KR0124412B1 - Electrolyte composition for screen printing - Google Patents

Abstract

TECHNICAL FIELD The present invention relates to an electrolyte composition for screen printing, and more particularly, to an electrolyte composition for screen printing used in a small oxygen electrode useful for many fields including the measurement of dissolved oxygen concentration of a solution. The electrolyte composition consists of an organic solvent, an inorganic salt in the form of a fine powder that can be dispersed in the organic solvent and passed through a screen printing network, and polyvinyl pyrrolidone dissolved in the organic solvent.

Description

Chinchilla composition for screen printing

1 is a sectional view showing the essential configuration of a conventional oxygen electrode.

2 (a) to 2 (c) show a small oxygen electrode as a plan view (a, b) and a sectional view (c).

3 (a) to 3 (n) show the process sequence according to the invention in cross section and in plan view;

4 is a graph showing the typical response of a small oxygen electrode according to the present invention as a relation between the elapsed time from the addition of Na ₂ O ₃ and the output current.

5 is a graph showing a linear calibration curve of a small oxygen electrode according to the present invention as a relationship between dissolved oxygen amount and output current.

6 (a) to 6 (f) show a process sequence according to the present invention in cross section and a plan view.

7 (a) to 7 (i) show the process sequence according to the invention in cross section and in plan view.

8 (a) to 8 (c) show small oxygen electrodes of three poles.

9 (a) to 9 (e) are sectional views and a plan view showing a manufacturing process sequence of a tripolar small oxygen electrode according to the present invention.

10 shows a small oxygen electrode installed in an adapter for use in a fermenter.

11 is a view showing the configuration of an oxygen concentration measuring apparatus to which a small oxygen electrode according to the present invention is applied.

TECHNICAL FIELD The present invention relates to an electrolyte composition for screen printing, and more particularly, to an electrolyte composition for screen printing used in a small oxygen electrode useful for many fields including the measurement of dissolved oxygen concentration of a solution.

Oxygen electrodes are very useful for measuring dissolved oxygen concentrations in many applications. As an example, it is used in the field of water management to measure the biochemical oxygen demand (BOD: Biochemiacl Oxygen Demand) in water. It is also used in the field of fermentation and brewing to measure the dissolved oxygen concentration in fermentation tanks to ensure efficient fermentation of alcohol.

Oxygen electrodes combine with enzymes to form enzyme electrodes or biosensors used to measure sugar and vitamin concentrations. As an example, the oxygen electrode may be combined with glucose oxidase to measure the concentration of glucose or glucose.

This is because glucose is oxidized by dissolved oxygen to form gluconolactone with the help of glucose oxidase catalysis, thereby reducing the amount of dissolved oxygen diffused to the oxygen electrode.

In addition to measuring the dissolved oxygen concentration of the solution, the oxygen electrode can be advantageously used to control the oxygen concentration in the gaseous state.

For example, if the oxygen concentration in the air is lowered to 18% or less, it is in a state of lack of oxygen, which is dangerous. In the medical apparatus such as oxygen intake and gas anesthesia, the oxygen concentration of the gas used must be strictly managed.

Thus, oxygen electrodes are very advantageously used in many fields such as environmental measurement, fermentation industry, clinical medical and industrial hygiene.

Conventional oxygen electrodes typically have the structure shown in FIG.

Here, the container 118 made of glass, plastic and stainless steel has a closed open end (lower end) covered with an oxygen gas permeable membrane 107 made of silicone resin and fluorescent resin. An aqueous solution of calcium chloride (KCl) and sodium hydroxide (NaOH) (119) is an anode (104) of silver (Ag), lead (Pb), and a cathode of platinum (Pt) and gold (Au). 105 is filled in a container 118 in which it is disposed.

The conventional oxygen electrode has a complicated structure. Therefore, not only miniaturization but also mass production is difficult.

The present inventors have disclosed a new type of small oxygen electrode that can be manufactured by using a semiconductor manufacturing process including photolithography and anisotropic etching, as disclosed in Japanese Patent Laid-Open No. 63-238,548 and US Pat. No. 4,975,175. Suggested.

The proposed oxygen electrode has a structure as shown in FIGS. 2 and 3. FIG. 2 (b) shows an incomplete structure in which the oxygen gas permeable membrane is not yet formed.

This structure is manufactured by the following procedure. Two grooves 202 filled with an electrolyte-containing material are formed on the silicon wafer 201 by anisotropic etching, and then coat the wafer surface with an SiO ₂ insulating layer 203 to form an electrically insulating substrate. . Next, two component electrodes, for example, the anode 204 and the cathode 205, are formed on the insulating layer 203. The anode 204 has one end 204A for electrically connecting with the outside and two other ends extending into the groove 202. The cathode 205 has one end 205A for electrically connecting to the outside and the other end extending to the top surface of the plateau held between the grooves 202. The electrolyte containing material 206 is filled in the groove 202, and the filled electrolyte containing material is in contact with the anode 204 and the cathode 205 on the plateau in the groove 202. The upper surface of the filled electrolyte containing material 206 is then covered with an oxygen gas permeable membrane 207.

Nevertheless, filling the electrolyte-containing material 206 into the groove 202 and covering the electrolyte-containing material 206 filled as the oxygen gas permeable film 207 are difficult to carry out in the semiconductor process. Therefore, the steps are performed manually after the wafer 201 on which the small oxygen electrode is formed is cut into chips that form each oxygen electrode.

This manual operation is a serious obstacle to realizing mass production and, moreover, involves a great deal of variation in the process for obtaining small oxygen electrodes with stable and uniform performance.

Therefore, there is a need for a structure of a small oxygen electrode and a method of manufacturing the same, in which the filling of the electrolyte-containing material and the formation of the oxygen gas permeable film can be performed collectively or almost uniformly on the wafer as a whole before the wafer is cut into chips.

The filling step of the electrolyte-containing material has the following problems.

The inventors have studied gels comprising a polyelectrolyte and an aqueous solution of potassium chloride, and since many of them are not photosensitive, photolithography used in semiconductor processes cannot actually be applied to the filling of electrolyte-containing materials.

The electrolyte-containing material must be a fluid that is fluid when filled in the groove, and the filled material must form a dense film after drying. In addition, whether or not the filled material contains water has a significant influence on the quality of the oxygen gas permeable membrane applied to the filled material.

Therefore, during application of the oxygen gas permeable membrane, the electrolyte-containing material is suitably dried. The water required for the measurement of the oxygen concentration is supplied as water vapor through the gasoline membrane just before the start of measurement.

The electrolyte containing material does not contain water during the preparation of the oxygen electrode.

Screen printing is a suitable method for filling electrolyte-containing materials in bulk on many small oxygen electrodes on a wafer. Such screen printing generally uses an emulsion mask and a metal mask to provide a printing pattern. The photosensitive resin is applied to the stainless steel mesh in emulsion form to provide a printed pattern.

Some resins have transparency that facilitates the fine alignment required when manufacturing small oxygen electrodes since the wafer covered by the resin mask is seen through the resin. However, the emulsion mask is very weak against water, as can be seen from the fact that the development of the emulsion is carried out using water, and printing of a water-containing substance is difficult.

Metal masks, on the other hand, are manufactured by forming holes in plates such as stainless steal. Therefore, it is strong against water. However, metal masks are disadvantageous for fine alignment because they do not have transparency. Moreover, metal masks sometimes provide lower print quality than those obtained by emulsion masks when using several kinds of inks.

The inventors have disclosed that, as disclosed in Japanese Patent Application Laid-Open No. 1-56,902, an electrolyte-containing gel is applied by screen printing, that is, calcium alginate gel, polyacrylamide gel, and agarose ( agarose) gel printing method has been proposed.

This method uses a metal mask to print an aqueous gel and cannot be advantageously used for the production of small oxygen electrodes for the reasons mentioned above. Moreover, a strong membrane cannot be obtained because the oxygen gas permeable membrane is formed on the wet gel.

Potassium chloride is generally used as the electrolyte of the oxygen electrode. Potassium chloride is an excellent electrolyte, but it is not suitable for use in small oxygen electrodes due to the drawback that it only dissolves in water and becomes a white, brittle powder when the aqueous solution is dried.

The present inventors also proposed a polymer electrolyte, as disclosed in Japanese Patent Laid-Open No. 2-240,556.

It has good film forming properties, but it also has a degree of copolymerization and is difficult to handle because of its high viscosity even in dilute solutions, and is soluble only in water.

Oxygen gas permeation film forming step has the following problems.

Gas permeable membranes are made of silicone resin, fluorescent or other electrically insulating material.

Therefore, the gas permeable membrane is not formed to cover the entire surface of water, but has a pattern in which pads or component electrode terminals 204a and 205 for electrical connection with the outside are exposed only. The gas permeable film is selectively applied to a predetermined wafer area other than the pad area to be exposed only by applying a resin to a predetermined area or by first forming a gas permeable film on the entire surface of the wafer and then removing the gas permeable film of the pad area to be exposed. Is formed.

Screen printing of liquid resins is known by the former method, that is, the selective coating method of resin.

This method has the advantage that the printing process can only perform the application and pattern of the resin at the same time, but since the silicone resin used for the formation of this gas permeable thin film is gradually cured by water in the air, the viscosity of the resin is printed. This can lead to uneven printing, and in the worst case, blockage of the printing stencil.

Lift-off processes using photoresists are known as the latter method, that is, the selective removal of gas permeable thin films.

This process has the advantage that the semiconductor process is advantageously applied and complex patterns are easily obtained. However, this method provides a fully cured gas permeable membrane that is so strong that it is difficult for the thin film to be selectively exfoliated at the portions to be exposed even when using ultrasonic treatment, when applied to the manufacture of small oxygen electrodes. Thus, this lift-off process cannot actually be used in the manufacture of the small oxygen electrode.

U.S. Patent No. 4,062,750 (JF Butler) discloses a thin film type electrochemical electrode formed on a silicon substrate having an electrically conductive layer extending through the thickness of the silicon substrate such that a signal from a sensor located on one side of the substrate is drawn to the other side of the substrate. It became. Since this electrode does not have the pad portion of the electrode of the present invention, the gas permeable film can cover the entire surface, and no patterning of the film is required for the exposure of the pad portion. However, this electrode requires a complicated manufacturing process that causes problems in practical applications.

The filling of the electrolyte is carried out by vacuum deposition, and although sodium chloride and potassium chloride can be vacuum deposited, many inorganic salts used as buffers are poorly degraded by dehydration and condensation when exposed to the heat accompanying vacuum deposition. Therefore, even when a buffered electrolyte is obtained, even if the obtained pH deviates greatly from the expected value, the obtained electrolyte composition should be very limited. So this process is not optimal. Moreover, problems arise when a single vacuum deposition apparatus is used for both deposition of electrolyte and deposition of electrode metal. Therefore, a separate deposition apparatus must be provided for each deposition.

M.J. Madou et al. US patent no. 4,874,500 and AICHE SYMPOSIUM SERIES, NO. 267, Vol. 85, pp. A microelectrochemical sensor as disclosed in 7-13 (1989) is proposed. This sensor also has the feature that the electrically conductive layer extends through the thickness of the silicon substrate and signals from the sensor located on one side of the substrate are drawn from the other side of the substrate. Therefore, J.F. It has the same drawbacks as Butler's technique. The electrolyte is filled with a method of applying an alcohol solution of poly (hydroxyethyl methacrylate), evaporating the solvent, injecting the electrolyte solution to form a gel, and then drying. The conventional problem is obviously eliminated because the electrolyte is introduced after application of the polymer. However, crystals grow when the potassium chloride solution evaporates. When the amount of potassium chloride is low, the grown crystals are enclosed as a polymer, but when the amount is high, many large crystals appear that cannot be supported by the polymer. On the other hand, the amount of electrolyte should be as low as possible. This is because the lifetime of the oxygen electrode is influenced by the amount of electrolyte contained therein.

Thus, a limited amount of electrolyte reduces the lifetime of the oxygen electrode.

An object of the present invention generally relates to a small oxygen electrode and a manufacturing method that can be mass-produced with high efficiency by treating the substrate intensively and uniformly.

According to the present invention, there is provided an electrolyte composition for screen printing comprising an organic solvent, an inorganic salt in the form of fine powder which can be dispersed in the organic solvent and pass through the screen printing network, and polyvinyl pyrrolidone dissolved in the organic solvent. .

Inorganic salts are suitably selected from potassium chloride and sodium chloride.

The inorganic salt used as the electrolyte should be in the form of fine particles having a diameter not larger than 50 μm, for example, in the form of fine powder that can pass through the screen printing network.

The organic solvent used in the present invention is preferably an alcohol such as butanol, pentanol or hexanol.

The electrolyte composition of the present invention is obtained by dispersing an excellent inorganic salt such as potassium chloride in a polymer polymer dissolved in an organic solvent in the form of fine particles suitable for screen printing.

The present invention uses polyvinyl pyrrolidone as a high polymer. Inorganic salts, such as potassium chloride, in the form of fine particles, can be pulverized or injected into an organic solvent, such as alcohol and acetone, which can be mixed with water in an aqueous solution in high concentration close to saturation where potassium chloride is saturated. It can be produced by a method of depositing fine particles. In either method, a fine powder having a uniform size can be obtained.

The electrolyte composition of the present invention may further include a buffer to ensure a constant pH (hydrogen ion concentration) of the electrolyte.

These buffers are phosphates, acetates, borates, citrates, phthalates, tetraborates, glycine salts and tris (hydroxymethyl) -amino methane salts, and are used in the form of fine powders like potassium chloride powder.

According to the present invention, an inorganic salt, polyvinyl pyrrolidone, and fine powder of an organic solvent are combined to form an electrolyte composition in the form of a paste, and then applied to predetermined portions of the substrate in a batch by screen printing. The printed electrolyte composition forms a dense membrane so that an oxygen gas permeable membrane can be properly formed when dried.

The present invention uses a thermosetting resin, a solution of polyvinylchloride of an organic solvent, or another resin as a material of the removable coating film. These resins are applied to predetermined areas of the substrate by screen printing and then cured by heating or drying to form a removable coating film.

In the present invention, the electrically insulating substrate on which the small oxygen electrode is formed may be an electrically insulating substrate that is smooth and flat enough to form the small oxygen electrode by using a semiconductor process. Silicon wafers are most usefully used as insulating substrates in terms of application of the most commonly used silicon semiconductor manufacturing methods.

It can be applied directly to the small oxygen electrode formed on the silicon wafer and the other insulating substrate of the present invention. That is, in the small oxygen electrode, the component electrode pattern is formed on the substrate, and the electrolyte-containing material is filled into the oxygen sensing position by screen printing of the electrolyte composition of the present invention, and then the oxygen gas permeable membrane is used for the pad region, that is, for external electrical connection. By using a flat substrate of electrical insulators, such as glass, quartz and plastic, to be selectively formed or patterned by screen printing thermosetting resin on a substrate region including component electrode ends to form a removable coating film. Are manufactured.

According to the present invention, the screen-printed electrolyte composition contains fine powder inorganic salts or electrolytes which are not dissolved in an organic solvent and are dispersed. Therefore, even when the electrolyte composition is dried, the inorganic salts do not form fragile crystals and remain in the fine powder state. And this makes it possible for the electrolyte containing material to be in the form of a solid material with a high density.

The electrolyte-containing material thus obtained consists essentially of inorganic salts and polyvinyl pyrrolidone. When operating the small oxygen electrode, water is introduced into the electrolyte containing material. Both inorganic salts and polyvinyl pyrrolidone are completely dissolved in the introduced water so that the electrolyte-containing material of the present invention remains solid during the formation of the oxygen gas permeation membrane and forms an aqueous solution when the small oxygen electrode is operated. Meet the requirements of

Potassium chloride and sodium chloride are excellent electrolytes, and can be usefully used as the inorganic salts according to the present invention in order to obtain the excellent performance of the small oxygen electrode.

Adding salts with a pH buffering effect, such as phosphate, to the electrolyte composition of the present invention ensures that the electrolyte has a constant pH. Since the electrochemical reaction at the oxygen electrode depends on the pH value, a constant pH improves the stability of the performance of the oxygen electrode.

The small oxygen electrode according to the present invention is manufactured by filling an electrolyte composition containing an inorganic salt as an electrolyte in the form of fine powder to a predetermined portion of the substrate by screen printing at once, thereby making the filling operation uniform. High production rates are obtained.

In the method for producing a small oxygen electrode according to the present invention, an electrolyte composition including an inorganic salt as a fine powder type electrolyte is collectively filled in a predetermined portion of a substrate by screen printing. Thus, even if the charged portion has a complicated phenomenon, it is ensured that the mass production and filling operation of the small oxygen electrode is made uniform. The manufacturing method of the present invention can also be coped with even if the number of filling parts is increased in connection with the enlargement of the substrate size.

Since the small oxygen electrode according to the present invention is patterned (or selectively formed) by removing the coating film formed into a predetermined shape, the oxygen gas transmitting film and its exposed portion have a high shape even when the oxygen gas transmitting film has a complicated shape. Guarantee the production rate. The oxygen gas permeable film is applied collectively on the entire substrate surface by spin-coating, so that a high production rate is ensured, and an oxygen gas permeable film having a uniform thickness is formed over the entire substrate surface.

The small oxygen electrode according to the present invention effectively forms an oxygen gas permeable film having a uniform thickness over the entire substrate surface, that is, firstly covers the substrate region to be exposed as a removable coating film, and collectively oxygens the entire substrate surface. It can be produced at a high production rate by forming a gas permeable membrane and selectively removing or patterning an oxygen gas permeable membrane by peeling off the removable coating membrane.

The method according to the present invention applies a thermosetting resin of a resin dissolved in an organic solvent to a portion to which an oxygen gas permeable membrane is to be exposed by screen-printing, and then cures by heating or drying to form a removable coating film, which is then removed. Since it is patterned by peeling a coating film, it is easy to cope with the increase of the number of parts to expose and the complicated pattern of an oxygen gas permeable film.

Example 1

Referring to FIG. 3, a process for producing a small oxygen electrode according to the present invention by using a silicon wafer is described in detail below. For convenience, the process is described for the case where a small oxygen electrode is formed on a 2 inch silicon wafer, but basically the same process can be used for larger wafers. The figures show the wafer with the corresponding process steps completed.

Step 1: Wafer Cleaning

The 2-inch silicon wafer 301 (400 μm thick, (100) crystal face) was washed thoroughly with a mixed solution of concentrated nitric acid, ammonia and hydrogen peroxide.

Step 2: Formation of SiO ₂ Layer (FIG. 3 (a))

The wafer 301 was wet thermally oxidized at 1000 ° C. for 200 minutes to form a 0.8 μm thick SiO ₂ layer on both sides. This SiO ₂ layer 312 is patterned in the next step 4 and used as a mask when anisotropically etching the silicon wafer in the next step 5.

Step 3: forming a resist pattern (FIG. 3B)

Photolithography by applying a negative photoresist (Tokyo Ohka Kogyo Co., Ltd., OMR-83, viscous 60cp) over the entire surface of the prebaked wafer at 80 ° C. for 30 minutes The resist pattern 31 was formed by processing. The resist pattern 313 covers the upper surface of the wafer 301 except for the region 302A for forming grooves 302 (FIG. 3 (d)) for receiving the electrolyte-containing material in the next step 5. Cover. The resist pattern 31 is used as a mask when etching the SiO ₂ layer 312 in the next step 4. The same photoresist was applied to the lower surface of the wafer 301 and baked at 150 ° C. for 30 minutes.

Step 4; Etching the SiO ₂ Layer (FIG. 3 (c))

The wafer 301 is immersed in an etchant of SiO ₂ (50% HF / 1 ml + NH ₄ F / 6 ml) to deposit the SiO ₂ layer 312 in the portion 302A that is not covered by the photoresist 31. Partially removed. The wafer 301 was immersed in a mixed solution of sulfuric acid and hydrogen peroxide to remove the photoresist 313.

Step 5: Anisotropic Etching of the Silicon Wafer (FIG. 3 (d))

The wafer 301 is immersed in silicon etchant (35% KOH) at 80 ° C. and the silicon wafer 301 is anisotropically etched by using the SiO ₂ layer as a mask, so that two 300 substrates for accommodating the electrolyte-containing material are accommodated. Grooves 302 of depth were formed. After completion of the anisotropic etching, the wafer 301 was washed with clean water.

Step 6: removing the SiO ₂ layer (FIG. 3 (e))

Following the water wash, the SiO ₂ layer 302 was removed by the same procedure as performed in step 4.

Step 7: forming a SiO ₂ layer (FIG. 3 (f))

Thermal oxidation of the wafer 301 was performed by performing the same processes as those performed in steps 1 and 2 to form a thick SiO ₂ layer having a thickness of 0.8 μm on both sides of the wafer 301.

The SiO ₂ layer 303 thus formed functions as an insulating layer of a small oxygen electrode or a finished product.

Step 8: Form a Thin Layer of Chromium and Silver (Figure 3 (g1), (g2))

A thin chromium layer 314 having a thickness of 400 mm 3 and a thin silver layer 315 having a thickness of 4,000 mm placed on the chromium layer 314 were formed on the entire upper surface of the wafer 301 by vacuum deposition. The thin silver layer 315 is an electrically conductive layer constituting substantial portions (anode and cathode) of the component electrodes and the thin chromium layer 314 is a thin silver layer 315 on the SiO ₂ insulating layer 303 formed on the wafer 301. Ground layer to ensure fixation.

Step 9: forming photoresist pattern

This step is performed by etching the thin silver layer 315 and thin chromium layer 314 to pattern the component electrodes (anode and canopy) of the small oxygen electrode in the following steps 10 and 11 as a photoresist pattern for use as a mask ( 316).

A positive type photoresist (Tokyo Ohka Kogyo Co. Ltd., oFPR-800, viscous 20cp or OFPR-5000, viscous 50cp) was dropped on the wafer 301 to uniformly cover the wafer 301. The photoresist has been suitably dropped to an amount that can preferably spread to the wafer peripheral edge. The wafer 301 was prebaked at 80 ° C. for 30 minutes.

The wafer 301 was pattern-aligned and exposed with the glass mask by mask centering to form a photoresist pattern 316. The exposure and development cycles were repeated repeatedly so that a complete exposure of the positive photoresist layer was achieved, which was too thick to expose completely over the thickness at one time.

Step 10: etching a thin layer of silver and chromium (Fig. 3 (i1) (i2))

Hayeoseo dipping to remove the exposed parts of the silver layer to chyeonteu (NH ₃ water _{/ 1ml + H 2 0 2 /} 1ml + water / 20ml) in the wafer 301, to form a substantial part of the kompeoneonteu electrode.

The wafer was immersed in chromium etchant (NaOH / 0.5g + K ₃ Fe (CN) ₆ / 1g + water / 4ml) to remove the exposed portion of the chromium layer 314.

Step 11: photoresist pattern formation (FIG. 3 (j1), (j2)

This step forms a photoresist pattern 317 for defining the oxygen sensing position of the small oxygen electrode. A negative photoresist layer 317 (Tokyo Ohka Kogyo Co., Ltd., OMR-83, Viscosity 60cp) was formed on the wafer 301 to provide an oxygen sensing location (two grooves and a flat plateau between them). The wafer surface of the region 309 and other portions other than the pad region 311 for forming the pad portions 304A and 305A of the component electrodes 304 and 305 are formed.

This is done by applying a photoresist to the wafer surface, prebaking the wafer for 30 minutes at 80 ° C, and exposing the photoresist layer to exposure. Thereafter, the photoresist layer was postbaked at 150 ° C. for 30 minutes.

Step 12: Screen-Printed Electrolyte Composition (FIG. 3 (k1), (k2), (k3))

The electrolyte composition was screen printed at an oxygen sensing location (two grooves and a flat plateau between them) 309 defined by photoresist 317 to form electrolyte-containing material 306. The preparation of the electrolyte used will be described later.

Step 13: Form the Pad Area Coating Film (FIG. 3 (l1, l2))

The thermosetting release coating (Fujikura kasei Co. XB-801) was screen-printed on the pad area 311 to a thickness of 100 μm, heated at 150 ° C. for 10 minutes, and cured to form a removable coating film 308.

Step 14: Oxygen Permeation Film Formation (FIG. 3 (m1), (m2))

An oxygen gas permeable film 307 having a double layer structure was formed on the wafer 301 to cover the entire upper surface of the wafer 301. First, the lower layer of the thin film 307 was applied onto the wafer 301 by spin coating a negative photoresist (Tokyo Ohka Kogyo Co., Ltd., OMR-83, viscous 100 cps), followed by 30 at 80 ° C. It was formed by prebaking for a minute, exposing the entire wafer surface and developing and post-baking for 30 minutes at 150 ° C.

Next, the upper layer of the thin film 307 is coated with a silicone resin (Toray-Dow Corning Silicone Co. SE9176) on the wafer 301 by spin coating and placed in a Petri dish or beaker in an oven. It was formed by curing the coated resin by heating at 70 ° C. for 30 minutes in an oven moistened with water.

Step 15: the exposure of the pad (third degree (n1), (n2))

The coating film 308 formed in the pad area 311 was peeled off with tweezers to selectively remove the oxygen gas permeation film from the area, thereby exposing the pads 304A and 305A of the small oxygen electrode.

Step 16: Separation of Small Oxygen Electrode

A large number of small oxygen electrodes were collectively formed on the wafer 301 at a time by proceeding from step 1 to step 15, and cut into chips by a dicing saw. The example shown provides 40 chips of small oxygen electrodes at one time.

Example 2

In the forming step 13 of the pad region coating film, a small oxygen electrode was manufactured by the same process as in the first embodiment except that the pad region coating film was deformed as follows.

Step 13: Form the Pad Area Coating Film

(transform)

The polyvinyl chloride resin dissolved in tetrahydrofuran was screen printed on the pad area 311 with a thickness of 50 µm, and cured by heating at 70 ° C to form a coating film 308.

The electrolyte composition according to the present invention used in step 12 of the first and second embodiments was prepared in the following manner.

Preparation process 1: provision of fine powder of inorganic salt

Particulates of potassium chloride or sodium chloride were formed by one of the following procedures (a) and (b).

(a) The solid material of potassium chloride or sodium chloride was ground into fine particles having a diameter smaller than 10 μm by a mill (Fritsch Co. Type p-5).

(b) A saturated aqueous solution of potassium chloride or sodium chloride was prepared. The solution was injected through a Teflon ball filter (Iuchiseieido Co., pore diameter 10 μm) into an organic solvent such as acetone or propanol or ethanol in 10 cultures of the solution.

The organic solvent was stirred thoroughly by a stirrer during injection. This was filtered by a glass filter and washed two to three times with the same kind of clean organic solvent to provide precipitation of the dried inorganic salt fine particles to obtain fine particles having a diameter of 10 mu m or less.

(*) Teflon: Trademark of Dupont Co. for Polytetrafluoroethylene (PTFE)

Preparation process 2: formulation of electrolyte composition

The inorganic salt fine particles, polyvinyl pyrrolidone and the organic solvent obtained above were combined to form an electrolyte composition in the form of a paste.

The following is an example of such a composition.

Electrolyte Composition: Case 1

0.15 g of potassium chloride fine particles

1 g of polyvinyl pyrrolidone

5 g pentanol

30% to 70% of the electrolyte composition is a solid part, the remainder is an organic solvent, and 50% to 90% of the solid part can be blended so as to be an inorganic salt. The following is an example of such a composition.

Electrolyte Composition: Case 2

4 g of potassium chloride fine particles

1 g of polyvinyl pyrrolidone

5 g pentanol

According to a preferred embodiment of the present invention, the electrolyte composition further includes a salt having a pH buffering effect.

Even if phosphoric acid is added in the following case, the buffering agent used in the present invention is composed of phosphate, acetate, borate, citrate, phthalate, tetraborate, glycine salt and tris (hydroxymethyl) aminomethane salt Can be selected from.

An electrolyte composition to which phosphate is added as a buffer may be prepared by, for example, the following method.

Preparation process 1: providing fine powder of inorganic salt

Particulates of potassium chloride or sodium chloride were formed by one of the following procedures (a) and (b).

(a) 71.55 g of potassium chloride and 8.71 g of dipotassium hydrogen phosphate were weighed and ground by particles (Fritsch Co., Type p-5) into particles having a diameter smaller than 10 μm.

(b) 74.55 g of potassium chloride and 8.71 g of dipotassium hydrogen phosphate were weighed and dissolved in 230 ml of water.

The aqueous solution was injected through the Teflon ball filter (Iuchiseieido co., Pore diameter 10㎛) in the amount of ethanol 10 times the aqueous solution. Ethanol was thoroughly stirred by the stirrer during injection. As a result, the fine particles of the inorganic salts were precipitated and filtered by a glass filter, washed two to three times with clean ethanol and dried to obtain fine particles having a diameter smaller than 10 μm.

Fine particles of potassium chloride or sodium chloride and fine particles of phosphate or buffer were prepared separately. For example, when forming a concentrated aqueous solution of potassium chloride or sodium chloride, an aqueous solution of potassium dihydrogen phosphate and sodium dihydrogen phosphate (molar ratio of 4: 6) may be formed separately.

Both solutions are preferably saturated and they provide a higher amount of particulate, ie high efficiency.

Weighed phosphates should be completely dissolved in water because the ratio of dissolved phosphates has a significant effect on the pH value.

Thus, the prepared aqueous solutions collect fine particles injected and precipitated into organic solvents such as ethanol, respectively, by the method described above.

Preparation process 2: formulation of electrolyte composition

The fine particles of the inorganic salt obtained above, polyvinyl pyrrolidone and an organic solvent were combined to form an electrolyte composition in the form of a paste. The following are examples of such compositions.

Electrolyte Composition: Case 3

0.25 g of a mixture of fine particles of potassium chloride and phosphate

1 g of polyvinyl pyrrolidone

5 g pentanol

Electrolyte Composition: Case 4 (Particulates of Separated Buffers)

3.5 g of potassium chloride fine particles

0.5 g of phosphate fine particles

1 g of polyvinyl pyrrolidone

5 g pentanol

The performance of the small oxygen electrodes prepared in Examples 1 and 2 was tested by measuring the dissolved oxygen concentration in 100 mM phosphate buffer solution with a pH value of 7.0 at a temperature of 25 ° C. and an applied voltage of 0.6 V.

4 shows the response curve observed when sodium sulfite is added to a solution saturated with 100% oxygen in order to reduce oxygen concentration to zero instantaneously.

The response time was 40 seconds, which corresponds to the change in dissolved oxygen concentration.

5 shows the measurement curve obtained in this case, from which it can be seen that good linear characteristics are ensured over the entire range of dissolved oxygen concentrations from 0 ppm to 8 ppm, that is, the saturation concentration.

Example 3

Referring to FIG. 6, a process for producing a small oxygen electrode according to the present invention by using an electrically insulating flat substrate in addition to a silicon wafer will be described.

Step: Form Component Electrode Pattern (FIG. 6 (a))

A washed electrically insulating flat substrate 401 having an area of 60 mm and a thickness of 1.6 mm was prepared. The insulating substrate 401 may be made of glass, quartz, ceramic, plastic or other electrical insulator.

A component electrode pattern constituting the anode 404 and the cathode 405 is formed on the insulating substrate by one of the following processes (a) and (b).

(a) The thin silver layer is formed by the vacuum vapor deposition method and the method as used in Examples 1 and 2 above is etched to form a predetermined electrode pattern.

(b) The electroconductive paste (Fujikura kasei Co., D-1230 modified) is screen-printed onto the substrate. The component electrodes 404 and 405 have ends for electrical connection pads 404A and 405A, respectively.

The auxiliary pad 420 provided between the pads 404A and 405A may be used for a small oxygen electrode having, for example, a three-pole structure.

Step 2: Screen-Printed Electrolyte Composition (FIG. 6 (b))

The same electrolyte composition as used in Example 1 was screen printed to fill the region 409 at the oxygen sensing location to form an electrolyte containing material 406.

Step 3: Form the Pad Area Coating Film (FIG. 6 (c))

A coating film 408 covering the pad area 411 by screen-printing a thermosetting release coating (Fujikura kasei Co., XB-801) in the pad area 411 containing the pads 404A and 405A and the auxiliary pad 420. ) Was formed.

Step 4: Oxygen Gas Permeation Film Formation (FIG. 6 (d))

In order to form an oxygen gas permeable film 407 having a double layer structure on the substrate 401 to cover the entire upper surface of the substrate 401, the lower and upper layers of the thin film 407 are negative photoresist (Tokyo Ohka Kogyo Co. , Ltd., OMR-83, viscosity 100cp) and a silicone resin (Toray-Dow Corning Silion Co., SE9176) were formed by spin coating, respectively, and then hardened by the applied layers.

Step 5: Exposing the Pad Area (FIG. 6 (e))

The coating film 408 formed on the pad region 411 was peeled off with tweezers to selectively remove the oxygen gas permeation film 407 from the portion, thereby exposing the pads 404A and 405A of the small oxygen electrode. The auxiliary pad 420 was simultaneously exposed.

Step 6: Separation of Small Oxygen Electrode (FIG. 6 (f))

A plurality of small oxygen electrodes were collectively formed on the electrically insulating substrate 401 by the preceding steps 1-6, and cut into chips by a dicing saw. The example shown provides seven chips of small oxygen electrodes simultaneously from a single substrate.

Although the component electrodes are formed of silver, the component electrodes may be formed of gold instead of silver, respectively.

For example, the component electrodes may be formed of gold instead of silver as follows by partial modification of the first embodiment.

Example 4

Steps 8 and 10 of Example 1 were changed in the following manner.

Example 1 (step 3, g1 and g2), except that the thin gold layer 315 (400 mm thick) is vacuum deposited instead of the thin silver layer 315 (thickness 4000 mm). The same procedure was followed.

Subsequent step 9 (FIGS. 3 h1 and 3 h2) was carried out in the same manner as in Example 1.

Step 10 (Example 3 except that in FIG. 3 (i1) and (i2) wafer 301 was immersed in gold etchant (K1 / 4g + I ₂ / Ig + water / 40ml) instead of silver etchant) The same process as in E.g.

These modifications provided a small oxygen electrode with component electrodes formed of gold.

Small electrodes having a gold cathode and a silver anode can be manufactured in the following manner.

Example 5

Referring to FIG. 7, a process for producing a small oxygen electrode having a gold cathode and a silver anode according to the present invention by using a glass substrate will be described.

Step 1: Substrate Cleaning (Fig. 7 (a))

The glass substrate 511 having an area of 60 mm and a thickness of 1.6 mm was completely washed with a detergent (eg, Furuuchi kagaku Co., semico clean 56) and acetone.

Step 2: forming a thin layer of chromium, gold and silver (Fig. 7 (b))

A thin chromium layer (eg 400 mm thick), a thin gold layer (eg 4000 mm thick), and a thin silver layer (eg 4000 mm thick) were sequentially formed on the substrate 511 by a vacuum deposition method. The thin chromium layer ensures good adhesion between the glass substrate 511 and the component electrodes of gold and silver.

Step 3: Forming a Photoresist Pattern (FIG. 7 (c))

A positive photoresist (e.g., Tokyo Ohka Kogyo CO., Ltd., OFPR-800, 20cp or OFPR-5000, 50cp) was applied onto the thin silver layer 512 and prebaked at 80 ° C for 30 minutes.

Thus, the formed photoresist layer was exposed and developed to form photoresist patterns 513 corresponding to all component electrodes.

Step 4: Formation of Thin Gold and Silver Layers (Fig. 7 (d))

The substrate 511 is a chyeonteu (e. _{G., 29% NH 4 OH / 1ml} + 31% H 2 O 2 / 1ml + water / 20ml) thin silver layer 512 was immersed in a pattern. Then, the substrate 511 was immersed in a gold etchant (eg, KI / 4g + I ₂ / 1g / + water / 40ml) to pattern a thin gold layer.

This exposed the thin chromium layer 514 in the portion not covered with the photoresist.

Step 5: Repatterning the Photoresist Pattern (Fig. 7 (e))

The positive photoresist layer 513 was again exposed to light so that the photoresist pattern 513 remained only at the portion where the anode was formed, and the other portion of the photoresist pattern 513 was removed to expose the thin silver layer 512.

Step 6: component electrode patterning (FIG. 7 (f))

The substrate 511 was immersed in the etchant to remove the thin silver layer exposed in the preceding step (5). So it exposed a thin layer of gold beneath. As a result, the gold cathode 504 was exposed, including the extended card edge portion (or pad) 503 and the floating card edge portion (or pad). The substrate was then immersed in chromium etchant (eg, NaOH / 0.5g + K ₃ Fe (CN) 6 / 1g + water / 4ml) to remove open portions of thin chromium layer 514.

The substrate was immersed in acetone to completely remove the photoresist pattern 513. Thus, the silver anode 505 was exposed by including an extended card edge portion (or pad) 503.

This completed the formation of the entire batch of component electrodes including the gold cathode 504 and the silver anode 505.

Step 7: forming a photoresist pattern (FIG. 7 (g))

A negative photoresist (e.g., Tokyo Ohka Kogyo Co., Ltd., OMR-83, Viscosity 60cp) is applied to the entire upper surface of the substrate 511 by spin coating and prebaked at 70-80 ° C for 30 minutes. It was. After exposure and development, the photoresist is post-baked at 150 ° C. for 30 minutes to cover the substrate except for the oxygen sensing position of the silver anode 505, the gold cathode 504 portion, and the card edge portion or pad, 503. (516) was formed.

Step 8: Screen-Printed Electrolyte Composition (FIG. 7 (h))

The electrolyte composition of the present invention was screen-printed on the oxygen position 515 defined by the photoresist pattern 516 to form the electrolyte containing material 517.

Step 9: Pad Area Coating Film (FIG. 7 (i))

The thermosetting release coating (Fujikura kesei co., XB-801) was screen-printed onto the pad area (or card edge portion) 503 to a thickness of 100 μm, and then cured by heating at 150 ° C. for 10 minutes. A film 508 was formed.

Step 10: Oxygen Gas-Permeable Film Formation (FIG. 7 (j))

An oxygen gas permeable film 507 having a double layer structure was formed on the glass substrate 511 to cover the entire upper surface of the substrate. First, the lower layer of the film 507 was spin coated with a negative photoresist (Tokyo Ohka Kogyo Co., Ltd. OMR-83, viscous 100 cps), prebaked at 80 ° C. for 30 minutes, and the entire substrate surface was exposed, It formed by post-baking at 150 degreeC for 30 minutes. The top layer is then spin coated with Toray-Dow Corning Silicone Co., SE 9176 and heated for 30 minutes at a temperature of 70 ° C. in an oven moistened with water contained in a petri dish or beaker placed therein. It formed by adding and hardening.

Step 11; Pad Exposure (Figure 7 (k))

The coating film 508 formed in the pad region 503 was peeled off with tweezers to selectively remove the oxygen gas permeable film 507 in that portion. Thus, the pads (or card edges 504A and 505A) of the small oxygen electrode were exposed.

When the coating film 508 is peeled off, the oxygen gas permeable film 507 is cut at the edge of the coating film 508 between a film portion located on the coating film 508 and another film portion away from the coating film 508. The oxygen gas permeation membrane 507 was selectively removed so as to be effective.

The portion of the oxygen gas permeable film remaining on the glass substrate was strongly adhered to the substrate, and was not peeled off by the post-treatment process including the water deposition treatment described later. In addition, it was not broken when used in a medical device of an oxygen gas permeable membrane and attached to a catheter or used to monitor the oxygen concentration in a fermenter that was sterilized for about 15 minutes at a temperature of 120 ° C. and a pressure of 1.2 atm.

Step 12: Separation of Small Oxygen Electrode (FIG. 7 (i))

A plurality of small oxygen electrodes were formed at once on the glass substrate 511 and cut into chips by a dicing saw. The example shown provides seven small oxygen electrodes at one time as a substrate.

The oxygen gas permeable film adhered strongly to the substrate and did not peel off during its cutting along the scribe line. Moreover, the reliability test did not show low reliability.

The small oxygen electrode according to the present invention can be applied to any clark type device for electrochemically detecting oxygen including galvani and tripolar oxygen electrodes.

8 (a), (b) and (c) show an example of a tripolar small oxygen electrode.

Here, the eighth (b) shows an unfinished structure in which the oxygen gas permeation membrane has not yet been formed.

The working electrode 702, the counter electrode 703 and the reference electrode 704 were formed on the silicon wafer 701 (see FIG. 8 (b)), and the oxygen gas permeable film 705 was pads 702A of each electrode. Cover surfaces except 703A, 704A).

FIG. 8C is a cross-sectional view taken along the line I-I of the oxygen sensing position where the electrolyte composition 715 is filled in the groove formed in the silicon wafer to form the electrolyte containing material.

Example 6

The tripolar small oxygen electrode according to the present invention having the basic structure shown in Figs. 8 (a) to 8 (c) was manufactured according to the present invention by the following procedure.

Step 1: forming a groove for accommodating the electrolyte-containing material (Figs. 9 (a1) and 9 (a2))

In the same process as that performed in step (1) to (7) of the first embodiment, both sides of the silicon wafer 701 are provided with a groove 706 and an SiO ₂ insulating layer 707 for accommodating an electrolyte-containing material. Formed on.

Step 2: forming the component electrode pattern (FIGS. 9 (b1) and 9 (b2))

In the same process performed in steps 2 to 6 of the fifth embodiment, the working electrode 702 and the counter electrode 703 are both gold and the reference electrode 704 is formed of silver.

Step 3: Form photoresist pattern (FIGS. 9 (c1) and 9 (c2))

By the same process as that performed in step 11 of the first embodiment, the photoresist pattern 311 was formed to cover the substrate surface except for the region 712 and the pad region 713 at the oxygen sensing position.

Step 4: Screen-Printed Electrolyte Composition (Figures 9 (d1) and 9 (d2))

By the same procedure performed in step 12 of Example 1, the electrolyte composition 715 was screen-printed on the oxygen sensing location 712.

Step 5: Forming Pad Area Coating Film (not shown)

By the same procedure performed in step 13 of Example 1, a removable coating film was formed.

Step 6: Oxygen Gas Permeation Membrane (not shown)

By the same process performed in step 14 of Example 1, an oxygen gas permeation membrane was formed.

Step 7: Pad Exposure (Figures 9 (e1) and 9 (e2))

By the same procedure executed in step 15 of the first embodiment, the pads 702A, 703A, and 704A were exposed.

Step 8: Small Oxygen Separation (not shown)

By the same process performed in step 16 of Example 1, a plurality of small oxygen electrodes formed on the silicon substrate were cut into chips.

In Examples 1 to 6, the small oxygen electrode was produced in a yield of 98% or more, and showed good response characteristics with an output variation of ± 3% or less when measured in water in which oxygen was saturated.

The prepared small oxygen electrode is stored in a dried state and can be operated when supplied with water through an oxygen gas permeable membrane by steam sterilization (eg, 121 ° C. and 2.2 atm), immersion in water, saturated steam, and the like.

When a small oxygen electrode is used as the fermentor, the above-mentioned preparation or water supply can be conveniently performed with sterilization of the culture medium. As shown in FIG. 10, the present invention provides that the small oxygen electrode 801 is conveniently attached to a specific adapter 802 designed for a fermenter (as suggested by the inventors in Japanese Patent Application 1-231,708). Lose.

The external electrical connection of the small oxygen electrode is usually carried out by inserting the edge portion of the card into the card edge connector (for example, Fujitsu Ltd., Type 760).

11 shows a configuration of an oxygen concentration measuring apparatus in which a small oxygen electrode of the present invention is used. Oxygen electrode measuring device 810 is composed of a small oxygen electrode 819 and the controller 820 of the present invention. The controller 820 includes a voltage supply device 821 for generating a voltage to be supplied to the oxygen electrode 819, a measuring unit 823 for measuring an output voltage from the oxygen electrode, and a display 824. .

Apparatus 810 measures dissolved oxygen concentrations and gaseous oxygen concentrations in many types of solutions.

As described herein, the present invention provides a small oxygen electrode capable of mass production of substrates in a uniform, highly efficient manner and generally using a semiconductor process, and a method of manufacturing the same.

Claims (4)

An electrolyte composition for screen printing comprising an organic solvent, an inorganic salt in the form of a fine powder that can be dispersed in the organic solvent and pass through a screen printing network, and polyvinyl pyrrolidone dissolved in the organic solvent. The screen printing electrolyte composition according to claim 1, wherein the inorganic salt is selected from potassium chloride and sodium chloride. The electrolyte composition for screen printing according to claim 1, further comprising a buffer. 4. The screen printing electrolyte composition according to claim 3, wherein the buffer is selected from the group consisting of phosphates, acetates, borates, citrates, phthalates, roof salts, clysin salts, and tris (hydroxymethyl) aminomethane salts.