Gas Sensor

Abstract

To provide a gas sensor capable of suppressing variation in characteristics of a sensor element due to substrate deformation.SOLUTION: A gas sensor 1 provided herein comprises a substrate 80, a sensor element 10 fixed onto at least one principal surface of the substrate 80, and a pad 100 fixed onto the other principal surface of the substrate 80 and configured to be connectable to an external substrate. At least a portion of the pad 100 overlaps with the sensor element 10 along a direction perpendicular to an installation surface of the pad 100.SELECTED DRAWING: Figure 5A

Description

[Technical Field]

[0001] The present invention relates to a gas sensor. [Background technology]

[0002] A gas sensor is a device for detecting, for example, gas leakage, and is mounted in home appliances, industrial equipment, environmental monitoring equipment, etc. For example, as described in Patent Document 1, a gas sensor has a sensor element and a substrate on which the sensor element is mounted.

[0003] The sensor element has a sensor sensitive body whose physical properties change in response to the gas concentration in the atmosphere, etc., and electrodes for extracting the change in physical properties as an electrical signal. The substrate is made up of a printed circuit board or the like, and is fixed to the module substrate of various electronic devices while holding the sensor element and the control element that controls it.

[0004] However, in this type of gas sensor, the substrate may warp due to the influence of temperature and humidity. In the gas sensor described in Patent Document 1, the inventors have found that the influence of the warp of the substrate causes the distance between the electrodes to fluctuate, which in turn causes the characteristics of the sensor element to fluctuate. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2019-120698 Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a gas sensor that can suppress fluctuations in the characteristics of the sensor element caused by deformation of the substrate. [Means for solving the problem]

[0007] In order to achieve the above object, the gas sensor according to the present invention comprises: A substrate; a sensor element fixed to one main surface of the substrate; a pad fixed to the other main surface of the substrate and connectable to an external substrate; At least a portion of the pad overlaps with the sensor element along a direction perpendicular to the mounting surface of the pad.

[0008] In the gas sensor according to the present invention, at least a portion of the pad overlaps with the sensor element along a direction perpendicular to the mounting surface of the pad. Therefore, at least in the overlapping area near the sensor element, the pad functions as a reinforcing material, suppressing deformation (warping) of the substrate and reducing interference between the substrate and the sensor element. This prevents deformation of the sensor element (such as distortion of the sensor sensitive portion) and suppresses fluctuations in the characteristics of the sensor element.

[0009] Preferably, at least a portion of the pad overlaps the corner of the sensor element along a direction perpendicular to the mounting surface of the pad, in which case warping of the substrate is suppressed in the vicinity of the corner of the sensor element, which is (generally) prone to warping, and interference between the substrate and the sensor element can be effectively prevented.

[0010] The pad may be configured by a plurality of the pads, which increases the degree of freedom in design and allows the gas sensor to be mounted on an external substrate via the plurality of pads using various layout patterns.

[0011] Preferably, the pads are arranged at positions corresponding to the corners of the sensor element, respectively, in which case warping of the substrate is suppressed at the positions corresponding to the corners of the sensor element, and interference between the substrate and the sensor element can be more effectively prevented.

[0012] The pads may be disposed at positions corresponding to non-corner portions of the sensor element, excluding the corner portions, in which case warping of the substrate is suppressed at various positions corresponding to the non-corner portions of the sensor element, and interference between the substrate and the sensor element can be effectively prevented.

[0013] The non-corner portion may be located in the center of the sensor element. In this case, warping of the substrate is suppressed at the position corresponding to the center of the sensor element. Therefore, deformation of the sensor element (distortion of the sensor sensitive portion, etc.) can be effectively prevented at the center of the sensor element.

[0014] The non-corner portion may be located at the outer edge of the sensor element. In this case, warping of the substrate is suppressed at the position corresponding to the outer edge of the sensor element. Therefore, deformation of the sensor element (distortion of the sensor sensitive portion, etc.) can be effectively prevented at the outer edge of the sensor element.

[0015] Preferably, the pad (the pad arranged at a position corresponding to the center or outer edge of the sensor element) consists of a plurality of the pads. This configuration improves design freedom and enables the gas sensor to be mounted on an external substrate via the plurality of pads using various layout patterns.

[0016] Preferably, the pad comprises a plurality of pads, one of which is disposed at a position corresponding to a corner of the sensor element, and the remaining pads are disposed at a position corresponding to a non-corner portion of the sensor element excluding the corner. In this case, warping of the substrate is suppressed near each of the corners and non-corner portions of the sensor element. Therefore, the amount of warping of the substrate is significantly reduced, and interference between the substrate and the sensor element can be more effectively prevented. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a schematic perspective view of a gas sensor according to a first embodiment of the present invention. [Figure 2]FIG. 2 is a plan view of the sensor element shown in FIG. [Figure 3] FIG. 3 is an exploded perspective view of the sensor element shown in FIG. [Figure 4] 4 is a cross-sectional view of the sensor element shown in FIG. 2 taken along line IV-IV. [Figure 5A] FIG. 5A is a perspective view showing pads in the gas sensor shown in FIG. [Figure 5B] FIG. 5B is a perspective view showing the pad shown in FIG. 5A as viewed from the bottom side of the substrate. [Figure 5C] FIG. 5C is a perspective view showing a state in which warpage occurs in the substrate shown in FIG. 5A. [Figure 6] FIG. 6 is a diagram showing the effect of the gas sensor shown in FIG. 5A. [Figure 7A] FIG. 7A is a schematic perspective view of a gas sensor according to a second embodiment of the present invention. [Figure 7B] FIG. 7B is a perspective view showing the pad shown in FIG. 7A as viewed from the bottom side of the substrate. [Figure 8] FIG. 8 is a schematic bottom view showing the configuration of a pad of a gas sensor according to a third embodiment of the present invention. [Figure 9] FIG. 9 is a schematic bottom view showing the configuration of a pad of a gas sensor according to a fourth embodiment of the present invention. [Figure 10] FIG. 10 is a schematic bottom view showing the configuration of a pad of a gas sensor according to a fifth embodiment of the present invention. [Figure 11] FIG. 11 is a schematic bottom view showing the configuration of a pad of a gas sensor according to a sixth embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, the present invention will be described based on the embodiments shown in the drawings.

[0019] As shown in Fig. 1, a gas sensor 1 according to a first embodiment of the present invention is a device for detecting gas leakage, and is mounted on, for example, a home appliance, an industrial device, or an environmental monitoring device. The gas sensor 1 includes a sensor element 10, a substrate 80, and a pad 100 (Fig. 5A). In the drawing, the X-axis and the Y-axis correspond to the perpendicular sides of the substrate 80, and the Z-axis is an axis perpendicular to the X-axis and the Y-axis.

[0020] The sensor element 10 is a thermal conduction sensor element that detects gases such as CO2, H2, He, or CO. As shown in Fig. 3, the sensor element 10 has a substantially rectangular parallelepiped shape and includes a base 20, insulating films 30a-30c, a heat source 40, electrodes 50a and 50b, a sensitive film 60, and pad electrodes 70a-70d. The sensor element 10 has an air bridge structure in which the sensitive film 60 and other components are fixed in a double-supported beam shape.

[0021] The base 20 is made of a hollow columnar body and has a roughly ring shape. The shape of the base 20 when viewed from the Z-axis direction is square. However, the shape of the base 20 in a plan view is not limited to this and may be rectangular or another polygon. Furthermore, the height of the base 20 is not limited to the height shown in FIG. 3.

[0022] The base 20 preferably has a mechanical strength sufficient to support the insulating films 30a to 30c, etc. The base 20 is also preferably made of a material suitable for microfabrication such as etching. Examples of materials that can be used to form the base 20 include a silicon single crystal substrate, a sapphire single crystal substrate, a ceramic substrate, a quartz substrate, and a glass substrate.

[0023] The insulating films 30a-30c are made of insulating material and have the same shape. The insulating films 30a-30c are made of films and are fabricated by known film formation methods (such as sputtering or CVD). The insulating layers 30a, 30b, and 30c are stacked in this order on the upper surface of the base 20 (see FIG. 4). The insulating films 30a-30c each have a main body 31, beams 32-35, a peripheral edge 36, and a hole 37.

[0024] The main body 31 has a substantially rectangular shape when viewed from the Z-axis direction. The main body 31 is disposed above the hollow portion (through-hole) of the base 20, and is positioned inside the inner periphery of the base 20. The shape of the main body 31 is not limited to the shape shown in FIG. 3 , and may be rectangular, another polygonal shape, circular, elliptical, or the like. The peripheral edge 36 has a substantially ring shape corresponding to the shape of the base 20, and is fixed to the upper surface of the base 20. The peripheral edge 36 is disposed to surround the outer periphery of the main body 31, with a predetermined gap between it and the main body 31.

[0025] The beams 32 to 35 are located between the main body 31 and the peripheral edge 36, and connect four corners of the main body 31 to four corners of the peripheral edge 36, respectively. The beams 32 to 35 support the main body 31 above the hollow portion (through hole) of the base 20. Four holes 37 separated by the beams 32 to 35 are formed between the main body 31 and the peripheral edge 36. The number of beams is not limited to four.

[0026] The thickness of each of the insulating films 30a to 30c is not particularly limited, but is, for example, 0.05 to 1.5 μm. Examples of materials that can form the insulating films 30a to 30c include silicon oxide and silicon nitride. The insulating films 30a to 30c are preferably formed from the same material. This is because this improves adhesion at the interfaces between the insulating films 30a to 30c and ensures the mechanical strength of the insulating films 30a to 30c. However, the insulating films 30a to 30c may be formed from different materials.

[0027] The heat source 40 is disposed between the insulating films 30a and 30b (see FIG. 4). The heat source 40 heats the sensitive film 60 to a predetermined temperature (operating temperature) when detecting a target gas. The heat source 40 is made of a film and is fabricated by a known film formation method. The heat source 40 has a heat source body 41 and lead-out portions 42 and 43.

[0028] As shown in Fig. 2, the heat source body 41 has a meander pattern and is disposed on the upper surface of the main body 31 of the insulating film 30a. By forming the heat source body 41 in a meander pattern, the sensitive film 60 can be heated uniformly. Furthermore, since the sensor element 10 has an air bridge structure, the power consumption of the heat source 40 can be reduced when heating the sensitive film 60. The shape of the heat source 40 is given by, for example, etching (patterning). The same applies to the insulating films 30a to 30c, etc.

[0029] The lead-out portion 42 is connected to one end of the heat source body 41 and extends to the position of the peripheral edge portion 36 on the insulating film 30a (FIG. 3) via the beam portion 35. The lead-out portion 43 is connected to the other end of the heat source body 41 and extends to the position of the peripheral edge portion 36 on the insulating film 30a via the beam portion 33.

[0030] The heat source 40 is preferably made of a conductive material with a relatively high melting point. Examples of materials that can be used to make the heat source 40 include molybdenum, platinum, gold, tungsten, tantalum, palladium, iridium, or alloys containing one or more of the above elements. Platinum is particularly preferred because it allows for high-precision dry etching (such as ion milling) and has high corrosion resistance. When the heat source 40 is made of platinum, it is preferable to form an adhesive layer made of titanium or the like between the insulating film 30a and the heat source 40.

[0031] 3, the electrodes 50a and 50b each have a curved shape and are disposed on the insulating film 30b. The electrodes 50a and 50b are used to extract changes in the physical properties (resistance value) of the sensor sensitive body 60 as electrical signals. The electrodes 50a and 50b are made of films and are fabricated by a known film formation method.

[0032] 2, the electrodes 50a and 50b are disposed opposite each other on the main body 31. A portion of the electrode 50a extends to the position of the peripheral edge 36 via the beam 32. A portion of the electrode 50b extends to the position of the peripheral edge 36 via the beam 34.

[0033] The electrodes 50a and 50b are preferably made of a conductive material with a relatively high melting point, such as molybdenum, platinum, gold, tungsten, tantalum, palladium, iridium, or an alloy containing one or more of the above elements.

[0034] As shown in Fig. 3, the sensitive film 60 has the property of changing its heat dissipation characteristics in response to the gas concentration in the atmosphere, and also changing its resistance value in response to the change in heat dissipation characteristics. The sensitive film 60 is made of a thermistor film, a platinum film, or the like, and is fabricated by a known film formation method. Examples of materials that can be used to form the thermistor film include composite metal oxides, amorphous silicon, polysilicon, and germanium.

[0035] The sensitive film 60 has a main body portion 61 and beam portions 62 to 65. The main body portion 61 of the sensitive film 60 has a shape corresponding to (preferably the same shape as) the main body portion 31 of the insulating films 30a to 30c. The beam portions 62 to 65 of the sensitive film 60 have a shape corresponding to (preferably the same shape as) the beam portions 32 to 35 of the insulating films 30a to 30c. Therefore, in the Z-axis direction, the main body portion 61 is disposed at a position corresponding to the main body portion 31, and the beam portions 62 to 65 are disposed at positions corresponding to the beam portions 32 to 35.

[0036] The main body 61 is disposed so as to be in contact with the electrodes 50a and 50b and is electrically connected to the electrodes 50a and 50b. The sensitive film 60 and the electrodes 50a and 50b are integrally disposed between the insulating film 30b and the insulating film 30c (see FIG. 4).

[0037] The electrode pads 70a to 70d are fixed to the four corners of the peripheral edge 36 of the insulating film 30c, respectively. The electrode pads 70a to 70d are formed by, for example, plating, lift-off, metal paste printing, or other methods. The electrode pad 70a is electrically connected to an end of the electrode 50a via a through-hole (not shown). The electrode pad 70b is electrically connected to an end of the lead-out portion 43 of the heat source 40 via a through-hole (not shown). The electrode pad 70c is electrically connected to an end of the electrode 50b via a through-hole (not shown). The electrode pad 70d is electrically connected to an end of the lead-out portion 42 of the heat source 40 via a through-hole (not shown).

[0038] The electrode pads 70a to 70d are electrically connected to an external circuit (not shown), for example, by wire bonding. For example, the external circuit supplies power to the heat source 40 via the electrode pads 70b and 70d. The external circuit also acquires a change in the resistance value of the sensitive film 60 as an electrical signal via the electrode pads 70a and 70c.

[0039] 1, the substrate 80 is formed of a printed circuit board or the like, and is fixed to a module substrate (not shown) of various electronic devices. The substrate 80 is formed of a plate body having a substantially flat plate shape, but may also be, for example, a package substrate for incorporating the sensor element 10. As shown in FIG. 4, the bottom surface of the base 20 is connected (fixed) to the top surface of the substrate 80 via an adhesive layer 90.

[0040] 5A, the substrate 80 has four side portions 80s1 to 80s4 and four corner portions 80c1 to 80c4. The angle formed by each of the corner portions 80c1 to 80c4 is approximately 90 degrees, but is not limited to this.

[0041] The sensor element 10 also has four side portions 10s1 to 10s4 and four corner portions 10c1 to 10c4. The angle formed by each of the corner portions 10c1 to 10c4 is approximately 90 degrees, but is not limited to this. The corner portion 10c1 refers to the intersection 10x (FIG. 5A) between the side portion 10s1 and the side portion 10s3 and its vicinity. For example, the corner portion 10c1 refers to a range of preferably 30%, more preferably 20%, of the longer length of either the side portion 10s1 or 10s3, centered on the intersection 10x. The corner portions 10c2 to 10c4 are defined in the same manner.

[0042] The sensor element 10 is disposed on the substrate 80 so that the position of its center (center of gravity) substantially coincides with the center (center of gravity) of the substrate 80. Side portions 10s1 to 10s4 of the sensor element 10 are disposed substantially parallel to the side portions 80s1 to 80s4 of the substrate 80, respectively. However, the fixed position of the sensor element 10 relative to the substrate 80 or the orientation of the sensor element 10 relative to the substrate 80 is not limited to the example shown in FIG. 5A.

[0043] As shown in FIG. 5B, the pad 100 is provided on the substrate 80. The pad 100 is fixed to the side of the substrate 80 opposite to the sensor element 10, i.e., to the bottom surface 80b of the substrate 80. The pad 100 is configured to be connectable to a module substrate (not shown), and is electrically connected to a land pattern of the module substrate (not shown), for example, by solder. The module substrate is provided in various electronic devices such as mobile phones, air conditioners, environmental monitoring devices, etc.

[0044] The pad 100 is made of a conductive material and is formed by, for example, plating or metal paste printing. The thickness of the pad 100 is, for example, 1 to 100 μm. Examples of materials that can be used to form the pad 100 include metals such as gold, aluminum, and copper.

[0045] The shape of the pad 100 as viewed from the Z-axis direction (shape in plan view) is substantially the same as the shape of the sensor element 10 as viewed from the Z-axis direction (particularly the shape of the bottom surface 10b of the sensor element 10), and is rectangular (oblong). The shape of the pad 100 as viewed from the Z-axis direction may be changed as appropriate depending on the shape of the sensor element 10 as viewed from the Z-axis direction, and may be a square or other polygon, a circle, an ellipse, or the like.

[0046] Along the Z-axis direction (as viewed from the Z-axis direction), the side portions 100s1 to 100s4 of the pad 100 are disposed at positions corresponding to the side portions 10s1 to 10s4 of the sensor element 10, respectively. That is, with respect to the Z-axis direction, the position of the outer periphery of the pad 100 corresponds to the position of the outer periphery of the sensor element 10. The outer periphery of the sensor element 10 is defined by the side portions 10s1 to 10s4.

[0047] At least one of the side portions 100s1 to 100s4 of the pad 100 may be disposed outside the outer periphery of the sensor element 10 (in a direction away from the center of the sensor element 10). Alternatively, at least one of the side portions 100s1 to 100s4 of the pad 100 may be disposed inside the outer periphery of the sensor element 10 (in a direction toward the center of the sensor element 10).

[0048] The area of ​​the pad 100 is approximately the same as the area of ​​the bottom surface 10b of the sensor element 10. However, the area of ​​the pad 100 may be larger than the area of ​​the bottom surface 10b of the sensor element 10. In this case, each of the side portions 100s1 to 100s4 of the pad 100 may be disposed outside the outer periphery of the sensor element 10. Alternatively, the area of ​​the pad 100 may be smaller than the area of ​​the bottom surface 10b of the sensor element 10. In this case, each of the side portions 100s1 to 100s4 of the pad 100 may be disposed inside the outer periphery of the sensor element 10.

[0049] The position of the center (center of gravity) of the pad 100 may be approximately coincident with the center (center of gravity) of the substrate 80. In this embodiment, the pad 100 and the sensor element 10 overlap along the Z-axis direction, which is a direction perpendicular to the installation surface (bottom surface 80b) of the pad 100 (when viewed from the Z-axis direction, which is a direction perpendicular to the installation surface of the pad 100, or in a plan view). More specifically, when viewed from the Z-axis direction (in a plan view), the entire area of ​​the pad 100 overlaps with the bottom surface 10b of the sensor element 10. Note that when viewed from the Z-axis direction, only a portion of the pad 100 may overlap with the bottom surface 10b of the sensor element 10.

[0050] 5B, the corners 100c1 to 100c4 of the pad 100 overlap with the corners 10c1 to 10c4 of the sensor element 10 along the Z-axis direction. In the example shown in FIG. 5B, the corners 100c1 to 100c4 of the pad 100 overlap with the corners 10c1 to 10c4 of the sensor element 10 along the Z-axis direction, respectively. Note that any one (any two, or any three) of the corners 100c1 to 100c4 of the pad 100 may overlap with only one (any two, or any three) of the corners 10c1 to 10c4 of the sensor element 10.

[0051] In this embodiment, the overlapping area between the pad 100 and the bottom surface 10b of the sensor element 10 (the area of ​​the portion of the bottom surface 10b of the sensor element 10 that overlaps with the pad 100 along the Z-axis direction) is preferably 70% or more of the area of ​​the bottom surface 10b, more preferably 80% or more of the area of ​​the bottom surface 10b, even more preferably 90% or more of the area of ​​the bottom surface 10b, and particularly preferably 100% of the area of ​​the bottom surface 10b.

[0052] As described above, in the gas sensor 1 of this embodiment, at least a portion of the pad 100 overlaps with the sensor element 10 along the Z-axis direction. Therefore, this embodiment can provide the following effects.

[0053] 5C, the substrate 80 tends to warp more significantly nearer the corners 80c1 to 80c4 due to the influence of temperature and humidity, so that warped portions 81 may be formed around each of the corners 80c1 to 80c4.

[0054] If no measures are taken, the warped portion 81 around the corners 80c1 to 80c4 may interfere with the sensor element 10 (particularly the corners 10c1 to 10c4), which may cause fluctuations in the characteristics of the sensor element 10. The fluctuations in the characteristics of the sensor element 10 may occur as a result of the interference between the warped portion 81 and the sensor element 10 causing distortion in the sensitive film 60 (FIG. 3), which causes fluctuations in the interelectrode distance between the electrodes 50a and 50b (FIG. 3), which in turn causes the change in the resistance value of the sensitive film 60, which is extracted as an electrical signal, to deviate from its original value.

[0055] On the other hand, in this embodiment, at least a portion of the pad 100 overlaps with the sensor element 10 along the Z-axis direction. Therefore, at least in the vicinity of the sensor element 10, which is the overlapping position, the pad 100 functions as a reinforcing material, thereby suppressing warping of the substrate 80, and a non-warped portion 82 with relatively small warping can be formed over a relatively wide area inside the warped portion 81 (toward the center of the substrate 80).

[0056] Therefore, interference is less likely to occur between the substrate 80 (warped portion 81) and the sensor element 10. This prevents deformation of the sensor element 10 (distortion of the sensitive film 60, etc.), and suppresses fluctuations in the characteristics of the sensor element 10.

[0057] Furthermore, in this embodiment, corners 100c1 to 100c4 of the pad 100 overlap corners 10c1 to 10c4 of the sensor element 10 along the Z-axis direction, respectively. This makes it possible to effectively suppress warping of the substrate 80 in the vicinity of the corners 10c1 to 10c4 of the sensor element 10, which are prone to warping of the substrate 80. This expands the range of the non-warped portion 82 (reducing the range of the warped portion 81) in the vicinity of the corners 10c1 to 10c4, making it possible to effectively prevent interference between the substrate 80 and the sensor element 10.

[0058] As shown in Fig. 6, in the example (Fig. 6: Example) in which the pad 100 is fixed to the bottom surface 80b of the substrate 80 in the manner shown in Fig. 5B, the displacement ΔZ of the sensor element 10 in the Z-axis direction is significantly reduced compared to the comparative example (Fig. 6: Comparative Example) in which the pad 100 is not fixed to the bottom surface 80b of the substrate 80. This indicates that the sensor element 10 can effectively avoid the influence of the warpage (warped portion 81) of the substrate 80. This shows that by overlapping at least a portion of the pad 100 with the sensor element 10 along the Z-axis direction, interference between the substrate 80 and the sensor element 10 can be effectively alleviated.

[0059] The side length L1 (FIG. 1) of the sensor element 10 is preferably 60% or less of the side length L2 (FIG. 1) of the substrate 80, and more preferably 50% or less of the side length L2 of the substrate 80. In this case, due to the miniaturization of the sensor element 10, the sensor element 10 appears to be disposed at a position away from the outer edge of the substrate 80 (toward the center of the substrate 80). Therefore, warping of the substrate 80 is less likely to affect the sensor element 10, and interference between the warped portion 81 (FIG. 5C) of the substrate 80 and the sensor element 10 can be further alleviated.

[0060] Second embodiment 7A has the same configuration as the gas sensor 1 of the first embodiment, except for the following points. In the following, the same reference numerals are used to designate the same components as those of the gas sensor 1 of the first embodiment, and detailed descriptions thereof will be omitted.

[0061] The gas sensor 1A has a plurality of (four in this embodiment) pads 100A_1 to 100A_4 in addition to the sensor element 10 and the substrate 80. The pads 100A_1 to 100A_4 each have the same shape. The pads 100A_1 to 100A_4 have a rectangular shape in a plan view, but may also be a square, other polygonal shapes, a circle, an ellipse, or the like. The pads 100A_1 to 100A_4 may be electrically connected to the electrode pads 70a to 70d via through holes, respectively.

[0062] 7B, the pads 100A_1 to 100A_4 are fixed to the bottom surface 80b of the substrate 80 at intervals in the X-axis direction or the Y-axis direction. The pads 100A_1 to 100A_4 are arranged to correspond to the corners 10c1 to 10c4 of the sensor element 10, respectively.

[0063] That is, along the Z-axis direction, a portion of the pad 100A_1 (one corner of the pad 100A_1) overlaps with a corner 10c1 of the sensor element 10. Also, along the Z-axis direction, a portion of the pad 100A_2 (one corner of the pad 100A_2) overlaps with a corner 10c2 of the sensor element 10. Also, along the Z-axis direction, a portion of the pad 100A_3 (one corner of the pad 100A_3) overlaps with a corner 10c3 of the sensor element 10. Also, along the Z-axis direction, a portion of the pad 100A_4 (one corner of the pad 100A_4) overlaps with a corner 10c4 of the sensor element 10.

[0064] The side portions (side portions extending in the X-axis direction) of the pads 100A_1 and 100A_4 are arranged at positions corresponding to the side portion 10s1 of the sensor element 10. The side portions (side portions extending in the X-axis direction) of the pads 100A_2 and 100A_3 are arranged at positions corresponding to the side portion 10s2 of the sensor element 10. The side portions (side portions extending in the Y-axis direction) of the pads 100A_1 and 100A_2 are arranged at positions corresponding to the side portion 10s3 of the sensor element 10. The side portions (side portions extending in the Y-axis direction) of the pads 100A_3 and 100A_4 are arranged at positions corresponding to the side portion 10s4 of the sensor element 10.

[0065] The pads 100A_1 to 100A_4 are preferably arranged inside the outer periphery of the sensor element 10. However, a part of the pad 100A_1 may protrude outside the outer periphery of the sensor element 10. The same applies to the pads 100A_2 to 100A_4.

[0066] The side length in the X-axis direction of each of the pads 100A_1 to 100A_4 is preferably less than 50% of the side length in the X-axis direction of the sensor element 10. Furthermore, the side length in the Y-axis direction of each of the pads 100A_1 to 100A_4 is preferably less than 50% of the side length in the Y-axis direction of the sensor element 10.

[0067] Four pads, 100A_1 to 100A_4, are fixed to the bottom surface 80b of the substrate 80, but the number of pads may be three or less. For example, two diagonally arranged pads (pad 100A_1 and pad 100A_3, or pad 100A_2 and pad 100A_4) may be arranged on the bottom surface 80b.

[0068] This embodiment can also achieve the same effects as those of Embodiment 1. In addition, in this embodiment, the plurality of pads 100A_1 to 100A_4 are provided on the substrate 80, which improves design freedom and allows the gas sensor 1A to be mounted on a module substrate using various layout patterns.

[0069] Third embodiment A gas sensor 1B according to a third embodiment of the present invention, shown in Fig. 8, has the same configuration as the gas sensor 1A according to the second embodiment, except for the following points. In the following, components that overlap with those of the gas sensor 1A according to the second embodiment are denoted by the same reference numerals, and detailed descriptions thereof will be omitted. Fig. 8 shows the gas sensor 1B as viewed from the bottom side.

[0070] The gas sensor 1B has a plurality of (four in this embodiment) pads 100B_1 to 100B_4 in addition to the sensor element 10 and the substrate 80. The pads 100B_1 to 100B_4 each have the same shape. The planar shape of the pads 100B_1 to 100B_4 is square, but may be rectangular, other polygonal, circular, elliptical, or the like.

[0071] The pads 100B_1 to 100B_4 may be electrically connected to the electrode pads 70a to 70d (see FIG. 7A) via through holes, respectively. Alternatively, the pads 100B_1 to 100B_4 may be electrically connected to the electrode pads 70a to 70d by wire bonding, respectively. Note that it is preferable to provide a plurality of upper surface pads on the upper surface of the substrate 80 that are electrically connected to the pads 100B_1 to 100B_4 via through holes. In this case, the electrode pads 70a to 70d and the pads 100B_1 to 100B_4 can be electrically connected to each other by physically connecting the electrode pads 70a to 70d of the sensor element 10 to the upper surface pads of the substrate 80 by wire bonding.

[0072] The orientation of the pads 100B_1 to 100B_4 is not limited to the orientation of the pads 100B_1 to 100B_4 shown in Fig. 8. For example, the orientation of the pads 100B_1 to 100B_4 shown in Fig. 8 may be rotated by 40 to 50 degrees around the Z axis.

[0073] In this embodiment, along the Z-axis direction, the pads 100B_1 to 100B_4 overlap with the corners 10c1 to 10c4 of the sensor element 10, respectively. In other words, with respect to the Z-axis direction, the pads 100B_1 to 100B_4 are arranged at positions corresponding to the corners 10c1 to 10c4 of the sensor element 10, respectively.

[0074] The intersection of the side portions 10s1 and 10s3 constituting the corner portion 10c1 of the sensor element 10 preferably overlaps the pad 100B_1 along the Z-axis direction. However, it is not essential that the intersection overlaps the pad 100B_1 along the Z-axis direction, and the vicinity of the intersection may overlap the pad 100B_1 along the Z-axis direction. The same applies to the pads 100B_2 to 100B_4.

[0075] The side length in the X-axis direction of each of the pads 100B_1 to 100B_4 is preferably less than 25% of the side length in the X-axis direction of the sensor element 10. Furthermore, the side length in the Y-axis direction of each of the pads 100B_1 to 100B_4 is preferably less than 25% of the side length in the Y-axis direction of the sensor element 10.

[0076] The pads 100B_1 to 100B_4 are arranged so as to protrude outward from the outer periphery of the sensor element 10. The outer periphery of the sensor element 10 is defined by side portions 10s1 to 10s4 indicated by dashed lines in FIG.

[0077] The center (center and its periphery) of pad 100B_1 is preferably located at a position corresponding to the intersection (point of intersection) of side portions 10s1 and 10s3 that form corner 10c1 of sensor element 10. The center of pad 100B_2 is preferably located at a position corresponding to the intersection (point of intersection) of side portions 10s2 and 10s3. The center of pad 100B_3 is preferably located at a position corresponding to the intersection (point of intersection) of side portions 10s2 and 10s4. The center of pad 100B_4 is preferably located at a position corresponding to the intersection (point of intersection) of side portions 10s1 and 10s4.

[0078] In this case, for example, the center-to-center distance between pad 100B_1 and pad 100B_2 corresponds to the length of side portion 10s3 in the Y-axis direction, and the center-to-center distance between pad 100B_1 and pad 100B_4 corresponds to the length of side portion 10s1 in the X-axis direction.

[0079] The area S1 of the overlapping portion between the pad 100B_1 and the bottom surface 10b of the sensor element 10 (the area of ​​the portion indicated by the diagonal lines slanting downward to the right in FIG. 8) is equal to or less than the area S2 of the non-overlapping portion between the pad 100B_1 and the bottom surface 10b of the sensor element 10 (the area of ​​the portion indicated by the diagonal lines slanting downward to the left in FIG. 8). Note that the area S1 may be larger than the area S2.

[0080] The area S1 of the overlapping portion between the pad 100B_1 and the bottom surface 10b of the sensor element 10 is preferably 10% to 90% of the area of ​​the pad 100B_1, and more preferably 20% to 50%. The same applies to the pads 100B_2 to 100B_4.

[0081] This embodiment can also achieve the same effects as those of the second embodiment. Additionally, in this embodiment, the pads 100B_1 to 100B_4 are arranged at positions corresponding to the corners 10c1 to 10c4 of the sensor element 10, respectively. Therefore, warping of the substrate 80 is suppressed at a plurality of positions corresponding to the corners 10c1 to 10c4, and interference between the substrate 80 and the sensor element 10 can be more effectively prevented.

[0082] Fourth embodiment A gas sensor 1C according to a fourth embodiment of the present invention, shown in Fig. 9, has the same configuration as the gas sensor 1B according to the third embodiment, except for the following points. In the following, components that overlap with those of the gas sensor 1B according to the third embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted. Fig. 9 shows the gas sensor 1C as viewed from the bottom side.

[0083] The gas sensor 1C has a plurality of (eight in this embodiment) pads 100C_1 to 100C_4 in addition to the sensor element 10 and the substrate 80. The pads 100C_1 to 100C_4 are arranged across the inner and outer regions of the outer periphery of the sensor element 10.

[0084] On the bottom surface 10b of the sensor element 10, at a position corresponding to the side portion 10s1 (or the side portion 10s2), a plurality of (two in this embodiment) pads 100C_1 (or 100C_2) are arranged along the outer periphery of the sensor element 10. At the position corresponding to the side portion 10s1 (or the side portion 10s2), these pads 100C_1 (or 100C_2) are arranged approximately in the center of the outer periphery of the sensor element 10 in the extension direction, but may be unevenly distributed to one side in the extension direction. Furthermore, the number of pads 100C_1 (or 100C_2) is not limited to two, and may be one or three or more.

[0085] Similarly, on the bottom surface 10b of the sensor element 10, at a position corresponding to the side portion 10s3 (or the side portion 80s4), a plurality of (two in this embodiment) pads 100C_3 (or 100C_4) are arranged along the outer periphery of the sensor element 10. At the position corresponding to the side portion 10s3 (or the side portion 10s4), these pads 100C_3 (or 100C_4) are arranged approximately in the center of the outer periphery of the sensor element 10 in the extension direction, but may be unevenly distributed to one side in the extension direction. Furthermore, the number of pads 100C_3 (or 100C_4) is not limited to two, and may be one or three or more.

[0086] Of the multiple (two) pads 100C_1 arranged at a position corresponding to the side portion 10s1, any one of the pads 100C_1 may be electrically connected to any one of the electrode pads 70a to 70d (FIG. 2) of the sensor element 10. In this case, the remaining pad 100C_1 functions as a dummy pad that does not contribute to the electrical connection with the electrode pads 70a to 70d. The same applies to the pads 100C_2 to 100C_3.

[0087] All of the pads 100C_1 to 100C_4 may be dummy pads that do not contribute to electrical connection with the electrode pads 70a to 70d. In this case, pads that contribute to electrical connection with the electrode pads 70a to 70d may be provided separately on the substrate 80.

[0088] In this embodiment, the pads 100C_1 to 100C_4 are arranged at positions (on the outer periphery of the sensor element 10) corresponding to non-corner portions excluding the corner portions 10c1 to 10c4 of the sensor element 10. Therefore, along the Z-axis direction, the pads 100C_1 to 100C_4 do not overlap with the corner portions 10c1 to 10c4 of the sensor element 10. Furthermore, with respect to the Z-axis direction, the pads 100C_1 to 100C_4 are not arranged at positions corresponding to the corner portions 10c1 to 10c4 of the sensor element 10.

[0089] This embodiment can also achieve the same effects as those of Embodiment 1. In addition, in this embodiment, the pads 100C_1 to 100C_4 are arranged at positions corresponding to non-corner portions (particularly, outer edge portions) of the sensor element 10, and therefore warping of the substrate 80 is suppressed at the positions corresponding to the non-corner portions (particularly, outer edge portions) of the sensor element 10, and interference between the substrate 80 and the sensor element 10 can be effectively prevented.

[0090] Fifth embodiment A gas sensor 1D according to a fifth embodiment of the present invention shown in Fig. 10 has the same configuration as the gas sensor 1C according to the fourth embodiment, except for the following points. In the following, components that overlap with those of the gas sensor 1C according to the fourth embodiment are denoted by the same reference numerals, and detailed descriptions thereof will be omitted. Fig. 10 shows the gas sensor 1D as viewed from the bottom side.

[0091] The gas sensor 1D has a plurality of (four in this embodiment) pads 100D_1 to 100D_4 in addition to the sensor element 10 and the substrate 80. The pads 100D_1 to 100D_4 are arranged inside the outer periphery of the sensor element 10. More specifically, the pads 100D_1 to 100D_4 are arranged at positions corresponding to the center of the sensor element 10, spaced apart from one another in the X-axis direction and the Y-axis direction.

[0092] That is, the pads 100D_1 to 100D_4 are arranged at positions corresponding to non-corner portions of the sensor element 10 excluding the corner portions 10c1 to 10c4. In terms of the Z-axis direction, the pads 100D_1 to 100D_4 do not overlap with the corner portions 10c1 to 10c4 of the sensor element 10, respectively. Furthermore, in terms of the Z-axis direction, the pads 100D_1 to 100D_4 do not overlap with the side portions 10s1 to 10s4 (the outer periphery of the sensor element 10) of the sensor element 10, respectively. That is, the arrangement positions of the pads 100D_1 to 100D_4 are positions of the non-corner portions of the sensor element 10 excluding the outer edge portions of the sensor element 10.

[0093] The pads 100D_1 to 100D_4 are preferably arranged closer to the center of the sensor element 10 than to the outer periphery of the sensor element 10. Furthermore, the pads 100D_1 to 100D_4 are preferably arranged on the bottom surface 80b of the substrate 80 so that the centers of the pads 100D_1 to 100D_4 are closer to the center of the sensor element 10 than to the outer periphery of the sensor element 10. In other words, the pads 100D_1 to 100D_4 are preferably unevenly distributed inside the outer periphery of the sensor element 10 and toward the center of the sensor element 10.

[0094] Four pads 100D_1 to 100D_4 are arranged at a position corresponding to the center of the sensor element 10, but the number of pads may be one, two, three, or five or more. Furthermore, the pads 100D_1 to 100D_4 may each have a different size or shape.

[0095] In this embodiment, the same effects as in the first embodiment can be obtained. In addition, in this embodiment, the pads 100D_1 to 100D_4 are arranged at positions corresponding to the center of the sensor element 10. Therefore, warping of the substrate 80 is suppressed at the positions corresponding to the center of the sensor element 10. Therefore, deformation of the sensor element 10 can be effectively prevented at the center of the sensor element 10.

[0096] Sixth embodiment A gas sensor 1E according to a sixth embodiment of the present invention shown in Fig. 11 has the same configuration as the gas sensors 1B to 1D according to the third to fifth embodiments, except for the following points. In the following, members that overlap with those of the gas sensors 1B to 1D according to the third to fifth embodiments are denoted by the same reference numerals, and detailed description thereof will be omitted. Fig. 11 shows the gas sensor 1E as viewed from the bottom side.

[0097] The gas sensor 1E has a plurality of (four in this embodiment) pads 100B_1 to 100B_4, a plurality of (eight in this embodiment) pads 100C_1 to 100C_4, and a plurality of (four in this embodiment) pads 100D_1 to 100D_4, in addition to the sensor element 10 and the substrate 80. That is, the gas sensor 1E is obtained by applying the configurations of the gas sensor 1C of the fourth embodiment and the gas sensor 1D of the fifth embodiment to the gas sensor 1B of the third embodiment (FIG. 8).

[0098] Therefore, on the bottom surface 80b of the substrate 80, pads 100B_1 to 100B_4 and 100C_1 to 100C_4 are arranged in a ring shape (to go around the outer periphery of the sensor element 10) at predetermined intervals along the outer periphery of the sensor element 10.

[0099] The pads 100B_1 to 100B_4 are arranged at positions corresponding to the corners 10c1 to 10c4, respectively, of the sensor element 10. The pads 100C_1 to 100C_4 and 100D_1 to 100D_4 are arranged at positions corresponding to the non-corner portions of the sensor element 10 (on the outer periphery of the sensor element 10 and the center of the sensor element 10).

[0100] This embodiment can achieve the same effects as the third to fifth embodiments. That is, warping of the substrate 80 is suppressed in the vicinity of each of the corners 10c1 to 10c4 and non-corner portions of the sensor element 10. Therefore, the amount of warping of the substrate 80 is significantly reduced, and interference between the substrate 80 and the sensor element 10 can be more effectively prevented.

[0101] Any of the pads 100B_1 to 100B_4, 100C_1 to 100C_4, and 100D_1 to 100D_4 may be omitted. For example, the pads 100C_1 to 100C_4 or 100D_1 to 100D_4 may not be provided on the bottom surface 80b of the substrate 80. In this case, warping of the substrate 80 can be suppressed in the vicinity of each of the corners 10c1 to 10c4 and non-corner portions of the sensor element 10.

[0102] Alternatively, the pads 100B_1 to 100B_4 may be omitted from the bottom surface 80b of the substrate 80. In this case, warping of the substrate 80 in the vicinity of the non-corner portions of the sensor element 10 can be suppressed.

[0103] The present invention is not limited to the above-described embodiment, and various modifications can be made within the scope of the present invention.

[0104] In the above embodiments, the shape of the substrate 80 is rectangular or square when viewed in the Z-axis direction, but this is not particularly limited. The shape of the substrate 80 may be, for example, another polygonal shape when viewed in the Z-axis direction.

[0105] In the first embodiment, other pads may be arranged on the outer edge of the bottom surface 80b of the substrate 80. For example, one or more pads may be arranged along the X-axis direction on the outer edge of the substrate 80 at a position corresponding to the side 80s1 (or the side 80s2) of the substrate 80 shown in FIG. 5B. Furthermore, one or more pads may be arranged along the Y-axis direction on the outer edge of the substrate 80 at a position corresponding to the side 80s3 (or the side 80s4) of the substrate 80. These pads may then be used as pads that contribute to electrical connection with the electrode pads 70a to 70d. The same applies to the second to sixth embodiments.

[0106] 10 (positions corresponding to the center of the sensor element 10), the positions of the pads 100D_1 to 100D_4 may be changed to any positions inside the outer periphery of the sensor element 10. Furthermore, the pads 100D_1 to 100D_4 may be arranged discretely in a region inside the outer periphery of the sensor element 10.

[0107] In each of the above embodiments, the gas sensor 1 includes one sensor element 10, but may include a plurality of sensor elements 10.

[0108] In each of the above embodiments, a control element for controlling the sensor element 10 may be fixed to the substrate 80. In this case, the control element may be interposed between the substrate 80 and the sensor element 10.

[0109] In each of the above embodiments, as shown in Figures 5A and 5B, the sensor element 10 is fixed directly to the top surface of the substrate 80, but it may be fixed indirectly via another member (for example, the control element described above). Also, the pad 100 is fixed directly to the bottom surface of the substrate 80, but it may be fixed indirectly via another member. That is, as long as the sensor element 10 and the pad 100 are fixed to one main surface side (top surface side) and the other main surface side (bottom surface side) of the substrate 80, respectively, their installation manner is not limited to the installation manner shown in Figures 5A and 5B. [Explanation of symbols]

[0110] 1, 1A, 1B, 1C, 1D, 1E...Gas sensors 10...Sensor element 20...Bass 30a to 30c: insulating film 31...Main body 32~35…beam part 36...periphery 37...hole 40…Heat source 41...Heat source body 42,43...Drawer part 50a,50b…electrode 60...Sensitive membrane 61...Main body 62~65…beam part 70a to 70d: Pad electrodes 80...Substrate 81...Cambered part 82...Non-warped part 90...adhesive layer 100, 100A_1~100A_4, 100B_1~100B_4, 100C_1~100C_4, 100D_1~100D_4...Pad

Claims

1. A substrate; a sensor element fixed to one main surface of the substrate and configured to detect CO 2 , H 2 or He gas; a pad fixed to the other main surface of the substrate and connectable to an external substrate; an adhesive layer that primarily bonds the sensor element and the substrate; At least a portion of the pad and the sensor element overlap in a direction perpendicular to a mounting surface of the pad, the substrate has an overlapping portion that overlaps with the sensor element in a plan view and a non-overlapping portion that is located outside an outer edge of the sensor element in a plan view and does not overlap with the sensor element, A gas sensor in which the center of the pad is located in the overlapping portion in a plan view.

2. 2. The gas sensor according to claim 1, wherein at least a portion of the pad and a corner of the sensor element overlap with each other along a direction perpendicular to a surface on which the pad is placed.

3. 3. The gas sensor according to claim 1, wherein the pad comprises a plurality of pads.

4. 4. The gas sensor according to claim 3, wherein the pads are arranged at positions corresponding to the corners of the sensor element, respectively.

5. 2. The gas sensor according to claim 1, wherein the pads are arranged at positions corresponding to non-corner portions of the sensor element excluding corner portions.

6. 6. The gas sensor according to claim 5, wherein the non-corner portion is located in a central portion of the sensor element.

7. 6. The gas sensor according to claim 5, wherein the non-corner portion is located on an outer edge of the sensor element.

8. 8. The gas sensor according to claim 6, wherein the pad comprises a plurality of pads.

9. The pad is made up of a plurality of the pads, 2. The gas sensor according to claim 1, wherein any of the plurality of pads is arranged at a position corresponding to a corner of the sensor element, and any of the remaining pads is arranged at a position corresponding to a non-corner portion of the sensor element excluding the corner.

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