JPH0216444A - Lead providing method for gas concentration sensor - Google Patents

Abstract

PURPOSE:To easily obtain uniform leads made of conductive metal powder by sticking a composite tape 30 formed by mixing a prescribed amount of conductive metal powder uniformly with an organic binder on a prescribed surface and baking the tape. CONSTITUTION:A metallic green sheet which has an adhesive layer 31, a conductive metal powder layer 32 which is provided on one surface of the layer 31 and solidified with the organic binder, and a separator 33 provided on the opposite surface of the adhesive layer 31 is cut to 1-2mm width equal to the line width of a lead 9 to obtain a tape. The separator 33 stuck on the composite tape 30 for lead formation is peeled off and the surface of the adhesive layer 31 is stuck at a prescribed position on the bottom surface and flank of the cap 5 of the element 1 of the gas concentration sensor which uses the solid electrolyte. Then the composite tape 30 is baked to remove the organic binder completely, thereby obtaining the lead 9.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a gas concentration sensor using a solid electrolyte as an ion conductor, in which a porous electrode attached to the ion conductor is electrically connected to a sensor element. Concerning how to give leads for external extraction.

[Prior Art] Gas concentration sensors using solid electrolytes, such as zirconia concentration oxygen sensors using stabilized zirconium oxide as an ion conductor, have been known for some time. An example of this will be explained with reference to FIG. 4. 4G is a sensor element, 41 and 42 are lead legs electrically connected to the anode and cathode of the sensor element 40, respectively, and 43 is a heater of the sensor element 40. The electrically connected lead legs 44 are the lead legs 41, 42.
43 is electrically insulated from each other and supported by passing through the sensor element 40 in a sealed manner; 45 is a mesh cover;
The stem 44 is supported by the sensor element 40 to prevent heat from being dissipated to the outside by the heater of the sensor element 40.
It also protects the sensor element 40 from external mechanical influences.

Now, by applying a constant voltage V to the anode and cathode of the sensor element 4o through the lead legs 41 and 42 by the constant voltage source 46, and measuring the current value A known as the limiting current, the current can be determined. The oxygen concentration can be determined in proportion to the value A.

In such a device, one conventional example of lead extraction from the cathode of the sensor element 4o is as follows:
This will be explained with reference to FIGS. 1 and 2. 1 is a sensor element, 2 is an ion conductive plate made of a solid electrolyte such as stabilized zirconium oxide, 3.4 is a porous electrode made of platinum, for example, formed on both sides of the ion conductive plate 2, and 5 is
A cap is sealed and fixed to one side of the ion conductive plate 2 with a sealing material 8 covering it, and this is provided with a diffusion hole 6 and a recess 7 for forming an internal chamber, and the diffusion hole 6 is provided with a recess 7 for forming an internal chamber. Hole 6
is communicated from the outside of the sensor element l to the internal chamber constituted by the recess 7, and at least a part of the bottom surface of the cap 5 excluding the recess 7 overlaps a part of the electrode 4. ing. Reference numeral 9 is a lead for electrically taking out the electrode 4 to the outside, and is formed continuously from the bottom surface portion of the cap 5 overlapping the electrode 4 to the outer surface. Note that 10 is a heater provided on the upper surface of the cap 5 of the sensor element l.

Conventionally, the leads 9 have been formed by screen printing platinum paste to a width of 1 to 2 cm or by applying it with a brush.

[Problems to be Solved by the Invention] When such a conventional lead applying method is used, the workability is poor due to manual work, and uneven coating due to insufficient stirring of the paste, uneven coating due to density of brush coating, etc. This tends to cause uneven coating width. As a result, if the electrical resistance of the lead increases, the voltage applied between the electrodes 3 and 4 from the constant voltage source will drop due to the resistance of the lead and become below the predetermined voltage, causing an error in the measured concentration. , narrowing the measurable concentration range.

[Means for Solving the Problems] The present invention uses conventional screen printing,
This method eliminates manual work such as brush painting and forms leads using a lead-forming composite tape that has a conductive metal powder layer hardened with an organic binder on one side of a pre-prepared adhesive layer. porous electrodes are formed on both sides of an ion conductive plate made of In the gas concentration sensor, a lead-forming composite tape having a conductive metal powder layer hardened with an organic binder on one side of an adhesive layer is continuously disposed from a portion of the bottom surface of the cap that overlaps with the electrode to the outer surface. The surface of the adhesive layer is attached to the bottom and outer surfaces of the cap, and then the organic binder is removed by firing, thereby forming leads on the surface of the cap to electrically take out the electrodes to the outside. The present invention is characterized by a method for attaching leads to a gas concentration sensor.

[Function] In order to form leads, this invention uses a composite tape for lead formation that has a conductive metal powder layer hardened with an organic binder on one side of an adhesive layer, but since this tape is made in advance, , the amount of conductive metal powder mixed in the organic binder can be set to a predetermined value, and it can be mixed uniformly, so that a tape in which a predetermined amount of conductive metal powder is uniformly mixed can be obtained. It is attached to the surface of the cap.

[Example] An embodiment of the invention will be described with reference to the drawings.

First, an embodiment of the lead-forming composite tape used in the present invention will be described with reference to FIG. 3. The composite tape 30 consists of an adhesive layer 31 and a conductive metal powder layer 32 provided on one side of the adhesive layer 31 and hardened with an organic binder.For example, the composite tape 30 is made of an acrylic organic binder mixed with platinum powder and hardened into a layer.

33 is a separator provided on the surface of the adhesive layer 31 opposite to the surface on which the conductive metal powder layer 32 is provided.

The sheet having the conductive metal powder layer 32 to which the separator 33 is attached is called a metal green sheet.
2 ■Cut to width and use as tape.

FIGS. 1 and 2 show an embodiment of the sensor element l used to carry out the method of the present invention and the cap 5 used therein, and their structure is similar to that of the conventional example. Although it is omitted here as it has been described above, a method of applying leads according to the present invention to the positions indicated by leads 9 continuously on the bottom surface and the outer surface of the cap 5 will be described below.

First, the separator 33 attached to the lead forming composite tape 30 shown in FIG. 3 is attached to the adhesive layer 3! The adhesive layer 31 of the composite tape 3G is applied to a predetermined position over the bottom and outer surfaces of the cap 5 shown in FIGS. 1 and 2. Thereafter, the bonded composite tape 30 is fired at, for example, 500'O to completely remove the organic binder. In this way, a lead 9 made only of conductive metal powder formed on the bottom and outer surfaces of the cap 5 is obtained.

[Effects of the Invention] According to the method of the present invention, a prefabricated composite tape 30 to which a separator 33 is attached in order to provide leads 9
is used, it is possible to uniformly mix a predetermined amount of conductive metal powder into the organic binder of the composite tape 30 and easily obtain a uniform thickness. If the organic binder is removed by firing the lead 9, the lead 9 will be made of only conductive metal powder and will have a predetermined thickness with no shading of coating and no large or small line width. can be easily obtained.

[Brief explanation of the drawing]

FIG. 1 is a side sectional view of a sensor element made using the method of the present invention, FIG. 2 is a bottom view of the cap in FIG. 1, and FIG. 3 is a lead formation used in the method of the present invention. FIG. 4 is a side sectional view of a composite tape with a separator attached thereto, and FIG. 4 is a side sectional view including a circuit diagram of a zirconia concentration type oxygen sensor to which the present invention is applied. 1: Sensor element, 2: Ion conductive plate, 3.4: Porous electrode, 5: Cap, 6: Diffusion hole, 7: Recess, 8:
Sealing material, 9: Lead, 10: Heater, 30: Composite tape for lead formation, 3! : adhesive layer, 32: conductive metal powder layer, 33: separator, 4D: sensor element, 41
．． 42.43: Sensor foot, 44: Stem, 45: Mesh force bar, 46: Constant voltage source.

Claims (1)

[Claims] Porous electrodes are formed on both sides of an ion conductive plate made of a solid electrolyte, and a cap having gas diffusion holes and an internal chamber is placed on one side of the plate so that at least a part of the bottom surface overlaps a part of the electrode. a composite tape for lead formation, which has a conductive metal powder layer hardened with an organic binder on one side of an adhesive layer, which extends continuously from the portion overlapping the electrode on the bottom surface of the cap to the outer surface; by attaching the adhesive layer with the surface of the adhesive layer facing the bottom and outer surface of the cap, and then baking and removing the organic binder to provide a lead on the cap surface for electrically taking out the electrode to the outside. A method for attaching leads to a gas concentration sensor, characterized by: