding to a thickness range of a silicon dioxide film from 0.2 µ/m to 2.0µm. The capacitor can be produced with very high yield Of approximately 100%, due to the defect-free anodic oxide film diminishing the importance of defects inevitably induced in the RF sputtered silicon dioxide film. The silicon dioxide film can be deposited without causing any deterioration of the anodic film of tantalum oxide by Control of the RFsputtering conditions. The capacitor remained stable with no failures occurring when aged under various conditions of voltage, temperature, and humidity. The capacitor can be processed in a manner compatible with the manufacturing process of the TM or TMM capacitor.

A new type of ceramic capacitor is described. A novel construction enables thin insulating layers of a high-permittivity material to be formed in such a manner that they are mechanically strong. The thickness of the layers is controllable, so that capacitances ranging from 0.5?F at 3 V to 0.05?F at 200 V are possible. The units have the form of discs of 1 cm2 area per side and a thickness of 0.1 cm. The junction ceramic capacitor is suitable for coupling and by-passing applications, particularly in transistor circuits, where it should be an inexpensive replacement for more conventional types. The construction and electrical characteristics of the new capacitor are given.

Clear ruby muscovite mica is classified as a low loss insulating material and many values for dielectric loss and dielectric constant are given in the literature. Such values presumably are based on measurements made in the direction perpendicular to the plane of basal cleavage. We find that mica inherently has a much higher dielectric loss parallel to the plane of cleavage and that impurities such as entrapped water, and semi-conducting mineral inclusions further exaggerate this condition. Such excessive parallel loss, particularly that due to entrapped moisture, may have some bearing on the anamolous behavior of some mica capacitors, with respect to poor life, excessive r-f heating, silver ion migration, low Q of small size capacitors, excessive temperature coefficient and other adverse effects.

Publisher Summary Capacitors are generally divided into classes according to their dielectric, for example, paper, mica, and ceramic. Impregnated-paper capacitors are general-purpose paper-dielectric capacitors, made by rolling paper as insulation between metal foils and filling with an impregnant. They are relatively inexpensive, have a high capacitance-to-volume ratio, and are capable of working at reasonably high voltages, but their power factor is comparatively high and the selection tolerances are fairly wide. The insulation resistance of impregnated-paper capacitors is high at room temperature—of the order of 2000-5000 ΩF—depending on the paper and impregnant—but falls rapidly as the ambient temperature is increased. The main characteristics of mica-dielectric capacitors are low power factor, high voltage operation, and excellent long-term stability at room temperature. The stability of the silvered-mica-plate type is about 1 % under normal conditions of use and that of the stacked-mica-plate type is about 2%. The high-permittivity ceramic capacitors provide a very high capacitance in a compact unit. However, the capacitance and the power factor change widely with temperature, the changes being neither linear nor very cyclic for either property.