Semiconductor hydrogen pressure sensor, and method for manufacturing same

Abstract

The semiconductor hydrogen pressure sensor (100) comprises: a semiconductor pressure detecting element (3) which accepts the pressure of a medium being measured, the medium containing hydrogen, and which electrically outputs a value corresponding to the absolute pressure of the medium being measured; a bonding wire (10a) extending from a terminal of the semiconductor pressure detecting element (3); and a protective film (12) which continuously covers parts of the semiconductor pressure detecting element (3) and the bonding wire (10a) that are exposed to the medium being measured.

Description

Semiconductor hydrogen pressure sensor and its manufacturing method

[0001] The present application relates to a semiconductor hydrogen pressure sensor and a method for manufacturing the same.

[0002] In fuel cell systems used in automobiles and other mobile vehicles, highly accurate control of the supply of hydrogen and air as fuel is necessary to optimize the power generation efficiency of the fuel cell. To precisely control the supply of hydrogen and air, a pressure sensor is required that can measure the pressure of these gases in real time with high accuracy. Semiconductor hydrogen pressure sensors have been developed and put to practical use in fuel cell systems. These sensors are mounted near the fuel cell and measure the pressure of the hydrogen and its mixture, air, and off-gas such as water vapor discharged from the fuel cell.

[0003] There are various types of fuel cell systems. For example, in the case of a polymer electrolyte fuel cell (PEFC) system, which is used in automobiles and other mobile vehicles, the fuel cell system has an anode subsystem and a cathode subsystem. The anode subsystem supplies hydrogen, which serves as fuel, to the fuel cell stack. The cathode subsystem supplies oxygen contained in the air to the fuel cell stack. The oxygen reacts with the fuel.

[0004] In such fuel cell systems, to optimize power generation efficiency, it is necessary to constantly control the amount of hydrogen in the anode subsystem and the amount of air in the cathode subsystem to maintain appropriate levels. For this reason, semiconductor hydrogen pressure sensors, which measure the pressure of media, primarily hydrogen, flowing in and out of the fuel cell stack, are considered to be one of the key components that greatly influence the efficiency of fuel cell systems. Semiconductor hydrogen pressure sensors that measure hydrogen pressure are required not only to measure pressure with high accuracy, as their primary function, but also to have high hydrogen reliability. In particular, semiconductor hydrogen pressure sensors in the anode subsystem must be able to handle hydrogen with up to 100% purity in a maintenance-free state over the system's lifetime. Therefore, high reliability for hydrogen is an essential requirement for applying semiconductor hydrogen pressure sensors to fuel cell systems. Meanwhile, in the cathode subsystem, the media handled is, in principle, air. However, in practice, pressure measurements are made on media containing hydrogen due to cross-leakage phenomena within the fuel cell stack, so the semiconductor hydrogen pressure sensors installed in the cathode subsystem must also be reliable for hydrogen.

[0005] However, hydrogen has properties that reduce the reliability of semiconductor pressure sensors, namely, its inherent ability to easily permeate many materials and its tendency to embrittle many metals. For this reason, achieving both high-precision pressure measurement and reliability has long been a major challenge for semiconductor pressure sensors that use hydrogen.

[0006] This paper describes the configuration of a conventional hydrogen pressure sensor that addresses these issues. The pressure sensor includes a metal pressure diaphragm made of stainless steel or the like that receives hydrogen pressure, an oil-enclosed section behind the metal pressure diaphragm, and a pressure detection element that detects stress generated by the pressure received by the metal pressure diaphragm through the oil behind the oil-enclosed section and converts it into an electrical signal. Conventional pressure sensors employ an indirect measurement method in which the pressure detection element detects stress transmitted through the oil. The primary reason for adopting this indirect measurement method is the lack of a pressure detection element that has proven practical for hydrogen reliability in environments directly exposed to hydrogen. Therefore, a structure that physically isolates hydrogen from the pressure detection element was necessary. While these measures are taken for the pressure detection element, hydrogen embrittlement of the metal pressure diaphragm, which is directly exposed to hydrogen, is prevented by applying baking or coating treatments to the metal pressure diaphragm. This configuration provides a certain level of reliability for the entire hydrogen pressure sensor.

[0007] Conventional hydrogen pressure sensors have the above-mentioned configuration to ensure reliability for hydrogen. However, because they use a metal pressure-receiving diaphragm to indirectly measure hydrogen pressure via oil, there remain problems that it is fundamentally very difficult to make the entire hydrogen pressure sensor smaller and lighter, and that the measurement principle of indirectly detecting pressure itself hinders high measurement accuracy.

[0008] A hydrogen pressure sensor configuration that solves these problems has been disclosed (see, for example, Non-Patent Document 1). In Non-Patent Document 1, the semiconductor hydrogen pressure sensor has a structure in which a semiconductor pressure detection element that directly receives hydrogen pressure using a small, lightweight single-crystal silicon diaphragm, instead of a metal material such as stainless steel, is mounted in a resin housing and is free from concerns about hydrogen embrittlement. The disclosed semiconductor hydrogen pressure sensor has been put to practical use, and this configuration has resulted in a highly accurate hydrogen pressure sensor that combines high hydrogen reliability with significant weight reduction.

[0009] The semiconductor pressure detection element installed in the pressure-receiving chamber is covered entirely with gel. Covering the semiconductor pressure detection element with gel prevents corrosion of the semiconductor pressure detection element caused by acids, etc. Because the housing and pressure-receiving diaphragm do not use metal components such as stainless steel, the hydrogen pressure sensor is significantly smaller and lighter. In addition, because the semiconductor pressure detection element directly receives hydrogen pressure without passing through oil and measures the absolute pressure of hydrogen, it is possible to measure hydrogen with high precision, contributing to the high efficiency of the entire system.

[0010] "Hydrogen Pressure Sensor for Fuel Cell Electric Vehicles," Mitsubishi Electric Technical Review, Vol. 96, No. 1, 2022

[0011] When a semiconductor hydrogen pressure sensor is configured as described above, it is possible to reduce the size and weight of the hydrogen pressure sensor and increase its accuracy. However, we have discovered that even the above-mentioned semiconductor hydrogen pressure sensor still has vulnerabilities that need to be improved due to the direct pressure sensing method using a semiconductor pressure detection element under limited complex conditions that combine a specific installation location within the system, specific system operating conditions, specific surrounding environmental conditions, etc. The vulnerabilities that we have discovered are described below.

[0012] The gel covering the semiconductor pressure sensor element provides excellent protection even when the measurement medium is a corrosive liquid such as acid under high temperature and normal pressure. However, under certain conditions that combine high temperature, high humidity, and high pressure, the measurement medium is absorbed into the gel at a constant rate, albeit very slowly over a period of several days. Even if the measurement medium is absorbed into the gel, it will be released from the gel if the supply of the measurement medium is stopped, such as when the system is shut down. The risk of problems begins to arise when certain conditions—the environment of the semiconductor hydrogen pressure sensor installation site, the state of the measurement medium, and system operation—combine and cause water vapor contained in the measurement medium absorbed into the gel to condense on the relatively cool surfaces of the semiconductor pressure sensor element and the bonding wires connected to the semiconductor pressure sensor element.

[0013] The areas where condensed water droplets adhere include conductive parts. Specifically, these include the entire surface of the bonding wire, the outer edge of the bonding pad on the semiconductor pressure sensing element that electrically connects the bonding wire to the semiconductor pressure sensing element, and the bonding part between the lead frame and the bonding wire that is connected to the outside. Condensation does not pose a problem as long as the system is stopped and power is not supplied to the semiconductor hydrogen pressure sensor. However, if the system is operated without condensation and power is supplied to the semiconductor pressure sensing element, electrolysis of the water droplets begins due to the potential difference between the condensed water droplets and other conductive parts through the condensed water droplets in contact with these conductive parts. This phenomenon has been confirmed to initiate corrosion of conductive parts such as the wiring on the semiconductor pressure sensing element and the bonding wire. Although this phenomenon occurs under limited conditions and at a very slow rate, depending on the operating conditions of the system, repeated occurrence of this phenomenon can accumulate corrosion, potentially resulting in a risk of such conductive parts breaking down before the system reaches its expected lifespan.

[0014] This ability to absorb and release gases is inherent in all potting gel materials and is an inherent characteristic of the gel material. Therefore, a gel material that does not absorb gases at all, or absorbs gases only to the extent that it does not adversely affect the expected lifespan of the system, can be used in a semiconductor hydrogen pressure sensor. However, at present, there is no gel material that completely prevents gas absorption and release under all media conditions expected in the system, which has led to the problem of water droplets adhering to the conductive parts of semiconductor hydrogen pressure sensors.

[0015] Therefore, an object of the present application is to provide a semiconductor hydrogen pressure sensor that is small, lightweight, highly accurate, and highly reliable, and a method for manufacturing the same.

[0016] The semiconductor hydrogen pressure sensor disclosed in the present application comprises a semiconductor pressure detection element that receives the pressure of a measurement medium containing hydrogen and electrically outputs a value corresponding to the absolute pressure of the measurement medium, a bonding wire extending from a terminal of the semiconductor pressure detection element, and a protective film that continuously covers the portions of the semiconductor pressure detection element and the bonding wire that are exposed to the measurement medium.

[0017] The method for manufacturing a semiconductor hydrogen pressure sensor disclosed in the present application comprises a component preparation step of preparing a semiconductor pressure detection element and a bonding wire that receives the pressure of the medium to be measured and electrically outputs a value corresponding to the absolute pressure of the medium to be measured, a connection step of electrically connecting the bonding wire to the semiconductor pressure detection element, and a film formation step of continuously covering the portions of the semiconductor pressure detection element and the bonding wire that are exposed to the medium to be measured with a protective film.

[0018] The semiconductor hydrogen pressure sensor disclosed in the present application comprises a semiconductor pressure detection element that receives the pressure of a measurement medium containing hydrogen and electrically outputs a value corresponding to the absolute pressure of the measurement medium, a bonding wire extending from the terminal of the semiconductor pressure detection element, and a protective film that continuously covers the portions of the semiconductor pressure detection element and the bonding wire that are exposed to the measurement medium.Therefore, even if condensation occurs on the protective film, water droplets will not adhere to the conductive portions of the semiconductor pressure detection element and the bonding wire, and corrosion and breakage of the conductive portions due to electrolysis of water droplets will not occur.As a result, a semiconductor hydrogen pressure sensor that is small, lightweight, and highly accurate and reliable can be obtained.

[0019] The manufacturing method for a semiconductor hydrogen pressure sensor disclosed in the present application includes a component preparation process for preparing a semiconductor pressure detection element and a bonding wire that receives the pressure of the medium to be measured and electrically outputs a value corresponding to the absolute pressure of the medium to be measured, a connection process for electrically connecting the bonding wire to the semiconductor pressure detection element, and a film formation process for continuously covering the portions of the semiconductor pressure detection element and the bonding wire that are exposed to the medium to be measured with a protective film.Therefore, even if condensation occurs on the protective film, water droplets will not adhere to the conductive portions of the semiconductor pressure detection element and the bonding wire, and corrosion and breakage of the conductive portions due to electrolysis of water droplets will not occur.As a result, a semiconductor hydrogen pressure sensor that is small, lightweight, and highly accurate and reliable can be manufactured.

[0020] 13 is a cross-sectional view showing an outline of a semiconductor hydrogen pressure sensor according to embodiment 1. FIG. 14 is a cross-sectional view showing an outline of a pressure-receiving chamber of a semiconductor hydrogen pressure sensor according to embodiment 1. FIG. 15 is a diagram explaining the effect of the semiconductor hydrogen pressure sensor according to embodiment 1. FIG. 16 is a diagram showing a manufacturing process for a semiconductor hydrogen pressure sensor according to embodiment 1. FIG. 17 is a cross-sectional view showing a main part of a pressure-receiving chamber of a semiconductor hydrogen pressure sensor according to embodiment 2. FIG. 18 is a diagram showing a manufacturing process for a semiconductor hydrogen pressure sensor according to embodiment 3. FIG. 19 is a diagram showing fluctuations in residual stress in a semiconductor hydrogen pressure sensor according to embodiment 3. FIG. 19 is a cross-sectional view showing an outline of a pressure-receiving chamber of a semiconductor hydrogen pressure sensor according to embodiment 4. FIG. 19 is a cross-sectional view showing an outline of a semiconductor hydrogen pressure sensor according to embodiment 5. FIG. 19 is a cross-sectional view showing an outline of a semiconductor hydrogen pressure sensor according to embodiment 6. FIG. 19 is a cross-sectional view showing an outline of a semiconductor hydrogen pressure sensor of a comparative example. FIG. 19 is a cross-sectional view showing an outline of a pressure-receiving chamber of a semiconductor hydrogen pressure sensor of a comparative example. FIG. 19 is a diagram showing water droplets on the pressure-receiving chamber of the semiconductor hydrogen pressure sensor of the comparative example shown in FIG. 12. FIG. 19 is a schematic view showing an outline of a gas supply system of a fuel cell system.

[0021] Hereinafter, a semiconductor hydrogen pressure sensor and a method of manufacturing the same according to an embodiment of the present invention will be described with reference to the drawings. Note that the same or corresponding members and parts in each drawing will be denoted by the same reference numerals.

[0022] Embodiment 1. Figure 1 is a cross-sectional view showing an outline of a semiconductor hydrogen pressure sensor 100 according to embodiment 1, with the protective film 12 omitted, Figure 2 is a cross-sectional view showing an outline of the pressure-receiving chamber 7 of semiconductor hydrogen pressure sensor 100, Figure 3 is a diagram explaining the effects of semiconductor hydrogen pressure sensor 100, and Figure 4 is a diagram showing the manufacturing process for semiconductor hydrogen pressure sensor 100 according to embodiment 1. Semiconductor hydrogen pressure sensor 100 is a sensor that receives pressure from a medium to be measured directly with semiconductor pressure detection element 3, measures the absolute pressure of the medium to be measured, and outputs the measurement result, without any other components such as oil between the part that receives the pressure of the medium to be measured and the detection element.

[0023] 2 , the semiconductor hydrogen pressure sensor 100 comprises a semiconductor pressure detection element 3 that receives the pressure of a hydrogen-containing measurement target medium and electrically outputs a value corresponding to the absolute pressure of the measurement target medium, a bonding wire 10a extending from the terminal of the semiconductor pressure detection element 3, and a protective film 12 that continuously covers the portions of the semiconductor pressure detection element 3 and the bonding wire 10a that are exposed to the measurement target medium. In this embodiment, the semiconductor hydrogen pressure sensor 100 comprises a lead frame 11 insert-molded into a resin pressure-receiving chamber 7 to which the semiconductor pressure detection element 3 is fixed, and an ASIC 9 that is a signal processing circuit that is fixed inside the pressure-receiving chamber 7 and connected to the semiconductor pressure detection element 3 via the bonding wire 10a and connected to the lead frame 11. In this embodiment, the protective film 12 continuously covers the portions of the semiconductor pressure detection element 3, the bonding wire 10, the ASIC 9, and the pressure-receiving chamber 7 that are exposed to the measurement target medium. The bonding wire 10 is, for example, a wire made of gold.

[0024] As shown in FIG. 1 , the semiconductor hydrogen pressure sensor 100 further includes a pressure-receiving chamber 7 having an opening 7a for introducing the medium to be measured into the pressure-receiving chamber 7, with the semiconductor pressure detection element 3 and ASIC 9 fixed therein, and a pressure guiding tube 2 that communicates with the pressure-receiving chamber 7 via the opening 7a and introduces the medium to be measured into the pressure-receiving chamber 7 from the outside. The medium to be measured is introduced into the pressure-receiving chamber 7 from the outside through the pressure guiding tube 2 in the direction of the arrow shown in the figure. In this embodiment, the medium to be measured is primarily hydrogen. The portion of the housing 1 surrounding the pressure-receiving chamber 7, the pressure-receiving chamber 7, and the pressure guiding tube 2 are connected via an O-ring 8a. The pressure guiding tube 2 is connected to an external flow path (not shown) for the medium to be measured via an O-ring 8b. In this way, the portion that serves as the flow path for the medium to be measured is sealed.

[0025] The pressure-receiving chamber 7 is the portion surrounding the semiconductor pressure detection element 3 and the ASIC 9, and is the portion in FIG. 2 where the protective film 12 is provided. The pressure-receiving chamber 7 is formed by insert molding, in which resin is filled around the lead frame 11 used to exchange electrical signals with the outside. The lead frame 11 is made of a metal such as copper. The lead frame 11 and the ASIC 9 are connected by bonding wires 10b. The portion surrounding the pressure-receiving chamber 7 that holds the pressure-receiving chamber 7 is the housing 1 of the semiconductor hydrogen pressure sensor 100. The housing 1 is made of resin. The pressure-conducting tube 2 is also made of the same material as the housing 1. The housing 1 has a connector portion 5 used for connecting to the outside. The connector portion 5 has terminals 6 on the inside. The terminals 6 are made of a metal such as copper. The terminals 6 are electrically connected to the lead frame 11 by, for example, soldering. The output of the semiconductor pressure detection element 3 is output to the outside from the terminals 6 via the ASIC 9. The semiconductor hydrogen pressure sensor 100 is small and lightweight because the housing 1 and the pressure guiding tube 2 are made of resin, and the terminals 6 and the lead frame 11 are integrated with resin.

[0026] The semiconductor pressure sensing element 3 senses the pressure of the medium being measured and converts the pressure into an electrical signal for output. The ASIC 9 amplifies the electrical signal output by the semiconductor pressure sensing element 3 and compensates for the detected pressure characteristics relative to temperature and pressure. The semiconductor pressure sensing element 3 is, for example, the element described in Japanese Patent No. 6300773. The semiconductor pressure sensing element 3 directly senses hydrogen pressure using a single-crystal silicon diaphragm and converts the diaphragm's distortion into an electrical signal using piezoresistors located on its outer edge, etc., providing sufficiently high hydrogen reliability even when used in an environment directly exposed to pure hydrogen. The semiconductor pressure sensing element 3 has terminals on its surface that are connected to bonding wires 10a. While only one bonding wire 10a is shown in the figure, multiple bonding wires 10a and terminals may be used.

[0027] <Comparative Example> Prior to describing the protective film 12, which is a key feature of the present application, a comparative example will be described. Fig. 11 is a cross-sectional view showing an outline of a semiconductor hydrogen pressure sensor 101 of the comparative example, Fig. 12 is a cross-sectional view showing an outline of the pressure-receiving chamber 7 of the semiconductor hydrogen pressure sensor 101 of the comparative example, and Fig. 13 is a diagram showing a water droplet 13 on the inside of the pressure-receiving chamber 7 of the semiconductor hydrogen pressure sensor 101 of the comparative example shown in Fig. 12. The semiconductor hydrogen pressure sensor 101 does not have a protective film 12, and the semiconductor pressure detection element 3, ASIC 9, and bonding wire 10 provided in the pressure-receiving chamber 7 are covered with gel 4. The semiconductor hydrogen pressure sensor 101 differs from the semiconductor hydrogen pressure sensor 100 in that the conductive portions of the semiconductor pressure detection element 3, ASIC 9, and bonding wire 10 are covered with gel 4.

[0028] The gel 4 covering the semiconductor pressure detection element 3 provides high protection even when the measurement medium is a corrosive liquid such as acid under high temperature and normal pressure. However, under certain combined conditions of high temperature, high humidity, and high pressure, the measurement medium is absorbed into the gel 4 at a constant rate, albeit very slowly over a period of several days. When the environment of the semiconductor hydrogen pressure sensor 101 mounting location, the state of the measurement medium, and the system operation status all combine under certain conditions, the water vapor contained in the measurement medium absorbed into the gel 4 may condense on the surfaces of the semiconductor pressure detection element 3, etc., which are relatively slightly cooler. Figure 13 shows an example of condensation on the surfaces of the semiconductor pressure detection element 3, ASIC 9, and bonding wire 10, resulting in water droplets 13 on these areas.

[0029] The areas where the water droplets 13 are attached include conductive parts. Specifically, the conductive parts are the entire surface of the bonding wire 10, the outer edge of the bonding pad, which is a terminal on the semiconductor pressure detection element 3 that electrically connects the bonding wire 10a to the semiconductor pressure detection element 3, and the bonding part between the lead frame 11 and the bonding wire 10b. Even if condensation occurs, no problem occurs as long as the system is stopped and power is not supplied to the semiconductor hydrogen pressure sensor 101. However, if the system operates and power is supplied to the semiconductor hydrogen pressure sensor 101 without the condensation being removed, a potential difference occurs between these conductive parts and any other conductive parts through the water droplets 13 that have condensed on the conductive parts. The resulting potential difference initiates electrolysis in the water droplets 13. This phenomenon initiates corrosion of these conductive parts. Although this phenomenon occurs under limited conditions and at a very slow speed, depending on the operating conditions of the system, this phenomenon can be repeated and accumulated, which may result in a risk of the corroded conductive parts breaking down before the expected life of the system is reached.

[0030] If a gel 4 that does not absorb gas at all, or absorbs gas only to the extent that it does not impair the expected lifespan of the system, is used in the semiconductor hydrogen pressure sensor 101, the conductive part will not break. However, at present, there is no gel 4 that completely prevents gas absorption and desorption under all the media conditions expected in the system, so it is important to avoid contact with the gel 4 and to prevent water droplets 13 from adhering to the conductive part of the semiconductor hydrogen pressure sensor 101.

[0031] <Protective Film 12> The protective film 12, a key feature of the present invention, will now be described. To prevent water droplets 13 from adhering to the conductive portion, the protective film 12 continuously covers the semiconductor pressure detection element 3 and the bonding wire 10 exposed to the medium to be measured. The areas covered by the protective film 12 are not limited to these. In this embodiment, as shown in FIG. 2 , the protective film 12 covers the entire area where the pressure-receiving chamber 7 is formed. The protective film 12 is a polymer coating film that has properties such as water repellency, water vapor impermeability, and acid corrosion resistance. A suitable example is a parylene film, which can be conformally coated. The protective film 12 is preferably formed by, for example, chemical vapor deposition (CVD). Forming the protective film 12 by chemical vapor deposition allows for continuous coating not only on the surface of the conductive portion but also on the inner wall of the pressure-receiving chamber 7 to maximize the coating effect.

[0032] The protective film 12 formed from the above-described material by the above-described manufacturing method exhibits excellent coating properties, since it uniformly penetrates not only the exposed surface of the adherend but also the complex and intricate microscopic grooves and pores to protect the adherend. Furthermore, precise control of the film thickness is possible, and the thickness of the protective film 12 is preferably 2 to 10 μm. In principle, the thicker the protective film 12, the greater the protective effect of the protective film 12. However, the thicker the protective film 12, the greater the residual stress in the protective film 12. Therefore, a thick protective film 12 increases undesirable effects such as nonlinearity in the strain-sensing characteristics of the piezoresistor. Furthermore, a thick protective film 12 increases the amount of fluctuation in residual stress due to high temperatures and other factors during use of the semiconductor hydrogen pressure sensor 100, leading to increased fluctuations in the detection characteristics of the semiconductor hydrogen pressure sensor 100 over time. In order to avoid such problems, by controlling the film thickness of the protective film 12 within the above-mentioned range, it is possible to improve the protective effect of the protective film 12 while maintaining high-precision measurement in the semiconductor hydrogen pressure sensor 100. Furthermore, since the semiconductor hydrogen pressure sensor 100 is configured such that only the protective film 12 is provided on the semiconductor pressure detection element 3 and bonding wire 10a, etc., which are provided in the pressure-receiving chamber 7, the semiconductor hydrogen pressure sensor 100 is made smaller and lighter without increasing its size.

[0033] By continuously covering the portions of the semiconductor pressure detection element 3 and the bonding wire 10a exposed to the medium to be measured with the protective film 12 in this manner, even if condensation occurs on the protective film 12 and water droplets 13 adhere to the conductive portions of the semiconductor pressure detection element 3 and the bonding wire 10a as shown in Figure 3, the water droplets 13 will not adhere to the conductive portions of the semiconductor pressure detection element 3 and the bonding wire 10a, and therefore corrosion and disconnection of the conductive portions due to electrolysis of the water droplets 13 will not occur, thereby making it possible to obtain a semiconductor hydrogen pressure sensor 100 that is small and lightweight, yet has high accuracy and reliability. Furthermore, in this embodiment, the protective film 12 continuously covers the portions of the semiconductor pressure detection element 3, the bonding wire 10, the ASIC 9, and the pressure-receiving chamber 7 that are exposed to the medium to be measured, so that the inside of the pressure-receiving chamber 7 is effectively protected from condensation, making it possible to obtain a semiconductor hydrogen pressure sensor 100 that has high accuracy and reliability.

[0034] <Fuel Cell System 1000> The relationship between the application location of the semiconductor hydrogen pressure sensor 100 shown in this embodiment in a fuel cell system 1000 and water droplets will be explained using Figure 14. Figure 14 is a schematic diagram showing an outline of the gas supply system of a typical PEFC-type fuel cell system 1000, with related accessories omitted. The composition and state of the medium that is the object of measurement by the semiconductor hydrogen pressure sensor 100 will vary greatly depending on the configuration of the fuel cell system 1000 and the measurement position of the semiconductor hydrogen pressure sensor 100.

[0035] The fuel cell system 1000 comprises an anode subsystem and a cathode subsystem. The anode subsystem supplies hydrogen from a hydrogen fuel tank 20 to the fuel cell stack 19. The cathode subsystem supplies air from the outside to the fuel cell stack 19 and discharges water or water vapor produced by the reaction from the fuel cell stack 19 to the outside. The arrows in FIG. 14 indicate the direction of medium flow. In the anode subsystem, pure hydrogen from the hydrogen fuel tank 20 is supplied to the fuel cell stack 19. Unreacted hydrogen and a portion of the water vapor produced by the reaction are combined with the pure hydrogen supplied from the hydrogen fuel tank 20 and supplied back to the fuel cell stack 19 for recirculation to the fuel cell stack 19. Meanwhile, in the cathode subsystem, water and water vapor, which are by-products of the reaction, are discharged to the outside without being recirculated.

[0036] In such a fuel cell system 1000, when the semiconductor hydrogen pressure sensor 100 is placed in section A1 of the anode subsystem, the medium to be measured by the semiconductor hydrogen pressure sensor 100 is hydrogen gas supplied from the hydrogen fuel tank 20. The medium to be measured in section A1 is hydrogen gas with a purity of nearly 100%, and other gas components such as water vapor are not contained in the medium to be measured. Therefore, problematic water droplets do not adhere to the semiconductor hydrogen pressure sensor 100, which has been designed and manufactured to have sufficient hydrogen reliability.

[0037] When the semiconductor hydrogen pressure sensor 100 is placed in section A2 or A3 of the anode subsystem, the measurement medium of the semiconductor hydrogen pressure sensor 100 is hydrogen, primarily hydrogen, but also containing a certain amount of water vapor. Sections A2 and A3 are the locations where the semiconductor hydrogen pressure sensor 100 is placed in the path where the recirculation described above occurs. Therefore, under certain combined conditions, the water vapor contained in the measurement medium will condense on the surfaces of the semiconductor pressure detection element 3, ASIC 9, bonding wire 10, etc. due to the temperature difference between the medium temperature and these components. Furthermore, depending on the operating state of the system, a medium containing water droplets may flow through the recirculation path. For example, at section A3, water droplets may not be completely removed due to the design or operation of the gas-liquid separator (not shown). In addition, at the position A2, the relatively high temperature and humidity medium returning from the recirculation path meets the relatively low temperature and dry hydrogen supplied from the hydrogen fuel tank 20, so the medium flowing in from the recirculation path side is rapidly cooled, making it easy for condensation to occur on the semiconductor hydrogen pressure sensor 100, and problematic water droplets may adhere to the semiconductor hydrogen pressure sensor 100.

[0038] When the semiconductor hydrogen pressure sensor 100 is placed in the C1 section of the cathode subsystem, the medium to be measured by the semiconductor hydrogen pressure sensor 100 is basically air taken in from the outside. However, under certain circumstances, hydrogen gas may diffuse from the anode side through the fuel cell stack 19, and a certain level of hydrogen resistance is required for pressure measurement, so the semiconductor hydrogen pressure sensor 100 is also used in the C1 section. Although the semiconductor hydrogen pressure sensor 100 is used, problematic water droplets do not adhere to the semiconductor hydrogen pressure sensor 100.

[0039] When the semiconductor hydrogen pressure sensor 100 is placed in section C2 of the cathode subsystem, the measurement medium of the semiconductor hydrogen pressure sensor 100 is a gas containing water or water vapor, which is generated as a by-product of the reaction and discharged from the fuel cell stack 19. Section C2 is the location where problematic water droplets are most likely to adhere to the semiconductor hydrogen pressure sensor 100. Section C2 is the location where water, a by-product of the reaction, is generated, in accordance with the principles of fuel cells. Unless special measures such as purging are taken, the medium is almost always at a high humidity of 90% or more during system operation, and a portion of the medium is in the form of water droplets. Therefore, it is necessary to assume a situation in which water droplets 13 are always attached to the surfaces of the semiconductor pressure detection element 3, ASIC 9, and bonding wire 10, as shown in FIG. 3 .

[0040] Thus, if the semiconductor hydrogen pressure sensor 100 is placed in the A2, A3, or C2 section, condensation is likely to occur on the semiconductor hydrogen pressure sensor 100, and problematic water droplets will adhere to the semiconductor hydrogen pressure sensor 100. Unlike the comparative semiconductor hydrogen pressure sensor 101 shown in FIG. 12 , in this embodiment, a protective film 12 is provided on the surfaces of the semiconductor pressure detection element 3, ASIC 9, and bonding wires 10. Therefore, even if condensation occurs on the semiconductor hydrogen pressure sensor 100 and water droplets are present, the water droplets are physically and electrically insulated from these conductive parts, so electrolysis of the water droplets does not occur, and corrosion does not occur, resulting in a significant improvement in reliability. Even if the fuel cell system 1000 is in an operating state and power is being supplied to the semiconductor hydrogen pressure sensor 100, a similar improvement in reliability can be achieved.

[0041] <Method of Manufacturing Semiconductor Hydrogen Pressure Sensor 100> A method of manufacturing the semiconductor hydrogen pressure sensor 100 will be described with reference to Fig. 4. The method of manufacturing the semiconductor hydrogen pressure sensor 100 includes a member preparation step (S11), a connection step (S12), and a film formation step (S13).

[0042] Each step will be described in detail below. The component preparation step is a step of preparing the semiconductor pressure detection element 3, which receives the pressure of the medium to be measured and electrically outputs a value corresponding to the absolute pressure of the medium to be measured, and the bonding wire 10. The semiconductor hydrogen pressure sensor 100 shown in Figure 1 further includes an ASIC 9, a lead frame 11, a pressure-receiving chamber 7, a terminal 6, O-rings 8a and 8b, and a pressure guiding tube 2, and these are also prepared in this step.

[0043] The connecting step is a step of electrically connecting the bonding wire 10a to the semiconductor pressure detection element 3. Prior to the connecting step, the pressure-receiving chamber 7, which receives the medium to be measured, is formed around the lead frame 11 by insert molding. When the pressure-receiving chamber 7 is formed, the portion of the lead frame 11 that is connected to the bonding wire 10b is exposed to the outside. After the semiconductor pressure detection element 3 and the ASIC 9 are fixed inside the pressure-receiving chamber 7, the semiconductor pressure detection element 3 and the ASIC 9 are connected by the bonding wire 10a, and the ASIC 9 is connected by the bonding wire 10b to the exposed portion of the lead frame 11. As shown in FIG. 2 , the semiconductor pressure detection element 3 and the ASIC 9 are arranged side by side and fixed via resin to the surface of the lead frame 11 facing the pressure-receiving chamber 7. The fixing method is, for example, adhesive bonding.

[0044] The film forming process is a process of continuously covering the portions of the semiconductor pressure detection element 3 and the bonding wire 10a that are exposed to the medium to be measured with the protective film 12. In this embodiment, the protective film 12 continuously covers the portions of the semiconductor pressure detection element 3, the bonding wire 10, the ASIC 9, and the pressure-receiving chamber 7 that are exposed to the medium to be measured. The protective film 12 is, for example, a polymer coating film, and is formed by chemical vapor deposition.

[0045] After the film formation process, the terminals 6 are electrically connected to the lead frame 11 by, for example, soldering. Next, the housing 1 is formed around the pressure-receiving chamber 7 by insert molding. Next, the portion of the housing 1 surrounding the pressure-receiving chamber 7, the pressure-receiving chamber 7, and the pressure-leading tube 2 are connected via an O-ring 8a. An external flow path (not shown) for the medium to be measured is connected to the pressure-leading tube 2 via an O-ring 8b. Through these processes, the semiconductor hydrogen pressure sensor 100 shown in FIG. 1 is manufactured.

[0046] By manufacturing the semiconductor hydrogen pressure sensor 100 in this manner, even if condensation occurs on the protective film 12, water droplets 13 will not adhere to the semiconductor pressure detection element 3 and the conductive portions of the bonding wire 10a, and corrosion and breakage of the conductive portions due to electrolysis of the water droplets 13 will not occur.As a result, a semiconductor hydrogen pressure sensor 100 can be manufactured that is compact, lightweight, and highly accurate and reliable.

[0047] As described above, the semiconductor hydrogen pressure sensor 100 according to embodiment 1 comprises a semiconductor pressure detection element 3 that receives the pressure of a measurement medium containing hydrogen and electrically outputs a value corresponding to the absolute pressure of the measurement medium, a bonding wire 10a extending from the terminal of the semiconductor pressure detection element 3, and a protective film 12 that continuously covers the portions of the semiconductor pressure detection element 3 and the bonding wire 10a that are exposed to the measurement medium. Therefore, even if condensation occurs on the protective film 12, water droplets 13 will not adhere to the conductive portions of the semiconductor pressure detection element 3 and the bonding wire 10a, and corrosion and breakage of the conductive portions due to electrolysis of the water droplets 13 will not occur. As a result, a semiconductor hydrogen pressure sensor 100 can be obtained that is compact, lightweight, and highly accurate and reliable.

[0048] When the protective film 12 continuously covers the semiconductor pressure detection element 3, bonding wire 10, ASIC 9, and pressure-receiving chamber 7 portions exposed to the medium to be measured, the interior of the pressure-receiving chamber 7 is effectively protected from condensation, resulting in a highly accurate and reliable semiconductor hydrogen pressure sensor 100. Furthermore, when the protective film 12 is a polymer coating film, the polymer coating film has properties such as water repellency, water vapor impermeability, and acid corrosion resistance, so that even if condensation occurs on the protective film 12, adhesion of water droplets 13 to the conductive portions of the semiconductor pressure detection element 3 and bonding wire 10a is reliably suppressed. This prevents corrosion and disconnection of the conductive portions due to electrolysis of the water droplets 13, resulting in a highly accurate and reliable semiconductor hydrogen pressure sensor 100.

[0049] The manufacturing method of the semiconductor hydrogen pressure sensor 100 according to embodiment 1 includes a component preparation step of preparing a semiconductor pressure detection element 3, which receives the pressure of the medium to be measured and electrically outputs a value corresponding to the absolute pressure of the medium to be measured, and a bonding wire 10a; a connection step of electrically connecting the bonding wire 10a to the semiconductor pressure detection element 3; and a film formation step of continuously covering the portions of the semiconductor pressure detection element 3 and the bonding wire 10a exposed to the medium to be measured with a protective film 12. Therefore, even if condensation occurs on the protective film 12, water droplets 13 will not adhere to the conductive portions of the semiconductor pressure detection element 3 and the bonding wire 10a, and corrosion and breakage of the conductive portions due to electrolysis of the water droplets 13 will not occur. As a result, a semiconductor hydrogen pressure sensor 100 can be manufactured that is compact, lightweight, and has high accuracy and reliability.

[0050] Embodiment 2. A semiconductor hydrogen pressure sensor 100 according to embodiment 2 will now be described. Figure 5 is a cross-sectional view showing the main part of the pressure-receiving chamber 7 of the semiconductor hydrogen pressure sensor 100 according to embodiment 2, enlarging the portion of the semiconductor pressure detection element 3 on the side of the medium to be measured, showing the semiconductor base 16, terminals 15, and protective film 12. The semiconductor hydrogen pressure sensor 100 according to embodiment 2 has a laminated protective film 12.

[0051] In this embodiment, the protective film 12 is a laminated film in which multiple films are stacked. The reason for stacking the protective film 12 will be explained. In a bonding pad portion, where the semiconductor pressure detection element 3 is electrically connected to the bonding wire 10a, there may be a portion where the terminal 15, which is a conductive portion, is exposed. As described in the first embodiment, such a portion is also basically covered with the protective film 12 conformally formed. However, in an actual manufacturing process, minute defects 14 such as pinholes may be generated in the protective film 12, and it is very difficult to completely prevent the generation of defects 14. If such defects 14 were to occur in a conductive portion such as the terminal 15, connecting the terminal 15 to the outside, a circuit via infiltrated water droplets would be formed at the defect 14 when power is supplied, and electrolysis of the water droplets may occur.

[0052] When the protective film 12 is formed as a laminated film in which a plurality of films are stacked, the protective film 12 can be stacked so that the defects 14 do not connect to each other, as shown in FIG. 5 . Because the defects 14 do not connect to each other, it is possible to prevent the terminals 15 from communicating with the outside through the defects 14. The protective film 12 to be stacked may be the same as that in the first embodiment. If a thick film is formed continuously at one time, there is a high risk that the defects 14 will communicate with each other. Therefore, by temporarily stopping the film formation during film formation and then restarting the film formation to form a laminated structure, it is possible to form a protective film 12 structure in which the defects 14 do not communicate with the outside.

[0053] Defects 14 occur with a certain probability during film formation, but unless the defects 14 occur in the same position each time layers are stacked and overlap and connect, the defects 14 will not penetrate the entire protective film 12. In other words, the probability of defects 14 penetrating the protective film 12 is proportional to the product of the probabilities of defects 14 occurring in each stacked film, so the greater the number of layers stacked, the more significantly the probability of defects 14 penetrating the protective film 12. In practice, the number of layers stacked in the protective film 12 should be appropriately selected from several to approximately 10 layers, taking into consideration the overall thickness and residual stress of the protective film 12.

[0054] As described above, in the semiconductor hydrogen pressure sensor 100 according to the second embodiment, the protective film 12 is a laminated film in which multiple films are stacked, so even if a minute defect 14 such as a pinhole is present in the protective film 12 provided on the semiconductor pressure detection element 3, the defect 14 can be prevented from reaching the outside. Because the defect 14 does not reach the outside, even if the medium to be measured is a high-humidity medium containing a large amount of water vapor, water droplets can be prevented from reaching the surface of the semiconductor pressure detection element 3. Because water droplets do not reach the surface of the semiconductor pressure detection element 3, the reliability of the semiconductor hydrogen pressure sensor 100 can be improved.

[0055] Embodiment 3. A method for manufacturing a semiconductor hydrogen pressure sensor 100 according to embodiment 3 will now be described. Figure 6 is a diagram showing the manufacturing process for the semiconductor hydrogen pressure sensor 100 according to embodiment 3, and Figure 7 is a diagram showing the variation in residual stress when the protective film 12 of the semiconductor hydrogen pressure sensor 100 is placed in a constant high-temperature environment. The manufacturing method for the semiconductor hydrogen pressure sensor 100 according to embodiment 3 adds a heat treatment step. The protective film 12 of the semiconductor hydrogen pressure sensor 100 according to embodiment 3 is subjected to heat treatment.

[0056] As shown in FIG. 6 , the method for manufacturing the semiconductor hydrogen pressure sensor 100 includes a heat treatment step (S14) for performing heat treatment on the protective film 12 after the film formation step (S13) described in the first embodiment. The reason for adding the heat treatment step will be explained. As described in the first embodiment, the protective film 12 is, for example, a parylene film. Although it depends on the type, parylene films have the characteristic that the residual stress varies with the applied time, as shown in FIG. 7 , even at approximately 100°C, which is roughly the maximum temperature of the medium used in PEFC-type fuel cell systems. In other words, the residual stress increases with time up to a certain time, but once that time is exceeded, the amount of variation in the residual stress saturates and stabilizes.

[0057] If an event that causes the residual stress of the protective film 12 to fluctuate occurs during the manufacturing process of the semiconductor hydrogen pressure sensor 100, the semiconductor hydrogen pressure sensor 100 will deviate from its intended detection characteristics, resulting in a decrease in the measurement accuracy of the semiconductor hydrogen pressure sensor 100. Alternatively, if an event that causes the residual stress of the protective film 12 to fluctuate occurs after the fuel cell system 1000 begins operation, the detection characteristics of the semiconductor hydrogen pressure sensor 100 will fluctuate while the semiconductor hydrogen pressure sensor 100 is in use. In either case, the high-precision measurement of the semiconductor hydrogen pressure sensor 100 will be hindered.

[0058] In the manufacturing process of the semiconductor hydrogen pressure sensor 100, immediately after forming the protective film 12, a heat treatment is performed for a time until the residual stress reaches the region shown in FIG. 7 where it stabilizes, thereby preventing the semiconductor hydrogen pressure sensor 100 from impeding high-precision measurement. Specifically, it is preferable to age the protective film 12 by heat treatment at 130°C for approximately 10 hours. The applied temperature can be set slightly higher than the temperature range used in the actual system, thereby shortening the heat treatment time. Furthermore, by reducing the sensitivity of the protective film 12 to high temperatures during actual use, it is possible to suppress fluctuations in the semiconductor hydrogen pressure sensor 100 over time. This allows the detection characteristics of the semiconductor hydrogen pressure sensor 100 to be maintained stable throughout the expected life of the fuel cell system 1000.

[0059] As described above, the manufacturing method of semiconductor hydrogen pressure sensor 100 according to embodiment 3 includes a heat treatment step in which protective film 12 is heat treated after the film formation step, so that the residual stress in protective film 12 is stabilized to a state that is not fluctuated by external factors such as high temperature, and therefore the detection characteristics of semiconductor hydrogen pressure sensor 100 do not fluctuate, and the high measurement accuracy of semiconductor hydrogen pressure sensor 100 can be maintained throughout the expected warranty period. Furthermore, because protective film 12 of semiconductor hydrogen pressure sensor 100 according to embodiment 3 has been heat treated, the detection characteristics of semiconductor hydrogen pressure sensor 100 do not fluctuate, and the high measurement accuracy of semiconductor hydrogen pressure sensor 100 can be maintained throughout the expected warranty period.

[0060] Embodiment 4 A semiconductor hydrogen pressure sensor 100 according to embodiment 4 will now be described. Figure 8 is a cross-sectional view showing an outline of the pressure-receiving chamber 7 of the semiconductor hydrogen pressure sensor 100 according to embodiment 4. The semiconductor hydrogen pressure sensor 100 according to embodiment 4 has a configuration in which a gel-like member is added.

[0061] In this embodiment, the surface of the protective film 12 that covers the semiconductor pressure detection element 3 is covered with a gel-like material. As shown in Fig. 8, a gel 4a is provided on the surface of the protective film 12 that covers the semiconductor pressure detection element 3, and a gel 4b is provided on the surface of the protective film 12 that covers the ASIC 9. The gel-like material is, for example, a silicone gel. The reason for adding the gel-like material will be explained below.

[0062] As described above, since the protective film 12 is provided on the surface of the conductive portion inside the pressure chamber 7, even if water droplets due to condensation form on the protective film 12 and power is supplied to the semiconductor hydrogen pressure sensor 100 during system operation, electrolysis does not occur in the water droplets. However, since the configuration shown in Figure 2 does not use gel 4, the impact absorbing effect of gel 4 is not obtained. In other words, the gel 4 also has the function of preventing physical damage to the pressure-receiving diaphragm and other components on the surface of the semiconductor pressure detection element 3 due to the impact when a solid foreign object or the like collides with the semiconductor pressure detection element 3 at high speed.

[0063] By adding a gel-like material to the surface of the protective film 12 covering the semiconductor pressure sensing element 3, physical damage to the semiconductor pressure sensing element 3 caused by the collision of a foreign object can be prevented. In the fuel cell system 1000, a large number of very fine flow paths are provided inside the fuel cell stack 19. To prevent these paths from being clogged by foreign objects and to prevent foreign objects from entering the gas supply system, filters are installed in the medium flow paths. Therefore, while there are not many large foreign objects like those in the piping of an internal combustion engine, there may be a certain amount of small solid foreign objects mixed into the flow paths. Considering this usage environment, it is not necessary to use a large amount of gel as shown in the comparative example of FIG. 12 to absorb impacts; it is appropriate to use an appropriate amount of gel only where necessary.

[0064] As described above, in the semiconductor hydrogen pressure sensor 100 according to embodiment 4, the surface of the protective film 12 covering the semiconductor pressure detection element 3 is covered with a gel-like material, thereby preventing the pressure-receiving diaphragm of the semiconductor pressure detection element 3 from being damaged by impact caused by collisions with particulate foreign matter or the like that has entered from the outside.

[0065] Embodiment 5. A semiconductor hydrogen pressure sensor 100 according to embodiment 5 will now be described. Figure 9 is a cross-sectional view showing an outline of the semiconductor hydrogen pressure sensor 100 according to embodiment 5, with the protective film 12 omitted. The semiconductor hydrogen pressure sensor 100 according to embodiment 5 is configured such that the pressure guiding tube 2 has a moisture absorbent member 17.

[0066] In this embodiment, the pressure guiding tube 2 has a moisture absorbent member 17 at the end of the pressure guiding tube 2 through which the medium to be measured is taken in. The moisture absorbent member 17 is provided, for example, on the entire inner wall surface of the tip of the pressure guiding tube 2 in a state of contact with the medium to be measured. The moisture absorbent member 17 is, for example, silica gel, which adsorbs water. With this configuration, water vapor contained in the medium to be measured is trapped by the moisture absorbent member 17 before it reaches the pressure-receiving chamber 7 in which the semiconductor pressure detection element 3 and the like are installed, thereby reducing the amount of moisture that reaches the pressure-receiving chamber 7. Because the amount of moisture that reaches the pressure-receiving chamber 7 is reduced, condensation in the pressure-receiving chamber 7 and problems caused by condensation can be reduced, further improving the reliability of the semiconductor hydrogen pressure sensor 100.

[0067] As described above, the semiconductor hydrogen pressure sensor 100 according to the fifth embodiment has the moisture absorbent member 17 at the end of the pressure guiding tube 2 where the pressure guiding tube 2 takes in the medium to be measured, and therefore, even if the medium to be measured contains a large amount of water droplets and water vapor, these are absorbed by the moisture absorbent member 17, and the amount of water droplets and water vapor that reaches the pressure receiving chamber 7 can be significantly reduced. Because the amount of water droplets and water vapor that reaches the pressure receiving chamber 7 is significantly reduced, the risk of condensation under certain complex environments and corrosion of conductive parts due to electrolysis caused by condensation can be significantly reduced.

[0068] Sixth Embodiment A semiconductor hydrogen pressure sensor 100 according to a sixth embodiment will now be described. Figure 10 is a cross-sectional view showing an outline of the semiconductor hydrogen pressure sensor 100 according to the sixth embodiment, with the protective film 12 omitted. The semiconductor hydrogen pressure sensor 100 according to the sixth embodiment is configured such that the pressure guiding tube 2 has a heating section 18.

[0069] In this embodiment, the pressure guiding tube 2 has a heating unit 18 adjacent to the moisture absorbent member 17. The heating unit 18 is disposed, for example, surrounding the moisture absorbent member 17. The heating unit 18 is, for example, a heater that is electrically heated. The reason for adding the heating unit 18 will be explained below.

[0070] As described above, providing the moisture absorbent member 17 at the end of the pressure guiding tube 2 reduces the amount of water vapor that reaches the pressure-receiving chamber 7, thereby improving the reliability of the semiconductor hydrogen pressure sensor 100. However, it is often difficult to maintain this effect over the expected lifespan of the fuel cell system 1000, although this depends on the system operating conditions, etc. This is because there is a limit to the amount of moisture that the moisture absorbent member 17 can absorb.

[0071] By providing a heating unit 18 adjacent to the moisture absorbent member 17, the water vapor absorbed by the moisture absorbent member 17 can be released by driving the heating unit 18 as part of a series of sequential operations, such as when the fuel cell system 1000 is stopped. By performing a purging process following the release of the water vapor, the released water vapor is discharged to the outside so that it does not remain in the pressure receiving chamber 7, and the inside of the pressure guiding tube 2 and the inside of the pressure receiving chamber 7 can be made into a dry environment. This also restores the moisture absorption function of the moisture absorbent member 17. This makes it possible to obtain a semiconductor hydrogen pressure sensor 100 that has stable reliability over a long period of time.

[0072] As described above, in the semiconductor hydrogen pressure sensor 100 according to the sixth embodiment, the pressure guiding tube 2 has the heating section 18 adjacent to the moisture absorbent member 17, so that the moisture absorbed by the moisture absorbent member 17 can be vaporized, thereby restoring the reduced moisture absorption capacity of the moisture absorbent member 17. Because the moisture absorption capacity of the moisture absorbent member 17 is restored, the semiconductor hydrogen pressure sensor 100 can maintain high reliability for a long period of time, even if the medium to be measured has a high humidity.

[0073] Furthermore, although various exemplary embodiments and examples are described in this application, the various features, aspects, and functions described in one or more embodiments are not limited to the application of a particular embodiment, but may be applied to the embodiments alone or in various combinations. Therefore, countless modifications not illustrated are contemplated within the scope of the technology disclosed in this specification. For example, this includes cases where at least one component is modified, added, or omitted, or where at least one component is extracted and combined with components of another embodiment.

[0074] REFERENCE SIGNS LIST 1 Housing, 2 Pressure guiding tube, 3 Semiconductor pressure detection element, 4, 4a, 4b Gel, 5 Connector portion, 6 Terminal, 7 Pressure receiving chamber, 7a Opening, 8a, 8b O-ring, 9 ASIC, 10, 10a, 10b Bonding wire, 11 Lead frame, 12 Protective film, 13 Water droplet, 14 Defect, 15 Terminal, 16 Semiconductor base, 17 Moisture absorbing member, 18 Heating portion, 19 Fuel cell stack, 20 Hydrogen fuel tank, 100, 101 Semiconductor hydrogen pressure sensor, 1000 Fuel cell system

Claims

1. a semiconductor pressure detection element that receives the pressure of a measurement target medium containing hydrogen and electrically outputs a value corresponding to the absolute pressure of the measurement target medium; a bonding wire extending from a terminal of the semiconductor pressure detection element; a protective film continuously covering the semiconductor pressure detection element and the bonding wires that are exposed to the medium to be measured.

2. 2. The semiconductor hydrogen pressure sensor according to claim 1, wherein the protective film is a laminated film in which a plurality of films are laminated.

3. 2. The semiconductor hydrogen pressure sensor according to claim 1, wherein the surface of said protective film covering said semiconductor pressure detection element is covered with a gel-like material.

4. a pressure receiving chamber to which the semiconductor pressure detection element is fixed and which has an opening for taking in the medium to be measured; a pressure guiding tube that communicates with the pressure receiving chamber through the opening and takes the measurement target medium from the outside into the pressure receiving chamber, 4. The semiconductor hydrogen pressure sensor according to claim 1, wherein the pressure guiding tube has a moisture absorbing member at an end of the pressure guiding tube that takes in the medium to be measured.

5. 5. The semiconductor hydrogen pressure sensor according to claim 4, wherein the pressure guiding tube has a heating portion adjacent to the moisture absorbent member.

6. a resin pressure-receiving chamber to which the semiconductor pressure detection element is fixed; A lead frame that is insert-molded into the pressure-receiving chamber; a signal processing circuit that is fixed inside the pressure receiving chamber, that is connected to the semiconductor pressure detection element via the bonding wire, and that is connected to the lead frame; A semiconductor hydrogen pressure sensor as described in any one of claims 1 to 3, wherein the protective film continuously covers the semiconductor pressure detection element, the bonding wire, the signal processing circuit, and the pressure-receiving chamber portions exposed to the medium to be measured.

7. 4. The semiconductor hydrogen pressure sensor according to claim 1, wherein the protective film is a polymer coating film.

8. 8. The semiconductor hydrogen pressure sensor according to claim 7, wherein the protective film is subjected to a heat treatment.

9. a member preparation step of preparing a semiconductor pressure detection element that receives the pressure of a medium to be measured and electrically outputs a value corresponding to the absolute pressure of the medium to be measured, and a bonding wire; a connecting step of electrically connecting the bonding wire to the semiconductor pressure detection element; and a film-forming step of continuously covering the portions of the semiconductor pressure detection element and the bonding wires exposed to the medium to be measured with a protective film.

10. 10. The method for manufacturing a semiconductor hydrogen pressure sensor according to claim 9, further comprising a heat treatment step of heat treating the protective film portion after the film forming step.