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SAL electrolytic capacitors (SAL = Solid Aluminum) are aluminum electrolytic capacitors with anodic oxidized aluminum oxide as dielectric and with the semiconducting solid manganese dioxide as electrolyte. They are made of etched and formed aluminum anodes, which are folded for the dipped pearl types or wound for the axial style. The solid manganese dioxide electrolyte is analogously prepared in a pyrolytic process like for solid tantalum capacitors. SAL-capacitors were developed and introduced in the market in the 1960s by Philips. It is a single source product, now (2014) manufactured by Vishay〔Vishay, Series 128 SAL-RPM, (PDF )〕〔Vishay, Series 123 SAL-A, (PDF )〕 ==Construction== Basic anode material of solid aluminum capacitors exists of highly purified aluminum with a purity of at least 99.99%. In an electrochemical process the anode material is etched (roughened) to increase the effective electrode surface. After that the roughened aluminum becomes oxidized or formed by an anodic oxidizing process. Thereby an electrical insulating oxide layer Al2O3 is formed on the aluminum surface by applying an electric current in correct polarity in an electrolytic bath. This process of oxide formation is carried out into two reaction steps: * 2 Al + 6 H2O → 2 Al(OH)3 + 3 H2 ↑ * 2 Al(OH)3 → 2 AlO(OH) + 2 H2O → Al2O3 + 3 H2O The aluminum oxide layer acts as a dielectric. After forming the dielectric the aluminum foils are folded for the dipped style or wound for the axial style, and than provided with electrolyte, the capacitors cathode. The electrolyte used in SAL capacitors is a solid state oxide semiconductor, manganese dioxide (MnO2). This electrolyte is formed by pyrolysing of the liquid manganese nitrate into the solid manganese dioxide. * Mn(NO3)2 • 6 H2O → MnO2 + 2 NO2 + 6 H2O After the pyrolising process the capacitor cell is reformed again to heal all impurities or cracks caused during the pyrolising process. Manganese dioxide is a hard, black crystalline substance. It has a fairly good electrical conductivity and has an excellent long-term stability. In an ideal case it covers 100% of the dielectric layer and acts as a solid cathode in the solid electrolytic capacitor. For contact purposes, a layer of carbon from a graphite dispersion is put on the MnO2 coating on the surface of the capacitor cell. Onto this a metallic conductive silver epoxy lacquer is applied. The graphite layer also prevents a direct contact between manganese dioxide and silver. Direct contact between these two materials forces a chemical reaction which oxidizes the silver and reduces manganese dioxide into high resistive manganese (III) oxide resulting in increasing ESR of the capacitor. This silver layer now can be contacted with the cathode terminal of the capacitor. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「SAL electrolytic capacitor」の詳細全文を読む スポンサード リンク
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