JPH06109682A - Manufacture of gas sensor and gas sensor manufactured by method thereof - Google Patents

Abstract

PURPOSE: To obtain a gas sensor in which a substrate and a gas detecting layer are firmly coupled with each other by heattreating a buffer layer provided on the surface of a substrate and successively heat-treating the gas detecting layer, a pair of electrodes, and a catalytic layer after they are successively provided on the buffer layer. CONSTITUTION: After a buffer layer 20 is provided on the surface of a substrate 10 by a spin coating method using a metal-organic solution, the layer 20 is heat-treated at a temperature between about 650 deg.C and 1,000 deg.C. Then, after a gas detecting layer 30 is provided on the surface of the buffer layer 20 by a spin coating method using a metalorganic solution, the layer 30 is heat-treated at a temperature between about 400 deg.C and 600 deg.C. In addition, after a pair of electrodes 41 and 42 are screen-printed on the surface of the layer 30 by using conductive paste, the electrodes 41 and 42 are heat-treated at a temperature between about 400'C and 600'C. Moreover, after a catalytic layer 50 is provided on the surface of the layer 30 by a spin coating method using the metal-organic solution, the layer 50 is heat- treated at a temperature between 400 deg.C and 600 deg.C. The electrodes 41 and 32 are positioned to the facing end sections of the substrate 10 and connect a gas sensor l to other electric parts. A plurality of heaters 60 is provided on the rear surface of the substrate 10 and covered with glass 70.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas sensor manufacturing method and a gas sensor manufactured by the method.

[0002]

2. Description of the Related Art A gas sensor is a device which utilizes the change in resistance value of gas molecules attached to the gas sensor. Materials for manufacturing gas sensors include tin oxide (SnO ₂ ), zinc oxide (ZnO), tungsten oxide (WO ₃ ), iron oxide (Fe ₂ O ₃ ), and indium oxide (In ₂ O ₃ ). Solid metal oxides are included. Elements such as palladium (Pd), platinum (Pt), nickel (Ni), antimony (Sb) and rare earth metal elements are added to the above materials in order to improve the detection sensitivity to those gases. Such gas sensors can be used to detect the presence of gases such as alcoholic odorants, hydrogen, petrochemicals and carbon monoxide.

Conventionally, the manufacture of this gas sensor has been
Three different methods were known. That is, the sintering method, the thick film method, and the thin film method.

The above gas sensor is generally required to be porous and have a wide gas detection area. Therefore, if the sintering method is adopted, the manufacturing process must be carefully monitored so that the gas sensor is not excessively sintered and the quality is deteriorated. However, in such a case, the bond strength between the molecules that detect the gas is lowered, and the gas sensor is easily broken. Further, compared with the thick film method and the thin film method which utilize the technique for manufacturing integrated circuits, the sintering method has a drawback that it is difficult to adapt to automation or consumes a large amount of material. Therefore, in the sintering method, the unit price for manufacturing the gas sensor is high, and it is not suitable for mass production.

In the thick film method, the heat treatment is 400 to 600 ° C.
This is possible only in the low temperature range of 1 hour and within a short time of 1 hour or less, and the mechanical strength of the obtained gas sensor is insufficient.

The thin film method has an advantage that the obtained gas sensor has high sensitivity, but requires a very expensive apparatus for thin film coating.

On the other hand, in Japanese Patent Application No. 63-233358, a screen printing technique is used to print an electrode using an electrically conductive alloy of platinum and tungsten on an insulating substrate, and then to print a metal on the electrode. Disclosed is a method for manufacturing a gas sensor, which comprises printing a gas detection layer using a paste composed of an organic compound and a binder and heat-treating these printed layers.

In the above method, electrodes made of a conductive alloy are printed before forming the gas sensing layer. As a result, in order to prevent the oxidation of the electrode, the heat treatment for the gas detection layer is performed at a low temperature range of 400 to 600 ° C.
It must be done within a short time, no more than an hour. Due to this limitation, the bond between the gas detection layer and the substrate is weakened, and the gas detection layer is easily separated from the substrate.

Further, in the above method, since the technique of screen printing is used, the gas detection layer cannot be made extremely thin, and the cost is high, but it is not qualitatively satisfactory. .

In addition, the production of the paste for forming the gas detection layer is a labor-intensive and time-consuming operation as a whole, and a skilled engineer is required to produce the gas sensor.

[Tin Oxide Gas Sensing Microsensors f
rom Mettalo-Organic Deposited (MOD) Thin Films "(Micheli et al, Ceramic Engineering and S
cience Proceedings, pp. 1095-1105 (1987), discloses an alternative method of making a gas sensor with a composite thin film heater formed on a supported thin film. However, even in this method, the heat treatment for the element for detecting the gas is limited to a low temperature range of 400 to 600 ° C. Therefore, the bond between the gas sensing layer and the substrate is
After all it becomes weak. In addition, this method uses integrated circuit technology, which requires expensive equipment.
In addition, the complicated manufacturing process requires a highly skilled technician, and the cost is very high.

[0012] The main object of the present invention is to provide a method for manufacturing a gas sensor which can solve the above-mentioned problems of the prior art.

[0013]

In order to achieve the above object, the present invention provides: (a) providing a buffer layer on the surface of a substrate by a spin coating method using a metal-organic solution, and then applying the buffer layer After heat treatment at a temperature of 650 to 1000 ° C., and (b) providing a gas detection layer on the surface of the buffer layer by a spin coating method using a metal-organic solution, the gas detection layer is about 65
Heat treatment is performed at a temperature of 0 to 1000 ° C., and (c) a pair of electrodes is screen-printed on the surface of the gas detection layer using a conductive paste, and the pair of electrodes is then set to about 400 to 60.
Heat treatment is performed at a temperature of 0 ° C., and (d) a catalyst layer is provided on the surface of the gas detection layer by a spin coating method using a metal-organic solution, and then the catalyst layer is heat treated at a temperature of about 400 to 600 ° C. A method of manufacturing a gas sensor, comprising the steps of:

In order to achieve the above object, the present invention provides
(A) After providing a buffer layer on the surface of the substrate by a spin coating method using a metal-organic solution, the buffer layer is heat-treated at a temperature of about 650 to 1000 ° C., and (b) on the surface of the buffer layer. After providing the first gas detection layer by a spin coating method using a metal-organic solution, the first gas detection layer is applied to about 6
Heat-treating at a temperature of 50 to 1000 ° C., and (c) the first
Screen-printing a pair of electrodes on the surface of the gas detection layer using a gel of an inductive substance, and then heat-treating the pair of electrodes at a temperature of about 400 to 600 ° C. (d) on the surface of the buffer layer. After providing the second gas detection layer by a spin coating method using a metal-organic solution, the second gas detection layer is heat-treated at a temperature of about 400 to 600 ° C., and (e) the second gas is used. After the catalyst layer was provided on the surface of the detection layer by a spin coating method using a metal-organic solution, the catalyst layer was applied to about 4
Provided is a method for manufacturing a gas sensor, which comprises a step of performing heat treatment at a temperature of 00 to 600 ° C.

Further, in order to achieve the above object, the present invention provides:
A substrate, a buffer layer provided on the surface of the substrate, at least one or more gas detection layers arranged on the buffer layer, a pair of electrodes provided on the gas detection layer, and the gas detection device. A gas sensor comprising a catalyst layer provided on the layer.

The present invention will be described in detail below with reference to the drawings.

FIG. 1 shows a gas sensor 1 manufactured by the method of the present invention. The gas sensor 1 of Example 1 has the gas detection layer 30 formed on the surface of the substrate 10. The buffer layer 20 includes the gas detection layer 30 and the substrate 10.
It is arranged between and. The pair of electrodes 41 and 42 is the substrate 1
Are arranged at opposite ends of 0, by which the gas sensor 1 is connected to other electrical components. The catalyst layer 50 is arranged on the gas detection layer 30. A plurality of heaters 60 are disposed on the backside of the substrate 10, which are glass layers 70.
Are covered by. Gas sensor 1 having such a structure
A method for manufacturing the is described below.

(1) Formation of Gas Sensing Layer on Substrate The first step of manufacturing the gas sensor 1 is to add an organic solution such as xylene to, for example, tin 2-ethylhexanoate (Tin 2-et).
hylhexanoate) to produce a metal-organic solution, in which the substrate 10 made of aluminum oxide (Al ₂ O ₃ ) is dipped.

The method for producing the metal-organic solution will be described with reference to a specific example. When tin is used as a metal component, first, 137 g (0.61 mol) of tin chloride (SnCl ₂ .2H) is used. ₂ O) was dissolved in 300 ml of water, and 121.37 g (1.2 mol) of 2-ethylhexanoic acid was neutralized with 75 ml (1.2 mol) of 30% ammonia water, and the solution was adjusted to 20-25. After stirring for 2 minutes and adding the tin chloride aqueous solution and the ammonium salt solution to the neutral solution, the solution is vigorously stirred to
Produce tin ethylhexanoate.

The above manufacturing process can be represented by the following chemical formula.

[Chemical 1]

Next, 20 g of the obtained white gum-like tin salt was added.
It is dissolved in 0 ml of xylene, and the aqueous layer is separated with a separating funnel. After filtering the layer with xylene, the solution was subjected to vacuum distillation at a temperature of about 40 ° C. to remove many xylene molecules and water molecules, and to give a solution of tin 2-ethylhexanoate.

The organic solution in which the substrate 10 is dipped is a photoresist coater (not shown) used for performing a spin coating method.
Put inside. The photoresistor coater spins the solution at an angular velocity of 2000-3000 rpm. Due to the centrifugal force, the metal-organotin contained in the solution becomes the substrate 10
Into the surface of the substrate, thereby forming the buffer layer 20. The metal-organotin-loaded layer is then heat treated,

[Chemical 2] The following structure is formed between the above layers and the substrate 10 made of aluminum oxide. This structure strengthens the bond between the layers and the substrate 10.

Next, the buffer layer 20 is sintered at a temperature of preferably 800 ° C. or higher, for example, for 5 hours or longer. The sintered buffer layer 20 becomes transparent and becomes a solid layer firmly bonded to the substrate 10.

The buffer layer 20 prevents the gas detection layer 30 to be provided later from reacting with the substrate 10. or,
Forming the buffer layer 20 before providing the gas detection layer 30 also means polishing the surface of the substrate 10.

The next step is to produce a mixed solution of metal-organic gold and metal-organotin such that the ratio of gold to tin is, for example, 0.5% by weight. Then, the substrate 10 is dipped in this mixed solution and the spin coating method is performed again, so that the metal-organogold and the metal-organotin contained in the solution enter the buffer layer 20. This layer is then sintered, preferably at a temperature above 800 ° C., to form the gas sensing layer 30.

In the second embodiment, after the electrodes 41 and 42 are formed (manufacturing method will be described later), as shown in FIG. 2, the gas detection layer 30 in which the second gas detection layer 35 is already formed is formed. Provided on top. The solution for providing the second gas detection layer 35 is a mixed solution of metal-organic lanthanum and metal-organotin, and the ratio of lanthanum oxide (La ₂ O ₃ ) to tin oxide (SnO ₂ ) is 10% by weight. It is as follows. The spin coating method is used to provide the gas sensing layer 35, and the second gas sensing layer 35 is then sintered, preferably at a temperature of 600 ° C (not 800 ° C).

The metal-organic solution is tin oxide (SnO ₂ ).
It is not limited to the one using, but in the case of producing a metal-organic solution, from a group containing zinc (Zn), nickel (Ni), iron (Fe), indium (In) or the like instead of tin. Other metal oxides can also be used, depending on the metal selected.

An experiment was conducted to measure the X-ray diffraction pattern of three types of gas sensors having a gas detection layer made of tin oxide, which was manufactured by the method described above.
All the gas sensing layers were heat treated for 2 hours,
The sintering temperature is 800 ° C, 600 ° C, 400 ° C, respectively.
And The X-ray diffraction patterns of A, B and C of FIG. 3 are shown. That is, FIG. 3A shows a product sintered at a temperature of 800 ° C., FIG. 3B shows a product sintered at a temperature of 600 ° C., and FIG.
Indicates the one sintered at a temperature of 400 ° C. As can be clearly seen, the one heat-treated at a temperature of 800 ° C. shows the best crystallinity.

(2) Construction of Electrodes on Gas Detection Layer After the gas detection layer 30 is formed, the electrodes 41 and 42 are arranged on the gas detection layer 30 using a screen printing technique. As a material for forming the electrode, for example, nickel paste, metal-organic gold, metal-organo platinum, or the like, which is inactive and crystallizes at a low sintering temperature (580 to 620 ° C.) is most preferable. preferable. Similar materials are used when making the heater 60 provided on the back surface of the substrate 10. After forming the heater 60, the glass layer 70 is formed thereon.

(3) Constitution of catalyst layer On the gas detection layer 30, a catalyst layer 50 is further provided by, for example, a metal-organo palladium containing 33 wt% palladium and a metal-organic gold solution. Second gas detection layer 3
The spin coating method is also used when the catalyst layer 50 is provided on the substrate 5 using the above solution. The catalyst layer 50 is preferably 6
It is sintered at 00 ° C (a high temperature of 800 ° C is not necessary in this process). The catalyst layer 50 thus formed is a very thin layer of 0.1 μm or less, and has good electrical conductivity.

The metal-organic solution for forming the catalyst layer is a resin acid containing any one of platinum (Pt), gold (Au), palladium (Pd), antimony (Sb), silver (Ag) and the like. A salt solution, an alkoxide, or a metal acetylacetonate can also be selected and used. still,
This catalyst layer prevents the deterioration of the sensitivity of the gas sensor, which is seen at low temperatures.

First manufactured by the method of the present invention described above
Regarding the gas sensor of the above example, the gas detection sensitivity (Ro
/ Rs) was measured. Here, Ro represents the resistance value of the gas sensor when reacting with the gas sample, and Rs represents the resistance value of the gas sensor when no gas is detected. A total of four gas samples were taken from alcohol, hydrogen, carbon monoxide, and carbohydrate, and used for the gas sensor test. The result is shown in FIG. In the figure, the horizontal axis represents the concentration of the gas sample, the vertical axis represents the sensitivity of the gas sensor, and four types of straight lines are drawn by connecting the points corresponding to the four types of gas. As is clear from the figure, the gas sensor manufactured by the method of the present invention has extremely good sensitivity.

The gas sensor of the second embodiment manufactured by the method of the present invention was connected to a power source (not shown) via electrodes 41 and 42, and the sensitivity was tested using an alcoholic odorant. did. The result is shown in FIG.

[0034]

As described above, in the present invention, the layer of the gas detecting material is formed on the substrate by utilizing the spin coating method. This spin coating method uses a centrifugal force to form a thin layer on the substrate, in which the gas sensing material has entered the average. Further, since the gas detection layer in the present invention is provided before forming the electrode, the heat treatment for the gas detection layer can be performed at a temperature of, for example, 800 ° C., and the upper limit of the heat treatment temperature according to the conventional technique is 600 ° C. Therefore, it can be said that it is extremely expensive. As a result, the bond between the gas detection layer and the substrate in the gas sensor manufactured by the method of the present invention becomes extremely strong as compared with the gas sensor manufactured by the conventional method.

The scope of the invention is not limited to the embodiments described above, but rather should be understood by the following claims.

[Brief description of drawings]

FIG. 1 is a sectional view showing an outline of a gas sensor manufactured according to a first embodiment of the present invention.

FIG. 2 is a sectional view schematically showing a gas sensor manufactured according to a second embodiment of the present invention.

FIG. 3 is an X-ray diffraction spectrum measured for a tin oxide gas detection layer formed by a spin coating method.
The spectra in FIGS. 3A, 3B and 3C are for gas sensing layers heat treated at different temperatures.

FIG. 4 is a graph showing detection characteristics for four types of gas samples.

FIG. 5 is a graph showing a response characteristic of a gas sensor manufactured by the method of the present invention to a gas sample.

[Explanation of symbols]

 1 Gas Sensor 10 Substrate 20 Buffer Layer 30 Gas Detection Layer 35 Second Gas Detection Layer 41, 42 Electrode 60 Heater 70 Glass Layer

[Procedure amendment]

[Submission date] September 28, 1993

[Procedure Amendment 2]

[Document name to be corrected] Drawing

[Correction target item name] All drawings

[Correction method] Change

[Correction content]

[Figure 1]

[Fig. 2]

[Figure 4]

[Figure 5]

[Figure 3]

Front Page Continuation (72) Inventor Min-Han Tseng Taiwan, Miaoli, Toufen, Min-Shu Sub-ward, Xinhua Array 20, No. 53 (72) Inventor Pin-Pin Tasai Taiwan, Shin-Zhu, Zhu Dong, Schroed, Rhein 520, Alley 8, Number 15 (72) Inventor Chu-Vong Liao Taiwan, Taipei, Section 1, Dong Hua S. Road, Number 344, 4-1 Floor (72) Inventor James C. H. Ku Taiwan, Taipei, Shin Ten, Zhuang Chen Road, Rain 280, Number 1-6, 5 Floor

Claims (7)

[Claims] 1. (a) After providing a buffer layer on the surface of a substrate by a spin coating method using a metal-organic solution, the buffer layer is heat-treated at a temperature of about 650 to 1000 ° C.,
(B) After providing a gas detection layer on the surface of the buffer layer by a spin coating method using a metal-organic solution, the gas detection layer is heat-treated at a temperature of about 650 to 1000 ° C.,
(C) Screen-printing a pair of electrodes using a conductive paste on the surface of the gas detection layer, and then heat-treating the pair of electrodes at a temperature of about 400 to 600 ° C., (d) of the gas detection layer. After providing a catalyst layer on the surface by a spin coating method using a metal-organic solution, the catalyst layer is applied to about 400
A method of manufacturing a gas sensor, which comprises a step of heat treatment at a temperature of from 600 to 600 ° C. 2. (a) After providing a buffer layer on the surface of a substrate by a spin coating method using a metal-organic solution, the buffer layer is heat-treated at a temperature of about 650 to 1000 ° C.,
(B) After providing a first gas detection layer on the surface of the buffer layer by a spin coating method using a metal-organic solution, the first gas detection layer is heat-treated at a temperature of about 650 to 1000 ° C. , (C) Screen-printing a pair of electrodes using a gel of a conductive material on the surface of the first gas detection layer, and then heat-treating the pair of electrodes at a temperature of about 400 to 600 ° C., (d) A second gas detection layer is provided on the surface of the buffer layer by a spin coating method using a metal-organic solution, and then the second gas detection layer is heat-treated at a temperature of about 400 to 600 ° C. ) A step of providing a catalyst layer on the surface of the second gas detection layer by a spin coating method using a metal-organic solution, and then heat treating the catalyst layer at a temperature of about 400 to 600 ° C. And a method of manufacturing a gas sensor. 3. The gas according to claim 1, wherein in the step (a), the metal contained in the metal-organic solution is selected from the group consisting of tin, zinc, nickel, iron and indium. Sensor manufacturing method. 4. The gas according to claim 1, wherein in the step (d), the metal-organic solution is a resin solution containing any of platinum, gold, palladium, antimony, silver and the like, alkoxide or metal acetylacetonate. Sensor manufacturing method. 5. The gas according to claim 2, wherein in the step (e), the metal-organic solution is a resin solution containing any of platinum, gold, palladium, antimony, silver and the like, alkoxide or metal acetylacetonate. Sensor manufacturing method. 6. A substrate, a buffer layer provided on the surface of the substrate, at least one or more gas detection layers arranged on the buffer layer, and a pair of electrodes provided on the gas detection layer. And a catalyst layer provided on the gas detection layer. 7. The gas sensor according to claim 6, wherein the substrate is formed of aluminum oxide.