Method of making an electrical thick-film, free-standing, self-supporting structure, particularly for sensors used with internal combustion engines

Claim 2

Method of making a self-supporting, free-standing membrane (3) over a substrate (1) while leaving a space (8) between said membrane and substrate to construct an article including a substrate (1) comprising at least one of the materials of the group consisting of: ceramic; glass; enameled metal; a self-supporting, free-standing membrane (3) comprising at least one of the materials of the group consisting of: glass ceramic; crystallized glass; said free-standing membrane being positioned on the substrate in areal form and bonded to the substrate, essentially throughout its marginal extent, leaving open a window, comprising the steps of providing the substrate (1) of high-temperature-resistant material; applying a removable filler (2) in paste form over the substrate and having at least approximately the shape of the space (8) to be formed under the self-supporting, free-standing membrane; applying, by thick-film technology, a cover layer (3) in form of a paste which includes as active components thick-film glass ceramic or thick-film crystallizing glass and covering a first portion of said removable filler while leaving the remaining portion thereof uncovered, which uncovered portion will form the window, and further covering directly a surface portion of the substrate adjacent said filler to for a subassembly; solidifying the thick-film cover layer by subjecting said subassembly to a first firing process in a protective gas atmosphere to thereby form a membrane-like cover by solidifying the thick-film cover layer over the filler; and then removing said filler; said membrane being formed as the solidified free-standing cover layer applied over the then removed filler, secured to the substrate and overlying a portion thereof, leaving the space (8) defining a chamber between the free-standing membrane and the substrate, said uncovered portion providing an access opening in form of the window to said space (8) after removal of the filler paste.

Claim 3

Method according to claim 1, wherein the filler comprises a material which, when exposed to high temperature, becomes volatile or gasifies or vaporizes; and wherein the step of removing the filler comprises heating the subassembly, after solidification of the thick-film paste, to render volatile, gasify, or vaporize the material forming said filler.

Claim 4

Method according to claim 2, wherein said heating step comprises combusting the material forming said filler by heating said subassembly in an oxidizing atmosphere to remove the material of said filler.

Claim 5

Method according to claim 2, wherein said step of solidifying the thick film comprises heating in an atmosphere of nitrogen.

Claim 6

Method according to claim 4, wherein said step of heating in a nitrogen atmosphere further comprises the step of firing said subassembly at a temperature below about 500° C. while maintaining a minor proportion of oxygen and forcing flow of said oxygen containing atmosphere with respect to said subassembly.

Claim 7

Method according to claim 2, wherein the step of solidifying said thick film comprises solidifying said thick film under conditions to form said thick film into a porous layer structure; and the step of heating the subassembly, after said solidification of the layer to the porous layer structure, comprises heating said filler to an extent to permit the volatile, gasified or vaporized materials thereof to escape through the pores of said solidified thick-film cover layer forming the membrane.

Claim 8

Method according to claim 1, wherein the filler comprises a material which is subject to removal by etching; and the step of removing said filler comprises exposing said substrate and solidified thick-film layer to an etching bath to remove said filler.

Claim 9

Method according to claim 7, wherein said filler consists essentially of copper, or copper paste.

Claim 10

Method according to claim 1, further including the step of applying a metal surface (6) to the substrate before applying the filler thereover.

Claim 11

Method according to claim 9, wherein said step of applying the metal surface comprises at least one of the steps: vapor deposition; printing; adhesion; bonding.

Claim 12

Method according to claim 1, further including the step of applying an electrically conductive or resistance layer (5) over the filler (2) and then applying, by thick-film technology, said thick-film layer (3) thereover whereby, upon removal of the filler, said electrically conductive or resistance layer (5) will bond to the thick-film layer.

Claim 13

Method according to claim 1, further comprising the step of applying an electrically conductive path or resistance layer on the thick-film layer (3) after the thick-film layer has been solidified.

Claim 14

Method according to claim 9, wherein the step of applying the removable filler on the substrate comprises applying said paste on the substrate in areal form, with a projecting path (2') leading therefrom; and the step of applying said thick-film layer thereover comprises covering said areal paste of filler while leaving uncovered the portion forming the window (2a) in the region of the projecting path to form the access opening to said space (8) after removal of the filler.

Claim 15

Method according to claim 1, wherein the step of applying said filler comprises applying said filler in areal form and having two opposed sides; and wherein the step of applying said thick-film layer (3) comprises applying said thick-film layer over said filler and on the substrate at only one side thereof to form, after removal of the filler, a cantilever projecting tongue (43) of the thick-film glass-ceramic or crystallized glass structure.

Claim 16

Method according to claim 1, including the step of making the portion to be left uncovered of said paste of removable filler (2) prior to application of said thick-film glass ceramic or crystallizing glass layer to, upon removal of said filler, provide said access opening in the form of the window.

Claim 17

Method according to claim 1, wherein said window is small in relation to the areal extent of the free-standing layer.

Claim 18

Method of making a self-supporting, free-standing membrane (3) over a substrate (1) while leaving a space (8) between said membrane and substrate to construct an article including a substrate (1) comprising at least one of the materials of the group consisting of: ceramic; glass; enameled metal; a self-supporting, free-standing membrane (3) comprising at least one of the materials of the group consisting of: glass ceramic; crystallized glass; said free-standing membrane being positioned over the substrate in areal form and bonded to the substrate essentially throughout its marginal extent, comprising the steps of providing the substrate (1) of high-temperature resistant material; applying a combustible filler (2) in paste form over the substrate and having at least approximately the shape of the space (8) to be formed under the self-supporting, free-standing membrane; applying, by thick-film technology, a cover layer (3) in form of a paste which includes as active components thick-film glass ceramic or thick-film crystallizing glass which, upon firing, results in a porous structure, said cover layer covering said removable filler and covering directly a surface portion of the substrate adjacent said filler to form a subassembly; solidifying the thick-film cover layer by subjecting said subassembly to a first firing process in a protective gas atmosphere to thereby form a gas-pervious, porous membrane-like cover by solidifying the thick-film cover layer over the filler; and then removing said filler by combustion of the material of the filler comprising the step of heating said subassembly in an oxidizing atmosphere and permitting combustion residues arising upon combustion of the filler material to escape to escape through the porous membrane-like cover, said membrane, upon removal of said filler, being formed as the solidified free-standing cover layer applied over the then removed filler, secured to the substrate, and overlying a portion thereof and leaving the space (8) defining a chamber between the free-standing membrane and the substrate.

Claim 19

Method of making a self-supporting, free-standing membrane (3) over a substrate (1) while leaving a space (8) between said membrane and substrate to construct an article including a substrate (1) comprising at least one of the materials of the group consisting of: ceramic; glass; enameled metal; a self-supporting, free-standing membrane (3) comprising at least one of the materials of the group consisting of: glass ceramic; crystallized glass; said free-standing membrane being positioned over the substrate in areal form and bonded to the substrate essentially throughout its marginal extent, comprising the steps of providing the substrate (1) of high-temperature resistant material; applying a combustible filler (2) in paste form over the substrate and having at least approximately the shape of the space (8) to be formed under the self-supporting, free-standing membrane; applying, by thick-film technology, a cover layer (3) in form of a paste which includes as active components thick-film glass ceramic or thick-film crystallizing glass which, upon firing, results in a porous structure, said cover layer covering said removable filler and covering directly a surface portion of the substrate adjacent said filler to form a subassembly; solidifying the thick-film cover layer by subjecting said subassembly to a first firing process in a protective gas atmosphere to thereby form a gas-pervious, porous membrane-like cover by solidifying the thick-film cover layer over the filler; and then removing said filler by combustion of the material of the filler comprising the step of heating said subassembly in an oxidizing atmosphere and permitting combustion residues arising upon combustion of the filler material to escape to escape through the porous membrane-like cover, said membrane, upon removal of said filler, being formed as the solidified free-standing cover layer applied over the then removed filler, secured to the substrate, and overlying a portion thereof and leaving the space (8) defining a chamber between the free-standing membrane and the substrate.

Claim 20

Method according to claim 17, wherein said step of solidifying the thick film cover layer comprises heating in an atmosphere of nitrogen.

Claim 21

Method according to claim 17, wherein the step of solidifying said thick-film cover layer comprises solidifying said thick-film cover layer under conditions to form said thick-film cover layer into said porous membrane-like cover, and the step of combusting said filler comprises heating the subassembly, after solidification of the membrane-like cover to not only combust the filler but additionally permit the volatile, gasified or vaporized materials thereof to escape through the pores of said solidified thick-film membrane-like cover.

Claim 22

Method according to claim 17, further including the step of applying a metal surface (6) to the substrate before applying the filler thereover.

Claim 23

Method according to claim 17, further including the step of applying an electrically conductive or resistance layer (5) over the filler (2) and then applying, by thick-film technology, said thick-film layer (3) thereover whereby, upon combusting the filler, said electrically conductive or resistance layer (5) will bond to the thick-film layer.