阅读说明：本技术 流速传感器 (Flow rate sensor ) 是由 池野智一 于 2020-04-13 设计创作，主要内容包括：提供一种耐候性优异的流速传感器。流速传感器(1)具有对来自电阻器(2、3)的信号进行处理的信号处理部,利用电阻器(2)的散热来探测流体的流速。另外,流速传感器(1)具有基板(6),该基板(6)具有暴露于流体的一侧的第一基板面(4)以及作为与第一基板面(4)相反的面的第二基板面(5)。安装于第二基板面(5)的电阻器(2、3)的发热部(2h、3h)被配置成与第二基板面(5)相向。(Provided is a flow velocity sensor having excellent weather resistance. The flow velocity sensor (1) has a signal processing unit that processes signals from the resistors (2, 3), and detects the flow velocity of a fluid by heat dissipation from the resistor (2). The flow velocity sensor (1) has a substrate (6), and the substrate (6) has a first substrate surface (4) on the side exposed to the fluid and a second substrate surface (5) that is the opposite surface to the first substrate surface (4). The heat generating parts (2h, 3h) of the resistors (2, 3) mounted on the second substrate surface (5) are arranged to face the second substrate surface (5).)

1. A flow rate sensor having a signal processing portion that processes a signal from a resistor, the flow rate sensor detecting a flow rate of a fluid using heat dissipation of the resistor, the flow rate sensor comprising:

a substrate having a first substrate surface on a side exposed to the fluid and a second substrate surface that is an opposite surface to the first substrate surface; and

the resistor is mounted on the second substrate surface,

wherein the heat generating portion of the resistor is disposed to face the second substrate surface.

2. The flow rate sensor according to claim 1,

the substrate is a film-like substrate or a thin-plate substrate having a thickness of 1mm or less.

3. Flow rate sensor according to claim 1 or 2,

the substrate has a hole in a portion thereof facing the region of the heat generating portion.

4. A flow rate sensor according to any one of claims 1 to 3,

the insulating film is formed by coating a part or the whole of the first substrate surface or a part or the whole of the second substrate surface with a resin film and/or a glass film.

5. The flow rate sensor according to claim 4,

and disposing a metal foil and/or a vapor deposition film on the insulating coating film.

6. The flow rate sensor according to any one of claims 1 to 5,

has a cover member covering the second substrate surface.

Technical Field

The present invention relates to a flow rate sensor.

Background

There is known a flow rate sensor for detecting a flow rate of a fluid by heat dissipation from a heat generating body corresponding to the flow rate of the fluid. In such a flow rate sensor, a resistance for heat generation (heat generating body) and a resistance for temperature compensation constitute a known resistance bridge circuit. The heat generating resistor is heated and controlled to a temperature higher than the temperature of the fluid by a predetermined amount. The temperature compensation resistor is used to detect the temperature of the fluid itself and compensate for the influence of the change in the fluid temperature.

Based on this technique, a flow velocity sensor has been proposed in which a heating resistor and a temperature compensation resistor, both of which are chip resistors, are disposed on the surface of an insulating substrate in close proximity to each other (see patent documents 1 and 2).

Documents of the prior art

Patent document

Patent document 1: japanese laid-open patent publication No. 9-53967

Patent document 2: japanese laid-open patent publication No. 8-35978

Disclosure of Invention

Problems to be solved by the invention

In the flow rate sensors described in patent documents 1 and 2, both the heating resistor and the temperature compensation resistor are likely to come into contact with the fluid, and are likely to be deteriorated or damaged by water or dirt contained in the fluid. That is, the flow velocity sensors described in patent documents 1 and 2 have poor weather resistance.

Accordingly, an object of the present invention is to provide a flow rate sensor having excellent weather resistance.

Means for solving the problems

In order to achieve the above object, a flow rate sensor according to the present invention includes a signal processing unit that processes a signal from a resistor, the flow rate sensor detecting a flow rate of a fluid by heat dissipation from the resistor, the flow rate sensor including: a substrate having a first substrate surface on a side exposed to the fluid and a second substrate surface that is an opposite surface to the first substrate surface; and a resistor mounted on the second substrate surface, wherein a heat generating portion of the resistor is disposed to face the second substrate surface.

Here, the substrate may be a film-like substrate or a thin-plate substrate having a thickness of 1mm or less.

Further, a portion of the substrate facing the region of the heat generating portion may have a hole.

Further, a resin film and/or a glass film may be provided as an insulating coating film covering a part or the whole of the first substrate surface or a part or the whole of the second substrate surface.

Further, a metal foil and/or a vapor deposition film may be disposed on the insulating coating.

Further, a cover member may be provided to cover the second substrate surface.

ADVANTAGEOUS EFFECTS OF INVENTION

In the present invention, a flow rate sensor having excellent weather resistance can be provided.

Drawings

Fig. 1 is a plan view of a flow rate sensor according to an embodiment of the present invention.

Fig. 2 is a bottom view of a flow rate sensor according to an embodiment of the present invention.

Fig. 3 is a schematic view of a-a sectional view of fig. 1.

Fig. 4 is a schematic diagram of a circuit constituting the flow rate sensor according to the embodiment of the present invention.

Fig. 5 is a view showing a portion corresponding to the section a-a in fig. 1 of a modified example of the flow velocity sensor according to the embodiment of the present invention.

Fig. 6 is a schematic perspective view of a cover member used in a modified example of the flow velocity sensor according to the embodiment of the present invention.

Detailed Description

(Structure and operation of flow velocity sensor according to embodiment of the present invention)

A flow rate sensor according to an embodiment of the present invention will be described below with reference to the drawings.

The flow velocity sensor 1 has a signal processing unit that processes signals from the resistors 2 and 3, and the flow velocity sensor 1 detects the flow velocity of the fluid by heat dissipation from the resistor 2. The flow velocity sensor 1 includes a substantially rectangular substrate 6, and the substrate 6 includes a first substrate surface 4 on a side exposed to the fluid and a second substrate surface 5 opposite to the first substrate surface 4. The heat generating portions 2h and 3h of the resistors 2 and 3 mounted on the second substrate surface 5 are arranged to face holes 21 and 22, which will be described later, of the second substrate surface 5.

Further, the second substrate surface 5 is formed with wirings 11, 12, 13, and 14. At the ends of the wirings 11, 12, 13, 14, terminal electrodes 2a, 2b, 3a, 3b of the resistors 2, 3 and pads 11a, 12a, 13a, 14a for connecting these terminal electrodes are formed. The terminal electrode 2a is connected to the pad 11a, the terminal electrode 2b is connected to the pad 12a, the terminal electrode 3a is connected to the pad 13a, and the terminal electrode 3b is connected to the pad 14 a. The connection is achieved by soldering, but a Conductive adhesive or an Anisotropic Conductive Film (ACF) may be used. The anisotropic conductive film can simultaneously realize electrical conduction, insulation and heat transfer.

The resistor 2 is a heat-generating resistor, and is heated and controlled to a temperature higher than the temperature of the fluid by a predetermined amount. The temperature rise of the resistor 2 is determined by the power consumption of the resistor 2 and the ease of heat dissipation from the resistor 2 to the fluid and the substrate 6, i.e. the thermal conductivity. The resistor 3 is a temperature compensation resistor for detecting the temperature of the fluid itself and compensating for the influence of the change in the fluid temperature.

The resistors 2 and 3 have resistance coating arrangement surfaces 2c and 3c facing the second substrate surface 5 and non-resistance coating arrangement surfaces 2d and 3d which are surfaces opposite to the resistance coating arrangement surfaces 2c and 3 c. The resistance coatings 2R and 3R generate heat when energized, and therefore are similar to the aforementioned "heat generating portions 2h and 3 h". The upper surfaces of the resistive coatings 2R and 3R, i.e., the surfaces facing the second substrate surface 5, are subjected to protective coating as a part of the resistors 2 and 3, and the protective coating is not shown. Since the pads 11a, 12a, 13a, and 14a and the terminal electrodes 2a, 2b, 3a, and 3b of the resistors 2 and 3 are connected so as to face the second substrate surface 5, the resistors 2 and 3 are mounted so as to be "flip-chip".

The substrate 6 is a thin plate substrate having a thickness of 0.1 mm. The substrate 6 is made of resin, but may be made of ceramic. As the substrate 6, a material used for a printed wiring board such as an epoxy resin mixed with glass fiber can be used.

The substrate 6 has holes 21 and 22 at portions thereof facing the heat generating portions 2h and 3h of the resistors 2 and 3, respectively. The holes 21 and 22 have the same shape and are long oblong in the direction orthogonal to the current flowing direction of the resistors 2 and 3.

As not shown explicitly in fig. 1 and 2, and as shown in fig. 3, the flow velocity sensor 1 includes a resin film 23 made of polypropylene resin, and the resin film 23 covers the entire first substrate surface 4, the resistors 2 and 3, and the entire second substrate surface 5. A metal foil 24 made of stainless steel is disposed over the entire area of the resin film 23. The resin film 23 and the metal foil 24 enter the holes 21 and 22 of the substrate 6 from the first substrate surface 4 side.

As shown in fig. 4, the resistor 2 for heat generation and the resistor 3 for temperature compensation of the flow sensor 1 constitute a known voltage divider circuit together with chip-like resistors 31 and 32. The signal processing unit 33, which is not shown in fig. 1 to 3, includes resistors 31 and 32, an operational amplifier 34, a transistor 35, and the like (illustration of other components of the signal processing unit 33 is omitted). Here, the Temperature Coefficient of Resistance (TCR) of the heating resistor 2 and the temperature compensation resistor 3 is larger than the TCR of the resistors 31, 32.

Here, air is blown toward the first substrate surface 4 side of the insulating substrate 6 of the fan flow velocity sensor 1. This lowers the temperature of the heating resistor 2. The signal processing unit 33 applies a drive voltage to the bridge circuit shown in fig. 4 so that the temperature difference between the heating resistor 2 and the temperature compensation resistor 3 is always constant. The flow velocity sensor 1 converts the change in voltage required for heating into a flow velocity (wind velocity, etc.) of the fluid and outputs the flow velocity. The intensity of the outputted flow velocity (wind velocity, etc.) is expressed by the Light quantity or Light emission color of an LED (Light Emitting Diode), for example. For example, the faster the flow velocity, the larger (brighter) the amount of light of the LED is represented, and the slower the flow velocity, the smaller (darker) the amount of light of the LED is represented, or the flow velocity is displayed as a specific numerical value.

(Main Effect obtained by the embodiment of the present invention)

As described above, the heat generating portions 2h and 3h of the resistors 2 and 3 of the flow rate sensor 1 according to the embodiment of the present invention are arranged to face the second substrate surface 5 that is not exposed to the fluid. Therefore, the resistors 2 and 3 are shielded by the substrate 6 from being exposed to the fluid, and thus the flow rate sensor 1 having excellent weather resistance can be provided. Even in the flow velocity sensor 1 having the structure in which the holes 21 and 22 of the substrate 6 are closed, the function thereof can be maintained by heat dissipation from the terminal portions of the resistors 2 and 3 to the pads 11a, 12a, 13a, 14a, and the like. However, in the case where the holes 21 and 22 are not provided, it is preferable to secure good heat conduction by interposing a heat conductive adhesive, a heat conductive film, or the like between the heat generating portions 2h and 3h of the resistors 2 and 3 and the substrate 6. Further, by using a film-like substrate or a thin plate substrate having a thickness of 0.1mm as the substrate 6, heat transfer in the thickness direction of the substrate 6 becomes easy, and even in the flow rate sensor 1 in which the holes 21 and 22 are closed, sensitivity can be maintained.

Further, the following flow velocity sensor 1 can be obtained: the components such as the resistors 2 and 3 of the flow sensor 1 and the wires 11, 12, 13, and 14 can operate so as not to contact the fluid to be measured. Further, the flow sensor 1 can be manufactured by a general printed circuit board manufacturing process such as reflow soldering, which advances cost reduction, without requiring a costly process such as metal grinding or resin molding. Further, the flow velocity sensor 1 is thin, easy to handle, and high in weather resistance, and therefore, can be expected to be used for various new applications.

Further, by providing the holes 21 and 22 in the substrate 6, the fluid is brought into direct contact with the heat generating portions 2h and 3h, and thus the sensitivity of the flow velocity sensor 1 is improved. Here, even if the holes 21, 22 are provided, the connection portions of the terminal electrodes 2a, 2b, 3a, 3b of the resistors 2, 3 and the pads 11a, 12a, 13a, 14a for connecting these terminal electrodes are still shielded by the substrate 6 and are not exposed to the fluid, so that the weather resistance of the flow rate sensor 1 can be ensured.

Further, since the fluid and the resistors 2 and 3 are in contact with each other through the holes 21 and 22, the difference in the flow direction of the fluid hardly affects the thermal conductivity, and the directivity of the flow velocity sensor 1 is good. In addition, the main cause of the difference in sensitivity of the flow velocity sensor 1 is the difference between whether the flow direction of the fluid coincides with the long side direction or the short side direction of the resistors 2, 3. Therefore, an actual measurement value of the sensitivity deviation with respect to the longitudinal direction or the short direction is measured. Thus, the sensitivity variation of the comparative sample in which the resistors 2 and 3 were mounted on the fluid side of the substrate 6 was-33%, whereas the sensitivity variation of the test sample of the present invention converged to-6%. The comparative sample and the test sample of the present invention were evaluated by blowing air to the substrate surface at an angle of elevation of from horizontal to 10 degrees, assuming that the resistors 2 and 3 had a size of 2.0mm × 1.25mm × 0.45mm, the substrate 6 had a thickness of 0.1mm, and the holes 21 and 22 had a size of 2.2mm × 1.0 mm. In addition, in the case where the holes 21 and 22 are not provided, the influence of the difference in the flow direction of the fluid can be made almost zero, and the directivity of the flow velocity sensor 1 can be further improved.

The flow velocity sensor 1 includes a resin film 23, and the resin film 23 covers all of the first substrate surface 4, the resistors 2 and 3, and all of the second substrate surface 5. Therefore, the flow velocity sensor 1 has further improved weather resistance against moisture, dust, and the like in the air. In addition, the circuit component can be protected from external factors, such as contact by a human hand, by the resin film 23.

Further, the metal foil 24 is disposed over the entire area of the resin film 23. Therefore, the flow velocity sensor 1 has further improved weather resistance against moisture, dust, and the like in the air. In addition, the flow rate sensor 1 can protect the resin film 23 from being damaged by mechanical impact or the like due to the presence of the metal foil 24. The adhesion of the resin film 23 or the metal foil 24 can be achieved by a technique which is provided at low cost, such as vacuum forming of a thermoplastic film, and the flow rate sensor 1 can be provided at lower cost.

(other means)

The flow velocity sensor 1 according to the embodiment of the present invention described above is an example of a preferred embodiment of the present invention, and is not limited to this, and various modifications can be made without departing from the spirit of the present invention.

For example, the holes 21 and 22 of the substrate 6 may be omitted. Even if the holes 21 and 22 of the substrate 6 are not provided, the functions can be maintained by heat dissipation from the terminal portions of the resistors 2 and 3 to the pads 11a, 12a, 13a, 14a, and the like. However, in the case where the holes 21 and 22 are not provided, it is preferable to secure good heat conduction by interposing a heat conductive adhesive, a heat conductive film, or the like between the heat generating portions 2h and 3h of the resistors 2 and 3 and the substrate 6. The holes 21 and 22 have the same shape, and are each formed in an oblong shape elongated in a direction orthogonal to the current flowing direction of the resistors 2 and 3. However, the shape of the holes 21, 22 may also be different. The shape of the holes 21 and 22 may not be an oblong long in the direction orthogonal to the current flowing direction of the resistors 2 and 3, and may be, for example, a circle or a polygon. Further, by using a film-like substrate or a thin plate substrate having a thickness of 0.1mm as the substrate 6, heat transfer in the thickness direction of the substrate 6 becomes easy, and even in the flow rate sensor 1 in which the holes 21 and 22 are closed, sensitivity can be maintained.

The substrate 6 is a resin thin substrate having a thickness of 0.1 mm. However, the thickness of the substrate 6 is not limited in many cases, since exceeding 0.1mm does not greatly affect the function of the flow rate sensor 1. In place of the substrate 6, a film-like substrate or a thin-plate substrate having a thickness of 1mm or less can be used. The thinner the thickness of the substrate 6 is, the more likely it is to exert a good influence on the design aspect of the flow rate sensor 1. If the flow sensor 1 is thin as a whole, the flow sensor 1 is likely to be thin and cool. The substrate 6 is made of resin, but may be made of ceramic, epoxy resin mixed with glass fiber, or other printed wiring board, or may be made of an insulator covering the surface of a metal plate such as a stainless steel plate.

The flow velocity sensor 1 includes a resin film 23, and the resin film 23 covers the entire first substrate surface 4, the resistors 2 and 3, and the entire second substrate surface 5. However, the resin film 23 is not an essential component and can be omitted. Even if the resin film 23 is provided, it is not necessary to provide the resin film so as to cover the entire surfaces of the substrate 6 and the resistors 2 and 3. For example, the resin film 23 may cover a part or the whole of the first substrate surface 4 or a part or the whole of the second substrate surface 5. For example, the resin film 23 may be provided so as to cover a part or the whole of the first substrate surface 4 exposed to the fluid. In addition, the resin film 23 may be provided only at the electrical connection portions between the pads 11a, 12a, 13a, and 14a and the terminal electrodes 2a, 2b, 3a, and 3b of the resistors 2 and 3, or the resin film 23 may be provided so as to cover the electronic components and the wiring lines such as the wiring lines 11, 12, 13, and 14 and the resistors 2 and 3. However, in order to expect weather resistance of the flow velocity sensor 1 against moisture, dust, or the like in the air, it is preferable that the entire first substrate surface 4, the resistors 2 and 3, and the entire second substrate surface 5 be covered with the resin film 23. The material of the resin film 23 is polypropylene, but other resins such as polyethylene and polyethylene terephthalate can be used.

Further, a stainless metal foil 24 is disposed over the entire area of the resin film 23. However, the metal foil 24 is not an essential component and can be omitted. Even if the metal foil 24 is provided, the metal foil 24 can be provided only at the electrical connection points such as the pads 11a, 12a, 13a, and 14a and the terminal electrodes 2a, 2b, 3a, and 3b of the resistors 2 and 3, for example. The material of the metal foil 24 is not limited to stainless steel, and may be other metals. However, as the portions covering the resistors 2 and 3, a metal having high heat conductivity, such as copper, which excessively dissipates heat generated by the resistors 2 and 3 is not preferable, but may be used.

As shown in fig. 4, the signal processing unit 33 includes resistors 31 and 32, an operational amplifier 34, a transistor 35, and the like. Then, the signal processing unit 33 applies a drive voltage to the bridge circuit so that the temperature difference between the heating resistor 2 and the temperature compensation resistor 3 is always constant. It is known that this drive voltage is a function of the thermal conductivity and circuit constant that constrains the temperature rise of the resistor 2. Since the thermal conductivity is a function of the flow velocity, the signal processing unit 33 can determine both the flow velocity and the thermal conductivity corresponding thereto.

The intensity of the output flow velocity is expressed by, for example, the light quantity of the LED, the emission color, or the like. For example, a plurality of flow velocity sensors 1 can be arranged in a plane in a criss-cross regular manner to visualize the flow velocity distribution as in a thermal image of thermal imaging. The flat surface can be made of a material that is hard and hardly deformable, but the flat surface can also be made of a sheet or cloth-like material that is soft and deformable into a curved surface. Further, if the flow velocity sensors 1 are arranged in a one-dimensional straight line, a ruler shape or the like in which the wind velocity can be seen can be formed. Further, if a plurality of flow velocity sensors 1 are provided on a three-dimensional mesh support body such as a play item called a climbing rack provided in a park, the distribution of the flow can be visualized or informationized without obstructing the flow by an opening sufficiently large with respect to the thickness of the support body. The flow rate sensor 1 may be disposed in a size such as a diameter of the support body of 3cm and an interval of 50cm, for example, and is not limited thereto. Further, it is also possible to arrange a plurality of flow velocity sensors 1 to obtain a flow velocity distribution by chance of natural wind or a flow velocity distribution by fan of a person or the like, and to control the scale, timbre, natural sound, and the like using the information.

In addition, by displaying the fluctuation of the air of the environment or the appearance of the wind by the flow velocity sensor 1, it is possible to construct, for example, the following spatial art: the light flashes in conjunction with the movement of the leaves of the plant to show changes such as sunlight penetrating the leaves, resulting in a calming or relaxing effect that is not available with preprogrammed expression. Further, illumination for performing a performance by using the flow velocity and the wind speed can be realized by the flow velocity sensor 1. As an example of performance, the rotational speed of a blade of a wind turbine itself, or an image, light, or the like of the blade of the wind turbine can be projected to a wall surface of a building by using a projection mapping technique or the like, and changed according to the wind speed. In addition, as another example of the performance, it is possible to detect the motion of a person, an object, or a living body as a wind speed to respond to the motion. As another example of the performance, the flow velocity sensor 1 may be attached to the surface of a moving object, and the moving speed of the object may be indirectly expressed as a wind speed or the like.

As another example of the performance, the following electronic candle can be obtained: the color, shape, and size of the light of the LED of the flow sensor 1 are different from those of a real candle, and the danger of the flame is not felt at a glance, but the characteristics of the change in the light emission form such as fluctuation suggest a candle, and thus high entertainment properties of the candle can be realized. For example, the light intensity of the LED of the flow velocity sensor 1 is set to be small as 1mm or large as 1 m. The color of the light of the LED of the flow rate sensor 1 is, for example, a candle color that flickers slightly in a breeze and looks like a candle, but only in a strong wind, the light is emitted in a color different from the candle color such as blue or red and with strong brightness. For the dramatic appearance, for example, a behavior such as a candle decorated on a birthday cake, which is sequentially turned off when the air is blown, or which is turned on again although it is soon turned off, can be performed by linking the blinking of the plurality of light sources with the movement of the air. Further, the wind speed distribution information may be stored and transmitted in association with video or audio information, and the associated wind speed distribution information may be provided when video or audio is reproduced in the real world or in the virtual space.

Further, an electronic wind chime or the like placed in a closed space that reacts to wind detected by the flow velocity sensor 1 placed outside the closed space can be obtained. Further, a device (flow rate sensor 1) capable of estimating the degree of difficulty of change in the surface state such as the degree of difficulty of drying the paint or food from the temperature and the thermal conductivity can be obtained.

In addition, it is sometimes necessary to give an important consideration to properties such as the atmosphere and the grade of the flow rate sensor 1. In this case, the substrate 6, the resin film 23, or the metal foil 24 may be designed to have an appearance not directly related to the flow velocity detection function. For example, the following considerations are made on the aforementioned appearance design: the aforementioned design includes various design elements such as natural wood grains, leaf patterns, wallpaper patterns, irregularities, contours, or heart marks imitating them, etc., and the flow sensor 1 exists in these design elements as a whole so as not to damage the atmosphere of the environment. Alternatively, the aforementioned appearance design is considered as follows: by making the flow rate sensor 1 exist in these design elements, the atmosphere of the environment is actively improved. By this design, a fashionable flow rate sensor 1 is realized.

(modification example)

Fig. 5 is a diagram showing a modification of flow rate sensor 1 shown in fig. 3 according to the embodiment of the present invention. The flow velocity sensor 41 of the modified example has the same structure as the flow velocity sensor 1 except for the cover member 42. Therefore, in the flow rate sensor 41, substantially the same components as those of the flow rate sensor 1 are denoted by the same reference numerals, and description thereof is omitted. Fig. 6 is a perspective view of the cover member. In the flow velocity sensor 41 of the modification, a cover member 42 made of stainless steel and having a thickness of 1mm covering the second substrate surface 5 is fixedly attached to an end 43 of the quadrangular portion of the substrate 6 of the flow velocity sensor 41 by an adhesive or the like.

By fixedly attaching the cover member 42 to the flow velocity sensor 41, the electronic components and the wiring such as the wirings 11, 12, 13, and 14 and the resistors 2 and 3 of the second substrate surface 5 are further covered, and weather resistance is further improved.

The cover member 42 is made of stainless steel, but may be made of other metals, resins, or ceramics. In addition, the thickness of the cover member 42 is 1mm, but may be thicker or thinner. In view of appearance, the thickness of the cover member 42 is preferably smaller, for example, 0.7 mm. In addition, when the cover member 42 is fixedly attached to the flow rate sensor 41, an adhesive tape or the like may be used instead of the adhesive, or both the adhesive and the adhesive may be used.

The internal space surrounded by the cover member 42 and the substrate 6 may be filled with a heat insulating material such as foamed plastic. This further improves the mechanical strength of the flow rate sensor. The flow rate sensor 41 may be filled with the above-described filled heat insulating material without the cover member 42.

The resin film 23 may be any insulating film, and may be, for example, only a glass film or a film obtained by laminating a glass film and the resin film 23.

Description of the reference numerals

1. 41: a flow rate sensor; 2: resistors (for heating); 2 h: a heat generating portion; 3: resistors (for temperature compensation); 3 h: a heat generating portion; 4: a first substrate surface; 5: a second substrate surface; 6: a substrate; 23: a resin film; 24: a metal foil; 33: a signal processing unit; 42: a cover member.