Cathode in a layered circuit and electrochemical cell for measurement of oxygen in fluids

• US 5,611,902 A
• Filed: 12/13/1994
• Issued: 03/18/1997
• Est. Priority Date: 12/10/1990
• Status: Expired due to Fees

• Current Assignee: Radiometer California, Inc.
• Original Assignee: PPG Industries Incorporated (Nouryon BV)
• Inventors: Graves, Jeffery A., Leader, Matthew J.
• Primary Examiner(s): TUNG, TA HSUNG
• Application Number:
  US08/355,423
• Time in Patent Office: 826 Days
• Field of Search: 204/400, 204/412, 204/415, 204/414, 204/429, 204/431
• US Class Current: 204/431
• CPC Class Codes: G01N 27/404 Cells with anode, cathode and cell electrolyte on the same side of a permeable membrane which separates them from the sample fluid , e.g. Clark-type oxygen sensors

Abstract

The electrode of the present invention has metallic surface within a laser produced opening where the metallic surface extends into an electronic metallic conductive pathway and the pathway is covered for electric insulation by an encapsulant layer. The encapsulant layer around the metallic surface has the opening to allow the exposure of the metallic surface from the encapsulant layer. The metallic pathway and encapsulant are resident on a substrate, and are produced from layered circuitry. The electrochemical cell has the aforementioned electrode juxtaposed to another electrode. This electrode is part of the patterned metallic layer that is produced by layered circuitry. The electrode extends into an electronic metallic conductive pathway that is spaced apart and electronically insulated from the other pathway. The insulation can be supplied by a covering of encapsulant material that covers the pathway except does not cover the second electrode. The encapsulant would not cover the second electrode by virtue of its removal by laser and/or masking during production of the layered circuitry. Both of the electrodes are covered with an oxygen permeable fluid electrolyte that provides ionic contact between the two electrodes. The electrodes and electrolyte are covered with one or more oxygen permeable membranes, and these along with the metallic conductive pathways are resident on a substrate. The cell is useful in detecting oxygen in fluids when a negative potential is applied to the laser-produced electrode relative to the other electrode through the pathways that are in contact with leads for external electrical contact from the substrate.

Claims

1. In a sensing device for measuring PO₂ in a fluid, the improvement comprising an electrode assembly for PO₂, wherein the electrode assembly is part of a printed wiring board and wherein the electrode assembly, comprises:

a nonconducting substrate,

at least one thick film metallic layer overlying the said nonconducting substrate in a pattern to provide distinct cathode and anode and conductive pathways to both electrodes where the pathways are electrically isolated from each other and where each is capable of eventual external electrical connection from the electrode assembly and where the anode has a semi-circular shape for uniform current density between the anode and cathode electrodes,

an encapsulant layer overlying that portion of said metallic layer other than the anode to electrically isolate the conductive pathway to the anode from the conductive pathway to the cathode in the metallic layer and having at least one laser-produced finite-sided opening with a bottom, where at least a portion of the walls of said opening are formed by the encapsulant layer, and where the opening exposes in addition to the portion of the walls of the opening that is comprised of the encapsulant layer, the remaining portion of the walls that is comprised of the metallic layer, and wherein the bottom of the opening is comprised of the metallic layer, so that the metallic portion of the walls and of the bottom act as the cathode, and where the opening is capable of ionic contact and where the cathode has a diameter between 0.001 and 0.0015±

0.0003 inches, and where the ratio of the surface area of the anode to the surface area of the cathode is between 50 to 1 and 300 to 1; and

an electrolyte present in the electrode assembly to provide ionic contact with the cathode and the adjacent anode for electrical ionic relationship between the cathode and anode.

2. The sensing device of claim 1 wherein the anode with the semi-circular shape is equidistant from the cathode opening at every point along the semicircle.

3. The sensing device of claim 1 wherein the electrolyte is selected from the group consisting of a gel and liquid and when a liquid there is a membrane covering the electrolyte.

4. The sensing device of claim 1 wherein cathode and anode are placed in the electrode assembly to have a distance from the center of the cathode to the edge of the anode in the range of around 0.013 to 0.015 of an inch.

5. In a sensing device for measuring PO₂ in a fluid, the improvement comprising an electrode assembly for PO₂, wherein the electrode assembly is part of a printed wiring board and wherein the electrode assembly, comprises:

a nonconducting substrate,

at least one thick film metallic layer overlying the said nonconducting substrate in a pattern to provide distinct cathode and anode and conductive pathways to both electrodes where the pathways are electrically isolated from each other and where each is capable of eventual external electrical connection from the electrode assembly and where the anode has a semi-circular shape for uniform current density between the anode and cathode electrodes,

an encapsulant layer overlying that portion of said metallic layer other than the anode to electrically isolate the conductive pathway to the anode from the conductive pathway to the cathode in the metallic layer and having at least one laser-produced finite-sided opening with a bottom, where at least a portion of the walls of said opening are formed by the encapsulant layer, and where the opening exposes in addition to the portion of the walls comprised of the encapsulant layer, the remaining portion of the walls comprised of the metallic layer, and wherein the bottom of the opening is at the nonconducting base so that the metallic portion of the walls forms an annular metallic portion of the walls that acts as the cathode, and where the opening is capable of ionic contact and where the cathode has a diameter between 0.001 and 0.0015±

0.0003 inches, and where the ratio of the surface area of the anode to the surface area of the cathode is between 50 to 1 and 300 to 1; and

an electrolyte present in the electrode assembly to provide ionic contact with the cathode and the adjacent anode for electrical ionic relationship between the cathode and anode.

6. The sensing device of claim 5 wherein the anode with the semi-circular shape is equidistant from the cathode opening at every point along the semicircle.

7. The sensing device of claim 5 wherein the electrolyte is selected from the group consisting of a gel and liquid and when a liquid there is a membrane covering the electrolyte.

8. The sensing device of claim 5 wherein cathode and anode are placed in the electrode assembly to have a distance from the center of the cathode to the edge of the anode in the range of around 0.013 to 0.015 of an inch.