Polymer capacitor

Polystyrene capacitors have exceptionally low tan S values (< 10 q, making them well suited for frequency-selective circuits in telecommunications equipment. Polymer capacitors are widely used for power-factor correction in fluorescent lighting units, and in start/run circuitry for medium-type electric motors used in washing machines, tumble-dryers and copying machines for example. They are also used in filter circuits to suppress radio frequencies transmitted along main leads. Such interference noise may originate from mechanical switches, furnace controllers and switch mode power supplies it not only spoils radio and television reception but can also cause serious faults in data-processing and computer equipment. 

The fabrication of humidity sensors on silicon chips has recently become possible using 1C. production technology [37, 49], This realizes a small, low cost humidity sensor, and makes it possible to integrate the humidity sensor with other sensors or signal-handling circuitry on the same chip. A new integrated temperature and humidity sensor developed by Yamamoto et al., consists of a polymer capacitor on the p-n diode of a temperature sensor [50] as illustrated in Figure 20-33. A thin film of polyimide is used as the moisture-sensitive material... 

One of the most widespread technical applications of PEDT is its use as a counterelectrode in solid aluminum, tantalum, and niobium electrolytic capacitors. As early as 1988, the application of PEDT as polymeric counter electrode in a tantalum capacitor was described in a patent application [62]. Since then, more than 100 patent applications have been filed which claim the use of PEDT in various capacitor configurations, and most major capacitor manufacturers today produce polymer capacitors. ... 

Impregnation is performed by dipping the anodes into the reactant solutions, using either a sequential dipping process in which the oxidant and monomer are deposited separately or a one-pot dipping process in which the monomer and oxidants are deposited from the same solution. Although more uniform, and therefore more conductive, PEDOT films can be deposited, a major obstacle to the one-pot method is the limited pot life. For this reason, most capacitor manufacturers have historically used a sequential dipping process to manufacture polymer capacitors. 

Normally, embedded formed polymer capacitors are made from purchased sheet materials. It is difficult for the board fabricator to apply a liquid dielectric formulation precisely to laminate, but one photolithographic capacitor formation technique has been developed. Unneeded dielectric is removed with a developer solution similar to hquid photoimageable solder mask. 

Nippon Kodoshi Corporation (NKK), headquartered in Kochi, Japan, has been established since 1941. NKK s product lines include separators for capacitors (aluminum electrolytic and conductive solid polymer capacitors), separators for electric doublelayer capacitors, separators for multiple types of batteries (alkaline, lithium-ion, and NiMH batteries), and lastly, inorganic and organic nanohybrid membranes. 

Figure 10.7 shows SEM pictures of a broken tantalum polymer capacitor. A thin PEDOT layer on top of the Ta205 dielectric, which covers a tantalum core, is clearly seen. 

The continuous improvement of PEDOTrPSS, or poly(3,4-ethylenedioxythio-phene) poly(styrenesulfonate), pol5uner dispersions over the last decade has made the application of these dispersions for polymer capacitors feasible. Waterborne PEDOT PSS dispersions were developed for the formation of the outer polymer layer first. The requirement on conductivity is much lower for this application than for the inner solid electrolyte because the electrical current passes perpendicular to the 5 to 50 microns thick outer polymer layer. Filmforming properties, adhesion to the anode body and edge, and comer coverage, which are critical to guarantee good barrier layer properties, are adjusted by appropriate formulations of PEDOTPSS. In Figure 10.10 a dense outer layer made of a PEDOTPSS dispersion on a tantalum capacitor is shown. 

For thin dielectrics, which are used for low voltage polymer capacitors, the quality of the dielectric oxide layer can be restored by the reformation or aging process for thicker dielectrics (capacitors with voltage rating of 25 V or higher) the restoration typically fails. The application of an insulating protection layer on the dielectric can help to reduce the degradation of the dielectric by chemical polymerization. ... 

Whatever the real reason for the degradation of the dielectric during chemical in situ polymerization is, the application of PEDOT PSS polymer dispersions does not only simplify the manufacturing process of polymer electrolyte capacitors but preserves the quality of the dielectric layer as well. PEDOTrPSS dispersions enable the manufacturing of high voltage polymer electrolyte capacitors for the first time and thus new markets like industrial and automotive applicahons can be accessed with polymer capacitors in future. 

E. Reed, J. Marshall, and R. Hahn. 2002. How low can you go—tantalum polymer capacitors with ESR under 7 mfi. In Proceedings of the 16th Passive Components Symposium CARTS Europe, 60-67. Port St. Laurent, Electronic Components Institute Internationale Ltd. 

J. Young, J. Qiu, and R. Hahn. 2008. High voltage tantalum polymer capacitors. In Proceedings of the 28th Passive Components Symposium CARTS US, 1-12. Newport Beach, Electronic Components Association. 

A significant market for electrochemically and chemically polymerized PEDOT originates from capacitor manufacturing, which uses PEDOT as solid electrolyte in aluminum and tantalum polymer capacitors. 

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