Thomson-csf

Francois Buchy

Michel Graciet

Mieczyslaw Hildebrandt

Pierre Merenda

Eliane Charles

Jacques Cadier

Jean Pierre D'Haenens

Annick Romann

The invention relates to a process for the manufacture of non-linear resistors (varistors) from thick-layer ceramic material, in particular on a hybrid circuit substrate, or any other device requiring that a predetermined temperature should not be exceeded during its manufacture. According to the invention, after crushing a ceramic material in order to obtain a very fine powder of varistor material, a powder is produced of conductive or semiconductive material able to assume the pasty state at a temperature lower than 850.degree. C. and a binder is incorporated therein to obtain a screen printing paste. The layer deposited by screen printing on a substrate such as glass, is dried and then heat treated so as to assure cohesion of the layer. This layer is either inserted between a previously deposited electrode and another electrode, or covered by two separate electrodes. The invention is particularly applicable to matrix access display screens.

Process for the manufacture of thick layer varistors on a hybrid circuit

A mixture of oxides or salts of barium, titanium and tin (principal materials) are initially ground with two different classes of dopants. The first class consists of oxides or salts of rare earths or of elements such as antimony. The second class consists of oxides or salts of elements such as manganese or copper. After calcining and sintering, cooling of the ceramic body is obtained by adjusting to a very low rate (negative gradient of 10 to 30.degree. C. per hour) in a pure oxygen atmosphere. The material is primarily suited for use in capacitors having one or a number of layers which may be separated by electrodes inserted prior to sintering. The material has high apparent permittivity and can be employed at much higher voltages than in barrier-layer capacitors.

Method of fabrication of dielectric material having volume-distributed

The device makes use of a simple and inexpensive mechanism for temperature stabilization of one or a number of points of an electric circuit such as the free ends of the bimetallic conductors of a thermocouple, or a connector designed to receive one or a number of pins connected to an electric circuit. A good thermal contact is established between the point to be temperature-controlled and a positive-temperature-coefficient resistor which may be surrounded by a second resistor of the same type. The resistors are supplied at constant voltage. One example of the connector consists of a metallic casing surrounding a resistor in the form of a cylindrical sleeve placed around a second resistor in the form of a cylindrical sleeve in which one or a number of jacks are embedded in heat-conducting material.

Self-regulated device for temperature stabilization of at least one

A device possessing three conduction states comprises two electrodes connected with one another through the agency of a compound in the form C.sub.x H.sub.y in which there are held in suspension particles of vanadium oxide, VO.sub.2, the proportion by volume being of the order of 7%.

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Paris, France

Francois Buchy