Electrochemical sensor

Abstract

To provide a technique of improving the durability of an electrochemical sensor including an electrode chip having a boron doped diamond film.SOLUTION: An electrochemical sensor includes a substrate, a wire formed on the substrate and having a port, a first insulating resin stacked on the substrate and the wire and having an opening part at a position of the port, and an electrode chip disposed so as to connect to the port through the opening part and having a boron doped diamond film. The electrode chip is disposed so as to cover the entire opening part. A part where a bottom surface of the electrode chip and the first insulating resin overlap is sealed entirely with a second insulating resin.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to electrochemical sensors. [Background technology]

[0002] In recent years, electrochemical sensors equipped with electrode tips having boron-doped diamond films have been proposed (for example, Patent Document 1). Boron-doped diamond films have a wide potential window and small background current, allowing for highly sensitive electrochemical detection of various substances such as uric acid. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2023-42373 Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present invention is to provide a technique for improving the durability of an electrochemical sensor having an electrode tip with a boron-doped diamond film. [Means for solving the problem]

[0005] According to one aspect of the present invention, A substrate; a wiring formed on the substrate and having a port; a first insulating resin layer laminated on the substrate and the wiring and having an opening at the position of the port; an electrode tip having a boron-doped diamond film, the electrode tip being arranged to connect with the port through the opening; the electrode tip is positioned to cover the entire opening; The electrochemical sensor is provided in which the entire area where the bottom surface of the electrode chip and the first insulating resin overlap is sealed with a second insulating resin.

[0006] According to another aspect of the present invention, An electrochemical sensor comprising an electrode having a boron-doped diamond film on at least a working electrode, An electrochemical sensor is provided that satisfies the following conditions (1), (2), and (3): (1) In 0.1M sulfuric acid, the current density was ±250 μA / cm at a sweep rate of 100 mV / s. 2 The range of the potential window that satisfies the above condition is 5.0 V or more, and the maximum value of the charging current density within ±1 V from the potential at the center position of the range of the potential window is 50 μA / cm 2 Within. (2) In 0.1 M sulfuric acid, the time variation of the current value is within 30% when a potential that is more than three times the positive potential window end potential is applied for 30 minutes, based on the potential at the center of the range of the potential window. (3) After the measurement in (2), the same measurement as in (1) is carried out and the same criteria are met.

[0007] According to another aspect of the present invention, An electrochemical sensor comprising an electrode having a boron-doped diamond film on at least a working electrode, An electrochemical sensor is provided that satisfies the following conditions (4) and (5): (4) In 0.1M sulfuric acid, when a potential of +10 V is applied to the working electrode for 30 minutes relative to an Ag / AgCl reference electrode, the time variation of the current value is within 30%. (5) After the measurement in (4), in 0.1 M sulfuric acid, a current density of ±250 μA / cm was measured at a sweep rate of 100 mV / s. 2 The range of the potential window that satisfies the above condition is 5.0 V or more, and the maximum value of the charging current density within ±1 V from the potential at the center position of the range of the potential window is 50 μA / cm 2 Within.

[0008] According to another aspect of the present invention, An electrochemical sensor comprising an electrode having a boron-doped diamond film on at least a working electrode, An electrochemical sensor is provided that satisfies the following conditions (6) and (7): (6) In 0.1 M sulfuric acid, when a potential of +10 V is applied to the working electrode for 30 minutes relative to an Ag / AgCl reference electrode, the time variation of the current value is within 30%. (7) After the measurement in (6) above, when cyclic voltammetry measurement was performed in a mixed solution of 1 mM potassium ferrocyanide and 0.2 M sodium sulfate, a potential of -0.6 V to +1 V was applied repeatedly at a sweep rate of 50 mV / s. The current peaks on the oxidation and reduction sides were each clear and gentle single peaks. [Effects of the Invention]

[0009] According to the present invention, a technique for improving the durability of an electrochemical sensor equipped with an electrode tip having a boron-doped diamond film can be provided. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic plan view of an electrochemical sensor 10 according to an embodiment of the present invention. [Figure 2A] FIG. 2A is a cross-sectional view of the electrochemical sensor 10 shown in FIG. 1 taken along line AA. [Figure 2B] FIG. 2B is an enlarged view of the electrode tip attachment portion of FIG. 2A. [Figure 3] FIG. 3 is a diagram showing the results of the potential window evaluation test (first time) of Sample 1 according to the embodiment of the present invention. [Figure 4] FIG. 4 is a diagram showing the results of a continuous potential application test of Sample 1 according to an embodiment of the present invention. [Figure 5] FIG. 5 is a diagram showing the results of a continuous potential application test of Sample 2 according to an embodiment of the present invention. [Figure 6] FIG. 6 is a diagram showing the results of a continuous potential application test of Sample 3 according to an embodiment of the present invention. [Figure 7] FIG. 7 is a diagram showing the results of the potential window evaluation test (second time) of Sample 1 according to the embodiment of the present invention. [Figure 8]FIG. 8 is an enlarged view of the vicinity of the origin in FIG. [Figure 9] FIG. 9 is a diagram showing the results of the potential window evaluation test (second time) of Sample 3 according to the embodiment of the present invention. [Figure 10] FIG. 10 is an enlarged view of the vicinity of the origin in FIG. [Figure 11] FIG. 11 is a diagram showing the results of a REDOX characteristic evaluation test of Sample 1 according to an embodiment of the present invention. [Figure 12] FIG. 12 is a diagram showing the results of a REDOX characteristic evaluation test of Sample 3 according to an embodiment of the present invention. [Figure 13A] FIG. 13A is a cross-sectional view of a conventional electrochemical sensor. [Figure 13B] FIG. 13B is an enlarged view of the electrode tip attachment portion of FIG. 13A. DETAILED DESCRIPTION OF THE INVENTION

[0011] <Insights gained by the inventor> First, the findings of the inventors will be explained.

[0012] Fig. 13A is a cross-sectional view of a conventional electrochemical sensor, and Fig. 13B is an enlarged view of the electrode chip mounting portion. As shown in Fig. 13A and Fig. 13B, the inventor initially followed the semiconductor chip mounting technology and covered wiring 12 provided on a substrate 11 with a first insulating resin 20 made of hardened solder resist, and then, as described in Patent Document 1, manufactured an electrochemical sensor in which the side of an electrode chip 15 having a boron-doped diamond (BDD) film (hereinafter also referred to as BDD chip 15) was sealed with a second insulating resin 19.

[0013] However, electrochemical sensors equipped with BDD chips (hereinafter referred to as BDD sensors) are suitable for measuring the concentrations of highly reactive analytes such as ozone and chlorine, taking advantage of the chemical stability of BDD. Therefore, they are often used in harsher environments than electrochemical sensors equipped with conventional semiconductor chips, such as when they are immersed in a strongly oxidizing liquid and a current is applied. Furthermore, due to the wide potential window of BDD sensors, higher voltages may be applied than to electrochemical sensors using other electrode materials, and large reverse bias currents may be applied to clean the electrode surface.

[0014] For this reason, even if the BDD chip itself can withstand the measurement environment described above, it was found that as a sensor, the resin insulating the periphery of the electrode chip deteriorates, allowing the highly acidic test solution to penetrate the metal wiring, resulting in leakage current or broken wiring, making it impossible to perform measurements correctly or even to perform measurements at all.

[0015] The inventors have conducted extensive research into the above-mentioned problems and have obtained the following findings.

[0016] The second insulating resin used to seal the BDD chip is required to have both insulating properties and adhesive properties to secure the electrode chip to the substrate. For this reason, epoxy-based thermosetting resins, which have lower water resistance than the first insulating resin, which is made by curing solder resist or other materials formed to insulate the metal wiring, are often used as the second insulating resin. When the BDD sensor is immersed in a test solution and a current is applied, this second insulating resin is sandwiched between the test solution (electrolyte) and the wiring, forming a capacitor. As shown by the arrows in Figure 13B, the thin area of ​​the second insulating resin 19, where the electrolyte is close to the wiring 12, experiences a particularly high electric field intensity, resulting in a high probability of dielectric breakdown in this area. Furthermore, we found that the heat generated during current application due to the electrical resistance between the BDD chip and the electrode pads and the electrical resistance of the wiring itself accelerates the degradation of the insulating resin.

[0017] As a result of further intensive research, the inventors have found a method for solving the above problem.

[0018] To address the above problem, as shown in FIG. 2B , the opening of the first insulating resin 20 is designed to be smaller than the BDD chip 15, so that the first insulating resin 20 overlaps the entire outer periphery of the bottom surface of the BDD chip 15. The overlapping portion between the first insulating resin 20 and the bottom surface of the BDD chip 15 is then sealed with a second insulating resin 19, which has relatively low water resistance (hereinafter referred to as an overlap structure). This overlap structure protects the wiring 12 from the electrolyte by providing a double structure with the first insulating resin 20 below the second insulating resin 19 in the area where the highest electric field strength is applied. This allows the distance between the electrolyte and the wiring 12 to be greater than in the conventional structure shown in FIG. 13B , thereby preventing localized high electric field density in a specific region of the second insulating resin 19. Furthermore, compared to the conventional structure, the contact area between the second insulating resin 19 and the wiring 12 can be minimized, thereby suppressing thermal degradation. Furthermore, in the conventional structure as shown in FIG. 13B, when the second insulating resin 19 deteriorates due to corrosion caused by electrolysis or the like, the path for water penetration into the wiring 12 is wide and tends to expand linearly from the part indicated by the arrow in FIG. 13B, whereas in the structure of the present invention as shown in FIG. 2B, the path for water penetration from the second insulating resin 19 to the wiring 12 is narrow and is no longer linear, making it easier to prevent water from penetrating from the part sealed with the second insulating resin 19.

[0019] The present invention can improve the durability of BDD sensors by using the above-mentioned method. Furthermore, the present invention is a novel invention that identifies specific problems of BDD sensors and develops a structure that can address these problems. Furthermore, while BDD chip mounting has traditionally been performed manually, the technology of the present invention can also be used in mounting processes using automated machines, paving the way for mass production of BDD sensors.

[0020] [Details of the embodiment of the present invention] Next, an embodiment of the present invention will be described below with reference to the drawings. Note that the present invention is not limited to these examples, but is defined by the claims, and is intended to include all modifications within the meaning and scope of the claims.

[0021] <Embodiments of the present invention> (1) Configuration of the electrochemical sensor 10 First, the configuration of an electrochemical sensor 10 (BDD sensor 10) according to this embodiment will be described. FIG. 1 is a schematic plan view of the BDD sensor 10 according to this embodiment. FIG. 2A is a cross-sectional view of the BDD sensor 10 shown in FIG. 1 taken along line AA, and FIG. 2B is an enlarged view of the electrode chip attachment portion of FIG. 2A. As shown in FIG. 1, the BDD sensor 10 includes, for example, a substrate 11, wiring 12 to 14, a first insulating resin 20, electrode chips 15 and 16 (BDD chips 15 and 16), and an AgCl electrode 17. In this embodiment, the BDD chip 15 is used as a working electrode, the BDD chip 16 is used as a counter electrode, and the AgCl electrode 17 made of AgCl is used as a reference electrode.

[0022] The substrate 11 is, for example, a plate-shaped rigid substrate (hard substrate) for supporting the wiring 12 to 14 and the BDD chips 15 and 16, and is not provided with any bending or moving parts. The substrate 11 can be formed, for example, from an insulating material such as an insulating composite resin, ceramic, glass, or plastic. The substrate 11 is preferably formed, for example, from glass epoxy resin or polyethylene terephthalate (PET). The planar shape of the substrate 11 can be, for example, rectangular. The substrate 11 preferably has a strength sufficient to prevent bending or breakage during measurement of the test liquid, for example.

[0023] On one of the two main surfaces of the substrate 11 (hereinafter also referred to as the "top surface of the substrate 11"), a plurality of wirings (three in this embodiment) 12-14 are arranged at a distance from one end of the substrate 11 toward the other end. Ports 12a and 13a for connecting BDD chips 15 and 16 and a port 14a for a reference electrode are provided at the ends of the wirings 12-14, respectively. Examples of materials for forming the wirings 12-14 include various noble metals such as copper (Cu), gold (Au), platinum (Pt), silver (Ag), and palladium (Pd), various metals such as aluminum (Al), iron (Fe), nickel (Ni), chromium (Cr), and titanium (Ti), alloys containing these noble metals or metals as their main components, oxides of the above noble metals, metals, or alloys, and carbon. The thickness of the wirings 12-14 is similar to that of typical semiconductor printed circuit board wiring, approximately 10 μm to 20 μm. The wirings 12 to 14 may be formed using the same material, or may be formed using different materials.

[0024] A first insulating resin 20 is laminated on the substrate 11 and the wiring 12-14. The material of the first insulating resin 20 can be, for example, a solder resist commonly used for insulating electric circuit boards, which is applied and then cured. Any of the following types of solder resist can be used: thermosetting, UV-curing, or alkaline-developable. As shown in FIG. 1, the first insulating resin 20 has openings 20a at the positions of the ports 12a-14a. It is preferable to select a material for the first insulating resin 20 that is as waterproof, smooth, and heat-resistant as possible, and has a low dielectric constant.

[0025] The BDD chips 15 and 16 have, for example, a boron-doped diamond film and are arranged to be electrically connected to the ports 12a and 13a through the opening 20a. As shown in FIG. 1, the BDD chips 15 and 16 are arranged to cover the entire opening 20a. As shown in FIGS. 2A and 2B, the BDD chips 15 and 16 are electrically connected to the ports 12a and 13a via a conductive bonding material 18. The BDD chip 15, which serves as a working electrode, is connected to the port 12a of the wiring 12, and the BDD chip 16, which serves as a counter electrode, is connected to the port 13a of the wiring 13. An AgCl electrode 17, which serves as a reference electrode, is formed on the port 14a of the wiring 14. The bonding material 18 can be a conductive paste (conductive adhesive) such as silver paste, or a conductive tape.

[0026] As shown in FIGS. 2A and 2B , the gap between the bottom surfaces of the BDD chips 15 and 16 (the surfaces connected to the ports 12 a and 13 a) and the first insulating resin 20 is sealed with a second insulating resin 19. The second insulating resin 19 may be, for example, a thermosetting resin or a room-temperature curing resin, such as an epoxy-based, novolac-based, or silicone-based insulating resin. The second insulating resin 19 is formed by applying a liquid insulating resin (hereinafter also referred to as liquid resin) to the periphery of the BDD chips 15 and 16 bonded together using the bonding material 18, and then allowing the liquid resin to penetrate and harden under the BDD chips 15 and 16 and around the bonding material 18 by heating or leaving it to harden at room temperature. The order of mounting the BDD chips 15 and 16 and applying the liquid resin may be reversed. Figures 2A and 2B show the case where the second insulating resin 19 is arranged to cover all or part of the side surfaces of the BDD chips 15 and 16, but the second insulating resin 19 may be arranged only in the overlapping portions so that the side surfaces of the BDD chips 15 and 16 are exposed.

[0027] As shown in FIGS. 2A and 2B, the BDD chips 15 and 16 are composed of, for example, a conductive substrate 22 and a boron-doped diamond film 21 (hereinafter also referred to as the BDD film 21) provided on the upper surface (exposed surface) of the conductive substrate 22. The BDD film 21 is, for example, a polycrystalline film (polycrystalline diamond film) composed of diamond crystals containing boron (B) as a dopant, i.e., diamond crystals having p-type conductivity. A diamond crystal is a crystal in which carbon (C) atoms are arranged in a pattern called a diamond crystal structure. The BDD film 21 may also be a diamond-like carbon (DLC) film doped with B. The B concentration in the BDD film 21 can be measured by secondary ion mass spectrometry (SIMS) and is, for example, 5×10 19 cm -3 5x10 or more 21 cm -3 The following can be mentioned: SIMS is a technique for measuring the concentration of a predetermined substance by detecting ions (secondary ions) generated when a beam of ions (primary ions) is irradiated onto the surface of the BDD film 21 using a mass spectrometer.

[0028] The BDD film 21 can be grown (deposited, synthesized) by, for example, a chemical vapor deposition (CVD) method or a physical vapor deposition (PVD) method. Examples of the CVD method include a hot filament CVD method using a tungsten filament and a plasma CVD method, and examples of the PVD method include an ion beam method and an ionization deposition method. The thickness of the BDD film 21 can be, for example, 0.5 μm to 10 μm, preferably 1 μm to 6 μm, and more preferably 2 μm to 4 μm.

[0029] The conductive substrate 22 may be, for example, a flat substrate made of a low-resistance material. The conductive substrate 22 may be, for example, a p-type single-crystal Si substrate, which is mainly composed of silicon (Si) and contains a predetermined concentration of a p-type dopant such as boron (B). The conductive substrate 22 may also be, for example, a p-type polycrystalline Si substrate. The B concentration in the conductive substrate 22 may be, for example, 5×10 18 cm -3 Over 1.5 x 10 20 cm -3 Less than or equal to 5 x 10 18 cm -3 Over 1.2 x 10 20 cm -3 When the B concentration in the conductive substrate 22 is within the above range, the resistivity of the conductive substrate 22 can be reduced, while preventing a decrease in the manufacturing yield and deterioration in the performance of the conductive substrate 22.

[0030] The thickness of the conductive substrate 22 can be, for example, 350 μm or more. This allows commercially available single-crystal Si substrates with a diameter of 6 inches or 8 inches to be used as the conductive substrate 22 without having to adjust the thickness by back-rapping. As a result, it is possible to improve the productivity of BDD electrodes and reduce manufacturing costs. There is no particular upper limit to the thickness of the conductive substrate 22, but the thickness of a Si substrate currently commonly available on the market is approximately 775 μm for a single-crystal Si substrate with a diameter of 12 inches. Therefore, the upper limit of the thickness of the conductive substrate 22 using current technology can be set to, for example, approximately 775 μm.

[0031] A substrate other than a substrate mainly composed of Si (Si substrate) can also be used as the conductive substrate 22. For example, a substrate composed of a Si compound, such as a silicon carbide substrate (SiC substrate), can also be used as the conductive substrate 22.

[0032] As shown in FIG. 1 , the opening 20a of the first insulating resin 20 is smaller than the bottom surfaces of the BDD chips 15 and 16. That is, the first insulating resin 20 overlaps the entire outer periphery of the bottom surfaces of the BDD chips 15 and 16. As described above, at least the entire area where the bottom surfaces of the BDD chips 15 and 16 overlap with the first insulating resin 20 is sealed with the second insulating resin 19. This overlapping structure allows the linear distance between the electrolyte solution via the second insulating resin 19 and the wiring 12 to be greater than in conventional structures. This prevents localized high electric field density in specific areas of the second insulating resin 19, which has relatively low water resistance, thereby improving the durability of the BDD sensor 10. Furthermore, because the water penetration path from the second insulating resin 19 to the wiring 12 and 13 is narrow and not linear, water penetration from the areas sealed with the second insulating resin 19 is also easily prevented.

[0033] As shown in FIG. 1, the outer shapes (planar shapes) of the opening 20a and the BDD chips 15 and 16 are rectangular (e.g., rectangular or square) when viewed perpendicularly to the top surface of the substrate 11. Furthermore, when viewed perpendicularly to the top surface of the substrate 11, it is preferable that the geometric center of the opening 20a and the geometric center of the BDD chips 15 and 16 approximately coincide (e.g., the deviation between the geometric centers is 0.5 mm or less). The BDD chips 15 and 16 may have the same shape or different shapes. In this embodiment, a case where the BDD chips 15 and 16 have the same shape will be described.

[0034] The plane area (bottom area) of the BDD chips 15 and 16 is, for example, 1 mm 2 More than 100mm 2 In this embodiment, since the BDD film 21 is provided over the entire upper surface of the conductive substrate 22, the plane area of ​​the BDD film 21 is equal to the plane area of ​​the BDD chips 15 and 16.

[0035] The surface area of ​​BDD chips 15 and 16 is 1mm 2If the planar area of ​​the BDD chips 15 and 16 is less than 1 mm, it is difficult to manufacture the BDD chips 15 and 16 with high accuracy and stability. 2 By satisfying the above, the BDD chips 15 and 16 can be manufactured easily and stably with high accuracy. In addition, it is possible to suppress a decrease in the handling ability and mounting stability of the BDD chips 15 and 16. On the other hand, when the plane area of ​​the BDD chips 15 and 16 is 100 mm 2 If the plane area of ​​the BDD chips 15 and 16 exceeds 100 mm, the BDD sensor 10 becomes too large. 2 or less, the BDD sensor 10 can be easily miniaturized.

[0036] The AgCl electrode 17 is not particularly limited in shape or size as long as it is formed so as to cover the wiring 14 and port 14a exposed from the opening 20a.

[0037] The area of ​​the opening 20a is preferably, for example, 20% to 80% of the bottom area of ​​the BDD chips 15 and 16. If the area of ​​the opening 20a is less than 20% of the bottom area of ​​the BDD chips 15 and 16, it may be difficult to connect the BDD chips 15 and 16 to the ports 12a and 13a. In contrast, by making the area of ​​the opening 20a 20% or more of the bottom area of ​​the BDD chips 15 and 16, the connection between the BDD chips 15 and 16 and the ports 12a and 13a is stabilized. On the other hand, if the area of ​​the opening 20a exceeds 80% of the bottom area of ​​the BDD chips 15 and 16, the overlap area becomes small, which may make it easier for water to seep in through the portions sealed with the second insulating resin 19. In contrast, by making the area of ​​the opening 20a 80% or less of the bottom area of ​​the BDD chips 15 and 16, it is easier to prevent water from seeping in through the portions sealed with the second insulating resin 19.

[0038] The gap between the bottom surfaces of the BDD chips 15 and 16 sealed with the second insulating resin 19 and the first insulating resin 20 (the thickness of the second insulating resin 19 in the overlapping portion) is preferably, for example, 10 μm or less. This makes it easier to prevent water from seeping in from the portion sealed with the second insulating resin 19. Note that the lower limit of the thickness between the bottom surfaces of the BDD chips 15 and 16 sealed with the second insulating resin 19 and the first insulating resin 20 is not particularly limited, but considering the ease of handling when applying the second insulating resin 19 and its ability to penetrate into gaps, it is preferably, for example, 1 μm or more.

[0039] The thickness of the first insulating resin 20 is preferably 15 μm or more and 100 μm or less. If the first insulating resin 20 is thinner than 15 μm, it becomes difficult to ensure insulation in areas with steps such as the wiring 12 and 13. On the other hand, if the thickness of the first insulating resin 20 exceeds 100 μm, the bonding material 18 must also be thick, which is disadvantageous in terms of cost. Furthermore, when silver paste is screen-printed as the bonding material 18, there is a large difference in height between the application area and the printing mask, which can cause the printing mask to float and increase errors in the silver paste printing.

[0040] The surface roughness Ra of the first insulating resin 20 (after curing) is preferably, for example, 0.02 μm or more and 1.5 μm or less. Furthermore, the surface roughness Ra is more preferably, for example, 0.02 μm or more and 0.5 μm or less. This makes it easier to make the thickness of the second insulating resin 19 thin and uniform. This reduces the gap between the first insulating resin 20 and the underside of the BDD chips 15, 16, making it easier to prevent water from seeping in through the portion sealed with the second insulating resin 19.

[0041] The first insulating resin 20 is preferably made of a different material from the second insulating resin 19 and has higher waterproofness than the second insulating resin 19. By using the first insulating resin 20 with excellent waterproofness and employing the above-described overlap structure, the waterproofness of the BDD sensor 10 can be efficiently improved. Here, high waterproofness means that when viewed as individual materials, rather than when the BDD chips 15 and 16 are mounted on the BDD sensor 10, the degree of deterioration under an electric field in an electrolyte solution under the same conditions is low and the waterproof performance is high.

[0042] 1, the BDD sensor 10 preferably has a plurality of wirings and ports, the first insulating resin 20 has openings 20a at the positions of the plurality of ports, and a plurality of BDD chips or electrode materials such as AgCl are individually connected to each of the plurality of ports. The BDD sensor 10 of this embodiment has three sets of wirings and ports, with BDD chips connected to the working electrode and counter electrode ports and an electrode made of AgCl formed at the reference electrode port.

[0043] (2) Method for manufacturing electrochemical sensor 10 Next, a method for manufacturing the electrochemical sensor 10 (BDD sensor 10) of this embodiment will be described.

[0044] (Fabrication of BDD chips 15 and 16) The BDD chips 15 and 16 can be fabricated by a known method, for example, as described in Patent Document 1.

[0045] (Fabrication of BDD sensor 10) Next, the resulting BDD chips 15 and 16 are used to fabricate the BDD sensor 10. The BDD sensor 10 may have a BDD chip mounted on each of the three electrodes: the working electrode, the counter electrode, and the reference electrode. Alternatively, the working electrode and the counter electrode may have a BDD chip mounted on each, and the reference electrode may be an electrode made of another material. Furthermore, the working electrode may have a BDD chip mounted on each, and the counter electrode and the reference electrode may be electrodes made of another material. In this embodiment, an example is described in which the working electrode and the counter electrode are mounted on BDD chips 15 and 16, and the reference electrode is an AgCl electrode 17 made of AgCl.

[0046] First, the substrate 11 is prepared. Then, the wirings 12 to 14 and the ports 12a to 14a in a predetermined pattern are provided on the substrate 11. Alternatively, the substrate 11 may be prepared on which the wirings 12 to 14 and the ports 12a to 14a are provided in advance.

[0047] Next, a first insulating resin 20 having openings 20a formed at the positions of the ports 12a to 14a is laminated on the substrate 11 and the wiring 12 to 14. Specifically, for example, an epoxy-based thermosetting resin such as solder resist is applied to the substrate 11 and the wiring 12 to 14 by screen printing and then cured by heating. Then, a conductive bonding material 18 is provided at the positions of the ports 12a and 13a, and the BDD chips 15 and 16 are placed on the bonding material 18 with the BDD film 21 facing upward, and the BDD chips 15 and 16 are electrically connected to the ports 12a and 13a (the wiring 12 and 13), respectively. Specifically, for example, the BDD chip 15 used as the working electrode is electrically connected to the port 12a, and the BDD chip 16 used as the counter electrode is electrically connected to the port 14a. The BDD chips 15 and 16 are arranged so that the opening 20a is hidden by the bottom of the BDD chips 15 and 16, i.e., so that the first insulating resin 20 overlaps the bottom of the BDD chips 15 and 16. AgCl paste is applied to cover the port 14a and wiring 14 exposed from the opening 20a, and the AgCl paste is cured by heating or at room temperature to form an AgCl electrode 17, which electrically connects the port 14a used as a reference electrode to the AgCl electrode 17.

[0048] Next, a thermosetting or room-temperature-setting liquid insulating resin (liquid resin) is applied as the second insulating resin 19 so as to cover the entire periphery of the side surfaces of the BDD chips 15 and 16. It is preferable to select a liquid resin with low viscosity (thermosetting resins lose viscosity when heated). By applying the low-viscosity liquid resin around the BDD chips 15 and 16, it penetrates between the bottom surfaces of the BDD chips 15 and 16 and the first insulating resin 20 by capillary action, filling the gaps completely. It is important to apply the liquid resin without adhering to the surfaces of the BDD chips 15 and 16 (the surfaces of the BDD films 21). The liquid resin is then cured by heating or by leaving it at room temperature, forming the second insulating resin 19. The side surfaces of the bonding material 18 and the second insulating resin 19 may or may not be in contact. The order of mounting the BDD chips 15 and 16 and applying the liquid resin may be reversed. That is, after applying a liquid resin around the bonding material 18, the BDD chips 15 and 16 may be mounted, and the liquid resin may be cured by heating or at room temperature. Also, the liquid resin may or may not be applied around the AgCl electrode 17. This is because the reference electrode does not receive a high potential like the working electrode, and therefore durability is less of a concern.

[0049] In this manner, the BDD sensor 10 shown in FIGS. 1, 2A, and 2B can be fabricated.

[0050] (3) Durability evaluation test of electrochemical sensor 10 Next, three tests performed to evaluate the durability of the electrochemical sensor 10 (BDD sensor 10) of this embodiment will be described.

[0051] (3-1) Potential window evaluation test In this potential window evaluation test, for example, a potential is applied to the BDD chip 15 as the working electrode relative to the AgCl electrode 17 as the reference electrode. Specifically, using a potentiostat, in 0.1 M (M represents the number of moles of solute dissolved in 1 liter of solution; the same applies below) sulfuric acid, the potential is swept at a rate of 100 mV / s by using cyclic voltammetry, lowering it from 0 V to -4 V, then turning it back up, raising it to +4 V, and then turning it back down to 0 V, and the current value is measured successively. The current measurement interval depends on the potentiostat, but is preferably about 100 msec, for example. If a normal potential window is obtained by the measurement in this test, the initial characteristics of the BDD sensor 10 are determined to be good. In this specification, the potential window is defined as a potential window where the current density is ±250 μA / cm on both the positive and negative sides. 2 A normal potential window is one in which the potential window range is 5.0 V or more, and in which no faradaic current flows in dilute sulfuric acid, which does not contain any reactants, the maximum value of the charging current (background current) density within ±1 V from the center of the potential window range is 50 μA / cm 2 The current density is defined as the actual current value normalized by the area of ​​the working electrode. The term "within ±1 V from the center of the potential window range" may be based on the potential of an AgCl reference electrode. If the subsequent continuous potential application causes deterioration of the second insulating resin 19 or the like, resulting in problems with insulation or conduction, abnormal waveforms will be observed within the potential window. Therefore, it is preferable to perform this potential window evaluation test on the BDD sensor 10 before and after the (3-2) continuous potential application test described below.

[0052] (3-2) Continuous potential application test In this continuous potential application test, the wiring connection method and electrolyte are the same as in (3-1). Then, a potential exceeding three times the potential at the positive end of the potential window is applied for 30 minutes, based on the potential at the center of the potential window range measured in (3-1). For example, if the potential window value measured in (3-1) is the reference potential ±3.3 V, a voltage of +10 V is applied for 30 minutes, and the change in current value is measured (the applied potential may be rounded up or down to the nearest 0.1 V). If a predetermined current value corresponding to the applied potential is measured (i.e., no breaks or leaks in the wiring occur) and the time variation of the current value is within a predetermined range, the durability of the BDD sensor 10 is determined to be good. The current value in this test is approximately 1 to 2 A / cm. 2 The current density is 100 s, which simulates an accelerated test under normal operating conditions, including pretreatment and cleaning of the BDD sensor 10. During application of the current, bubbles are generated due to the electrolytic reaction, resulting in some fluctuation in the current value over time. However, if the fluctuation in the current value over time during application of the potential is within 30%, the durability of the BDD sensor 10 is deemed satisfactory. If the test solution penetrates the metal wiring due to deterioration of the insulating resin material around the BDD chip 15, causing electrochemical corrosion, the current will decrease significantly. If this progresses further and the wiring breaks, the current value will drop to zero. Furthermore, if the second insulating resin 19 decomposes and the metal material remains exposed in the liquid, an electrical short circuit will occur, causing a significant increase in the current. It is also known that the potential window of a BDD electrode is approximately ±3.3 V relative to the reference potential when an Ag / AgCl electrode is used as the reference electrode. Therefore, in this continuous potential application test, the preliminary (3-1) potential window evaluation test may be omitted, and a +10 V voltage relative to the reference potential may be applied to the working electrode for 30 minutes using an external Ag / AgCl electrode, and the time variation of the current value may be measured.

[0053] If the BDD sensor 10 is slightly damaged after the measurement in (3-2) (deterioration of the second insulating resin 19 has occurred but has not progressed to the point of electrolyte penetration), time fluctuations in the current value may not be observed. However, even in this case, measuring the potential window will likely result in abnormal current values ​​flowing in the low-potential region within the potential window. Therefore, it is preferable to perform the measurement in (3-1) again after the measurement in (3-2). If a normal potential window is obtained, the durability of the BDD sensor 10 is determined to be good. Note that if the electrode surface is contaminated, the current will increase due to the decomposition reaction of the contaminants. Therefore, it is recommended to perform the measurement in a clean state by cleaning the electrode surface using anodization or cathodic reduction to confirm stability.

[0054] (3-3) REDOX characteristic evaluation test This REDOX characteristic evaluation test is preferably performed on the BDD sensor 10 after the continuous potential application test (3-2). The wiring connection method for this test is the same as (3-1). In this test, a potential of -0.6 V to +1 V is applied repeatedly (sweep rate 50 mV / s) in a mixed solution of 1 mM potassium ferrocyanide and 0.2 M sodium sulfate, and the current value is measured. When a redox reaction occurs and the current peaks on the oxidation and reduction sides are clear and gentle single peaks, the durability of the BDD sensor 10 is determined to be good. In the REDOX characteristic test, if the electrode surface is dirty, abnormal peaks will occur due to the decomposition reaction of the dirt. Therefore, it is recommended to measure the electrode surface in a clean state by cleaning it using anodization or cathodic reduction to confirm stability.

[0055] The BDD sensor 10 of this embodiment has excellent durability and satisfies the characteristic test conditions (3-1) and (3-3) even after the continuous potential application test (3-2). Specifically, the BDD sensor 10 of this embodiment is an electrochemical sensor including an electrode having a BDD film 21 at least on the working electrode, and satisfies the following conditions (1), (2), and (3). (1) In 0.1M sulfuric acid, the current density was ±250 μA / cm at a sweep rate of 100 mV / s. 2The range of the potential window that satisfies the above condition is 5.0 V or more, and the maximum value of the charging current density within ±1 V from the potential at the center position of the range of the potential window is 50 μA / cm 2 Within. (2) In 0.1 M sulfuric acid, the time variation of the current value is within 30% when a potential that is more than three times the positive potential window end potential is applied for 30 minutes, based on the potential at the center of the range of the potential window. (3) After the measurement in (2), the same measurement as in (1) is carried out and the same criteria are met.

[0056] The BDD sensor 10 of this embodiment is an electrochemical sensor including an electrode having a BDD film 21 at least on the working electrode, and satisfies the following conditions (4) and (5). (4) In 0.1M sulfuric acid, when a potential of +10 V is applied to the working electrode for 30 minutes relative to an Ag / AgCl reference electrode, the time variation of the current value is within 30%. (5) After the measurement in (4), in 0.1 M sulfuric acid, a current density of ±250 μA / cm was measured at a sweep rate of 100 mV / s. 2 The range of the potential window that satisfies the above condition is 5.0 V or more, and the maximum value of the charging current density within ±1 V from the potential at the center position of the range of the potential window is 50 μA / cm 2 Within.

[0057] The BDD sensor 10 of this embodiment is an electrochemical sensor including an electrode having a BDD film 21 at least on the working electrode, and satisfies the following conditions (6) and (7). (6) In 0.1 M sulfuric acid, when a potential of +10 V is applied to the working electrode for 30 minutes relative to an Ag / AgCl reference electrode, the time variation of the current value is within 30%. (7) After the measurement in (6) above, when cyclic voltammetry measurement was performed in a mixed solution of 1 mM potassium ferrocyanide and 0.2 M sodium sulfate, a potential of -0.6 V to +1 V was applied repeatedly at a sweep rate of 50 mV / s. The current peaks on the oxidation and reduction sides were each clear and gentle single peaks.

[0058] <Other Embodiments of the Present Invention> Although the embodiments of the present invention have been specifically described above, the present invention is not limited to the above-described embodiments and can be modified in various ways without departing from the spirit of the present invention.

[0059] For example, in the above-described embodiment, the BDD sensor 10 includes a BDD chip 15 used as a working electrode, a BDD chip 16 used as a counter electrode, and an AgCl electrode 17 used as a reference electrode. However, the reference electrode may be a BDD chip or another electrode. The counter electrode may also be an electrode without a BDD chip. For example, the reference electrode or counter electrode may be an electrode made of a metal such as Pt, Au, Cu, Pd, Ni, or Ag, or a carbon electrode. The BDD sensor 10 may also include a working electrode and a counter electrode but no reference electrode. In this case, an external electrode made of AgCl may be separately prepared and used as the reference electrode.

[0060] For example, in the above-described embodiment, the first insulating resin 20 is described as being formed by applying and then curing solder resist. Alternatively, a coverlay film made of polyimide or PET can be used. Solder resist has relatively high water resistance, but pinholes can occur due to the presence of foreign matter such as tiny chips of the substrate or air bubbles during the coating process. If such pinholes exist on the wiring, the risk of leakage current originating from the pinholes increases. Even if there are no pinholes, when a current is passed through a BDD sensor in an electrolyte, the wiring and the electrolyte sandwich the solder resist, forming a capacitor. Therefore, if there are areas where the solder resist is thin or contains water, the electric field can concentrate there, degrading the solder resist and potentially causing dielectric breakdown.

[0061] To avoid the risks inherent in the solder resist mounting process, it is preferable to use a coverlay film instead of solder resist. Coverlay film is an insulating film made of materials such as polyimide or PET. Following the example of semiconductor chip mounting technology, coverlay film is typically used to protect the circuitry of flexible substrates. While solder resist is typically used for the rigid substrates of BDD sensors, the use of coverlay film makes it easier to achieve high surface flatness than solder resist, further improving the effectiveness of preventing the intrusion of test liquids. This is because coverlay film is pinhole-free and, compared to solder resist, is more waterproof, smooth, and has a lower dielectric constant, thereby solving the aforementioned problems.

[0062] For example, in the above embodiment, the first insulating resin 20 of the BDD sensor 10 is described as being either a solder resist or a coverlay film, but the BDD sensor 10 may have both a solder resist and a coverlay film. For example, the first insulating resin 20 may be a solder resist provided on a coverlay film to protect the BDD sensor 10. [Example]

[0063] Next, examples of the present invention will be described. These examples are merely examples of the present invention, and the present invention is not limited to these examples.

[0064] (1) Preparation of BDD sensor The BDD sensor described in the above-described embodiment was prepared and designated Sample 1. A glass epoxy resin substrate was used, and copper wiring was formed using a subtractive method. After that, a UV-curable solder resist was applied to the required areas, excluding the chip mounting area and terminal area, using mask printing, and then cured. The viscosity of the solder resist and the amount of inorganic powder mixed in were adjusted to ensure a flat solder resist surface after curing. As a result, the unevenness (Ra) on the solder resist was 1.05 μm. For comparison, two BDD sensors with the same structure as that shown in Patent Document 1 but without an overlapping structure were prepared and designated Samples 2 and 3.

[0065] (2) Durability evaluation test Next, the durability evaluation test described in the above embodiment was carried out on each of the sensors of Samples 1 to 3.

[0066] (2-1) Potential window evaluation test (1st time) The potential window evaluation test described in the above embodiment was carried out on each of the sensors of Samples 1 to 3. The conditions were as follows. Electrolyte: Dilute sulfuric acid 0.1M Cyclic voltammetry conditions: ±4 V, sweep rate 100 mV / s Current density ±250μA / cm 2 The range of the potential window was evaluated with the end point of 4 mm. 2 Because of the size, the current value is divided by the surface area of ​​the electrode to obtain the current density (μA / cm 2 ) was converted to

[0067] Figure 3 shows the results of the potential window evaluation test (first time) for Sample 1. The results for Samples 2 and 3 are not shown. For Sample 1, the potential window range was 6.4 V, and the maximum value of the charging current density in the range of ±1 V from the potential of the AgCl reference electrode was 8 μA / cm. 2 In addition, for sample 2, the potential window range was 6.5 V, and the maximum value of the charging current density in the range of ±1 V from the potential of the AgCl reference electrode was 12 μA / cm 2In addition, for sample 3, the potential window range was 6.5 V, and the maximum value of the charging current density in the range of ±1 V from the potential of the AgCl reference electrode was 11 μA / cm 2 That is, all of Samples 1 to 3 satisfied the conditions for the initial characteristics in the potential window evaluation test (first time).

[0068] (2-2) Continuous potential application test For each of the sensors of Samples 1 to 3, the potential between the working electrode and the counter electrode was controlled relative to the AgCl reference electrode in 0.1 M sulfuric acid as follows, and the current value was measured. ·4V, standby for 5 minutes 5V, 5 minutes standby 6V, 5 minutes standby ·7V, standby for 5 minutes 8V, 5 minutes standby ·9V, standby for 5 minutes 10V, 30 minutes standby

[0069] Figure 4 shows the results of the continuous potential application test for Sample 1, Figure 5 shows the results for Sample 2, and Figure 6 shows the results for Sample 3. For comparison, Figure 5 also shows the plots from Figure 4 in gray. As shown in Figures 4 and 6, the sensors for Sample 1 and Sample 3 measured a predetermined current value corresponding to the applied potential, with the time variation of the current value being within 30%. On the other hand, as shown in Figure 5, the sensor for Sample 2 experienced corrosion of the second insulating resin, causing electrolyte to penetrate the wiring when 9 V was applied, 25 minutes after the start of measurement. This caused the wiring to break, resulting in the loss of current. In other words, Samples 1 and 3 met the durability requirements for the continuous potential application test, but Sample 2 did not.

[0070] (2-3) Potential window evaluation test (2nd time) After the continuous potential application test, the potential window of each sensor was evaluated under the same conditions as in (2-1).

[0071] Figure 7 shows the results of the second potential window evaluation test for Sample 1. Figure 8 is an enlarged view of the vicinity of the origin in Figure 7. As shown in Figures 7 and 8, the sensor for Sample 1 was able to perform measurements within the normal potential window range, and the current density was ±250 μA / cm 2 The potential window in which this condition is satisfied is 6.5 V, and the maximum charging current density in the range of ±1 V from the AgCl reference electrode potential is 5.6 μA / cm 2 On the other hand, the potential window of the sensor of sample 2 could not be measured due to a disconnection (not shown). FIG. 9 shows the results of the second potential window evaluation test of sample 3. FIG. 10 is an enlarged view of the vicinity of the origin in FIG. 9. As shown in FIGS. 9 and 10, the sensor of sample 3 had a large waveform disturbance, and the maximum current value in the range of ±1 V from the potential of the AgCl reference electrode was 230 μA, which corresponds to a current density of 5750 μA / cm. 2 The background current of the sensor of Sample 3 increased, making it difficult to use as a sensor. In other words, in the second potential window evaluation test, Sample 1 met the durability conditions, but Samples 2 and 3 did not.

[0072] (2-4) REDOX characteristic evaluation test After the continuous potential application test, the sensors of Sample 1 and Sample 3 were subjected to the REDOX characteristic evaluation test described in the above embodiment. The electrolyte was a mixture of 1 mM potassium ferrocyanide and 0.2 M sodium sulfate, and the potential between the working electrode and the reference electrode was controlled as follows to measure the current value. Increase the voltage from -0.6V to +1V, then decrease it to -0.6V. The sweep speed was 50 mV / s, and the current measurement interval was 100 msec.

[0073] Figure 11 shows the results of the REDOX characteristic evaluation test for Sample 1, and Figure 12 shows the results for Sample 3. As shown in Figure 11, Sample 1 had clear current peaks on the oxidation and reduction sides, each of which was a gentle single peak. Sample 3 met the durability requirements in the continuous potential application test, but did not meet the requirements for the potential window and charging current value in the subsequent potential window evaluation test. As shown in Figure 12, the waveform in the REDOX test for Sample 3 was also significantly distorted, indicating that it did not function as a normal electrochemical sensor.

[0074] In some cases, such as Sample 2, the insulating resin corrodes and the wiring breaks when the continuous potential application test is performed, but in other cases the insulating resin corrodes in areas hidden by the chip, allowing the electrolyte to penetrate, making it impossible to determine the condition based on appearance alone. Therefore, we confirmed that it is possible to reliably identify degraded sensors by performing the above-mentioned potential window evaluation test, continuous potential application test, and further potential window evaluation test together, or by performing the REDOX characteristics evaluation test after the continuous potential application test.

[0075] From the above, it was confirmed that the BDD sensor employing the overlap structure according to the present invention satisfies the above test conditions and has excellent durability.

[0076] In the continuous potential application test in this example, the potential was increased in steps, but there is no problem if +10 V is applied directly without following this procedure. In that case, Sample 2, which broke at 9 V, is expected to break again within 30 minutes, which is considered sufficient for selecting highly durable sensors.

[0077] <Preferred embodiment of the present invention> Preferred embodiments of the present invention will be described below.

[0078] (Appendix 1) According to one aspect of the present invention, A substrate; a wiring formed on the substrate and having a port; a first insulating resin layer laminated on the substrate and the wiring and having an opening at the position of the port; an electrode tip having a boron-doped diamond film, the electrode tip being arranged to connect with the port through the opening; the electrode tip is positioned to cover the entire opening; The electrochemical sensor is provided in which the entire area where the bottom surface of the electrode chip and the first insulating resin overlap is sealed with a second insulating resin.

[0079] (Appendix 2) 10. The electrochemical sensor of claim 1, Used to measure the concentration of ozone or chlorine in liquid.

[0080] (Appendix 3) 10. The electrochemical sensor of claim 1, The area of ​​the opening is 20% or more and 80% or less of the bottom area of ​​the electrode tip.

[0081] (Appendix 4) 10. The electrochemical sensor of claim 1, The thickness between the bottom surface of the electrode tip, which is sealed with the second insulating resin, and the first insulating resin is 10 μm or less.

[0082] (Appendix 5) 10. The electrochemical sensor of claim 1, The thickness of the first insulating resin is not less than 15 μm and not more than 100 μm.

[0083] (Appendix 6) 10. The electrochemical sensor of claim 1, The surface roughness Ra of the first insulating resin is 0.02 μm or more and 1.5 μm or less.

[0084] (Appendix 7) 10. The electrochemical sensor of claim 1, The first insulating resin is made of a different material from the second insulating resin.

[0085] (Appendix 8) 10. The electrochemical sensor of claim 1, At the interface between the first insulating resin and the second insulating resin, a boundary is observed, which indicates that the first insulating resin had already hardened before the second insulating resin was applied.

[0086] (Appendix 9) 10. The electrochemical sensor of claim 1, The first insulating resin has higher waterproofing properties than the second insulating resin.

[0087] (Appendix 10) 10. The electrochemical sensor of claim 1, The first insulating resin is formed by applying a solder resist and then curing it.

[0088] (Appendix 11) 10. The electrochemical sensor of claim 1, The first insulating resin is a coverlay film made of polyimide or PET.

[0089] (Appendix 12) 12. The electrochemical sensor of any one of claims 1 to 11, a plurality of the wirings and the ports; the first insulating resin has the openings at the positions of the plurality of ports, A plurality of the electrode tips are individually connected to each of the plurality of the ports.

[0090] (Appendix 13) 13. The electrochemical sensor of claim 12, The wiring and the port are provided in three sets, The electrode chips are connected to the working electrode and counter electrode ports, and an electrode made of AgCl is formed on the reference electrode port.

[0091] (Appendix 14) According to another aspect of the present invention, An electrochemical sensor comprising an electrode having a boron-doped diamond film on at least a working electrode, An electrochemical sensor is provided that satisfies the following conditions (1), (2), and (3): (1) In 0.1M sulfuric acid, the current density was ±250 μA / cm at a sweep rate of 100 mV / s. 2 The range of the potential window that satisfies the above condition is 5.0 V or more, and the maximum value of the charging current density within ±1 V from the potential at the center position of the range of the potential window is 50 μA / cm 2 Within. (2) In 0.1 M sulfuric acid, the time variation of the current value is within 30% when a potential that is more than three times the positive potential window end potential is applied for 30 minutes, based on the potential at the center of the range of the potential window. (3) After the measurement in (2), the same measurement as in (1) is carried out and the same criteria are met.

[0092] (Appendix 15) According to another aspect of the present invention, An electrochemical sensor comprising an electrode having a boron-doped diamond film on at least a working electrode, An electrochemical sensor is provided that satisfies the following conditions (4) and (5): (4) In 0.1M sulfuric acid, when a potential of +10 V is applied to the working electrode for 30 minutes relative to an Ag / AgCl reference electrode, the time variation of the current value is within 30%. (5) After the measurement in (4), in 0.1 M sulfuric acid, a current density of ±250 μA / cm was measured at a sweep rate of 100 mV / s. 2 The range of the potential window that satisfies the above condition is 5.0 V or more, and the maximum value of the charging current density within ±1 V from the potential at the center position of the range of the potential window is 50 μA / cm 2 Within.

[0093] (Appendix 16) According to another aspect of the present invention, An electrochemical sensor comprising an electrode having a boron-doped diamond film on at least a working electrode, An electrochemical sensor is provided that satisfies the following conditions (6) and (7): (6) In 0.1 M sulfuric acid, when a potential of +10 V is applied to the working electrode for 30 minutes relative to an Ag / AgCl reference electrode, the time variation of the current value is within 30%. (7) After the measurement in (6) above, when cyclic voltammetry measurement was performed in a mixed solution of 1 mM potassium ferrocyanide and 0.2 M sodium sulfate, a potential of -0.6 V to +1 V was applied repeatedly at a sweep rate of 50 mV / s. The current peaks on the oxidation and reduction sides were each clear and gentle single peaks. [Explanation of symbols]

[0094] 10 Electrochemical sensor (BDD sensor) 11 Circuit Board 12~14 Wiring Ports 12a~14a 15, 16 Electrode chip (BDD chip) 17 AgCl electrode 18 Bonding material 19 Second insulating resin 20 First insulating resin 20a opening 21 Boron-doped diamond film (BDD film) 22 Conductive substrate

Claims

1. A substrate; a wiring formed on the substrate and having a port; a first insulating resin layer laminated on the substrate and the wiring and having an opening at the position of the port; an electrode tip having a boron-doped diamond film, the electrode tip being arranged to connect with the port through the opening; the electrode tip is positioned to cover the entire opening; The electrochemical sensor comprises a portion where the bottom surface of the electrode chip and the first insulating resin overlap, the entire area of ​​which is sealed with a second insulating resin.

2. 2. The electrochemical sensor according to claim 1, wherein the area of ​​the opening is 20% to 80% of the bottom area of ​​the electrode tip.

3. 2. The electrochemical sensor according to claim 1, wherein a thickness between the bottom surface of the electrode chip sealed with the second insulating resin and the first insulating resin is 10 [mu]m or less.

4. 2. The electrochemical sensor according to claim 1, wherein the first insulating resin is a solder resist that has been applied and then cured.

5. 2. The electrochemical sensor according to claim 1, wherein the first insulating resin is a coverlay film made of polyimide or PET.

6. a plurality of the wirings and the ports; the first insulating resin has the openings at the positions of the plurality of ports, The electrochemical sensor according to claim 1 , wherein a plurality of the electrode tips are individually connected to a plurality of the ports, respectively.

7. The wiring and the port are provided in three sets, 7. The electrochemical sensor according to claim 6, wherein the electrode chips are connected to the working electrode and counter electrode ports, and an electrode made of AgCl is formed at the reference electrode port.

8. An electrochemical sensor comprising an electrode having a boron-doped diamond film on at least a working electrode, An electrochemical sensor that satisfies the following conditions (1), (2), and (3): (1) In 0.1 M sulfuric acid, a current density of ±250 μA / cm was measured at a sweep rate of 100 mV / s. ２ The range of the potential window that satisfies the above condition is 5.0 V or more, and the maximum value of the charging current density within ±1 V from the potential at the center position of the range of the potential window is 50 μA / cm ２ Within. (2) In 0.1 M sulfuric acid, the time variation of the current value is within 30% when a potential exceeding three times the positive potential window end potential is applied for 30 minutes, based on the potential at the center of the range of the potential window. (3) After the measurement in (2), the same measurement as in (1) is carried out and the same criteria are met.

9. An electrochemical sensor comprising an electrode having a boron-doped diamond film on at least a working electrode, An electrochemical sensor that satisfies the following conditions (4) and (5): (4) In 0.1 M sulfuric acid, when a potential of +10 V is applied to the working electrode for 30 minutes relative to an Ag / AgCl reference electrode, the fluctuation of the current value with time is within 30%. (5) After the measurement in (4), in 0.1 M sulfuric acid, a current density of ±250 μA / cm was measured at a sweep rate of 100 mV / s. ２ The range of the potential window that satisfies the above condition is 5.0 V or more, and the maximum value of the charging current density within ±1 V from the potential at the center position of the range of the potential window is 50 μA / cm ２ Within.

10. An electrochemical sensor comprising an electrode having a boron-doped diamond film on at least a working electrode, An electrochemical sensor that satisfies the following conditions (6) and (7): (6) In 0.1 M sulfuric acid, when a potential of +10 V is applied to the working electrode for 30 minutes relative to an Ag / AgCl reference electrode, the fluctuation of the current value with time is within 30%. (7) After the measurement in (6) above, when cyclic voltammetry measurement was performed in a mixed solution of 1 mM potassium ferrocyanide and 0.2 M sodium sulfate, a potential of −0.6 V to +1 V was repeatedly applied at a sweep rate of 50 mV / s. The current peaks on the oxidation side and reduction side were each clear and gentle single peaks.

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