Sprague Electric Company

Clinton E Hutchins

Trung H Nguyen

Sidney D Ross

Galeb H Maher

Richard A Bemis

Walter W Schroeder

Mulk R Arora

John J Randall, Jr

Phyllis M Schmidt

Edward J Markland

Thomas E Chalmers

Eugene W Kuzia

Derek E Rougeau

An aluminum electrolytic capacitor is housed in an aluminum can having one open end. A standard glass-to-metal seal having an outer tantalum ring is seated snugly within the mouth of the can. With the edge of the tantalum ring positioned flush with, or slightly below, the lip of the aluminum can, the beam of a pulsing infra red laser is directed at the interface between the tantalum ring of the seal and the aluminum lip of the can causing the lip of the can to melt, to flow over and to form a continuous annular Al-Ta weld with the tantalum ring and to hermetically seal the ring to the can continuously and completely at a peripheral edge of the tantalum ring.

Hermetically sealed aluminum electrolytic capacitor

Dried emulsion of precursors for ceramic additives are added to paints containing fine particle ceramic materials for use in ceramic capacitors. The precursors are converted into the desired additives in the paints during the sintering of the capacitor bodies.

Dried emulsion ceramic process

Water soluble precursors of ceramic compounds are emulsified in an organic fluid containing an organic surfactant. The emulsion is subsequently mildly heated at a pressure of about 0.05 atmospheres to remove the free water from the emulsion droplets. The resulting sludge consists of particles deriving from the dehydrated emulsion droplets. These particles may only be bound by the surfactant, all or most of the original organic fluid having been boiling off under low pressure. This sludge is then heated in a standard air atmosphere to char the surfactant, which char is to maintain the separation between the dried droplet-derived particles to prevent forming sintered or fused agglomerates thereof. With continued heating the transient char is subsequently burned off and the particles are calcined to controllably and simply produce a fine ceramic powder of spherical particles having a narrow size distribution and an average size in the particularly useful range of 0.1 micron to 1.0 micron.

Emulsion-char method for making fine ceramic powders

Aluminum capacitor foil is etched by passing it through a bath of electrolyte under the influence of pulsed direct current. The pulse duration is at least nine times as long as the interval between pulses when the current falls to zero and is preferably 3 to 27 milliseconds. The pulse current density is 2 to 10 A/in.sup.2, etching temperature is 50.degree. to 90.degree. C., and the electrolyte is an aqueous solution containing sodium chloride and sodium sulfate.

Etching of aluminum capacitor foil

Aluminum electrolytic capacitor foil is etched by first subjecting high-cubicity foil to a chemical etching stage in which the etchant is an acidic aqueous solution containing an acid having anions for anodizing aluminum, hydrochloric acid, transition metal ions, and aluminum ions. Preferably, the anodizing anions are present in a greater concentration than the chloride ions. The foil is then subjected to a second etching step which may be chemical or electrochemical. The process produces a high capacitance foil with high bend strength.

Etching of aluminum electrolytic capacitor foil

In the production of low voltage aluminum foil capacitor electrodes, etched and clean foil is subjected to a thermal treatment at about 595.degree. to 650.degree. C. and then anodized in an adipate formation electrolyte. The electrolyte may contain a minor amount of a phosphate salt, or the final reanodization may be carried out in a phosphate electrolyte.

Production of aluminum foil capacitor electrodes

Aluminum electrolytic capacitor foil is treated after etching but before anodizing by first contacting it with a phosphate solution and then heat treating for 30 to 90 seconds to form a thermal oxide layer of controlled thickness. On subsequent anodization, the thermal oxide layer modifies the barrier oxide layer increasing its dielectric strength and hence capacitance and also stabilizes the barrier oxide layer.

Process for treating aluminum electrolytic capacitor foil

Aluminum capacitor foil is etched in a bath at 30.degree. to 45.degree. C. containing 0.5 to 1.8 M hydrochloric acid, 0.05 to 0.3 M phosphoric acid, 0.2 to 0.5 aluminum chloride and 0.09 to 1.0 M alkali or alkaline earth metal chloride while being subjected to alternating current at 15 to 36 Hz frequency.

Growing community of inventors

Pownal, VT, United States of America

Clinton E Hutchins