JP2024012731A - strain sensor - Google Patents

Abstract

To provide a strain sensor having a configuration that makes it easy to detect strain in an object.SOLUTION: A strain sensor according to one embodiment of the present invention detects strain in a strain body and comprises: a package substrate; a base substrate that is disposed on the package substrate and includes an electrical wiring unit; a sensor substrate that is disposed on the base substrate and includes a plurality of piezoresistive elements; and a mold resin that covers the base substrate and sensor substrate on the package substrate. The surface of the sensor substrate protrudes further than the surface of the mold resin, and the surfaces of the mold resin and sensor substrate are the surfaces that are attached to the strain body.SELECTED DRAWING: Figure 1

Description

The present invention relates to a strain sensor, and more particularly to a strain sensor that detects strain when force is applied to an object.

As a strain sensor, Patent Document 1 discloses a mechanical quantity measuring device that measures strain in a specific direction with a small error. In this mechanical quantity measuring device, in the silicon substrate of the semiconductor mechanical quantity measuring device, for example, the ratio of the substrate thickness to the substrate length in the measurement direction is made small, and the ratio of the substrate thickness to the substrate length in the direction perpendicular to the measurement direction is made small. is increasing.

Further, Patent Document 2 discloses a mechanical quantity measuring device that is less susceptible to noise effects and capable of highly accurate measurement even when circuit operating power is supplied by electromagnetic induction or microwaves. In this mechanical quantity measuring device, strain is measured by bonding the adhesive portion to the object to be measured.

Japanese Patent Application Publication No. 2006-003182 Japanese Patent Application Publication No. 2005-114443

In order to detect minute distortions in an object with high precision, it is necessary to effectively transmit the distortion of the strain body to the strain sensor. As the object becomes smaller, the area for attaching the strain sensor becomes more limited, making it more difficult to effectively transmit strain.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a strain sensor configured to easily detect distortion of an object.

One aspect of the present invention is a strain sensor that detects strain in a strain-generating body, the strain sensor comprising: a package substrate; a base substrate disposed on the package substrate; and a base substrate having an electrical wiring section; The sensor board includes a sensor board having a plurality of piezoresistive elements, and a molded resin that covers the base board and the sensor board on the package board, and the surface of the sensor board protrudes beyond the surface of the molding resin, and This strain sensor is characterized in that its surface serves as a mounting surface for a strain-generating body.

In this way, the surface of the sensor board protrudes beyond the surface of the molded resin, and the surface of the molded resin and the surface of the sensor board serve as attachment surfaces for the flexure element, allowing it to be firmly fixed to the flexure element around the sensor board. while making it easier to detect distortion from the flexure element.

In the strain sensor described above, the sensor substrate may be provided separately from the molded resin. In this way, by providing the protruding sensor board and the sealing mold resin separately, the part covered by the mold resin is fixed, making it easier for the sensor board to detect distortion. .

In the strain sensor described above, it is preferable that the Young's modulus of the sensor substrate is higher than the Young's modulus of the mold resin. Since the Young's modulus of the sensor substrate is higher than the Young's modulus of the mold resin, the mold resin is softer, so when it is distorted, it moves together with the strain body and becomes easily distorted.

In the strain sensor described above, it is preferable that the longitudinal direction of the sensor substrate be substantially parallel to the strain direction of the flexure element. In this way, the longitudinal direction of the sensor substrate is parallel to the strain direction of the strain body, making it easier to detect strain.

In the strain sensor described above, it is preferable that an adhesive layer is provided between the surface of the molded resin and the strain body. This allows the strain sensor to be fixed on the surface of the molded resin when attached to the strain body using the adhesive layer.

In the above strain sensor, an adhesive layer is provided between the surface of the molded resin and the flexure element, and between the surface of the sensor substrate and the flexure element, and the adhesive layer extends from the surface of the sensor substrate to the flexure element. The thickness of the adhesive layer is preferably thinner than the thickness of the adhesive layer from the surface of the mold resin to the flexure element. As a result, when the strain sensor is attached to the strain-generating body using the adhesive layer, the surface of the mold resin and the surface of the sensor board can be securely fixed, and the attenuation caused by the adhesive layer when strain is transmitted to the sensor board is suppressed. , it becomes easier to detect distortion.

In the strain sensor described above, a circuit board having a signal processing circuit for processing signals output from the sensor board may be provided between the package board and the base board. In this way, since the circuit board is also sealed with the molding resin, it is possible to protect the circuit board, and the circuit board is also housed in one package, so that the installation space can be reduced.

According to the present invention, it is possible to provide a strain sensor configured to easily detect distortion of an object.

FIG. 1 is a perspective view illustrating the configuration of a strain sensor according to the present embodiment. FIG. 1 is a cross-sectional view illustrating the configuration of a strain sensor according to the present embodiment. FIG. 2 is an exploded perspective view illustrating a sensor board. FIG. 3 is a cross-sectional view illustrating a state in which a strain sensor is attached to a strain body. FIG. 3 is a schematic cross-sectional view illustrating the positional relationship between a displacement portion and a piezoresistive element. (a) and (b) are schematic diagrams illustrating the layout of piezoresistive elements. (a) and (b) are schematic diagrams illustrating the layout of piezoresistive elements. (a) and (b) are schematic diagrams illustrating the layout of piezoresistive elements. FIG. 3 is a diagram showing the relationship between the exposed height of a sensor substrate and the amount of sensor distortion in a strain sensor. (a) to (e) are schematic diagrams illustrating exposed states of the sensor substrate.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description, the same members are given the same reference numerals, and the description of the members that have been described once will be omitted as appropriate.

(Strain sensor configuration)
FIG. 1 is a perspective view illustrating the configuration of a strain sensor according to this embodiment.
FIG. 2 is a cross-sectional view illustrating the configuration of the strain sensor according to this embodiment.
FIG. 3 is an exploded perspective view illustrating the sensor board.
Note that FIG. 1 shows a state in which the mold resin 40 is seen through. Further, in FIG. 2, a cross section taken along the line AA shown in FIG. 1 is shown. Further, FIG. 3A shows an exploded perspective view of the sensor board 30 from the front side, and FIG. 3B shows an exploded perspective view of the sensor board 30 from the back side.

This embodiment is a strain sensor 1 that detects strain in a strain body, and includes a package substrate 10, a base substrate 20, a sensor substrate 30, and a mold resin 40. In the description of the embodiment, the normal direction of the board mounting surface 10a of the package substrate 10 is referred to as the Z direction, one of the directions orthogonal to the normal direction (Z direction) is referred to as the X direction, and the other direction is referred to as the Y direction. do.

The package substrate 10 is a part that constitutes the appearance of the strain sensor 1 together with the mold resin 40, and is a substrate provided on the bottom side of the strain sensor 1. The size of the package substrate 10 in plan view in the Z direction is about 2 millimeters (mm) long x about 2 mm wide.

The package substrate 10 has a substrate mounting surface 10a on which the base substrate 20 is mounted, and a pad surface 10b provided on the opposite side to the substrate mounting surface 10a. A pad portion 16 is provided on the extended surface of the board mounting surface 10a of the package substrate 10. A plurality of electrode terminals 11 are provided on the pad surface 10b of the package substrate 10 in order to obtain electrical continuity with the outside. Connection and conduction with the outside (for example, flexible substrate F (see FIG. 4 described later)) are performed through this electrode terminal 11.

The base substrate 20 is placed on the package substrate 10 (stacked in the Z direction). The base substrate 20 has a sensor mounting surface 20a on which the sensor substrate 30 is mounted. Furthermore, the base substrate 20 has an electrical wiring section 25 that is electrically connected to each of the plurality of piezoresistive elements 35 provided on the sensor substrate 30.

The sensor substrate 30 is placed on the base substrate 20 (stacked in the Z direction). The sensor substrate 30 has a displacement section 31 and a piezoresistive element 35. The sensor substrate 30 has a substantially rectangular shape when viewed from above in the Z direction, and a displacement portion 31 is provided in the center portion. The displacement portion 31 is a portion that is displaced in response to distortion of the strain-generating body 100, and is provided on the surface of the sensor substrate 30 on the base substrate 20 side. The piezoresistive element 35 is an element that electrically detects the amount of displacement of the displacement portion 31.

A circuit board 50 may be provided between the package board 10 and the base board 20. The circuit board 50 has a signal processing circuit (signal processing IC) that processes the signal output from the sensor board 30. When the circuit board 50 is provided, the base board 20 and the circuit board 50 are electrically connected through the first bonding wire 61, and the circuit board 50 and the package board 10 are electrically connected through the second bonding wire 62.

The mold resin 40 is a sealing resin that covers the base substrate 20 and the sensor substrate 30 on the package substrate 10. The mold resin 40 may be made of only resin, or may include a filler component made of an inorganic material or the like. The mold resin 40 is a part that constitutes the appearance of the strain sensor 1 together with the package substrate 10. When the circuit board 50 is provided, the circuit board 50 is covered with the mold resin 40 along with the base board 20 and the sensor board 30.

In the strain sensor 1 according to the present embodiment having such a configuration, the surface 30a of the sensor substrate 30 protrudes from the surface 40a of the molded resin 40, and the surface 40a of the molded resin 40 and the surface 30a of the sensor substrate 30 are strained. This serves as a mounting surface for the body 100 (see FIG. 4, which will be described later). In this way, the surface 30a of the sensor substrate 30 protrudes beyond the surface 40a of the molded resin 40, and the surface 40a of the molded resin 40 and the surface 30a of the sensor substrate 30 serve as attachment surfaces for the flexure element 100. To make it easier to detect distortion from the strain body 100 while firmly fixing the area around the strain body 30 to the strain body 100.

Further, in the strain sensor 1 according to the present embodiment, it is preferable that the sensor substrate 30 is provided separately from the mold resin 40. This makes it difficult for the deformation of the sensor substrate 30 and the deformation of the molded resin 40 to interfere with each other, so that the sensor substrate 30 can easily detect distortion even if the portion covered with the molded resin 40 is fixed.

Further, it is preferable that the Young's modulus of the sensor substrate 30 is higher than that of the mold resin 40. Since the Young's modulus of the sensor substrate 30 is higher than that of the mold resin 40, the mold resin 40 is softer, and when the strain body 100 is distorted, the mold resin 40 moves with it. It becomes easier to distort, and the sensor board 30 can easily detect the distortion. Furthermore, when the sensor substrate 30 deforms in accordance with the strain of the strain-generating body 100, the mold resin 40 is less likely to act as deformation resistance. Here, when the sensor substrate 30 is made of a semiconductor such as silicon, its Young's modulus is 100 GPa or more, so the Young's modulus of the mold resin 40 is preferably 20 GPa or less, and 10 GPa or less. It is more preferable that there be. In other words, the Young's modulus of the mold resin 40 is preferably 20% or less, more preferably 10% or less, relative to the Young's modulus of the sensor substrate 30.

(Attachment state of strain sensor to strain body)
FIG. 4 is a cross-sectional view illustrating a state in which the strain sensor is attached to the strain body.
The strain sensor 1 according to this embodiment is attached to the surface of the strain-generating body 100 using, for example, an adhesive layer 80. The adhesive layer 80 is made of, for example, a resin material, and is provided between the surface 40a of the molded resin 40 and the strain body 100. Since the area of the surface 40a of the molded resin 40 is wider than the area of the surface 30a of the sensor substrate 30, the surface 40a is bonded to the flexure element 100 by the adhesive layer 80, thereby making the strain sensor 1 a flexure element. You can now firmly fix it to 100.

In the strain sensor 1 according to the present embodiment, the longitudinal direction (for example, the X direction) of the sensor substrate 30 is preferably substantially parallel to the strain direction SD of the strain body 100. This makes it easier for the strain body 100 to be distorted by the sensor substrate 30, making it easier for the strain sensor 1 to detect strain.

Further, the adhesive layer 80 may be provided between the surface 30a of the sensor substrate 30 protruding from the surface 40a of the molded resin 40 and the strain body 100. A portion of the adhesive layer 80 between the surface 30a of the sensor substrate 30 and the strain body 100 is referred to as a first portion 80a, and a portion between the surface 40a of the molded resin 40 and the strain body 100 is referred to as a second portion 80b. The thickness t1 of the first portion 80a (the thickness t1 of the adhesive layer 80 from the surface 30a of the sensor substrate 30 to the strain body 100) is the thickness t2 of the second portion 80b (the thickness t1 from the surface 40a of the molded resin 40). It becomes thinner than the thickness t2) of the adhesive layer 80 up to the strained body 100.

Thereby, when the strain sensor 1 is attached to the strain body 100 using the adhesive layer 80, the functions of the adhesive layer 80 can be separated. That is, since the second portion 80b of the adhesive layer 80 located between the surface 40a of the molded resin 40 and the surface of the flexure element 100 is relatively thick, the strain sensor 1 can be securely attached to the flexure element 100. Can be fixed. When the strain-generating body 100 is distorted, the relatively thick second portion 80b can absorb the distortion and suppress separation between the second portion 80b and the mold resin 40. Moreover, since the mold resin 40 has a lower Young's modulus than the sensor substrate 30, even if the strain from the strain-generating body 100 is transmitted to the mold resin 40, the mold resin 40 can absorb this strain.

On the other hand, since the first portion 80a of the adhesive layer 80 located between the surface 30a of the sensor substrate 30 and the surface of the flexure body 100 is relatively thin, when the strain of the flexure body 100 is transmitted to the sensor substrate 30, the first portion 80a of the adhesive layer 80 is relatively thin. Attenuation is difficult to occur in the first portion 80a, and the distortion can be easily detected by the piezoresistive element 35 of the sensor substrate 30. Moreover, since the Young's modulus of the molded resin 40 located around the sensor substrate 30 is lower than that of the sensor substrate 30, the molded resin 40 resists deformation while the sensor substrate 30 deforms in accordance with the strain of the strain-generating body 100. It's hard to be. In this way, by making the thickness of the first portion 80a and the second portion 80b of the adhesive layer 80 different, even if the strain sensor 1 is downsized and its mounting area to the strain body 100 is reduced, The strain sensor 1 is unlikely to fall off when the strain body 100 is distorted, and the strain of the strain body 100 can be appropriately detected on the sensor substrate 30.

Note that the hardness of the adhesive layer 80 may be different between the first portion 80a and the second portion 80b. In this case, it is preferable to make the adhesive layer 80 of the first portion 80a harder than the adhesive layer 80 of the second portion 80b. This makes it easier for the sensor substrate 30 to detect the distortion of the strain-generating body 100 via the hard adhesive layer 80. The hardness of the adhesive layer 80 can be adjusted as appropriate by changing its components, for example by including a hard filler component in addition to the resin component.

On the other hand, from a manufacturing standpoint, it is preferable to use the same adhesive layer 80 for the first portion 80a and the second portion 80b. In this case, the hardness of the adhesive layer 80 is the same in the first portion 80a and the second portion 80b. In this embodiment, the thickness t1 of the adhesive layer 80 of the first portion 80a is thinner than the thickness t2 of the adhesive layer 80 of the second portion 80b. Even if the hardness of the adhesive layer 80 in both parts is the same, the buffering effect of the adhesive layer 80 is weak until the strain from the strain-generating body 100 is transmitted to the sensor substrate 30, making it easier to detect the strain. .

In particular, since the strain sensor 1 according to the present embodiment is minute in plan view size (package board 10 size) of about 2 mm in length and width, the strain sensor 1 is attached to the strain body 100 by a fastening member such as a bolt. Since it is difficult to fix, adhesive fixation using the adhesive layer 80 is advantageous. Fixing the strain sensor 1 to the strain body 100 using the adhesive layer 80 requires a sufficient adhesive area. In the strain sensor 1 according to the present embodiment, even when the strain sensor 1 is fixed to the strain body 100 using one type of adhesive layer 80, which is advantageous in manufacturing, the strain sensor 1 can be securely fixed to the strain body 100. It is possible to achieve both this and highly sensitive strain detection by the strain sensor 1.

(Example layout of piezoresistive element)
Next, a layout example of the piezoresistive element 35 used in the strain sensor 1 according to the present embodiment will be described.
FIG. 5 is a schematic cross-sectional view illustrating the positional relationship between the displacement portion and the piezoresistive element.
A seal 26 is provided between the base substrate 20 and the sensor substrate 30. The seal 26 is made of metal such as gold or silver, and serves to support the sensor substrate 30 on the base substrate 20 and to make electrical connections. A displacement portion 31 is provided in a region inside the seal 26 on the surface of the sensor substrate 30 on the base substrate 20 side. In the strain sensor 1, the plurality of piezoresistive elements 35 are arranged inside the displacement section 31.

6 to 8 are schematic diagrams illustrating layouts of piezoresistive elements.
6 to 8, each (a) shows a layout of the piezoresistive element 35 in a plan view, and (b) shows a circuit diagram of the piezoresistance element 35.

The sensor substrate 30 has a substantially rectangular shape in plan view, and the displacement portion 31 is disposed in the center portion. The illustrated arrow indicates the strain direction SD. When the sensor substrate 30 has a substantially rectangular shape, the distortion can be easily detected by making the longitudinal direction (for example, the X direction) substantially parallel to the distortion direction SD.

FIGS. 6A and 6B show an example in which a full bridge is formed by a plurality of piezoresistive elements 35. Further, FIGS. 7A and 7B and FIGS. 8A and 8B show examples in which a half bridge is formed by a plurality of piezoresistive elements 35.

In each example, the piezoresistive elements 35 constitute four element groups 35G (first element group 35G1, second element group 35G2, third element group 35G3, and fourth element group 35G4). One element group 35G is provided with three piezoresistive elements 35, each arranged in parallel in the same direction and electrically connected in series. For example, in FIG. 6, the first element group 35G1 includes three piezoresistive elements 35 extending in the Y direction and connected in series. The relative arrangement of the four element groups 35G on the sensor substrate 30 is as follows. That is, the first element group 35G1 is arranged at the upper left, the second element group 35G2 is arranged at the upper right, the third element group 35G3 is arranged at the lower left, and the fourth element group 35G4 is arranged at the lower right.

In the example shown in FIG. 6A, the piezoresistive elements 35 of the first element group 35G1 and the fourth element group 35G4 are arranged in a direction perpendicular to the strain direction SD, and the piezoresistive elements 35 of the second element group 35G2 and the third element group 35G3 A piezoresistive element 35 is arranged in the strain direction SD.

As shown in FIG. 6(b), to configure a full bridge, the first element group 35G1 and the third element group 35G3 are connected in series, and the second element group 35G2 and the fourth element group 35G4 are connected in series. Conduct. The first element group 35G1 and the third element group 35G3 are electrically connected in parallel to the second element group 35G2 and the fourth element group 35G4. The power supply voltage VDD is applied between the first element group 35G1 and the second element group 35G2, and the ground potential GND is applied between the third element group 35G3 and the fourth element group 35G4. Further, the output potential V1 is between the first element group 35G1 and the third element group 35G3, and the output potential V2 is between the second element group 35G2 and the fourth element group 35G4.

In the example shown in FIG. 7(a), the piezoresistive elements 35 of the first element group 35G1 are arranged in a direction perpendicular to the strain direction SD, and the piezoresistive elements 35 of the first element group 35G1, the third element group 35G3, and the fourth element group 35G4 A piezoresistive element 35 is arranged in the strain direction SD.

As shown in FIG. 7(b), to configure a half bridge, the first element group 35G1 and the second element group 35G2 are connected in series, and the third element group 35G3 and the fourth element group 35G4 are connected in series. Conduct. Of the series connection of the first element group 35G1 and the second element group 35G2, the second element group 35G2 side has the power supply voltage VDD, and the first element group 35G1 has the output potential V1. Moreover, of the series connection of the third element group 35G3 and the fourth element group 35G4, the fourth element group 35G4 side becomes the ground potential GND. In this half-bridge configuration, the first element group 35G1 and the second element group 35G2 are reference resistors, and the third element group 35G3 and fourth element group 35G4 are sensor resistors.

In the example shown in FIG. 8A, the piezoresistive elements 35 of the first element group 35G1 and the second element group 35G2 are arranged in a direction perpendicular to the strain direction SD, and the piezoresistive elements 35 of the third element group 35G3 and the fourth element group 35G4 A piezoresistive element 35 is arranged in the strain direction SD.

As shown in FIG. 8(b), to configure a half bridge, the first element group 35G1 and the second element group 35G2 are connected in series, and the third element group 35G3 and the fourth element group 35G4 are connected in series. Conduct. Of the series connection of the first element group 35G1 and the second element group 35G2, the second element group 35G2 side has the power supply voltage VDD, and the first element group 35G1 has the output potential V1. Moreover, of the series connection of the third element group 35G3 and the fourth element group 35G4, the fourth element group 35G4 side becomes the ground potential GND. In this half-bridge configuration, the resistance values of the first element group 35G1 and the second element group 35G2 decrease with respect to strain, and the resistance values of the third element group 35G3 and the fourth element group 35G4 increase. Therefore, the half-bridge configuration shown in FIG. 8 has a larger output value than the half-bridge configuration shown in FIG. 7.

(Characteristics of strain sensor)
Next, the characteristics of the strain sensor according to this embodiment will be explained.
FIG. 9 is a diagram showing the relationship between the exposed height of the sensor substrate and the amount of sensor distortion in the strain sensor.
In FIG. 9, the horizontal axis indicates the exposed height (micrometers: μm) of the surface 30a of the sensor substrate 30 from the surface 40a of the mold resin 40, and the vertical axis indicates the amount of strain (microstrain: μst). The amount of strain on the vertical axis is a simulation result of the amount of strain on the sensor substrate 30 when 14.3 kilonewtons (kN) is applied to the strain body 100 in the X direction.
FIGS. 10A to 10E are schematic diagrams illustrating the exposed state of the sensor substrate.
The exposed states of the sensor substrate 30 shown in FIGS. 10(a) to 10(e) correspond to the exposed heights at the plot positions shown in FIGS. 9(a) to 9(e).

Here, the exposed height of the sensor substrate 30 is set by changing the thickness of the molding resin 40 without changing the thickness of the sensor substrate 30. Further, the thickness of the adhesive layer 80 between the surface 40a of the mold resin 40 and the strain-generating body 100 is constant at 0.11 millimeters (mm).

As a result of the simulation, the amount of distortion was 34.0 μst at the exposure height of −100 μm shown in FIGS. 9(a) and 10(a), and the amount of distortion was 34.0 μst at the exposed height of −50 μm shown in FIG. 9(b) and FIG. 10(b). The amount of distortion is 36.9 μst, and at the exposure height of 0 μm shown in FIGS. 5(c) and 6(c), the amount of distortion is 39.2 μst.

Further, the amount of distortion is 42.0 μst at the exposed height +50 μm shown in FIGS. 9(d) and 10(d), and the amount of distortion is 53.0 μst at the exposed height +100 μm shown in FIGS. 9(e) and 10(e). It is 0μst.

In this way, as the exposed height of the surface 30a of the sensor substrate 30 from the surface 40a of the mold resin 40 increases, the amount of distortion increases (the detection sensitivity increases), and when the exposed height exceeds +50 μm, the amount of distortion increases more. (detection sensitivity is further increased).

Note that if the thickness of the mold resin 40 is made too thin in order to increase the exposed height of the sensor substrate 30, the loop portion of the first bonding wire 61, etc. may be exposed from the mold resin 40. Therefore, it is desirable that the thickness of the molding resin 40 is such that the first bonding wire 61 is not exposed and the exposed height of the sensor substrate 30 is set high.

As described above, according to the present embodiment, the surface 30a of the sensor substrate 30 protrudes from the surface 40a of the molded resin 40, and the surface 40a of the molded resin 40 and the surface 30a of the sensor substrate 30 are the mounting surfaces for the strain body 100. This makes it easier for the sensor substrate 30 to detect strain from the strain body 100 while firmly fixing the sensor substrate 30 to the strain body 100 around the sensor substrate 30 . Therefore, it is possible to provide a strain sensor 1 that is configured to easily detect strain in the strain body 100.

Note that although the present embodiment has been described above, the present invention is not limited to these examples. For example, a person skilled in the art may appropriately add, delete, or change the design of each of the above-described embodiments, or may appropriately combine features of the configuration examples of each embodiment. As long as it has the following, it is included within the scope of the present invention.

1... Strain sensor 10... Package substrate 10a... Board mounting surface 10b... Pad surface 11... Electrode terminal 16... Pad portion 20... Base substrate 20a... Sensor mounting surface 25... Electrical wiring section 26... Seal 30... Sensor substrate 30a... Surface 31 ...Displacement portion 35...Piezoresistance element 35G...Element group 35G1...First element group 35G2...Second element group 35G3...Third element group 35G4...Fourth element group 40...Mold resin 40a...Surface 50...Circuit board 61...No. 1 bonding wire 62...Second bonding wire 80...Adhesive layer 80a...First portion 80b...Second portion 100...Strain element F...Flexible substrate GND...Ground potential SD...Distortion direction V1...Output potential V2...Output potential VDD ...Power supply voltage t1...Thickness of the first part t2...Thickness of the second part

Claims (7)

A strain sensor that detects strain in a flexure element,
a package board;
a base substrate disposed on the package substrate and having an electrical wiring section;
a sensor substrate disposed on the base substrate and having a plurality of piezoresistive elements;
a mold resin that covers the base substrate and the sensor substrate on the package substrate;
Equipped with
A strain sensor characterized in that a surface of the sensor substrate protrudes beyond a surface of the molded resin, and the surface of the molded resin and the surface of the sensor substrate serve as attachment surfaces for the strain body. The strain sensor according to claim 1, wherein the sensor substrate is provided separately from the molded resin. The strain sensor according to claim 1 or 2, wherein the Young's modulus of the sensor substrate is higher than the Young's modulus of the mold resin. The strain sensor according to any one of claims 1 to 3, wherein the longitudinal direction of the sensor substrate is substantially parallel to the strain direction of the flexure element. The strain sensor according to any one of claims 1 to 4, wherein an adhesive layer is provided between the surface of the molded resin and the strain body. An adhesive layer is provided between the surface of the mold resin and the flexure element, and between the surface of the sensor substrate and the flexure element,
The thickness of the adhesive layer from the surface of the sensor substrate to the flexure element is thinner than the thickness of the adhesive layer from the surface of the mold resin to the flexure element. The strain sensor according to any one of the above. 7. The circuit board according to claim 1, further comprising a circuit board having a signal processing circuit for processing a signal output from the sensor board, provided between the package board and the base board. Strain sensor.