Odor detection device and odor detection method

Abstract

To provide a smell detection device and a smell detection method, excellent in real-time properties and capable of detecting smell components with high accuracy.SOLUTION: A smell detection device according to the invention includes a first detection element, a second detection element, and a calculation unit. The first detection element includes a first oscillator as an elastic wave resonator, and a first sensitive membrane formed on the first oscillator. The second detection element includes a second oscillator as an elastic wave resonator. The calculation unit corrects a variation amount of a resonance frequency of the first oscillator by subtracting a variation amount of a resonance frequency of the second oscillator output from the second detection element from the variation amount of the resonance frequency of the first oscillator output from the first detection element.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an odor detection device and an odor detection method for detecting odor components. [Background technology]

[0002] Conventionally, odor sensors have been known that have an oscillator that vibrates at a specific resonant frequency and a sensitive membrane that adsorbs odor components in gas. In this odor sensor, the oscillator is vibrated at a specific resonant frequency, and odor components can be detected by observing the change in the resonant frequency due to the adsorption of the odor components. The oscillator is composed of a piezoelectric resonator such as a QCM (Quartz Crystal Microbalance), a SAW (Surface acoustic wave) resonator, or an FBAR (Film bulk acoustic resonator).

[0003] Here, when the gas to be detected by the odor sensor contains humidity, the resonant frequency of the vibrator may vary depending on the humidity. The resonant frequency of the vibrator may also vary depending on the temperature of the odor sensor. For this reason, in order to accurately detect odor components, a correction is required to eliminate the variation in the resonant frequency due to humidity and temperature.

[0004] For example, Patent Document 1 discloses a humidity correction method that utilizes the electrode corrosiveness of a QCM. Patent Document 2 discloses a method in which a QCM is used as a humidity reference element and a temperature reference element, a correction coefficient is calculated using these reference elements, and correction is performed using the correction coefficient. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2014-145608 A [Patent Document 2] JP 2018-48930 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, the method described in Patent Document 1 obtains the amount of change in the resonant frequency for a certain period of time, and corrects the amount of change in the resonant frequency based on the amount of electrode corrosion during that period, and does not correct odor components in real time. High real-time performance is required for applications such as poison gas detection and fire detection. In addition, the method described in Patent Document 2 is based on linear correction, so it cannot be used in a wide temperature and humidity range where the temperature and humidity dependence of the resonant frequency deviates from linearity.

[0007] Furthermore, there is a method of detecting the temperature and humidity using a temperature and humidity sensor and correcting the effects of temperature and humidity, but this requires a separate sensor and control circuit, and also requires complex calculations, making it difficult to achieve real-time results.

[0008] In view of the above circumstances, an object of the present invention is to provide an odor detection device and an odor detection method that are excellent in real-time performance and capable of detecting odor components with high accuracy. [Means for solving the problem]

[0009] In order to achieve the above object, an odor detection device according to one embodiment of the present invention includes a first detection element, a second detection element, and a calculation unit. The first detection element includes a first vibrator which is an acoustic wave resonator, and a first sensitive film formed on the first vibrator. The second sensing element includes a second oscillator which is an acoustic wave resonator. The calculation unit corrects the amount of fluctuation in the resonant frequency of the first oscillator by subtracting the amount of fluctuation in the resonant frequency of the second oscillator output from the second detection element from the amount of fluctuation in the resonant frequency of the first oscillator output from the first detection element.

[0010] The odor detection device further includes a third detection element including a third oscillator that is an elastic wave resonator and a second sensitive film formed on the third oscillator, the third oscillator and the second sensitive film being shielded from outside air; The calculation unit may perform the correction by subtracting an amount of fluctuation in the resonant frequency of the second oscillator and an amount of fluctuation in the resonant frequency of the third oscillator output from the third detection element from an amount of fluctuation in the resonant frequency of the first oscillator.

[0011] The second transducer may have the same characteristics as the first transducer.

[0012] The third vibrator may have characteristics equivalent to those of the first vibrator, and the second sensitive film may have characteristics equivalent to those of the first sensitive film.

[0013] The acoustic wave resonator may be a Film Bulk Acoustic Resonator (FBAR).

[0014] The acoustic wave resonator may be a SAW (Surface Acoustic Wave) resonator.

[0015] In order to achieve the above-mentioned object, an odor detection method according to one embodiment of the present invention corrects the amount of fluctuation in the resonant frequency of the first oscillator by subtracting the amount of fluctuation in the resonant frequency of the second oscillator output from a second detection element having a second oscillator which is an elastic wave resonator from the amount of fluctuation in the resonant frequency of the first oscillator output from a first detection element having a first oscillator which is an elastic wave resonator and a first sensitive membrane formed on the first oscillator. Effect of the Invention

[0016] As described above, according to the present invention, it is possible to provide an odor detection device and an odor detection method that are excellent in real-time performance and capable of detecting odor components with high accuracy. [Brief description of the drawings]

[0017] [Figure 1] 1 is a block diagram of an odor detection device according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a schematic diagram of a first detection element (FBAR) included in the odor detection device. [Diagram 3] FIG. 2 is a schematic diagram of a second detection element (FBAR) included in the odor detection device. [Figure 4] FIG. 4 is a schematic diagram of a third detection element (FBAR) included in the odor detection device. [Diagram 5] FIG. 2 is a schematic diagram showing a mounting structure 1 of the odor detection device. [Figure 6] FIG. 2 is a schematic diagram showing a mounting structure 2 of the odor detection device. [Figure 7] FIG. 4 is a cross-sectional view of a first detection element in the second mounting structure. [Figure 8] FIG. 11 is a cross-sectional view of a third detection element in the second mounting structure. [Figure 9] FIG. 2 is a schematic diagram of a first detection element (SAW resonator) included in the odor detection device. [Figure 10] 3 is a schematic diagram of a second detection element (SAW resonator) included in the odor detection device. FIG. [Figure 11] 4 is a schematic diagram of a third detection element (SAW resonator) included in the odor detection device. FIG. [Figure 12] FIG. 2 is a block diagram of an odor detection device according to a first modified example of the present invention. [Figure 13] FIG. 11 is a block diagram of an odor detection device according to a second modified example of the present invention. [Figure 14] 4 is a graph showing the measurement results according to Example 1 of the present invention. [Figure 15] 11 is a graph showing the measurement results according to Example 2 of the present invention. [Figure 16] 16 is a graph showing an enlarged view of a part of FIG. 15. [Figure 17] 11 is a graph showing the measurement results according to Example 3 of the present invention. [Figure 18] 11 is a graph showing the measurement results according to Example 3 of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] An odor detection device according to an embodiment of the present invention will be described. The three orthogonal directions are defined as the X direction, the Y direction, and the Z direction, respectively.

[0019] [Configuration of odor detection device] 1 is a block diagram showing the configuration of an odor detection device 100 according to this embodiment. As shown in the figure, the odor detection device 100 includes a first detection element 111, a first oscillation circuit 112, a second detection element 113, a second oscillation circuit 114, a third detection element 115, a third oscillation circuit 116, a connection unit 117, a calculation unit 118, and a communication unit 119.

[0020] The first detection element 111 functions as an odor detection element. Fig. 2(a) is a cross-sectional view of the first detection element 111, and Fig. 2(b) is a plan view illustrating a sensitive film 132 of the first detection element 111. As shown in the figure, the first detection element 111 includes a first oscillator 131 and a first sensitive film 132. The first oscillator 131 is an acoustic wave resonator, and is an FBAR (Film bulk acoustic resonator).

[0021] Specifically, the first oscillator 131 includes a support substrate 141, a piezoelectric film 142, a lower electrode 143, and an upper electrode 144. The support substrate 141 may be, for example, a semiconductor substrate such as a silicon (Si) substrate or a gallium arsenide (GaAs) substrate, or a ceramic substrate such as a quartz substrate, a glass substrate, or an alumina substrate.

[0022] The piezoelectric film 142 is a film made of a piezoelectric material, and is made of, for example, aluminum nitride (AlN). The piezoelectric film 142 may also be made of other piezoelectric materials, such as zinc oxide (ZnO). The thickness of the piezoelectric film 142 is, for example, 500 nm.

[0023] The lower electrode 143 is provided on the support substrate 141, and functions as one of the electrodes of the first oscillator 131. The lower electrode 143 is made of a conductive material such as aluminum (Al) and has a thickness of, for example, 240 nm. The upper electrode 144 is provided on the piezoelectric film 142, and sandwiches the piezoelectric film 142 together with the lower electrode 143, and functions as the other electrode of the first oscillator 131. The upper electrode 144 is made of a conductive material such as aluminum (Al) and has a thickness of, for example, 240 nm. The surface of the upper electrode 144 is covered with a SiO X A protective film made of, for example,

[0024] The first oscillator 131 has a resonance region R where a lower electrode 143 and an upper electrode 144 face each other with a piezoelectric film 142 sandwiched therebetween. In the resonance region R, a gap K is provided between the support substrate 141 and the lower electrode 143. The resonance region R is a region that resonates in a thickness extensional vibration mode when an AC voltage of a resonance frequency is input between the lower electrode 143 and the upper electrode 144. The resonance frequency of the resonance region R is not particularly limited, and is, for example, 2.4 GHz.

[0025] The first sensitive film 132 is provided on the resonance region R of the first oscillator 131, and adsorbs a predetermined odor component. The material constituting the first sensitive film 132 can be arbitrarily selected depending on the type of odor component to be adsorbed, and is, for example, an organic polymer film, an organic dye film, or an inorganic film. As shown in FIG. 1, the odor detection device 100 includes a plurality of first detection elements 111, for example, eight first detection elements 111. The first sensitive film 132 included in each first detection element 111 can be capable of adsorbing a different odor component, and the output of each first detection element 111 is defined as channel 1 to channel 8 (hereinafter, ch1 to ch8). The number of first detection elements 111 is not limited to eight, and may be one or more.

[0026] The first oscillator circuit 112 is connected to the first detection element 111, and applies an AC voltage between the lower electrode 143 and the upper electrode 144 of the first oscillator 131 to drive the first oscillator 131. This AC voltage causes the first oscillator 131 to vibrate at a predetermined resonance frequency. The first oscillator circuit 112 outputs the resonance frequency of the first oscillator 131 to the connection unit 117. The first oscillator circuit 112 can output a count value of the resonance frequency as a digital signal to the connection unit 117. The first oscillator circuit 112 may be anything that can supply an AC voltage to the first oscillator 131, and is, for example, an IC (Integrated Circuit). Note that one first oscillator circuit 112 may drive a plurality of first oscillators 131.

[0027] In Fig. 3, the second detection element 113 functions as a humidity correction element. Fig. 3 is a cross-sectional view of the second detection element 113. The second detection element 113 includes a second vibrator 133. The second vibrator 133 is an acoustic wave resonator, for example, an FBAR. The second vibrator 133 preferably has characteristics equivalent to those of the first vibrator 131. The second detection element 113 has characteristics equivalent to those of the first detection element 111 that does not have the first sensitive film 132.

[0028] Specifically, like the first oscillator 131, the second oscillator 133 includes a support substrate 141, a piezoelectric film 142, a lower electrode 143, and an upper electrode 144, and has a resonance region R. As shown in the block diagram of Fig. 1, the odor detection device 100 includes one second detection element 113. However, a plurality of second detection elements 113 may be included.

[0029] The second oscillator circuit 114 is connected to the second detection element 113, and applies an AC voltage between the lower electrode 143 and the upper electrode 144 of the second oscillator 133 to drive the second oscillator 133. This AC voltage causes the second oscillator 133 to vibrate at a predetermined resonance frequency. The second oscillator circuit 114 outputs the resonance frequency of the second oscillator 133 to the connection unit 117. The second oscillator circuit 114 can output a count value of the resonance frequency as a digital signal to the connection unit 117. The second oscillator circuit 114 may be any circuit capable of supplying an AC voltage to the second oscillator 133, and is, for example, an IC in this embodiment. Note that one second oscillator circuit 114 may drive a plurality of second oscillators 133.

[0030] The third detection element 115 functions as a temperature correction element. FIG. 4 is a cross-sectional view of the third detection element 115. The third detection element 115 includes a third oscillator 134 and a second sensitive film 135. The third oscillator 134 is an elastic wave resonator, and is an FBAR. The third oscillator 134 preferably has characteristics similar to those of the first oscillator 131. Specifically, the third oscillator 134 includes a support substrate 141, a piezoelectric film 142, a lower electrode 143, and an upper electrode 144, similar to the first oscillator 131, and has a resonance region R.

[0031] The second sensitive film 135 is provided on the resonance region R of the third oscillator 134, and adsorbs a predetermined odor component. The second sensitive film 135 is preferably made of the same material as the first sensitive film 132 and has the same film thickness as the first sensitive film 132. The third detection element 115 is sealed by a sealant 136 as shown in FIG. 4, and the third oscillator 134 and the second sensitive film 135 are shielded from the outside air by the sealant 136.

[0032] As shown in FIG. 1, the odor detection device 100 includes a plurality of third detection elements 115, each of which corresponds to a first detection element 111, and the number of third detection elements 115 is equal to the number of first detection elements 111. Specifically, each third detection element 115 has the same characteristics as the first detection element 111 of each ch, except that it is sealed by a sealer 136, and includes a second sensitive film 135 that is the same as the first sensitive film 132 of the first detection element 111 of each ch. Hereinafter, the third detection element 115 having the same characteristics as the first detection element 111 of ch1 will be referred to as the third detection element 115 of ch1. Similarly, the third detection element 115 having the same characteristics as the first detection element 111 of each ch will be referred to as the third detection element 115 of each ch.

[0033] The third oscillator circuit 116 is connected to the third detection element 115, and applies an AC voltage between the lower electrode 143 and the upper electrode 144 of the third oscillator 134 to drive the third oscillator 134. This AC voltage causes the third oscillator 134 to vibrate at a predetermined resonance frequency. The third oscillator circuit 116 outputs the resonance frequency of the third oscillator 134 to the connection unit 117. The third oscillator circuit 116 outputs a count value of the resonance frequency as a digital signal to the connection unit 117. The third oscillator circuit 116 may be any circuit capable of supplying an AC voltage to the third oscillator 134, and is, for example, an IC in this embodiment. Note that a single third oscillator circuit 116 may drive a plurality of third oscillators 134.

[0034] 4, the sealant 136 seals the third detection elements 115 as described above, and shields the third oscillator 134 and the second sensitive film 135 from the outside air. For example, it is a wall-like structure surrounding the periphery of the third oscillator 134 and the second sensitive film 135. For example, it may be a metal can type or a resin box type, and the inside of the wall-like structure may be filled with an inert gas such as nitrogen. The sealant 136 may be configured such that one sealant 136 seals all of the third detection elements 115, or such that multiple sealants 136 seal one or multiple third detection elements 115, respectively.

[0035] The connection unit 117 connects the first detection element 111, the second detection element 113, and the third detection element 115 to the calculation unit 118, and supplies the resonance frequencies of the first oscillator 131, the second oscillator 133, and the third oscillator 134 to the calculation unit 118. The connection unit 117 can employ a multiplexer capable of switching the connection between the calculation unit 118 and each detection element.

[0036] The calculation unit 118 corrects the amount of change in resonant frequency of the first detection element 111 based on the amount of change in resonant frequency of the second detection element 113 and the third detection element 115. This will be described in detail later. The calculation unit 118 is configured, for example, with an FPGA (field-programmable gate array). The calculation unit 118 supplies the corrected amount of change in resonant frequency to the communication unit 119. The FPGA may be a reconfigurable semiconductor device, for example, an MPLD (registered trademark) or an MRLD.

[0037] The communication unit 119 transfers the amount of resonance frequency variation corrected by the calculation unit 118 to another information processing device such as a PC or a tablet terminal. The user can check the amount of resonance frequency variation corrected in the other information processing device. The communication unit 119 may also transfer the amount of resonance frequency variation corrected to the cloud via a gateway. This allows data to be accumulated in the cloud and odor types to be determined using AI (artificial intelligence). The communication unit 119 is a module capable of wireless communication such as BLE (Bluetooth (registered trademark) Low Energy) or wired communication.

[0038] The odor detection device 100 has the above-mentioned configuration. The calculation unit 118 may be mounted on an information processing device separate from the odor detection device 100 and may execute the above-mentioned operations. Also, it is possible for a user to execute the operations of the calculation unit 118 instead of the calculation unit 118.

[0039] [Regarding correction by the calculation unit] As described above, the calculation section 118 corrects the amount of variation in the resonant frequency of the first detection element 111 based on the amount of variation in the resonant frequency of the second detection element 113 and the third detection element 115.

[0040] The resonant frequency of the first detection element 111 varies depending on the weight of the first sensitive film 132, i.e., the amount of odor components adsorbed to the first sensitive film 132. Furthermore, the resonant frequency of the first detection element 111 also varies depending on the influence of humidity and temperature. Therefore, if the amount of change in the resonant frequency of the nch first detection element 111 is ΔFn(total), the amount of change in the resonant frequency due to odor component adsorption is ΔFn(gas), the amount of change in the resonant frequency due to humidity is ΔFn(hum.), and the amount of change in the resonant frequency due to temperature is ΔFn(tem.), the following (Equation 1) holds.

[0041] ΔFn(total)=ΔFn(gas)+ΔFn(hum.)+ΔFn(tem.) (Formula 1)

[0042] As shown in the above (Equation 1), the resonant frequency variation ΔFn(total) output from the nch first detection element 111 includes the resonant frequency variation ΔFn(gas) due to the adsorption of odor components, as well as the resonant frequency variation ΔFn(hum.) due to humidity and the resonant frequency variation ΔFn(tem.). Therefore, the calculation unit 118 performs the following correction so as to obtain the resonant frequency variation ΔFn(gas) due to the adsorption of odor components.

[0043] Here, the second detection element 113 includes a second oscillator 133 having the same characteristics as the first oscillator 131. Also, the second detection element 113 does not have a sensitive film. In an odor detection element using an FBAR oscillator, the main cause of the effect of humidity is the hygroscopicity of the FBAR oscillator itself, and the effect of moisture absorption by the sensitive film is small. In particular, an FBAR oscillator is generally made of multi-layered thin films, and the piezoelectric film is made of AlN and the protective film is made of SiO. X Since it is formed by sputtering, it has high hygroscopicity.

[0044] Therefore, the amount of change in the resonant frequency of the second detection element 113 can be considered to be due to humidity. For this reason, if the amount of change in the resonant frequency of the second detection element 113 is ΔFref1, the amount of change in the resonant frequency ΔFn(hum.) due to humidity can be considered to be the amount of change in the resonant frequency ΔFref1.

[0045] Furthermore, the third detection element 115 includes a third oscillator 134 having characteristics equivalent to those of the first oscillator 131, and a second sensitive film 135 having characteristics equivalent to those of the first sensitive film 132. The third oscillator 134 and the second sensitive film 135 are shielded from the outside air by a sealant 136. For this reason, the sealant 136 prevents odor components and water molecules from reaching the third oscillator 134 and the second sensitive film 135.

[0046] In an odor detection element using an FBAR oscillator, the main cause of the effect of temperature is the change in the elastic constant of each material constituting the oscillator and the sensitive film. Therefore, the resonant frequency variation of the third detection element 115, which has the same characteristics as the first detection element 111 and is shielded by the sealing body 136, can be considered to be due to temperature. Therefore, if the resonant frequency variation of the nch third detection element 115 is ΔFref2n, the resonant frequency variation ΔFn(tem.) due to temperature can be considered to be the resonant frequency variation ΔFref2n.

[0047] Therefore, the above (Equation 1) can be transformed into the following (Equation 2).

[0048] ΔFn(total)=ΔFn(gas)+ΔFref1+ΔFref2n (Formula 2)

[0049] Furthermore, the above (Equation 2) can be transformed into the following (Equation 3).

[0050] ΔFn(gas)=ΔFn(total)-ΔFref1-ΔFref2n (Equation 3)

[0051] In this way, the calculation unit 118 can calculate the resonant frequency fluctuation ΔFn(gas) due to odor components by subtracting the resonant frequency fluctuation ΔFref1 output from the second detection element 113 and the resonant frequency fluctuation ΔFref2n output from the third detection element 115 from the resonant frequency fluctuation ΔFn(total) output from the first detection element 111.

[0052] [Effects of odor detection devices] As described above, in the odor detection device 100, the calculation unit 118 calculates the resonant frequency fluctuation ΔFn(gas) caused by the odor component adsorbed on the first sensitive film 132 based on the resonant frequency fluctuations of the first detection element 111, the second detection element 113, and the third detection element 115. The calculation unit 118 can calculate the resonant frequency fluctuation ΔFn(gas) by subtracting the resonant frequency fluctuations of the second detection element 113 and the third detection element 115 from the resonant frequency fluctuation of the first detection element 111, and therefore can perform the above calculation as the measurement time elapses, resulting in excellent real-time performance. On the other hand, in the correction method as described in Patent Document 2, it is necessary to calculate the coefficient of the reference element in advance and to call the coefficient at the time of correction, and calculating the coefficient of the reference element in advance is time-consuming.

[0053] In addition, in odor detection device 100, there is no need to evaluate the temperature dependency or humidity dependency of first detection element 111 in advance, and the temperature and humidity range in which accurate correction is possible is not limited as in linear correction, so that highly accurate detection results can be obtained over a wide temperature and humidity range. Furthermore, in odor detection device 100, there is no need to provide first detection element 111 with a structure for temperature and humidity correction, such as a temperature compensation film, so temperature and humidity correction is possible without degrading the vibration characteristics of first detection element 111.

[0054] [Mounting structure 1] A specific mounting structure of the odor detection device 100 will be described. Fig. 5 is a schematic diagram showing the mounting structure of the odor detection device 100. Note that this is realized by mounting techniques such as a mounting device and a wire bonding device. As shown in the figure, the odor detection device 100 is composed of a main board 151, a first sensor board 152, a second sensor board 153, a third sensor board 154, a first detection element 111, a first oscillation circuit 112, a second detection element 113, a second oscillation circuit 114, a third detection element 115, a third oscillation circuit 116, a can package 155, a multiplexer 156, an FPGA 157, and a BLE module 158.

[0055] The main board 151 and the sensor board are boards on which each component is mounted, and are general wiring boards. Two first detection elements 111 and one first oscillation circuit 112 that drives these first detection elements 111 are mounted on the first sensor board 152 by a mounting device or the like. Electrical connection is made to the main board 151 by a pin header, solder, or bonding wire. Four first sensor boards 152 are mounted on the main board 151, but the number of first sensor boards 152 is not particularly limited.

[0056] The second sensor board 153 has two second detection elements 113 and one second oscillation circuit 114 that drives these second detection elements 113 mounted thereon, and is electrically connected to the second sensor board 153 by a bonding wire or the like. The second sensor board 153 is connected to the main board 151 by a pin header or solder reflow. One second sensor board 153 is mounted on the main board 151, but the number of second sensor boards 153 is not particularly limited.

[0057] The third sensor board 154 is a board on which two third detection elements 115 and one third oscillation circuit 116 that drives these third detection elements 115 are mounted, and is electrically connected and mounted on the main board 151 by a pin header, solder reflow, or wire bonding. Four third sensor boards 154 are mounted on the main board 151, but the number of third sensor boards 154 is not particularly limited.

[0058] The can package 155 covers the third sensor substrates 154 and seals the third detection elements 115 on each third sensor substrate 154. An inert gas such as nitrogen gas is filled inside the can package 155. The can package 155 functions as a sealant 136 (see FIG. 4) that shields the third oscillator 134 and the second sensitive film 135 from the outside air.

[0059] The multiplexer 156 is mounted on the main board 151 and functions as the connection unit 117 (see FIG. 1). The FPGA 157 is mounted on the main board 151 and functions as the calculation unit 118 (see FIG. 1). The BLE module 158 is mounted on the main board 151 and functions as the communication unit 119 (see FIG. 1). Note that the multiplexer 156, the FPGA 157, and the BLE module 158 may be mounted on the surface of the main board 151 opposite to the surface on which the first sensor board 152 and the like are mounted, and may be connected to each oscillation circuit and the like via wiring on the main board 151.

[0060] The odor detection device 100 can be realized by the above-mentioned mounting structure. In this configuration, the first detection element 111, the second detection element 113, and the third detection element 115 are mounted on a sensor board separate from the main board 151, so that these detection elements can be replaced for each sensor board.

[0061] [Mounting structure 2] Another specific mounting structure of odor detection device 100 will now be described. Odor detection device 100 can be manufactured by face-down surface mounting. Fig. 6 is a schematic diagram showing a mounting structure of odor detection device 100 in which the odor detection device 100 is surface-mounted face-down, and Figs. 7 and 8 are cross-sectional views thereof.

[0062] As shown in Fig. 6(a), the odor detection device 100 is composed of a main board 161, a first multi-chip 191, a second multi-chip 192, a second oscillator circuit 114, a fourth oscillator circuit 162, a multiplexer 163, an FPGA 164, and a BLE module 165. Fig. 6(b) is an enlarged view of the first multi-chip 191. As shown in the figure, the first detection element 111 and the second detection element 113 are mounted on the first multi-chip 191. Fig. 6(c) is an enlarged view of the second multi-chip 192. As shown in the figure, the second multi-chip 192 is mounted with a third detection element 115.

[0063] The main board 161 is a board on which each component is mounted. Two first grooves 161a and two second grooves 161b are provided on one surface of the main board 161. The first grooves 161a are supplied with outside air by a pump (not shown) and function as a flow path. On the other hand, the second grooves 161b are filled with a filler 166 (see FIG. 8) and sealed. The filler 166 is an inert gas such as nitrogen.

[0064] 7, the first detection element 111 is mounted on the main board 161 by flip-chip mounting, and is connected to an electrode 168 of the main board 161 by a joint 167. The joint 167 is a solder bump, a gold bump, an anisotropic conductive film, or the like. The first detection element 111 is disposed so that the first sensitive film 132 faces the first groove 161a.

[0065] The second detection element 113 is mounted on the main substrate 161 by flip-chip mounting, and is connected to an electrode of the main substrate 161 by a joint such as a solder bump, a gold bump, or an anisotropic conductive film. The second detection element 111 is disposed such that the resonance region R (see FIG. 3) faces the first groove 161a.

[0066] 8, the third detection element 115 is mounted on the main board 161 by flip-chip mounting, and is connected to an electrode 168 of the main board 161 by a joint 167. The joint 171 is a solder bump, a gold bump, an anisotropic conductive film, or the like. The third detection element 115 is disposed so that the second sensitive film 135 faces the second groove 161b.

[0067] With this arrangement, the first detection element 111 has outside air supplied to the sensitive film 132 via the first groove 161a, and the second detection element 113 has outside air supplied to the resonance region R via the first groove 161a. On the other hand, the third detection element 115 has the second groove 161b sealed by the filler 166, so that the outside air does not reach the third vibrator 134 and the second sensitive film 135. That is, the filler 166 functions as the sealer 136 (see FIG. 4).

[0068] The first oscillation circuit 112 and the third oscillation circuit 116 are mounted on the main board 161 by flip-chip mounting as a single fourth oscillation circuit 162 that combines these functions. The fourth oscillation circuit 162 drives the first detection element 111 and the third detection element 115 that sandwich the fourth oscillation circuit 162, thereby making it possible to equalize the voltage conditions supplied to the first detection element 111 and the third detection element 115. The second oscillation circuit 114 is also mounted on the main board 161 by flip-chip mounting.

[0069] The multiplexer 163 is mounted on the main board 161 and functions as the connection unit 117 (see FIG. 1). The FPGA 164 is mounted on the main board 151 and functions as the calculation unit 118 (see FIG. 1). The BLE module 165 is mounted on the main board 151 and functions as the communication unit 119 (see FIG. 1). The multiplexer 163, the FPGA 164, and the BLE module 165 may be mounted on the surface of the main board 161 opposite to the surface on which the first detection element 111 and the like are mounted, and may be connected to each oscillation circuit and the like via wiring within the main board 161.

[0070] The odor detection device 100 can be realized by the above-mentioned mounting structure. In this configuration, the first groove 161a can be entirely covered by the first multi-chip 191, and the second groove 161b can be entirely covered by the second multi-chip 191. Since the first detection element 111 and the third detection element 115 can be mounted on one first multi-chip 191, it is possible to improve the accuracy of the differential operation.

[0071] [Detection element] In the above description, the first detection element 111, the second detection element 113, and the third detection element 115 are each provided with an oscillator that is an FBAR, but the oscillator is not limited to an FBAR and may be another type of acoustic wave resonator. Specifically, the first detection element 111, the second detection element 113, and the third detection element 115 may each be provided with an oscillator that is a SAW (Surface acoustic wave) resonator.

[0072] 9 is a plan view of a first detection element 111 including a vibrator that is a SAW resonator. As shown in the figure, the first detection element 111 includes a first vibrator 131 and a first sensitive film 132. The first vibrator 131 is a SAW resonator.

[0073] Specifically, the first oscillator 131 includes a piezoelectric substrate 181, a first electrode 182, a second electrode 183, and a reflector 184. The piezoelectric substrate 181 is a substrate made of a piezoelectric material such as LiTaO3 or LiNbO3. The first electrode 182 and the second electrode 183 are comb-shaped electrodes (IDT; Interdigital Transducers) provided on the piezoelectric substrate 181, and are made of any conductive material patterned into a comb shape. The reflector 184 is provided in pair on the piezoelectric substrate 181 so as to sandwich the first electrode 182 and the second electrode 183, and is made of any conductive material patterned into a lattice shape.

[0074] The first oscillator 131 has a resonance region R between a pair of reflectors 184. The resonance region R is a region where surface acoustic waves are generated on the surface of the piezoelectric substrate 181 when an AC voltage of a resonance frequency is input between the first electrode 182 and the second electrode 183. When the surface acoustic waves are incident on the reflector 184, they are reflected by the reflector 184 toward the resonance region R. The resonance frequency of the resonance region R is not particularly limited, and is, for example, 700 MHz. The first sensitive film 132 is provided on the resonance region R of the first oscillator 131, and adsorbs a predetermined odor component.

[0075] 10 is a plan view of the second detection element 113 including a vibrator that is a SAW resonator. As shown in the figure, the second detection element 113 includes a second vibrator 133 that is a SAW resonator. The second vibrator 133 preferably has the same characteristics as the first vibrator 131, that is, the second detection element 113 has the same characteristics as the first detection element 111 that does not have the first sensitive film 132. Specifically, the second detection element 113 includes a piezoelectric substrate 181, a first electrode 182, a second electrode 183, and a reflector 184, similar to the first vibrator 131, and has a resonance region R.

[0076] 11 is a plan view of a third detection element 115 including a vibrator that is a SAW resonator. As shown in the figure, the third detection element 115 includes a third vibrator 134 that is a SAW resonator and a second sensitive film 135. The third vibrator 134 preferably has characteristics similar to those of the first vibrator 131. Specifically, the third detection element 115 includes a piezoelectric substrate 181, a first electrode 182, a second electrode 183, and a reflector 184, similar to the first vibrator 131, and has a resonance region R.

[0077] The second sensitive film 135 is provided on the resonance region R of the third oscillator 134, and adsorbs a predetermined odor component. The third detection element 115 is sealed by a sealant 136 as shown in FIG. 11, and the third oscillator 134 and the second sensitive film 135 are shielded from the outside air by the sealant 136.

[0078] When the vibrator is a SAW resonator, the odor detection device 100 operates in the same manner. That is, as shown in the above (Equation 3), the calculation unit 118 can obtain the resonant frequency fluctuation ΔFn(gas) due to the odor component by subtracting the resonant frequency fluctuation ΔFref1 output from the second detection element 113 and the resonant frequency fluctuation ΔFref2n output from the third detection element 115 from the resonant frequency fluctuation ΔFn(total) output from the first detection element 111.

[0079] In odor detection elements using a SAW resonator as an oscillator, the main cause of the effect of humidity is the hygroscopicity of the SAW resonator itself, and the effect of moisture absorption of the sensitive film is small. In particular, SAW resonators are generally made of multi-layered thin films, and the SiO X is formed by sputtering deposition, and is therefore highly hygroscopic. Therefore, the amount of change in the resonant frequency of the second detection element 113 can be regarded as being due to humidity. For this reason, if the amount of change in the resonant frequency of the second detection element 113 is ΔFref1, the amount of change in the resonant frequency ΔFn(hum.) due to humidity can be regarded as the amount of change in the resonant frequency ΔFref1.

[0080] Furthermore, even in an odor detection element using a vibrator that is a SAW resonator, the main cause of the effect of temperature is the change in the elastic constant of each material that constitutes the vibrator and the sensitive film. Therefore, the resonant frequency variation of the third detection element 115, which has the same characteristics as the first detection element 111 and is shielded by the sealing body 136, can be considered to be due to temperature. Therefore, if the resonant frequency variation of the nch third detection element 115 is ΔFref2n, the resonant frequency variation ΔFn(tem.) due to temperature can be considered to be the resonant frequency variation ΔFref2n.

[0081] Therefore, even when the transducer is a SAW resonator, the calculation unit 118 can obtain the amount of resonance frequency fluctuation ΔFn(gas) due to odor components using the above (Equation 3).

[0082] The first detection element 111, the second detection element 113, and the third detection element 115 may each include an oscillator such as a QCM (Quartz Crystal Microbalance) in addition to the FBAR and the SAW resonator.

[0083] [Variations] A modification of the odor detection device 100 will now be described.

[0084] (Variation 1) Fig. 12 is a block diagram showing the configuration of an odor detection device 100 according to Modification 1. As described above, the odor detection device 100 includes one second detection element 113 (see Fig. 1), but as shown in Fig. 12, the odor detection device 100 may include a second detection element 113 of nch corresponding to the first detection element 111 of nch. Specifically, when the structure of the first oscillator 131 differs between the first detection elements 111 of nch, the odor detection device 100 includes the second detection element 113 of nch having a second oscillator 133 having the same structure as the respective first oscillators 131.

[0085] In this case, if the amount of change in the resonant frequency of the nch second detection element 113 is denoted by ΔFref1n, then The amount of resonant frequency variation ΔFn(hum.) due to humidity in the above (Equation 1) can be regarded as the amount of resonant frequency variation ΔFref1n.

[0086] Therefore, the above (Equation 1) can be transformed into the following (Equation 4).

[0087] ΔFn(total)=ΔFn(gas)+ΔFref1n+ΔFref2n (Equation 4)

[0088] Furthermore, the above (Equation 4) can be transformed into the following (Equation 5).

[0089] ΔFn(gas)=ΔFn(total)-ΔFref1n-ΔFref2n (Equation 5)

[0090] From the above, even when the odor detection device 100 has a second detection element 113 of nch, the calculation unit 118 can calculate the resonant frequency fluctuation ΔFn(gas) due to odor components by subtracting the resonant frequency fluctuation ΔFref1n output from the second detection element 113 and the resonant frequency fluctuation ΔFref2n output from the third detection element 115 from the resonant frequency fluctuation ΔFn(total) output from the first detection element 111.

[0091] (Variation 2) Fig. 13 is a block diagram showing the configuration of odor detection device 100 according to Modification 1. As described above, odor detection device 100 includes first detection element 111, second detection element 113, and third detection element 115, but it is also possible to include only first detection element 111 and second detection element 113 without including third detection element 115, as shown in Fig. 13.

[0092] In this case, the calculation unit 118 can obtain the resonant frequency fluctuation ΔFn(gas) due to the odor component with the influence of humidity corrected by subtracting the resonant frequency fluctuation ΔFref1 output from the second detection element 113 from the resonant frequency fluctuation ΔFn(total) output from the first detection element 111. In cases such as when the sensitive film of the odor detection device 100 is not easily affected by temperature, the second detection element 113 may be used to correct only the influence of humidity in this manner. Furthermore, this odor detection device 100 may be equipped with a second detection element 113 of nch as shown in Modification 1 (see FIG. 12). EXAMPLES

[0093] Example 1 An odor detection device according to the above embodiment was created and measurements were performed. The odor detection device had a first oscillator that was an FBAR and a first detection element having a sensitive film, and a second oscillator that was an FBAR and had no sensitive film. The first and second oscillators had the same characteristics and were oscillators with a resonance frequency of 2.4 GHz. The sensitive film of the first detection element was a hydrophobic sensitive film (thickness 250 nm). The first detection element and the second detection element were connected to a Pierce type oscillation circuit, and the oscillation frequency was measured by a frequency counter.

[0094] FIG. 14 is a graph showing the measurement results. The odor detection device was housed in a chamber, and gas G1 and gas G2 were alternately flowed into the chamber every 20 minutes. Gas G1 is a gas containing 10 ppm toluene, and gas G2 is a gas containing 0 ppm toluene. In FIG. 14, the frequency fluctuation of the first detection element is shown as "ΔF(total)", the frequency fluctuation of the second detection element is shown as "ΔFref1", the difference between the frequency fluctuations of the first detection element and the second detection element (ΔF(total)-ΔFref1) is shown as "difference", and the humidity (RH) in the chamber is shown as "humidity". The humidity in the chamber was measured using a capacitance-type humidity sensor.

[0095] As shown in Figure 14, the frequency fluctuation ΔF(total) increases while gas G1 is being supplied. Normally, the frequency fluctuation should decrease due to the adsorption of toluene to the sensitive film, but the humidity decreases from 7% to 5%, and the resonant frequency increases. It is believed that the decrease in humidity reduces the amount of moisture adhering to the sensitive film, causing the resonant frequency to increase. On the other hand, the "difference" (ΔF(total)-ΔFref1) decreases while gas G1 is being supplied, which shows that the effect of humidity is excluded and the frequency fluctuation due to the adsorption of toluene to the sensitive film is detected.

[0096] Example 2 An odor detection device according to the above embodiment was created and measurements were performed. The odor detection device had a first oscillator, which was a SAW resonator, and a first detection element having a sensitive film, and a second oscillator, which was a SAW resonator, and a second detection element without a sensitive film. The first and second oscillators had the same characteristics and were oscillators with a resonant frequency of 700 MHz. The sensitive film of the first detection element was a hydrophobic sensitive film (thickness 250 nm). The first detection element and the second detection element were connected to a Pierce-type oscillation circuit, and the oscillation frequency was measured with a frequency counter.

[0097] FIG. 15 is a graph showing the measurement results, and FIG. 16 is a graph showing an enlarged portion of FIG. 15. The odor detection device was housed in a chamber, and gas G3 and gas G4 were alternately flowed into the chamber every 20 minutes. Gas G3 is a gas containing 10 ppm acetone, and gas G4 is a gas containing 0 ppm acetone. In FIG. 15 and FIG. 16, the frequency fluctuation of the first detection element is shown as "ΔF(total)", the frequency fluctuation of the second detection element is shown as "ΔFref1", the difference between the frequency fluctuations of the first detection element and the second detection element (ΔF(total)-ΔFref1) is shown as "difference", and the humidity (RH) in the chamber is shown as "humidity". The humidity in the chamber was measured using a capacitance-type humidity sensor.

[0098] As shown in Figures 15 and 16, the frequency fluctuation ΔF(total) decreases slightly while gas G3 is being supplied. This is thought to be due to the sum of the decrease in the resonant frequency due to the adsorption of acetone to the sensitive film and the increase in the resonant frequency due to the decrease in the amount of moisture adhering to the sensitive film caused by the decrease in humidity (6% to 5.5%). On the other hand, the "difference" (ΔF(total)-ΔFref1) decreases significantly while gas G3 is being supplied, which shows that the effect of humidity is excluded and the frequency fluctuation due to the adsorption of acetone to the sensitive film is detected.

[0099] Example 3 An odor detection device according to the above embodiment was created and measurements were performed. The odor detection device was equipped with a first detection element having a first oscillator and a sensitive film, which is an FBAR, and a third detection element in which a detection element having the same characteristics as the first detection element is sealed with a sealant. The first detection element and the third detection element were connected to a Pierce-type oscillation circuit, and the oscillation frequency was measured with a frequency counter.

[0100] Fig. 17 is a graph showing the measurement results. The odor detection device was placed in a chamber, and gas G5 and gas G6 were alternately flowed into the chamber. Gas G5 was a gas containing 10 ppm ethanol, and gas G6 was a gas containing 0 ppm ethanol. In Fig. 17, the frequency variation of the first detection element is shown as "ΔF(total)", and the frequency variation of the third detection element is shown as "ΔFref2".

[0101] Figure 18 is a graph showing the difference (ΔF(total)-ΔFref2) in the frequency variation between the first and third detection elements. As shown in the figure, the effect of temperature is eliminated, and the frequency variation due to the adsorption of ethanol to the sensitive film is detected. [Explanation of symbols]

[0102] 100...Odor detection device 111...First detection element 112…First oscillator circuit 113...Second detection element 114…Second oscillator circuit 115...Third detection element 116…Third oscillator circuit 117…Connection 118...Arithmetic section 119…Communications Department 131…First transducer 132…First sensitive membrane 133…Second transducer 134…Third transducer 135…Second sensitive membrane 136...Sealing body

Claims

1. A first detection element including a first vibrator that is an acoustic wave resonator and a first sensitive film formed on the first vibrator; A second detection element including a second oscillator that is an acoustic wave resonator; a third detection element including a third vibrator that is an elastic wave resonator and a second sensitive film formed on the third vibrator, the third vibrator and the second sensitive film being shielded from the outside air; a calculation unit that corrects an amount of variation in the resonance frequency of the first oscillator by subtracting an amount of variation in the resonance frequency of the second oscillator output from the second detection element and an amount of variation in the resonance frequency of the third oscillator output from the third detection element from an amount of variation in the resonance frequency of the first oscillator output from the first detection element; Equipped with The second oscillator and the third oscillator have the same characteristics as the first oscillator in terms of resonance frequency. Odor detection device.

2. The odor detection device according to claim 1, The second sensitive film is made of the same material as the first sensitive film and has the same thickness as the first sensitive film. Odor detection device.

3. The odor detection device according to claim 1 or 2, The elastic wave resonator is a film bulk acoustic resonator (FBAR). Odor detection device.

4. The odor detection device according to any one of claims 1 to 3, The elastic wave resonator is a SAW (Surface Acoustic Wave) resonator. Odor detection device.

5. An odor detection device according to any one of claims 1 to 4, A sealant that seals the third detection element is provided. Odor detection device.

6. correcting the amount of variation in the resonance frequency of the first oscillator by subtracting, from the amount of variation in the resonance frequency of the first oscillator outputted from a first detection element having a first oscillator which is an elastic wave resonator and a first sensitive film formed on the first oscillator, the amount of variation in the resonance frequency of the second oscillator outputted from a second detection element having a second oscillator which is an elastic wave resonator and the amount of variation in the resonance frequency of the third oscillator outputted from a third detection element which has a third oscillator which is an elastic wave resonator and a second sensitive film formed on the third oscillator, the third oscillator and the second sensitive film being shielded from the outside air; The second oscillator and the third oscillator have the same characteristics as the first oscillator in terms of resonance frequency. Odor detection methods.

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