JP2005337852A - Substrate for gas sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a substrate for a gas sensor used for measurement of a component concentration of gas including a specific component, having a small size, excellent responsiveness and high reliability, and drivable with a low power consumption. <P>SOLUTION: This substrate for the gas sensor has characteristics wherein an electrode pattern 3 where a gas detection element 9 is loaded is formed on one main surface of an insulating substrate 1, and an electrode pad 4 connected electrically to the electrode pattern 3 through a penetration conductor 2 is formed on a portion opposite to the electrode pattern 3 on the other main surface of the insulating substrate 1, and a pattern 6 for a heater and an electrode pad 5 for the heater formed on both ends thereof are also formed there. The electrode pad 4 is not exposed to high-temperature and high-concentration gas. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a gas sensor substrate used for measuring the concentration of a component contained in a gas, and particularly has a small size and excellent responsiveness and high reliability used for measuring the concentration of a gas component containing a specific component. The present invention relates to a gas sensor substrate driven by power consumption.

  Gas sensors that detect the concentration of a specific component contained in a gas are used in many fields. For example, in recent years, environmental issues on a global scale are being discussed, and research and development of fuel cells as a highly efficient power source are actively conducted because there are few environmental harmful substances such as carbon dioxide exhausted into the environment. Yes. In the case of a fuel cell, it is considered promising to use hydrogen obtained by reforming methanol or the like as a fuel. In order to improve the power generation efficiency of the fuel cell, the hydrogen concentration in the reformed gas, etc. There is an increasing demand for gas sensors that can directly detect gas. In addition, for the exhaust gas of fuel cells for in-vehicle use, the concentration of hydrogen contained in the exhaust gas can be measured with higher sensitivity in order to reduce the adverse effects of harmful substances contained in the exhaust gas on the global environment. Expectations for small and highly reliable gas sensors are increasing. Hereinafter, a gas sensor substrate for the purpose of detecting the hydrogen concentration of a gas containing hydrogen will be described as an example.

  A conventional hydrogen detection gas sensor is formed by forming a metal semiconductor element such as indium oxide as a gas detection element on a substrate made of alumina ceramic or a glass substrate made of quartz or the like by a vacuum deposition method or a sputtering method. A comb-shaped Pt electrode or Au electrode is formed on the gas sensing element by a vacuum deposition method, a sputtering method, or the like, and the alumina ceramics is used to keep the gas sensing element active against reducing hydrogen gas. There has been proposed a structure in which a heating element such as a heater is provided on the back surface of a glass substrate made of a substrate, quartz or the like, and the gas detection element is controlled to a constant operating temperature at which the gas concentration can be detected (for example, , See Patent Document 1).

  An example of a conventional gas sensor substrate is shown in FIG. FIG. 2A is a cross-sectional view of a conventional gas sensor substrate, and is a cross-sectional view taken along line A-A ′ of FIG. 2B showing a plan view of the conventional gas sensor substrate.

As shown in FIGS. 2 (a) and 2 (b), an indium (In) thin film is formed on one main surface of an insulating substrate 21 made of alumina ceramic or glass by vacuum deposition, and then heat-treated in air. A gas sensing element 29 made of a desired indium oxide (In ₂ O ₃ ) thin film is formed. Next, a comb-shaped electrode 30 made of platinum (Pt) is formed on the gas detecting element 29 by a vacuum deposition method. In many cases, a lead wire (not shown) made of the same platinum (Pt) as that of the comb electrode 30 is bonded on the comb electrode 30 in order to supply a voltage to the gas detection element 29.

  The comb electrode 30 may be provided between the gas detection element 29 and the insulating substrate 21. In this case, in order to bond the lead wire to the comb electrode 30, a part of the comb electrode 30 is provided. A gas detection element 29 is formed so as to be exposed.

Thereafter, a heating element (heater) 31 for temperature control of the gas detection element 29 is pressed or joined to the other main surface of the insulating substrate 21 to produce a gas sensor substrate.
JP-A-6-148112

  However, in the structure of the gas sensor substrate proposed in Patent Document 1, for example, the comb-shaped electrode 30 made of Pt and the lead wire have an insulating substrate 21 on which a gas detection element 29 made of a metal semiconductor element such as indium oxide is formed. Therefore, it is always exposed to a gas containing high-concentration hydrogen at a high temperature. Since Pt has a so-called hydrogen embrittlement when it comes into contact with hydrogen, the comb electrode 30 and the lead wire are exposed to a gas containing hydrogen at a high temperature and high concentration over a long period of time. When used, the comb electrode 30 and the lead wire are embrittled by hydrogen and the performance of the gas sensor substrate deteriorates. In the worst case, there is a problem that it is impossible to supply voltage to the gas detection element 29. .

  Further, when the comb-shaped electrode 30 is formed of a single metal layer of Pt or gold (Au) on one main surface of the insulating substrate 21 made of glass such as alumina ceramics or quartz by a vacuum deposition method, a sputtering method, or the like. Since the bonding strength between the single metal layer of Pt or Au and the insulating substrate 21 made of glass such as alumina ceramics or quartz is generally weak, this comb is used after a reliability test such as a temperature cycle. There is a problem that the adhesion strength between the mold electrode 30 and the insulating substrate 21 deteriorates due to an internal stress generated due to a difference in thermal expansion coefficient between the two, and peeling easily occurs.

  Further, when the insulating substrate 21 made of glass such as quartz is used, the heat conductivity is 2 W / m · K or less, so that the heating element 31 such as a heater provided on the other main surface of the insulating substrate 21. Is not conducted quickly to the gas sensing element 29 formed on one main surface of the insulating substrate 21, and it takes time to reach a desired constant operating temperature at which the gas sensing element 29 is activated. It was. As a result, there is a problem that the quick response as a gas sensor is inferior. In particular, when the heating element 31 such as a heater is integrated by pressure welding or bonding that causes a non-uniform and partial gap with respect to the insulating substrate 21, heat conduction to the gas detection element 29 is remarkably high. This hinders the sensitivity of the gas sensor and causes a problem in that the insulating substrate 21 breaks due to a difference in expansibility of the insulating substrate 21 between the high temperature portion and the low temperature portion.

  Furthermore, since the gas sensor substrate described above has a structure in which the heating element 31 such as a heater is pressed or joined to the insulating substrate 21, there is a problem that there is a certain limit to further downsizing and low profile. Had.

  The present invention has been completed in view of the above problems, and its purpose is used for measuring the component concentration of a gas containing a specific component, and has a small size and excellent responsiveness and high reliability. Another object of the present invention is to provide a gas sensor substrate that can be driven with low power consumption.

  The gas sensor substrate of the present invention is a gas sensor substrate in which an electrode pattern on which a gas detection element is mounted is formed on one main surface of an insulating substrate, and the gas sensor substrate has a portion facing the electrode pattern on the other main surface of the insulating substrate. An electrode pad electrically connected to the electrode pattern via a through conductor is formed, and a heater pattern and heater electrode pads formed at both ends thereof are formed. Is.

  In the gas sensor substrate of the present invention, preferably, the insulating substrate has a metal layer formed in a portion thereof facing a portion where the gas detection element on one main surface is mounted. One end is connected to the other end of another through conductor led to the other main surface of the insulating substrate.

  In the gas sensor substrate of the present invention, preferably, the electrode pattern, the electrode pad, and the heater electrode pad are formed by sequentially laminating an adhesion metal layer, a Pt layer, and an Au layer, respectively, and the heater pattern is an adhesion metal layer. And a Pt layer are sequentially laminated.

  According to the gas sensor substrate of the present invention, the electrode pad is formed in a portion facing the electrode pattern on the other main surface of the insulating substrate and electrically connected to the electrode pattern through the through conductor. This electrode pad is not in direct contact with a gas containing hydrogen at a high concentration at a high temperature, so that an electrode pad having excellent reliability can be obtained. In addition, since the lead wire for supplying voltage to the electrode pad does not come into contact with a gas containing a high concentration of hydrogen at a high temperature, the material of the lead wire and the electrode pad is not limited, and the durability is reliable. It can be excellent.

  Further, since the electrode pad and the heater electrode pad are formed on the same other main surface, there is an advantage that the work of connecting the lead wires for supplying voltage and power to each pad by bonding or the like can be efficiently performed. . Furthermore, since the heater pattern is incorporated in the insulating substrate, there is no need to press or bond the heating element to the insulating substrate. As a result, a gas sensor substrate that can be further reduced in size and height can be obtained.

  Further, according to the gas sensor substrate of the present invention, preferably, the heater pattern is connected to a metal layer provided inside the insulating substrate via another through conductor, so that the heater pattern is separated from the heater pattern. Most of the generated heat is quickly conducted to the metal layer through other through conductors and is transmitted to the gas detection element. As a result, the gas sensing element has excellent responsiveness and heat is efficiently transferred, so that the power consumption of the heater pattern can be reduced. At this time, the metal layer also functions as a stable heat accumulator having a constant heat capacity, so that the gas detection element can be easily maintained at a desired constant operating temperature. Therefore, it is possible to provide a gas sensor substrate that has excellent responsiveness and can be driven with low power consumption.

  According to the gas sensor substrate of the present invention, preferably, the electrode pattern on which the gas detection element is mounted on one main surface of the insulating substrate is formed by sequentially laminating an adhesion metal layer, a Pt layer, and an Au layer. Therefore, even if the electrode pattern is exposed to a gas containing high concentration of hydrogen at a high temperature, the lower Pt layer is protected by the uppermost Au layer, and hydrogen embrittlement of the Pt layer is greatly reduced. At the same time, the electrode pattern can be firmly bonded to the insulating substrate by the adhesion metal layer, and an electrode pattern having excellent adhesion strength and reliability can be formed.

  Further, according to the gas sensor substrate of the present invention, preferably, the electrode pad and the heater electrode pad are formed by sequentially laminating an adhesion metal layer, a Pt layer, and an Au layer on the other main surface on the insulating substrate. Since the adhesion pattern is formed by sequentially laminating the adhesion metal layer and the Pt layer, the electrode pad, the heater electrode pad, and the heater pattern can be firmly bonded to the insulating substrate by the adhesion metal layer, and adhesion strength and reliability can be obtained. It is possible to form an electrode pad, a heater electrode pad, and a heater pattern that are excellent in performance.

The gas sensor substrate of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 shows an example of an embodiment of a gas sensor substrate according to the present invention. (A) is a cross-sectional view of the gas sensor substrate, and a cross-sectional view taken along line AA ′ of (b) showing a top view of the gas sensor substrate. (B) is a top view of the gas sensor substrate, and (c) is a bottom view of the gas sensor substrate.

  In FIG. 1, 1 is an insulating substrate, 2 is a through conductor, 3 is an electrode pattern on which the gas detection element 9 is mounted, 3a, 4a, 5a and 6a are adhesive metal layers, 3b, 4b, 5b and 6b are Pt layers, 3c 4c and 5c are Au layers, 4 is an electrode pad electrically connected to the electrode pattern 3 through the through conductor 2, 5 is a heater electrode pad formed at both ends of the heater pattern 6, and 6 is a heater. The pattern for use 7 is another through conductor whose one end is led to the other main surface of the insulating substrate 1, 8 is a metal layer provided inside the insulating substrate 1 and connected to the other end of the other through conductor 7, 9 is gas detection.

Insulating substrate 1, for example, alumina ceramics, mullite _{(3Al 2 O 3 · 2SiO 2} ) ceramics, aluminum nitride (AlN) ceramics, silicon carbide (SiC) ceramics, silicon nitride _(Si 3 _{N 4)} ceramics such as ceramics and the boron It consists of inorganic materials such as silicate glass and quartz.

  If the insulating substrate 1 is made of alumina ceramics, for example, an appropriate organic binder, solvent, plasticizer, dispersant, etc. are added to and mixed with the raw material powder of aluminum oxide to make a mud, Conventionally known sheet forming methods such as a doctor blade method and a calender roll method are used to form a sheet to obtain a ceramic green sheet (ceramic green sheet). Thereafter, the ceramic green sheet is punched into a predetermined shape and is electrically A through-hole conductor 2 for establishing a general connection, another through-conductor 7 for quickly conducting heat, and a metal layer 8 for storing the heat, a high melting point such as molybdenum (Mo) or tungsten (W) It is formed by a printing method using a paste containing a metal as a main component, and if necessary, a plurality of these layers are laminated to a temperature of about 1600 ° C. Manufactured by firing at high temperature.

  The other through conductors 7 are arranged in the insulating substrate 1 by providing as many other through conductors 7 as possible so as not to be electrically connected to the heater pattern 6 in the vicinity of the heater pattern 6 to be described later. preferable. Further, the other through conductors 7 are preferably formed to be thick and spaced apart from each other in order to improve heat conduction. For example, the through conductors 7 may be close-packed with a diameter of 0.2 mm and a spacing of 0.635 mm. If it arrange | positions to, it will become suitable from a viewpoint on the heat conductivity and the intensity | strength of the insulated substrate 1. Further, in order to adjust the temperature distribution in the surface on which the gas detection element 9 is mounted, the interval between the other through conductors 7 is partially made nectar or the thickness of the other through conductors 7 is changed. You can also.

  If the other through conductor 7 exceeds φ0.2 mm, a stress is generated due to a difference in thermal expansion between the alumina ceramic and a refractory metal such as Mo or W, which is the main component of the other through conductor 7, and a crack is generated. It becomes easy to do. When the arrangement interval of the other through conductors 7 is less than 0.635 mm, similarly, stress is generated due to the difference in thermal expansion between the alumina ceramics and the refractory metal that is the main component of the other through conductors 7, and the other through conductors. Cracks are likely to occur in the insulating substrate 1 between 7.

  On the other hand, the through conductor 2 has a function of electrically connecting the electrode pattern 3 formed on one main surface of the insulating substrate 1 and the electrode pad 4 formed on the other main surface. Accordingly, the through conductor 2 may be thick enough to allow the current supplied to the gas detection element 9 to flow, and may be thinner than the other through conductors 7. Further, if necessary, a plurality of through conductors 2 are provided, and when the current supplied to the gas detection element 9 is shunted to the plurality of through conductors 2, the respective through conductors 2 can be formed even thinner. It is possible to easily suppress the occurrence of cracks due to the difference in thermal expansion from the refractory metal that is the main component of the through conductor 2.

  In order to transmit the heat stored in the metal layer 8 more efficiently and stably to the one main surface on which the gas detection element 9 of the insulating substrate 1 is mounted, the metal layer 8 is provided inside the insulating substrate 1 on the one main surface. It is preferable to be formed in a part facing the part where the gas detection element 9 at a position of 50 to 100 μm is mounted from the surface. When the position from the surface is less than 50 μm, microcracks are easily generated on the surface of the insulating substrate 1 due to the difference in thermal expansion between the alumina ceramic and the refractory metal that is the main component of the metal layer 8 due to the stored heat. . On the other hand, when it is formed at a position exceeding 100 μm from the surface, the efficiency of heat transfer transmitted to the one main surface on which the gas detection element 9 of the insulating substrate 1 is mounted tends to be lowered.

  Further, it is sufficient that the size of the metal layer 8 in plan view is equal to or larger than the size of the gas detection element 9 mounted on the insulating substrate 1, and is uniform within the plane on which the gas detection element 9 is mounted. Can distribute and convey heat. The thickness of the metal layer 8 is preferably thicker from the viewpoint of exhibiting a function of distributing heat and distributing heat evenly.

  The metal layer 8 may be formed by being divided into a plurality of metal layers 8. For example, the metal layer 8 in FIG. 1 is divided into two vertically, and a plurality of (for example, two) metal layers 8 are formed in a portion facing the portion where the gas detection element 9 on one main surface is mounted inside the insulating substrate 1. The other through conductors 7 are formed between the plurality of metal layers 8 and between the metal layers 8 and the other main surface of the insulating substrate 1 with an alumina ceramic layer interposed therebetween. May be. By setting it as the some metal layer 8, the volume of the metal layer 8 whole can be enlarged, and a thermal storage effect can be enlarged.

  Further, the metal layer 8 may be a net-like metal layer 8 in which metal lines are arranged in a vertical direction, a horizontal direction, an oblique direction, or a vertical and horizontal oblique direction in a plan view, instead of a single sheet. By forming the net-like metal layer 8, alumina ceramics can be filled between the metal wires and the upper and lower alumina ceramic layers of the metal layer 8 can be connected. It is possible to suppress the occurrence of delamination above and below the metal layer 8. In addition, by adjusting the thickness and direction of the metal wire, the amount of heat transferred by the metal wire is adjusted, and a uniform temperature distribution is achieved within the surface on which the gas detection element 9 on the main surface is mounted. Can be easily designed.

  Next, the comb-shaped electrode pattern 3 is formed, for example, by forming a photoresist by a photolithography method or the like on a portion of the insulating substrate 1 where the electrode pattern 3 is not formed, and using the photoresist as a mask. 3a, a platinum (Pt) layer 3b, and a gold (Au) layer 3c are sequentially formed in a desired thickness using a vacuum deposition method or a sputtering method. As a material for the adhesion metal layer 3a, it is preferable to use chromium (Cr), titanium (Ti), molybdenum (Mo), or the like. Thereafter, the photoresist is peeled off to obtain a desired electrode pattern 3.

  The adhesion metal layer 3a preferably has a thickness in the range of 0.01 to 0.5 μm. If the thickness is less than 0.01 μm, the adhesion strength with the insulating substrate 1 tends to decrease, and if it exceeds 0.5 μm. There is a tendency that the film stress of the adhesion metal layer 3a becomes large and it is easy to peel off from the insulating substrate 1.

  The Pt layer 3b preferably has a thickness in the range of 0.5 to 2 μm. When the thickness is less than 0.5 μm, the gas detection element 9 made of indium oxide or the like is placed in an oxidizing atmosphere at 700 to 750 ° C. in a later step. When baking, the uppermost Au layer 3c cannot be prevented from diffusing into the lowermost adhesion metal layer 3a, and as a result, it tends to be difficult for the insulating substrate 1 and the adhesion metal layer 3a to adhere firmly. If the thickness exceeds 2 μm, the film stress of the Pt layer 3b itself becomes large and tends to be easily peeled off from the adhesion metal layer 3a. Further, since Pt is a noble metal, it is advantageous in terms of cost to make it as thin as possible.

  The thickness of the Au layer 3c is preferably in the range of 2 to 5 μm. If the thickness is less than 2 μm, the gas detection element 9 made of indium oxide or the like is baked in an oxidizing atmosphere at 700 to 750 ° C. in a later step. Au in the Au layer 3c is thermally diffused to the lower Pt layer 3b, and becomes thinner. In this state, when the electrode pattern 3 is exposed to a gas containing a high concentration of hydrogen at a high temperature, the uppermost layer is formed. The Au layer 3c cannot sufficiently protect the lower Pt layer 3b, and as a result, the Pt layer 3b tends to be embrittled by hydrogen and easily peeled off. On the other hand, if the thickness of the Au layer 3c exceeds 5 μm, the film stress of the Au layer 3c becomes large and tends to be easily peeled off from the Pt layer 3b.

  The electrode pad 4 and the heater electrode pad 5 are formed by applying a photoresist to a part facing the electrode pattern 3 on the other main surface of the insulating substrate 1, for example, a part where the electrode pad 4 and the heater electrode pad 5 are not formed. Using this photoresist as a mask, the adhesion metal layers 4a and 5a, the Pt layers 4b and 5b, and the Au layers 4c and 5c are sequentially laminated to a desired thickness using a vacuum deposition method or a sputtering method. As a material for the adhesion metal layers 4a and 5a, Cr, Ti, Mo or the like is preferably used. Thereafter, the photoresist is peeled off to obtain the desired electrode pad 4 and heater electrode pad 5.

  The adhesion metal layers 4a and 5a preferably have a thickness in the range of 0.01 to 0.5 μm. When the thickness is less than 0.01 μm, the adhesion strength with the insulating substrate 1 tends to decrease, and 0.5 μm is reduced. If it exceeds, the film stress of the adhesion metal layers 4a and 5a becomes large and tends to be easily peeled off from the insulating substrate 1.

  The Pt layers 4b and 5b preferably have a thickness in the range of 0.5 to 2 [mu] m. When the thickness is less than 0.5 [mu] m, the indium of the gas detection element 9 made of indium oxide or the like is heated to 700 to 750 [deg.] C. When indium oxide is formed by baking in an oxidizing atmosphere, the uppermost Au layers 4c and 5c cannot be prevented from diffusing into the lowermost adhesion metal layers 4a and 5a. There is a tendency that it is difficult to firmly adhere to the layers 4a and 5a. When the thickness exceeds 2 μm, the film stress of the Pt layers 4b and 5b itself becomes large, and the layer 4a and 5a tends to be easily peeled off. There is. Further, since Pt is a noble metal, it is advantageous in terms of cost to make it as thin as possible.

  The Au layers 4c and 5c have a function as a main part of a connection terminal for supplying voltage and power from the outside to the electrode pad 4 and the heater electrode pad 5, respectively, and the thickness thereof is in the range of 2 to 5 μm. It is preferable to do. If the thickness is less than 2 μm, indium oxide in the gas detection element 9 made of indium oxide or the like is baked in an oxidizing atmosphere at 700 to 750 ° C. in the subsequent process to form indium oxide. , 5b is further diffused by heat diffusion. In this state, when lead wires made of, for example, Au wires for supplying voltage and power to the electrode pad 4 and the heater electrode pad 5 are connected by bonding, the connection In this case, a strong Au—Au bonding structure cannot be obtained, and the connection reliability tends to decrease. On the other hand, if the thickness of the Au layers 4c and 5c exceeds 5 μm, the film stress of the Au layers 4c and 5c becomes large and tends to be easily peeled off from the Pt layers 4b and 5b.

  When the Au layers 4c and 5c are stacked on the Pt layers 4b and 5b to perform the function of the conductive layer, the electrode pads 4b and 5b are stacked. In addition, a lead wire made of Au can be connected to the heater electrode pad 5 by bonding or the like, and a connection method using Au that is widely used can be adopted. More advantageous.

  Next, the heater pattern 6 is formed by forming a photoresist on a portion where the heater pattern 6 is not formed by a photolithography method or the like, and using the photoresist as a mask, the adhesion metal layer 6a and the Pt layer 6b are formed by a vacuum deposition method or the like. What is necessary is just to laminate | stack one by one in desired thickness using a sputtering method. Alternatively, when the adhesion metal layers 4a and 5a, the Pt layers 4b and 5b, and the Au layers 4c and 5c are sequentially stacked on the electrode pad 4 and the heater electrode pad 5, the portions that become the heater pattern 6 are simultaneously formed. After forming the same metal layer, and finally masking the part where the heater pattern 6 is not formed, the uppermost Au layer is removed with an etching solution such as potassium cyanide, and then the photoresist is peeled off to form a desired heater pattern. It may be 6.

  The adhesion metal layer 6a of the heater pattern 6 is made of Cr, Ti, Mo, or the like, and has a function of firmly bonding the heater pattern 6 to the insulating substrate 1 and bonding them. The thickness of the adhesion metal layer 6a of the heater pattern 6 is preferably in the range of 0.01 to 0.5 μm. When the thickness is less than 0.01 μm, the adhesion strength with the insulating substrate 1 tends to be reduced, and 0.5 μm Exceeding the above value tends to increase the film stress of the adhesive metal layer 6a and facilitate separation from the insulating substrate 1.

  Further, the Pt layer 6b of the heater pattern 6 has a function as a heating element, and preferably has a thickness in the range of 0.5 to 2 μm. When the thickness is less than 0.5 μm, the power resistance of the Pt layer 6b itself For example, when heat is generated at about 400 ° C. and a high temperature operation is performed for a long time, the function as a desired heating element tends to be difficult to be exhibited, and if it exceeds 2 μm, the film stress of the Pt layer 6b itself Tends to be large, and tends to be peeled off from the adhesive metal layer 6a. Further, since Pt is a noble metal, it is advantageous in terms of cost to make it as thin as possible.

  The thickness of the Pt layer 6b is preferably the same as that of the Pt layer 4b of the electrode pad 4 and the Pt layer 5b of the heater electrode pad 5 because these Pt layers 4b, 5b, and 6b can be laminated at the same time, thereby reducing the number of processes. .

If a gas detection element having a function of detecting a desired gas component is formed so as to connect between the two electrode patterns 3 of the gas sensor substrate of the present invention, the gas sensor operates as a gas sensor. For example, in the case of detecting a hydrogen component, an indium (In) thin film is formed by vacuum deposition or the like so as to communicate between the electrode patterns 3, and then heat-treated in air to form indium oxide (In _{If a 2} O ₃ ) thin film is formed, a gas sensor substrate for detecting a hydrogen component can be obtained.

  Thus, according to the gas sensor substrate of the present invention, the electrode pad 4 is electrically connected to the electrode pattern 3 through the through conductor 2 at a portion facing the electrode pattern 3 on the other main surface of the insulating substrate 1. Therefore, when the electrode pad 4 is not exposed to a gas containing high-concentration hydrogen at a high temperature and the electrode pad 4 is formed through the adhesion metal layer 4a, the adhesion metal layer 4a is insulated. Since it has a function of firmly bonding to the substrate 1, the electrode pad 4 having excellent adhesion strength and reliability can be formed. In addition, since the lead wire for supplying a voltage to the electrode pad 4 does not come into contact with a gas containing high concentration of hydrogen at a high temperature, the material of the lead wire or the electrode pad 4 is not limited, and the durability is reliable. It can be made excellent in properties.

  Further, the electrode pattern 3 on which the gas detection element 9 is mounted on one main surface of the insulating substrate 1 is preferably formed by sequentially laminating the adhesion metal layer 3a, the Pt layer 3b, and the Au layer 3c. Even when the electrode pattern 3 is exposed to a gas containing hydrogen at a high concentration at a high temperature, the lower Pt layer 3b is protected by the uppermost Au layer 3c, and hydrogen embrittlement of the Pt layer 3b is greatly reduced. At the same time, the electrode pattern 3 can be firmly bonded to the insulating substrate 1 by the adhesion metal layer 3a, and the electrode pattern 3 having excellent adhesion strength and reliability can be formed.

  Further, according to the gas sensor substrate of the present invention, preferably, the insulating substrate 1 has the metal layer 8 formed in a portion facing the portion where the gas detection element 9 on one main surface is mounted, Since one end of the metal layer 8 is connected to the other end of the other through conductor 7 led out to the other main surface of the insulating substrate 1, the heat generated from the heater pattern 6 is transferred to the other through conductor 7 and Since it is efficiently and promptly transmitted to the gas detection element 9 through the metal layer 8, it is possible to provide an efficient gas sensor substrate that has excellent gas detection responsiveness and that consumes less power in the heater pattern 6.

  Further, since the adhesion metal layers 5a and 6a have a function of firmly bonding to the insulating substrate 1, the heater electrode pad 5 and the heater pattern 6 having excellent adhesion strength and reliability can be formed. At the same time, since it is not necessary to press-contact or join the heating element to the insulating substrate 1, a gas sensor that can be further reduced in size and height can be obtained.

  The gas sensor substrate of the present invention is not limited to the above-described embodiment, and various modifications may be made without departing from the scope of the present invention. For example, in the above-described example, the shape of the heater pattern 6 is a pattern bent four times in a crank shape. However, from the viewpoint of heating the insulating substrate 1 uniformly, the heater pattern 6 is The pattern width, shape, etc. may be arbitrarily designed. In addition, the gas sensor substrate for detecting hydrogen has been described as an example, but it goes without saying that the configuration of the gas sensor substrate of the present invention can be applied to a gas sensor substrate for detecting components other than hydrogen. For example, by using an appropriate gas detection element made of tin oxide or the like in addition to indium oxide, a gas sensor substrate for detecting LP gas, city gas, carbon monoxide, humidity, and the like can be obtained.

An example of embodiment of the substrate for gas sensors of the present invention is shown, (a) is a sectional view of a gas sensor substrate, (b) is a top view of a gas sensor substrate, and (c) is a bottom view of a gas sensor substrate. The example of the conventional gas sensor board | substrate is shown, (a) is sectional drawing of the board | substrate for gas sensors, (b) is a top view of the board | substrate for gas sensors.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Insulation board 2 ... Through-conductor 3 ... Electrode pattern 3a, 4a, 5a, 6a ... adhesion metal layer 3b, 4b, 5b, 6b ... Pt layer 3c, 4c, 5c ... Au layer 4 ... Electrode pad 5 ... Electrode pad for heater 6 ... Pattern for heater 7 ...・ Other through conductors 8 ・ ・ ・ ・ ・ ・ ・ ・ Metal layer 9 ・ ・ ・ ・ ・ ・ ・ ・ Gas detection element

Claims (3)

In the gas sensor substrate in which an electrode pattern on which a gas detection element is mounted is formed on one main surface of the insulating substrate, the electrode is disposed on a portion of the other main surface of the insulating substrate facing the electrode pattern via a through conductor. An electrode pad electrically connected to a pattern is formed, and a heater pattern and heater electrode pads formed at both ends thereof are formed. The insulating substrate has a metal layer formed in a portion thereof facing a portion of the main surface on which the gas detection element is mounted, and one end of the metal layer is led out to the other main surface of the insulating substrate. The gas sensor substrate according to claim 1, wherein the gas sensor substrate is connected to the other end of the other through conductor. The electrode pattern, the electrode pad, and the heater electrode pad are formed by sequentially laminating an adhesive metal layer, a Pt layer, and an Au layer, respectively, and the heater pattern is formed by sequentially laminating an adhesive metal layer and a Pt layer. 3. The gas sensor substrate according to claim 1, wherein the gas sensor substrate is a gas sensor substrate.

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