Physical quantity sensor and physical quantity detection device

Abstract

To provide a physical quantity sensor and a physical quantity detection device that prevent tilting of a weight and exhibit small variation in detection sensitivity.SOLUTION: A physical quantity sensor 10 comprises a base portion 21, a support portion 22 that supports the base portion 21, a plate-shaped movable portion 24 extending in one direction from the base portion 21 via a hinge portion 23, a physical quantity detection element 40 joined to the base portion 21 and the movable portion 24 across the hinge portion 23, a package 50 that supports the support portion 22 at a fixed region 25, and a weight 30 having a pair of recessed portions 32 each recessed toward a center of gravity 80 of a weight portion 31 when viewed in a direction perpendicular to a main surface 24a of the movable portion 24.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a physical quantity sensor and a physical quantity detection device. [Background technology]

[0002] For example, Patent Document 1 discloses a physical quantity detection device including a base having a fixed part and a movable part extending along a first direction via a joint part on the fixed part and displacing in response to a change in physical quantity, a physical quantity detection element that is fixed across the fixed part and the movable part and detects the physical quantity in response to displacement of the movable part, a weight part provided on the movable part, and a pillow part that is provided with a gap from the base and is arranged so that at least a part of the movable part or the weight part overlaps in a plan view seen from the direction in which the movable part is displaced. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-145755 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the physical quantity detection device described in Patent Document 1, when the weight is fixed to the movable part of the base, the weight is pinched with tweezers or the like to fix it to the movable part, so there is a risk that the weight will be fixed tilted and deviated from the first direction. If the weight is tilted, for example, the weight will adhere to the adhesive that fixes the base to which the weight is fixed to the package, resulting in deterioration or variation in detection sensitivity. [Means for solving the problem]

[0005] The physical quantity sensor includes a base, a support portion that supports the base, a plate-shaped movable portion that extends in one direction from the base via a hinge portion, a physical quantity detection element that straddles the hinge portion and is joined to the base and the movable portion, a package that supports the support portion in a fixed region, and a weight having a pair of recesses that are each recessed toward the center of gravity of the weight portion when viewed in a direction perpendicular to the main surface of the movable portion.

[0006] A physical quantity detection device includes the above-described physical quantity sensor and a processing circuit that drives the physical quantity sensor and processes a detection signal. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a plan view showing a schematic structure of a physical quantity sensor according to a first embodiment. [Figure 2] Cross-sectional view taken along line AA in Figure 1. [Figure 3] FIG. 2 is a plan view showing a schematic structure of a weight included in the physical quantity sensor according to the first embodiment. [Figure 4] FIG. 10 is a plan view showing a schematic structure of a weight included in a physical quantity sensor according to a second embodiment. [Figure 5] FIG. 10 is an exploded perspective view of a physical quantity detection device according to a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] 1. First embodiment 1.1.Physical Quantity Sensor First, an acceleration sensor that detects acceleration in the vertical direction will be taken as an example of the physical quantity sensor 10 according to the first embodiment and will be described with reference to Figures 1, 2, and 3. Note that Figure 1 illustrates a state in which the lid 70 is removed for the convenience of explaining the internal configuration of the physical quantity sensor 10.

[0009] For ease of explanation, the following plan views, cross-sectional views, and exploded perspective views illustrate three mutually perpendicular axes: the X-axis, the Y-axis, and the Z-axis. The direction along the X-axis is referred to as the "X-direction," the direction along the Y-axis as the "Y-direction," and the direction along the Z-axis as the "Z-direction." The arrowed side of each axis is also referred to as the "plus side," and the opposite side as the "minus side." The plus Z-direction side is also referred to as the "upper side," and the minus Z-direction side as the "lower side."

[0010] The physical quantity sensor 10 of this embodiment can detect, as a physical quantity, acceleration in the Z direction, which is the vertical direction of the physical quantity detection element 40. Such a physical quantity sensor 10 includes a cantilever structure 20 to which the physical quantity detection element 40 and a weight 30 are fixed, a package 50 that houses the cantilever structure 20, and a lid 70 that serves as a cover for the package 50, as shown in FIGS.

[0011] The cantilever structure 20 is made of a quartz substrate and has a base 21, a support 22, and a cantilever. The cantilever has a hinge 23 and a movable part 24. The base 21 extends in the X direction, and three support parts 22 are connected to both ends in the X direction. Note that a support part 22 extending in the positive Y direction and a support part 22 extending in the negative Y direction are connected to the end of the base 21 on the positive X direction, and a support part 22 extending in the positive Y direction is connected to the end of the base 21 on the negative X direction.

[0012] The three support parts 22 support the base part 21, have their base ends connected to the base part 21, and are each provided with a fixing area 25 on the free end side that is fixed to the step part 51 of the package 50 via adhesive 61.

[0013] The hinge portion 23 is disposed between the base portion 21 and the movable portion 24 and connects the base portion 21 and the movable portion 24 together. The movable part 24 is a plate-like member extending in one direction, the positive Y direction, from the base part 21 via the hinge part 23. The movable part 24 is disposed between two support parts 22 extending from both ends of the base part 21 in the X direction to the positive Y direction.

[0014] The weight 30 is made of a metal such as SUS or copper, and is bonded to the upper and lower surfaces of the free end of the movable part 24 via an adhesive 62. Furthermore, the weight 30 has a pair of recesses 32, each recessed toward the center of gravity 80 of the weight part 31, as shown in FIG. 3 , when viewed in a direction perpendicular to the main surface 24a of the movable part 24. The pair of recesses 32 have a pair of bottoms 33 that are arranged such that the center of gravity 80 is located within a region connecting the pair of recesses 32 when viewed in a direction perpendicular to the main surface 24a of the movable part 24. The pair of bottoms 33 have surfaces 34 that are parallel to each other. The pair of recesses 32 are spaced apart from the fixed region 25 of the support part 22 when viewed in a direction perpendicular to the main surface 24a of the movable part 24.

[0015] Because bottoms 33 of the pair of recesses 32 are positioned to sandwich center of gravity 80 of weight portion 31, when weight 30 is pinched with tweezers or the like and fixed to movable portion 24, weight 30 can be lifted in a well-balanced manner and placed accurately on movable portion 24, reducing the likelihood of weight 30 being fixed at an angle. This reduces the likelihood of adhesive 61, which fixes cantilever structure 20 to package 50, adhering to weight 30 and variations in detection sensitivity, which occur when weight 30 tilts.

[0016] The physical quantity detection element 40 is configured, for example, by a double-ended tuning fork type quartz crystal oscillator, and detects physical quantities such as acceleration and pressure. The physical quantity detection element 40 is disposed across the hinge part 23, and is bonded to the base part 21 and the movable part 24 via an adhesive 63.

[0017] When the movable part 24 is displaced in response to acceleration, with the hinge part 23 as a fulcrum, stress is generated in the physical quantity detection element 40 attached to the base part 21 and the movable part 24. The resonant frequency, which is the vibration frequency of the physical quantity detection element 40, changes in response to the stress applied to the physical quantity detection element 40. Acceleration can be detected based on this change in the resonant frequency.

[0018] The package 50 is made of, for example, ceramic and has a step 51 that protrudes upward from an inner bottom 50a in the positive Z direction. The cantilever structure 20 is fixed to the package 50 by fixing the three fixing regions 25 of the cantilever structure 20 onto the step 51 via adhesive 61. A pair of internal terminals 52 are provided on the step 51 so as to sandwich the physical quantity detection element 40 located on the base 21. The internal terminals 52 are electrically connected via bonding wires 65 to electrode pads 41 that are electrically connected to excitation electrodes (not shown) for driving the physical quantity detection element 40. An external terminal 53 is provided on the surface of the inner bottom 50a opposite the lid 70 and is electrically connected to the internal terminals 52 via through electrodes and wiring (not shown).

[0019] A lid 70 is bonded to the top surface of the package 50 via a bonding member 60, forming a storage space 55 that houses the cantilever structure 20 to which the physical quantity detection element 40 and the weight 30 are fixed. A through-hole 54 for hermetically sealing the storage space 55 is provided in the inner bottom 50a, and a sealing member 64 is placed in the through-hole 54, heated to melt the sealing member 64, and then solidified to hermetically seal the storage space 55.

[0020] As described above, in the physical quantity sensor 10 of this embodiment, the weight 30 has a pair of recesses 32 that are recessed toward the center of gravity 80 of the weight portion 31 when viewed in a direction perpendicular to the main surface 24a of the movable portion 24. Therefore, when the weight 30 is fixed to the movable portion 24 by pinching it with tweezers or the like, the weight 30 can be lifted in a well-balanced manner and accurately positioned on the movable portion 24, thereby reducing the likelihood of the weight 30 being fixed at an angle. This reduces adhesion of the adhesive 61 that fixes the cantilever structure 20 to the package 50 to the weight 30 and variations in detection sensitivity that occur due to tilting of the weight 30. Therefore, the physical quantity sensor 10 can be obtained in which the weight 30 is accurately positioned and tilting of the weight 30 is reduced, suppressing increases in manufacturing costs, and reducing variations in detection sensitivity.

[0021] 2. Second embodiment Next, a physical quantity sensor 10a according to a second embodiment will be described with reference to FIG. FIG. 4 is a plan view showing the structure of a weight 30a in a physical quantity sensor 10a of the second embodiment.

[0022] The physical quantity sensor 10a of this embodiment is similar to the physical quantity sensor 10 of the first embodiment except that the structure of the recessed portion 32a of the weight 30a is different from that of the physical quantity sensor 10 of the first embodiment. Note that the following description will focus on the differences from the first embodiment described above, and similar items will be denoted by the same reference numerals and their description will be omitted.

[0023] 4, the weight 30a of the physical quantity sensor 10a is defined by a surface 34a inclined with respect to the direction connecting the bottom 33a of the recessed portion 32a when viewed in a direction perpendicular to the main surface 24a of the movable portion 24, and the center of gravity 80 is a point on the line connecting the recessed portions 32a. In other words, the pair of recessed portions 32a are tapered with a pair of points on the line connecting the recessed portions 32a when viewed in a direction perpendicular to the main surface 24a of the movable portion 24, where the center of gravity 80 is located, as vertices. In other words, the recessed portions 32a are recessed in a triangular shape, and the center of gravity 80 of the weight portion 31a is located on the line connecting the tip of the triangle of one recessed portion 32a to the tip of the triangle of the other recessed portion 32a.

[0024] The tips of the pair of recessed portions 32a are positioned to sandwich the center of gravity 80 of the weight portion 31a, so when the weight 30a is clamped with tweezers or the like and fixed to the movable portion 24, the weight 30a can be lifted in a balanced manner and placed accurately on the movable portion 24, thereby further reducing the risk of the weight 30a being fixed at an angle.

[0025] With this configuration, it is possible to obtain the same effect as the physical quantity sensor 10 of the first embodiment. Note that the shape of each of the pair of recesses 32a when viewed in a direction perpendicular to the main surface 24a does not need to be strictly triangular, and may be any shape that is inclined so as to guide tweezers or the like to the bottom portion 33a when gripping the weight 30a. In other words, the surface 34a may be a curved surface.

[0026] 3. Third embodiment Next, a physical quantity detection device 100 according to a third embodiment will be described with reference to FIG. 5, taking a device including three physical quantity sensors 10 as an example.

[0027] The physical quantity detection device 100 has three physical quantity sensors 10 and can detect physical quantities on three orthogonal axes. The physical quantity in the physical quantity detection device 100 of this embodiment is acceleration.

[0028] 5 , the physical quantity detection device 100 has three physical quantity sensors 10 mounted on a circuit board 110 having a processing circuit 111 that drives the physical quantity sensors 10 and processes detection signals. The three physical quantity sensors 10 are mounted on the circuit board 110 with their detection axes aligned with three orthogonal axes. The circuit board 110 is electrically connected to a connector board 120. The circuit board 110 and connector board 120 are housed and held in a package formed by a package base 130 and a lid 140.

[0029] As described above, the physical quantity detection device 100 of this embodiment is configured such that the three physical quantity sensors 10, each with the weight 30 precisely arranged, are mounted along three orthogonal axes that serve as detection axes, and therefore can detect acceleration along three axes with high precision. The same applies when the physical quantity detection device 100 includes three physical quantity sensors 10a. [Explanation of symbols]

[0030] 10, 10a...physical quantity sensor, 20...cantilever structure, 21...base, 22...support portion, 23...hinge portion, 24...movable portion, 24a...main surface, 25...fixing region, 30...weight, 31...weight portion, 32...recessed portion, 33...bottom, 34...surface, 40...physical quantity detection element, 41...electrode pad, 50...package, 50a...inner bottom portion, 51...step portion, 52...internal terminal, 53...external terminal, 54...through hole, 55...accommodation space, 60...bonding member, 61, 62, 63...adhesive, 64...sealing member, 65...bonding wire, 70...lid, 80...center of gravity, 100...physical quantity detection device, 110...circuit board, 111...processing circuit, 120...connector board, 130...package base, 140...lid body.

Claims

1. A base and a support portion that supports the base portion; a plate-shaped movable part extending in one direction from the base part via a hinge part; a physical quantity detection element joined to the base portion and the movable portion across the hinge portion; a package that supports the support portion at a fixed region; a weight having a pair of recessed portions each recessed toward the center of gravity of the weight portion when viewed in a direction perpendicular to the main surface of the movable portion, Physical quantity sensor.

2. the pair of recessed portions have a pair of bottom portions that are arranged such that the center of gravity is located within a region connecting the pair of bottom portions when viewed in a direction perpendicular to the main surface of the movable portion; The physical quantity sensor according to claim 1 .

3. The pair of bottoms are surfaces parallel to each other. The physical quantity sensor according to claim 2 .

4. the pair of recesses have a tapered shape with a pair of points on a line connecting the pair of recesses, at which the center of gravity is located, as vertices, when viewed in a direction perpendicular to the main surface of the movable part; The physical quantity sensor according to claim 1 .

5. the pair of recessed portions are spaced apart from the fixed region when viewed in a direction perpendicular to the main surface of the movable portion; The physical quantity sensor according to claim 1 .

6. The physical quantity sensor according to any one of claims 1 to 5; a processing circuit that drives the physical quantity sensor and processes a detection signal; Physical quantity detection device.

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