Physical quantity measurement device and method for manufacturing physical quantity measurement device

Abstract

This physical quantity measurement device (20) comprises: an optical component (40) having a surface (17) on which a mirror is at least partially formed; and a circuit board (30) that is at least partially joined to the optical component. The optical component has a first through-hole (41) in top view. The circuit board has a second through-hole (31) in top view. One of the first through-hole and the second through-hole at least partially overlaps the other in top view.

Description

Physical quantity measurement device and method for manufacturing a physical quantity measurement device

[0001] The present disclosure relates to a physical quantity measurement device and a method for manufacturing a physical quantity measurement device.

[0002] Physical quantity measurement devices for measuring physical quantities of measurement objects are used in various fields. As an example of a physical quantity measurement device, a gas sensor that detects the concentration of a detected gas can be mentioned. With the progress of semiconductor technology and MEMS technology, the miniaturization of gas sensors has advanced, and their mounting into the housings of various electronic devices has been promoted (see, for example, Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2019-91489

[0004] The device disclosed in Patent Document 1 may include a detector that detects the presence of carbon monoxide gas and issues an alarm when it is determined that the level of carbon monoxide gas is high. When the concentration of the detected gas increases or decreases in the space where the sensor unit is arranged, it is desirable for the gas sensor to output a measurement value following this increase or decrease in concentration as soon as possible.

[0005] Here, there is a demand for further miniaturization of electronic devices, and when the degree of integration of other surrounding electronic components or other environmental sensors is high, it is difficult for the air around the gas sensor to be replaced. As a result, the response of the measurement may be delayed. Also, for example, when wind blows towards the gas sensor, if there is no escape route for the wind, the pressure of the gas near the gas sensor increases, making accurate measurement difficult.

[0006] In view of such circumstances, an object of the present disclosure is to provide a physical quantity measurement device and a method for manufacturing a physical quantity measurement device that enable both high integration and an improvement in the response speed of physical quantity measurement.

[0007] (1) A physical quantity measurement device according to an embodiment of the present disclosure includes an optical component having a surface on which at least a part of a mirror is formed, and a circuit board at least partially joined to the optical component. The optical component has a first through-hole in a top view, the circuit board has a second through-hole in a top view, and the first through-hole and the second through-hole at least partially overlap each other in a top view.

[0008] (2) In one embodiment of the present disclosure, in (1), the circuit board has a light-emitting element on the side facing the optical component, the optical component guides light emitted from the light-emitting element, and the first through hole and the second through hole are provided such that, in a top view, they do not overlap with the path through which the light is guided by the optical component.

[0009] (3) In one embodiment of the present disclosure, in (1) or (2), the first through hole and the second through hole enclose the other when viewed from above.

[0010] (4) In one embodiment of the present disclosure, in any of (1) to (3), the diameter of the second through hole is greater than the diameter of the first through hole.

[0011] (5) In one embodiment of the present disclosure, in any of (1) to (3), the diameter of the first through hole is greater than the diameter of the second through hole.

[0012] (6) In one embodiment of the present disclosure, in any of (1) to (5), the diameter of the first through hole and the diameter of the second through hole are in the range of 1 mm to 5 mm.

[0013] (7) In one embodiment of the present disclosure, in any of (1) to (5), the first through hole and the second through hole are polygonal or cross-shaped in top view.

[0014] (8) In one embodiment of the present disclosure, in any of (1) to (7), the optical component has a ventilation hole for introducing gas into the gas detection space, and the first through hole is not connected to the gas detection space.

[0015] (9) In one embodiment of the present disclosure, in any of (1) to (8), the optical component has a ventilation hole for introducing gas into the gas detection space, and the diameter of the first through hole and the opening area of ​​the second through hole are greater than the opening area of ​​the ventilation hole.

[0016] (10) A method for manufacturing a physical quantity measuring device according to one embodiment of the present disclosure is a method for manufacturing a physical quantity measuring device comprising: an optical component having a surface on which at least a mirror is formed; and a circuit board at least partially joined to the optical component, wherein the optical component has a first through hole when viewed from above, and the circuit board has a second through hole when viewed from above, and the optical component and the circuit board are joined such that one of the first through hole and the second through hole at least partially overlaps the other when viewed from above.

[0017] According to this disclosure, it is possible to provide a physical quantity measuring device and a method for manufacturing a physical quantity measuring device that can achieve both high integration and improved response speed of physical quantity measurement.

[0018] Figure 1 is a diagram showing an example configuration of a physical quantity measuring device according to this embodiment. Figure 2 is a perspective view of the physical quantity measuring device of Figure 1. Figure 3 is a diagram showing the configuration of a physical quantity measuring device of a comparative example. Figure 4 is a schematic and oblique perspective view of the main part showing a circular feature portion. Figure 5 is a schematic and oblique perspective view of the main part showing another example of a circular feature portion. Figure 6 is a schematic and oblique perspective view of the main part showing yet another example of a circular feature portion.

[0019] Hereinafter, a physical quantity measuring device 20 (see Figure 1) and a method for manufacturing the physical quantity measuring device 20 according to one embodiment of the present disclosure will be described with reference to the drawings. In each figure, the same or corresponding parts are denoted by the same reference numerals. In the description of this embodiment, the description of the same or corresponding parts will be omitted or simplified as appropriate.

[0020] Figure 1 is a cross-sectional view showing an example of the configuration of the physical quantity measuring device 20 according to this embodiment. Figure 2 is a perspective view of the portion of the physical quantity measuring device 20 in Figure 1 that includes the optical component 40. The physical quantity measuring device 20 measures the physical quantity of an object to be measured. The physical quantity measuring device 20 according to this embodiment will be described as a gas sensor in which the object to be measured is air and the physical quantity is the concentration of the gas to be detected in the air. However, the object to be measured and the physical quantity are not limited to specific ones. Here, the gas to be detected is, for example, carbon dioxide, water vapor, carbon monoxide, nitric oxide, ammonia, sulfur dioxide, alcohol, formaldehyde, and hydrocarbon gases such as methane and propane.

[0021] As shown in Figure 1, the physical quantity measuring device 20 according to this embodiment constitutes an electronic device together with other components 50. In this embodiment, the electronic device has at least a gas detection function and may be, for example, an alcohol detector, an air purifier, a gas alarm, etc., but is not limited to any specific one. The other components 50 are components of the electronic device other than the physical quantity measuring device 20. The other components 50 may include one or more processors that control the entire electronic device. The processor may, for example, perform calculation processing on the measurement value measured by the optical component 40 to calculate the concentration of the gas to be detected. The other components 50 may also include sensors that detect gases other than the gas to be detected. In the example in Figure 1, the other components 50 are mounted on the circuit board 30 together with the physical quantity measuring device 20, but the configuration is not limited to this. For example, there may be a main board different from the circuit board 30, and the physical quantity measuring device 20 and the other components 50 may be mounted on the main board.

[0022] Furthermore, as shown in Figure 1, the electronic device has a housing 10, and a physical quantity measuring device 20 is arranged inside the housing 10 together with other components 50. The housing 10 is provided with two ventilation openings 19 through which air, which is the object to be measured, enters and exits. The housing 10 may be made of metal, glass, resin, or a composite material thereof.

[0023] The physical quantity measuring device 20 according to this embodiment comprises an optical component 40 having a surface on which at least a mirror is formed, and a circuit board 30 that is at least partially bonded to the optical component 40. As shown in Figure 1, the optical component 40 is placed on the surface of the circuit board 30, with one of the surfaces with the largest area (main surface) being the front surface and the other being the back surface. In the following description, viewing the surface of the circuit board 30 from the optical component 40 (viewing in the direction of arrow V in Figure 1) will be referred to as "top view".

[0024] In this embodiment, the optical component 40 functions as the gas measuring unit of an NDIR (Non-Dispersive Infrared) type gas sensor. The NDIR type gas sensor measures the concentration of the detected gas using a light-receiving element 12 that receives infrared light in the absorption wavelength band corresponding to the gas to be detected, and a light-emitting element 11 that emits infrared light in the same absorption wavelength band. The light-emitting element 11 is, for example, an LED (Light Emitting Diode). The light-receiving element 12 is, for example, a photodiode.

[0025] The circuit board 30 has a light-emitting element 11 on the side facing the optical component 40. The circuit board 30 also has a light-receiving element 12 on the side facing the optical component 40. In this embodiment, the optical component 40 has a reflective portion 17 that reflects light 18 (infrared rays) emitted from the light-emitting element 11 and causes it to enter the light-receiving element 12. In other words, the reflective portion 17 corresponds to the "surface on which the mirror is formed". In the example in Figure 1, the reflective portion 17 is a concave mirror. The reflective surface of the reflective portion 17 may be made of a metal with high reflectivity, such as aluminum or gold. The optical component 40 also has a gas detection space 42 as an internal space, which is provided with ventilation holes 43. Gas (air in this embodiment) is taken into the gas detection space 42 through the ventilation holes 43. The optical component 40 uses a reflector 17 to guide light 18 emitted from the light-emitting element 11 through the gas detection space 42 to the light-receiving element 12, so that the concentration of the gas to be detected in the air taken into the gas detection space 42 can be measured.

[0026] In recent years, electronic devices have been required to be even smaller, making it difficult to have ample space around the gas sensor, and thus making it difficult for the air around the gas sensor to be replaced. For example, Figure 3 shows the configuration of a conventional physical quantity measuring device 120, which is a comparative example. When the physical quantity measuring device 120 is placed inside the housing 10, a circuit board 30 is located between one and the other of the ventilation section 19. As a result, air entering from one side of the ventilation section 19 flows around the circuit board 30 to the other side of the ventilation section 19. In other words, it is difficult for the air around the gas sensor to be replaced. Consequently, when the concentration of the gas to be detected in the air changes, it takes time for the changed air to be taken into the gas detection space 42, resulting in a slower measurement response. Also, for example, if wind blows in from one side of the ventilation section 19, the air does not pass through easily, causing the pressure of the gas near the gas sensor to rise, making accurate measurement difficult.

[0027] To address the issue of slow response speed, the physical quantity measuring device 20 according to this embodiment has a first through-hole 41 and a second through-hole 31. The optical component 40 has the first through-hole 41 when viewed from above. The circuit board 30 also has the second through-hole 31 when viewed from above. As shown in Figures 1 and 2, when viewed from above, one of the first through-hole 41 and the second through-hole 31 overlaps with the other at least partially. Because the physical quantity measuring device 20 has the first through-hole 41 and the second through-hole 31, air entering from one side of the ventilation section 19 passes through the first through-hole 41 and the second through-hole 31 and reaches the other side of the ventilation section 19 without having to bypass the circuit board 30. Therefore, the physical quantity measuring device 20 according to this embodiment enables both high integration (miniaturization of electronic devices) and improved response speed of physical quantity measurement. Here, the height of the first through-hole 41 (length in the direction of arrow V in Figure 1) may be less than the maximum height of the gas detection space 42, and may be less than half the maximum height of the gas detection space 42.

[0028] Furthermore, the optical component 40 may have a particle filter on its outer surface so as to cover the ventilation holes 43, in order to prevent foreign matter other than gas, such as dust, from entering the gas detection space 42. The particle filter may be made primarily of polymer fibers such as nonwoven fabric or PTFE (polytetrafluoroethylene).

[0029] Furthermore, the first through-hole 41 and the second through-hole 31 may be provided such that, when viewed from above, they do not overlap with the path through which the light 18 is guided by the optical component 40. In other words, the first through-hole 41 is provided separately from the ventilation hole 43 in the optical component 40, and the first through-hole 41 is not connected to the gas detection space 42. Alternatively, the circuit board 30 has a first part that is joined to the optical component 40 when viewed from the direction of arrow V or the opposite direction, and a second part that forms the gas detection space 42 between the surface on which the reflective part 17 is formed, and the second through-hole 31 is formed in the first part of the circuit board 30. With such a configuration, it is possible to easily replace the air around the gas sensor without affecting the measurement of the concentration of the gas to be detected. Furthermore, with such a configuration, it is possible to prevent foreign matter from entering the gas detection space 42 through the first through-hole 41.

[0030] The first through-hole 41 and the second through-hole 31 may be configured such that one encloses the other when viewed from above. For example, the diameter of the second through-hole 31 may be larger than the diameter of the first through-hole 41. Also, for example, the diameter of the first through-hole 41 may be larger than the diameter of the second through-hole 31. For example, the second through-hole 31 may be formed by machining the circuit board 30 using a drill or the like. Also, the first through-hole 41 and the second through-hole 31 may serve as holes for aligning the optical component 40 and the circuit board 30. For example, alignment may be performed by inserting pins into the second through-hole 31 and the first through-hole 41 from the back side of the circuit board 30. Also, for example, alignment may be performed by inserting tapered pins into the second through-hole 31 and the first through-hole 41 from the back side of the circuit board 30. The material of the circuit board 30 may be, for example, resin, glass cloth, ceramics, etc. Examples of resins include phenolic resins, epoxy resins, polyimide resins, bismaleimidotriazine resins, fluororesins, and polyphenylene oxide resins.

[0031] Furthermore, the diameters of the first through-hole 41 and the second through-hole 31 may be within the range of 1 mm to 5 mm. Here, the first through-hole 41 and the second through-hole 31 are not limited to being circular in top view, but may be polygonal or cross-shaped in top view, for example.

[0032] Furthermore, when viewed from above, the diameter of the first through-hole 41 and the opening area of ​​the second through-hole 31 may be larger than the opening area of ​​the ventilation hole 43. By doing so, the exchange of gas near the gas sensor can be accelerated in relation to the exchange of gas in the gas detection space 42, thereby enhancing the effects of having the first through-hole 41 and the second through-hole 31.

[0033] Furthermore, the optical component 40 has a third through-hole when viewed from above, and the circuit board 30 has a fourth through-hole when viewed from above, and the third and fourth through-holes may at least partially overlap with the other when viewed from above. By having multiple sets of through-holes similar to the first through-hole 41 and the second through-hole 31, it is possible to further facilitate the exchange of air around the gas sensor. Moreover, when these through-holes are used as holes for aligning the optical component 40 and the circuit board 30, more accurate alignment can be achieved.

[0034] Furthermore, the manufacturing method of the physical quantity measuring device 20 may include a step of joining the optical component 40 and the circuit board 30 such that, when viewed from above, one of the first through hole 41 and the second through hole 31 at least partially overlaps with the other.

[0035] Furthermore, the base body of the optical component 40 may be made of resin manufactured by injection molding or cutting, and a mirror may be formed in part by metal deposition, sputtering, or plating. The mirror may also have a protective film to suppress dirt, oxidation, or corrosion.

[0036] Furthermore, the optical component 40 may have at least one circular feature portion 8 at a position visible when the optical component 40 is viewed in the direction of arrow V in Figure 1 or in the opposite direction. The circular feature portion 8 may be a circular recess as shown in Figure 4, a circular protrusion as shown in Figure 5, or an annular protrusion as shown in Figure 6, and may be integrally molded with the optical component 40. More specifically, the circular feature portion 8 may be molded at the same time as the base body of the optical component 40 when it is manufactured by injection molding. In Figure 4, a circular recess 8a, which is an example of a circular feature portion 8, is formed by a circular flat bottom surface 8a1 and an inner circumferential surface 8a2 surrounding the bottom surface 8a1. In Figure 5, a cylindrical protrusion 8b, which is an example of a circular feature portion 8, is formed by a circular flat top surface 8b1 and an outer circumferential surface 8b2 surrounding the top surface 8b1. In Figure 6, an annular protrusion 8c, which is an example of a circular feature portion 8, protrudes from a flat portion (F1) on the surface of the optical component 40. Here, the circular feature 8 is not limited to a perfect circle, but also includes an ellipse or a shape consisting of a line segment and a circular arc.

[0037] The physical quantity measuring device 120 joins the circuit board 30 and the optical component 40 at least partially, but if the relative position deviates from its intended position during joining, the light 18 emitted from the light-emitting element 11 cannot be correctly guided to the light-receiving element 12 via the reflecting part 17. If the optical component 40 has at least one circular feature portion 8, the relative position can be determined by comparing the position of the circular feature portion 8 with the terminal pattern on the circuit board 30, and joining can be performed at the correct position. Furthermore, the circuit board 30 may have a feature portion for alignment for this purpose.

[0038] Furthermore, the height of the circular feature portion 8 may be 100 μm or less. Here, the height is the depth of the bottom surface 8a1 of the recess relative to the surroundings when the circular feature portion 8 is a circular recess 8a (Ha in Figure 4). Also, the height is the height of the top surface 8b1 of the convex portion relative to the surroundings when the circular feature portion 8 is a cylindrical convex portion 8b (Hb in Figure 5). Also, the height is the height of the convex portion relative to the surroundings when the circular feature portion 8 is an annular convex portion 8c (Hc in Figure 6). When molding the base body of the optical component 40 by injection molding, it is desirable that the resin thickness of the molded product be nearly uniform. By setting the height of the circular feature portion 8 to 100 μm or less, the difference in resin thickness between the circular feature portion 8 and its surroundings can be reduced. Consequently, the influence on the flow of resin around the circular feature portion 8 during injection molding can be suppressed, making it easier to mold the circular feature portion 8 and its surroundings cleanly.

[0039] Furthermore, the height of the circular feature portion 8 may be 10% or less of the resin thickness around it (Ta in Figure 4, Tb in Figure 5, and Tc in Figure 6). By setting the height of the circular feature portion 8 to 10% or less of the resin thickness around it, the difference in resin thickness between the circular feature portion 8 and its surroundings can be reduced. Consequently, the influence on the flow of resin around the circular feature portion 8 during injection molding can be suppressed, making it easier to mold the circular feature portion 8 and its surroundings cleanly.

[0040] Furthermore, the diameter of the circular feature portion 8 may be 1 to 5 mm. Here, the diameter is the maximum length of the line segment connecting any two points on the perimeter of the bottom surface 8a1 of the recess when the circular feature portion 8 is a circular recess 8a (Da in Figure 4). Also, the diameter is the maximum length of the line segment connecting any two points on the perimeter of the top surface 8b1 of the convex when the circular feature portion 8 is a cylindrical convex portion 8b (Db in Figure 5). Also, the diameter is the maximum length of the line segment connecting any two points of the convex portion when the circular feature portion 8 is an annular convex portion (Dc in Figure 6). By setting the diameter of the circular feature portion 8 to 1 to 5 mm, the position of the circular feature portion 8 can be more easily recognized by image processing technology when the circuit board 30 and optical component 40 are joined by an automated machine. Consequently, the relative positional deviation when the circuit board 30 and optical component 40 are joined can be reduced.

[0041] As described above, the physical quantity measuring device 20 and the method for manufacturing the physical quantity measuring device 20 according to this embodiment enable rapid replacement of the surrounding air, thereby achieving both high integration and improved response speed of physical quantity measurement.

[0042] While embodiments of this disclosure have been described based on the drawings and examples, it should be noted that those skilled in the art will find it easy to make various modifications or alterations based on this disclosure. Therefore, it should be noted that these modifications or alterations are included within the scope of this disclosure.

[0043] 8 Circular feature part 8a Circular recess (circular recess) 8b Cylindrical protrusion (circular protrusion) 8c Annular protrusion (annular protrusion) 10 Housing 11 Light-emitting element 12 Light-receiving element 17 Reflector 18 Light 19 Ventilation part 20 Physical quantity measuring device 30 Circuit board 31 Second through hole 40 Optical component 41 First through hole 42 Gas detection space 43 Ventilation hole 50 Other parts 120 Physical quantity measuring device

Claims

1. A physical quantity measuring device comprising: an optical component having a surface on which at least a portion of a mirror is formed; and a circuit board at least partially bonded to the optical component, wherein the optical component has a first through hole when viewed from above, and the circuit board has a second through hole when viewed from above, and the first through hole and the second through hole at least partially overlap each other when viewed from above.

2. The physical quantity measuring device according to claim 1, wherein the circuit board has a light-emitting element on the side facing the optical component, the optical component guides light emitted from the light-emitting element, and the first through hole and the second through hole are provided such that, when viewed from above, they do not overlap with the path through which the light is guided by the optical component.

3. The physical quantity measuring device according to claim 1 or 2, wherein, when viewed from above, one of the first through-holes and the second through-hole encloses the other.

4. The physical quantity measuring device according to claim 1 or 2, wherein the diameter of the second through hole is larger than the diameter of the first through hole.

5. The physical quantity measuring device according to claim 1 or 2, wherein the diameter of the first through hole is greater than the diameter of the second through hole.

6. The physical quantity measuring device according to claim 1 or 2, wherein the diameter of the first through hole and the diameter of the second through hole are in the range of 1 mm to 5 mm.

7. The physical quantity measuring device according to claim 1 or 2, wherein the first through hole and the second through hole are polygonal or cross-shaped when viewed from above.

8. The physical quantity measuring device according to claim 1 or 2, wherein the optical component has a ventilation hole for introducing gas into the gas detection space, and the first through hole is not connected to the gas detection space.

9. The physical quantity measuring device according to claim 1 or 2, wherein the optical component has a ventilation hole for introducing gas into the gas detection space, and the diameter of the first through hole and the opening area of ​​the second through hole are greater than the opening area of ​​the ventilation hole.

10. A method for manufacturing a physical quantity measuring device comprising an optical component having a surface on which at least partially a mirror is formed, and a circuit board at least partially joined to the optical component, wherein the optical component has a first through hole when viewed from above, the circuit board has a second through hole when viewed from above, and the optical component and the circuit board are joined such that one of the first through hole and the second through hole at least partially overlaps the other when viewed from above.

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