JP2017116460A - Porous electrode, manufacturing method for the same, and humidity sensor using porous electrode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a porous electrode the size and formation range of whose penetrating part can be controlled.SOLUTION: An upper electrode 4, consisting of a porous electrode, of a humidity sensor 1 heats over a glass substrate 2 heated base material deposited in the order of a lower electrode 3 and a humidity-sensitive polymeric membrane 5 at an aggregation temperature, and in this heated state subjects low melting point metal LM to physical vapor deposition over the surface of the humidity-sensitive polymeric membrane 5. Then, after the heated base material over which the low melting point metal LM is vapor-deposited to be returned to normal temperature and the electrode material EM is subjected to physical vapor deposition, the low melting point metal LM is obtained by etching this metal alone.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a porous electrode mounted on a gas sensing device that measures, for example, a gas concentration or humidity in an atmosphere in a measurement space, a method for manufacturing the electrode, and a humidity sensor using the porous electrode.

  Conventionally, in an environment where indoor air conditioning management is severely performed such as a clean room or a constant temperature and humidity room installed in a laboratory, a hospital, a semiconductor factory, etc., the gas concentration contained in the atmosphere measured in the measurement space Gas sensing devices that measure temperature (air temperature) and humidity are widely used.

  The humidity sensor provided in this type of gas sensing device is a moisture-sensitive polymer film (for example, a cellulosic compound) serving as a dielectric between a lower electrode and an upper electrode formed on a ceramic or glass substrate. A parallel plate capacitor is formed by sandwiching engineering plastics (engineering plastics) or super engineering plastics (super engineering plastics) made of aromatic compounds, polyvinyl compounds, and aromatic polymers. With the change in the dielectric constant of the moisture-sensitive polymer film The humidity is measured by measuring the changing capacitance.

  The upper electrode is formed with minute cracks (penetrating parts) that allow the moisture contained in the measurement atmosphere to pass through, and the moisture in the atmosphere passes through the crack and is absorbed by the moisture-sensitive polymer film. It has become so.

  In addition, as a method of forming a porous thin film such as the upper electrode, although the type of sensor is different, Patent Document 1 listed below describes at least one of the thin films formed by dispersing two or more different substances. A technique for forming a porous layer by removing one kind of substance is disclosed.

Japanese Patent No. 3928856

  However, the conventional upper electrode is formed, for example, by generating fine cracks by stress caused by depositing a thin film of Au (gold) or Cr (chromium) on the moisture-sensitive polymer film. For this reason, the size and formation range of cracks cannot be accurately controlled, and there is a problem that the yield of products is not stable.

  Further, when the technique disclosed in Patent Document 1 is adopted as a method for producing an upper electrode of a humidity sensor, for example, Cr (chromium) and Cu (copper) described in the document are simultaneously vacuum deposited, It is necessary to heat the resulting moisture-sensitive polymer film to about 400 to 600 ° C.

  However, since engineering plastics and super engineering plastics used for moisture-sensitive polymer films have a heat-resistant temperature of about 200 ° C., if they are heated at a temperature of 400 ° C. or higher as in Patent Document 1, the moisture-sensitive polymer film Since the heat-resistant temperature is exceeded, there is a possibility that the moisture-sensitive polymer film is altered and a problem is caused in product quality.

  Accordingly, the present invention has been made in view of the above problems, and a porous electrode capable of improving the yield of a product while controlling the size and the formation range of the penetrating portion of the electrode portion to some extent, and a method of manufacturing the electrode An object of the present invention is to provide a humidity sensor using the porous electrode.

In order to achieve the above object, the first aspect of the present invention includes a low melting point metal having a melting point lower than that of at least lead and removed by etching,
An electrode material not removed by the etching process;
A substrate to be heated that is heated at an agglomeration temperature at which the low-melting-point metal agglomerates into fine particles;
A porous electrode produced using
Physical vapor deposition of the low melting point metal on the surface of the heated substrate heated at the aggregation temperature,
The electrode material is formed by physical vapor deposition in a state where the substrate to be heated is returned to room temperature,
A porous electrode obtained by etching the substrate to be heated on which both the low melting point metal and the electrode material are deposited to remove only the low melting point metal.

The second aspect of the present invention is a low melting point metal having a melting point lower than that of lead and removed by etching,
An electrode material not removed by the etching process;
A substrate to be heated that is heated at an agglomeration temperature at which the low-melting-point metal agglomerates into fine particles;
A method for producing a porous electrode produced using
Physical vapor deposition of the low melting point metal on the surface of the heated substrate heated at the aggregation temperature,
The electrode material is formed by physical vapor deposition in a state where the substrate to be heated is returned to room temperature,
It is a method for producing a porous electrode, which is obtained by etching the substrate to be heated on which both the low melting point metal and the electrode material are deposited to remove only the low melting point metal.

  Further, according to a third aspect of the present invention, the porous electrode according to the first aspect is used as a first electrode, and the moisture-sensitive polymer film is sandwiched between the first electrode and the second electrode. It is a humidity sensor characterized by having the electrode structure used as the parallel plate type capacitor formed in this way.

  According to the present invention, it is possible to form through holes in the shape of fine particles of a low melting point metal removed by etching treatment in the electrode material, so that the through holes on the electrode surface are not irregular cracks as in the conventional product. It is possible to provide a porous electrode in which the formation range, the diameter of the through hole, and the like can be controlled.

  Further, when this porous electrode is used as an electrode of a humidity sensor, for example, moisture can be appropriately adsorbed to the moisture-sensitive polymer film, and the yield of the product is increased. Furthermore, since the size of the electrode material to be aggregated and the aggregation density on the electrode surface can be controlled, the responsiveness of the sensor can be controlled.

  Further, since a low melting point metal LM having a melting point lower than that of lead (melting point: 327.5 ° C.) is used, the upper limit is a temperature at which the moisture sensitive polymer film 5 does not change when used as an electrode of a humidity sensor. It becomes possible to perform physical vapor deposition at temperature.

It is a schematic sectional drawing of the humidity sensor which employ | adopted the porous electrode which concerns on this invention. (A)-(c) is a schematic diagram which shows the manufacturing process of the upper electrode of the humidity sensor which employ | adopted the porous electrode. It is a schematic sectional drawing which shows the other example of a humidity sensor.

  Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the accompanying drawings. It should be noted that the present invention is not limited by this embodiment, and all other forms, examples, operation techniques, etc. that can be implemented by those skilled in the art based on this form are included in the scope of the present invention. .

  The porous electrode of the present invention is, for example, a gas concentration contained in the atmosphere of a measurement space in an environment with severe indoor air conditioning management such as a clean room or a constant temperature and humidity room installed in a laboratory, a hospital, a semiconductor factory, etc. It is used as an electrode for humidity sensors and oxygen sensors that are mounted on gas sensing devices that measure humidity.

First, the configuration of a humidity sensor using the porous electrode of the present invention will be described.
As shown in FIG. 1, the humidity sensor 1 includes a lower electrode 3, an upper electrode 4, and a moisture-sensitive polymer film 5 on a substrate 2 made of ceramics or glass.

  Further, the lower electrode 3 and the upper electrode 4 are connected to the arithmetic unit 7 via a lead wire 6, respectively. Further, the lower electrode 3, the upper electrode 4, and the moisture-sensitive polymer film 5 have an electrode structure that becomes a parallel plate capacitor.

  Since the humidity sensor 1 of the present embodiment is a capacitance type humidity sensor having the above electrode structure, the change in the capacitance between the electrodes caused by the change in the dielectric constant due to the moisture adsorption to the moisture sensitive polymer film 5 occurs. Based on this, the calculation unit 7 calculates the humidity in the measurement atmosphere.

  The lower electrode 3 (corresponding to the “second electrode” in the claims) is a metal that functions as an electrode such as Ni (nickel), Ta (tantalum), Al (aluminum), or Cr (chromium) on the substrate 2. After forming a film or an alloy, an unnecessary portion is removed by etching to form a desired shape.

  The upper electrode 4 (corresponding to “first electrode” in the claims) is formed on the upper surface of the moisture-sensitive polymer film 5, and the surface has innumerable minute through holes in the measurement atmosphere over the entire electrode surface. It is the porous electrode formed in this.

The upper electrode 4 becomes a porous electrode in which an infinite number of through-holes are formed on the electrode surface by being manufactured along the procedure of the working steps 1 to 3 as shown in FIGS. .
The substrate 2, the lower electrode 3, and the moisture-sensitive polymer film 5 function as a “heated substrate” that is heated to agglomerate the low melting point metal LM into fine particles during physical vapor deposition in step 1. To do. Further, in each drawing shown in FIG. 2, the particle diameter of the low melting point metal LM, the film thickness of the electrode material EM, the moisture sensitive polymer film 5, and the like are expressed in a deformed state.

-Step 1 (low melting point metal deposition process)-
First, the substrate to be heated is heated to a temperature (hereinafter referred to as “aggregation temperature”) at least so that the low-melting point metal LM aggregates to form fine particles and the moisture-sensitive polymer film 5 does not change in quality. The low melting point metal LM is formed on the surface of the substrate (here, the surface of the moisture-sensitive polymer film 5) by physical vapor deposition (not particularly limited as long as vapor deposition is performed while heating the substrate to be heated to the aggregation temperature). .

  The low-melting-point metal LM used in step 1 is a metal or alloy that is at least lower than the melting point of Pb (lead) (327.5 ° C.) and can be removed by an etching process described later. For example, Sn (tin, melting point: 231) 9 ° C) and In (indium, melting point: 156.6 ° C), single metal, solder (for example, Sn (tin) -Ag (silver) -Cu (copper) alloy, melting point: about 180-220 ° C) Such as easy fusion money.

  Further, in step 1, as shown in FIG. 2A, when the low melting point metal LM is physically vapor-deposited on the surface of the moisture-sensitive polymer film 5 heated at the aggregation temperature, it aggregates into fine particles. Thereby, countless agglomerated fine particle low melting point metal LM is deposited on the surface of the moisture sensitive polymer film 5. Further, the average particle diameter of the low melting point metal LM is controlled within a range of about 0.01 to 10 μm, although it varies depending on the temperature (aggregation temperature) at which the substrate to be heated is heated.

-Step 2 (physical vapor deposition treatment)-
Next, after heating of the substrate 2 is stopped and the temperature is returned to room temperature (in a range of 20 ° C. ± 15 ° C.), the metal that is not removed (etched) by the etching process in the next step is PVD (Physical Vapor Deposition) such as sputtering. Is deposited on the surface of the substrate to be heated on which the low melting point metal LM is deposited (the surface of the moisture sensitive polymer film 5).

  In step 2, as shown in FIG. 2B, an electrode material EM (for example, Au (gold) is formed on the surface of the moisture-sensitive polymer film 5 on which a myriad of low-melting metal LM finely divided and aggregated is deposited. The metal or alloy that functions as an electrode and is not etched away) is deposited. The electrode material EM deposited in step 2 may be any metal or alloy as long as it functions as the upper electrode 4 and is not removed by the etching process in step 3.

-Step 3 (Etching treatment)-
Then, only the low-melting point metal LM deposited in step 1 is removed by an etching process, so that a porous upper electrode 4 having innumerable through holes is produced.

  In step 3, as shown in FIG. 2 (c), the low melting point metal LM deposited on the surface of the moisture sensitive polymer film 5 is removed by the etching process, so that the low melting point on the surface of the moisture sensitive polymer film 5 is obtained. The metal that becomes the upper electrode 4 remains in a region other than the portion where the metal LM exists. As a result, innumerable through holes having the shape of the low melting point metal LM are formed in the upper electrode 4.

  Thus, in the upper electrode 4 according to the present invention, the heating temperature at the time of physical vapor deposition in the step 1 is within a range not exceeding the heat resistance temperature of the moisture-sensitive polymer film 5 which is an organic substance, and the low melting point metal LM aggregates. By adjusting to the temperature at which the fine particles are formed, the low-melting-point metal LM that is finely divided and aggregated can be deposited on the surface of the film without changing the moisture-sensitive polymer film 5.

  Therefore, the upper electrode 4 produced through the above steps 1 to 3 is different from cracks that are difficult to control as in the conventional product, and has an average particle diameter of about 0.01 to 10 μm over the entire electrode surface. Since it can be formed, the unevenness of moisture adsorbed on the moisture-sensitive polymer film 5 and poor passage are suppressed, and the yield rate of the humidity sensor 1 can be increased. In addition, since no cracks are generated on the electrode surface, the sensitivity characteristics of the sensor can be stabilized.

  The agglomeration temperature for heating the substrate to be heated is a temperature at which the low melting point metal LM agglomerates and forms fine particles on the surface of the substrate to be heated as a lower limit, and is at least lower than the melting point of Pb (lead) as the upper limit. It is necessary to set the temperature at which the moisture-sensitive polymer film 5 that is an organic substance does not change. Therefore, although it depends on the type of the moisture-sensitive polymer film 5, it is preferable to select the low melting point metal LM that aggregates in the range of about 100 to 250 ° C.

  Moreover, since the low melting point metal LM tends to aggregate as the heating temperature of the substrate to be heated becomes high, when controlling the average particle size, the temperature condition of the above aggregation temperature is satisfied. The temperature may be adjusted.

  The moisture sensitive polymer film 5 is made of, for example, an engineering plastic (engineering plastic) or super engineering plastic (super engineering plastic) such as a cellulose compound, a polyvinyl compound, or an aromatic polymer. It is a dielectric (insulator) sandwiched between them to form a parallel plate type capacitor.

  As described above, the upper electrode 4 of the humidity sensor 1 described above heats the substrate to be heated formed in this order on the substrate 2 in the order of the lower electrode 3 and the moisture-sensitive polymer film 5 at the aggregation temperature. In the state, a low melting point metal LM is physically vapor-deposited on the surface of the moisture sensitive polymer film 5. Next, it is a porous electrode obtained by returning the substrate to be heated on which the low melting point metal LM is deposited to room temperature to physically deposit the electrode material EM, and then removing only the low melting point metal LM by etching.

  Thereby, during physical vapor deposition, the low melting point metal LM finely divided and aggregated, whose average particle diameter can be controlled to some extent by the aggregation temperature, can be deposited in a state distributed over the entire surface of the electrode material EM, and After the etching treatment, the through holes forming the fine particles of the low melting point metal LM were formed substantially uniformly over the surface of the moisture-sensitive polymer film 5 instead of the irregular cracks as in the conventional product. A porous electrode can be provided.

  Moreover, when this porous electrode is used as an electrode of a humidity sensor, for example, moisture can be adsorbed appropriately to the moisture-sensitive polymer film 5, and the yield of products can be increased. Furthermore, since no cracks are generated on the electrode surface, the sensitivity characteristics of the sensor can be stabilized.

  In addition, since a low melting point metal LM having a melting point lower than that of lead (melting point: 327.5 ° C.) is used, it is physically applied to the substrate to be heated at a temperature at which the moisture sensitive polymer film 5 that is an organic substance does not change. It can be evaporated.

[Other embodiments]
In addition, this invention is not limited to embodiment mentioned above, For example, as shown below, according to a use environment etc., it can also change suitably and can implement. Also, the following modifications can be implemented in any combination within the scope not departing from the gist of the present invention.

  In the embodiment described above, the substrate 2, the lower electrode 3, and the moisture-sensitive polymer film 5 have been described as functioning as heated substrates, but the substrate 2 is not an essential component. Therefore, as shown in FIG. 3, the moisture sensitive polymer film 5 can be made thick enough to maintain the strength of the substrate, and the lower electrode 3 and the upper electrode 4 can be formed on the front and back surfaces. In such a configuration, the lower electrode 3 and the moisture-sensitive polymer film 5 function as a substrate to be heated.

  Moreover, when it is set as the structure as the said modification, since at least one electrode should just be a porous electrode, the structure which used the lower electrode 3 as the porous electrode, for example, the lower electrode 3 and the upper electrode 4 Both may be configured to be porous electrodes.

  Furthermore, in the embodiment described above, an example in which the porous electrode of the present invention is used as the upper electrode 4 of the humidity sensor 1 has been described. For example, a cathode of a limiting current oxygen sensor in which a pair of electrodes are provided on a stabilized zirconia solid electrolyte. It can also be used as

DESCRIPTION OF SYMBOLS 1 ... Humidity sensor 2 ... Board | substrate 3 ... Lower electrode (2nd electrode in a claim)
4 ... Upper electrode (the porous electrode according to the present invention, the first electrode in the claims)
5 ... Humidity sensitive polymer film 6 ... Lead wire 7 ... Calculation unit LM ... Low melting point metal EM ... Electrode material

Claims (3)

A low melting point metal having a melting point lower than that of lead and removed by etching;
An electrode material not removed by the etching process;
A substrate to be heated that is heated at an agglomeration temperature at which the low-melting-point metal agglomerates into fine particles;
A porous electrode produced using
Physical vapor deposition of the low melting point metal on the surface of the heated substrate heated at the aggregation temperature,
The electrode material is formed by physical vapor deposition in a state where the substrate to be heated is returned to room temperature,
A porous electrode obtained by etching the substrate to be heated on which both the low melting point metal and the electrode material are deposited to remove only the low melting point metal. A low melting point metal having a melting point lower than that of lead and removed by etching;
An electrode material not removed by the etching process;
A substrate to be heated that is heated at an agglomeration temperature at which the low-melting-point metal agglomerates into fine particles;
A method for producing a porous electrode produced using
Physical vapor deposition of the low melting point metal on the surface of the heated substrate heated at the aggregation temperature,
The electrode material is formed by physical vapor deposition in a state where the substrate to be heated is returned to room temperature,
A method for producing a porous electrode, which is obtained by etching the substrate to be heated on which both the low melting point metal and the electrode material are vapor-deposited to remove only the low melting point metal. The porous electrode according to claim 1 is a first electrode,
A humidity sensor having an electrode structure that becomes a parallel plate capacitor formed by sandwiching a moisture-sensitive polymer film between the first electrode and the second electrode.

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