Process for the manufacture of small heat-generating printed circuits

Claim 2

A PROCESS OF MANUFACTURING SMALL PRINTED CIRUITS FOR THE GENERATION OF HEAT, COMPRISING THE STEPS OF DESPOSITING A CERAMIC DIELECTRIC COATING ON A METAL SUBSTRATE, ALLOWING THE CERAMIC-COATED SUBSTRATE TO STAND AT ROOM TEMPERATURE FOR A PERIOD LONG ENOUGH FOR ANY DEFECTS IN SAID CERAMIC COATING TO BECOME EVIDENT, DEGREASING SAID CERAMIC COATING, DEPOSITING FROM A METAL-SPRAY GUN AN ADHERENT CONDUCTIVE COATING OF A METAL CHOSEN FROM THE GROUP CONSISTING OF ALUMINUM, ZINC AND COPPER MIXED WITH THE OXIDE OF SAID CHOSEN METAL ON SAID CERAMIC COATING, SAID CERAMIC-COATED SUBSTRATE HAVING BEEN PREHEATED TO A TEMPERATURE SUFFICIENT TO PROVIDE GOOD ADHESION THERETO OF SAID SPRAYED CONDUCTIVE COATINGS, SAID ADHERENT CONDUCTIVE COATING HAVING A RESISTIVITY MUCH HIGHER THAN THAT OF THE METAL ALONE AS THE RESULT OF INCLUSION OF THE METAL OXIDE THEREIN, DEPOSITING A RESIST ON SAID ADHERENT CONDUCTIVE COATING AND SHAPING SAID CONDUCTIVE COATING INTO A DESIRED FORM BY ETCHING.

Claim 3

The process as defined in claim 1, wherein said metallic plate is of iron containing not more than 0.04%C.

Claim 4

The process as defined in claim 1, wherein said adherent conductive coating is deposited from a metal-spray gun in the form of molten droplets each coating with a thin film of metal oxide, said coated droplets being formed by spraying pure molten metal droplets through an oxidizing atmosphere onto said coated substrate, said droplets breaking, spattering and solidifying on deposition.

Claim 5

The process as defined in claim 3, wherein the forming of said mixed adherent conductive coating layer is subdivided into the steps of depositing a thin film of mixed metal and metal oxide from a metalspray gun, allowing said film to cool, and depositing at least one more of such films, allowing each film to cool before adding any succeeding film.

Claim 6

The process as defined in claim 1, wherein said substrate and degreased ceramic coating, plus one or more films of mixed metal and oxide, is heated to a temperature just below that at which said ceramic coating softens or becomes pasty immediately prior to depositing a subsequent film.

Claim 7

The process as defined in claim 1, wherein the thickness of said adherent conductive coating is up to 35 microns, the thickness being selected on the basis of the desired resistivity of said coating.

Claim 8

The process as defined in claim 1, wherein said ceramic coating is applied in the form of at least two successive deposits with firing following each deposition, thereby decreasing the probability of a continuous flaw in the ceramic coating reacching from the outer surface to the metal substrate.

Claim 9

The process as defined in claim 1, wherein said metal is aluminum and said metal oxide is aluminum oxide.

Claim 10

A SMALL PRINTING CIRCUIT SUITABLE FOR THE GENERATION OF HEAT, COMPRISING A METAL SUBSTRATE, A PLURALITY OF INDIVIDUALLY FIRED CERAMIC COATINGS ON SAID METAL SUBSTRATE, SAID CERAMIC COATINGS BEING FREE OF SCALING, CRACKS AND OTHER VISIBLE DEFECTS, AND AN ADHERENT, SHAPED COATING OF A FLAME SPRAYED METAL CONTAINING INCLUSIONS OF ITS OXIDE IN SUFFICIENT QUANTITY SO THAT THE RESISTIVITY OF SAID SHAPED COATING MAKES SAID CIRCUIT SUITABLE FOR USE AT VOLTAGES AS HIGH AS 220 VOLTS, SAID METAL BEING SELECTED FROM THE GROUP CONSISTING OF ALUMINUM, ZINC AND COPPER.

Claim 11

A SMALL PRINTING CIRCUIT SUITABLE FOR THE GENERATION OF HEAT, COMPRISING A METAL SUBSTRATE, A PLURALITY OF INDIVIDUALLY FIRED CERAMIC COATINGS ON SAID METAL SUBSTRATE, SAID CERAMIC COATINGS BEING FREE OF SCALING, CRACKS AND OTHER VISIBLE DEFECTS, AND AN ADHERENT, SHAPED COATING OF A FLAME SPRAYED METAL CONTAINING INCLUSIONS OF ITS OXIDE IN SUFFICIENT QUANTITY SO THAT THE RESISTIVITY OF SAID SHAPED COATING MAKES SAID CIRCUIT SUITABLE FOR USE AT VOLTAGES AS HIGH AS 220 VOLTS, SAID METAL BEING SELECTED FROM THE GROUP CONSISTING OF ALUMINUM, ZINC AND COPPER.

Claim 12

The process as defined in claim 3 wherein said droplets have a diameter of about 8 microns.

Claim 13

A process of manufacturing small printed circuits for the generation of heat, comprising the steps of firing and coating a plurality of ceramic coatings on an iron substrate containing not more that 0.04% of carbon, allowing said coated substrate to stand at room temperature for several days to permit any flaws on said ceramic coatings to become evident, cleaning and degreasing said coated substrate, heating said ceramic-coated substrate to a temperature sufficiently high to provide good adhesion between a sprayed-on metal film and said coated substrate, spraying said heated ceramic-coated substrate with molten droplets of a metal coated with its oxide by means of a metal-spray gun with an oxidizing flame in an oxidizing atmosphere, said metal being selected from the group consisting of aluminum, copper and tin, said droplets on striking said coated substrate spattering and solidifying to form a film including metal oxide dispersed therein, allowing said film to cool to room temperature, repeating the metal-spraying and cooling to form a succession of metal layers until the deposit of metal including metal oxide reaches a desired thickness, and shaping said metal-metal oxide deposit into a desired pattern.

Claim 14

A process of manufacturing small printed circuits for the generation of heat, comprising the steps of firing and coating a plurality of ceramic coatings on an iron substrate containing not more that 0.04% of carbon, allowing said coated substrate to stand at room temperature for several days to permit any flaws on said ceramic coatings to become evident, cleaning and degreasing said coated substrate, heating said ceramic-coated substrate to a temperature sufficiently high to provide good adhesion between a sprayed-on metal film and said coated substrate, spraying said heated ceramic-coated substrate with molten droplets of a metal coated with its oxide by means of a metal-spray gun with an oxidizing flame in an oxidizing atmosphere, said metal being selected from the group consisting of aluminum, copper and tin, said droplets on striking said coated substrate spattering and solidifying to form a film including metal oxide dispersed therein, allowing said film to cool to room temperature, repeating the metal-spraying and cooling to form a succession of metal layers until the deposit of metal including metal oxide reaches a desired thickness, and shaping said metal-metal oxide deposit into a desired pattern.