JPH11281665A - Semiconductor acceleration sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor acceleration sensor which can be protected against damage due to dropping impact and can be assembled easily. SOLUTION: A rectangular prism weight 20 having a conical opening 30 is fixed at the free end of a rectangular prism cantilever sensor element 10 of silicon having a strain-sensitive part 60 for detecting acceleration in the vicinity of fixed end, and a conical rod 40 for regulating movement of the sensor element 10 is fixed to a supporting part 50 and inserted into the opening 30 of the weight 20. The gap (t) between the opening 30 and the rod 40 can be set easily at a specified value by controlling the inter-vertex distance (a) thereof accurately. When an undue acceleration is applied due to dropping impact, or the like, the sensor element 10 flexes to abut the opening 30 and the rod 40 thus protecting the sensor element 10 against damage.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is applied to an automobile, a robot, and the like.
The present invention relates to an acceleration sensor that measures acceleration such as inclination.

[0002]

2. Description of the Related Art In a conventional semiconductor acceleration sensor,
For example, there is one described in JP-A-1-10665.
FIG. 6 is a plan view of a conventional acceleration sensor. 6, a weight 20 is attached to one end of a silicon sensor element 10 having a strain-sensitive portion 60, and the movement of the sensor element is regulated by regulating members 21 and 22. In FIG. 6, the acceleration in the vertical direction of the paper is detected.
When an excessive acceleration is applied to the sensor element 10, the silicon sensor element 10 bends, and the slopes 21a and 22a of the regulating members 21 and 22 and the weight 20 are adjusted so that the displacement does not reach the breaking displacement of the sensor element 10. The contact restricts the movement of the sensor element 10 in the vertical direction on the paper surface, and has a structure in which a large stress is not generated in the bending portion, thereby preventing the sensor element 1 from being damaged at the time of a drop impact or the like.

FIG. 7 is a plan view of a conventional semiconductor acceleration sensor described in Japanese Patent Application Laid-Open No. 4-106766. When the sensor element 10 bends in response to vertical acceleration on the paper, the value of the diffusion resistance of the strain-sensitive section 60 attached to the sensor element 10 changes, and the acceleration is detected. 7, the package 300 and the pedestal 200 are provided with regulating members 310 and 210 for regulating the movement of the sensor element 10 with respect to the silicon sensor element 10 having the strain-sensitive portion 60. By restricting the movement of the sensor 10, the sensor element 10 does not have a large displacement at the time of a drop impact or the like.

[0004]

The conventional semiconductor acceleration sensor is configured as described above. For example, in FIG.
A surface like a, 22a must be made, and it has a complicated structure. Further, the contact surface between the weight portion 20 and the regulating members 21 and 22
The distance between 21a and 22a must be limited to within the breaking displacement of the sensor element 10.

[0005] For example, in the example of FIG.
If the sensor element 10 has a length of 1 mm, the weight of the weight 20 is 40 mg, and the cross-section of the sensor element 10 is about 300 μm × 300 μm, the sensor element 20
6, the distance between the sensor element 1 and the stoppers 21a and 22a needs to be suppressed to this value or less in FIG.
In this case, there is a problem that the gap between the joint surfaces 21a and 22a must be controlled and manufactured.

Further, in the example of FIG.
A regulating member 310 is attached to 300, and a regulating member 210 is further attached to the base 200.
Excessive acceleration is applied to 0, and the deformation of the sensor element 10 beyond the breaking displacement, by pumping up these parts,
The gap between the sensor element 10 and the regulating members 210 and 310 is limited to within the breaking limit of the sensor element 10 and the movement of the sensor element 10 is regulated within the breaking displacement, so that the sensor element 10 does not break. In the case of manufacturing by assembling parts as shown in FIG. 7, it is necessary to accurately perform positioning of the package 300, the pedestal 200, and the sensor element 10 and the above-described processing of the parts. There was a problem.

[0007] In both cases of FIGS. 6 and 7, it is possible to prevent the sensor element 10 from being damaged by bending in the vertical direction on the paper due to excessive acceleration to the sensor element 10 at the time of a drop impact or the like.
Unless a similar structure is provided in the direction perpendicular to the paper surface, it is impossible to prevent damage in the vertical direction on the paper surface, and it is necessary to assemble with the gap kept below 300 μm in the vertical and vertical directions on the paper surface, which is difficult to manufacture. .

Further, this method is effective only when the sensor element is broken by simple bending, and no measures have been taken when the sensor element is broken by twisting around the sensor element.

[0009]

According to the semiconductor acceleration sensor of the present invention, a rod is provided with a fixed gap in the opening of the weight attached to the sensor element so that a large stress does not act on the sensor element at the time of a drop impact or the like. With a simple structure of inserting the sensor element, the movement of the sensor element is restricted by the contact between the opening and the rod, and the durability of the sensor element is improved.

[0010] Further, the structure in which the distance between the opening and the contact surface between the rod and the rod can be accurately controlled by providing the rod with a portion fitted into the opening. In addition, by arranging two or more structures of the opening and the rod as described above, it is possible to prevent the sensor element from being broken by twisting around the sensor element at the time of a drop impact or the like.

[0011]

Embodiments of the present invention will be described below with reference to the drawings.

[0012]

(Embodiment 1) FIG. 1 is a perspective view showing a structure of a semiconductor acceleration sensor according to one embodiment of the present invention. FIG.
FIG. 2 is a sectional view of the acceleration sensor of FIG. The structure of this embodiment will be described with reference to FIGS. The silicon rectangular sensor element 10 has a strain-sensitive portion 60 for detecting acceleration near a fixed end, and one end is fixed by an element supporting portion 70. The strain sensing part 60 is formed by assembling a diffusion resistor into a Wheatstone bridge circuit.

At the free end of the sensor element 10, a rectangular parallelepiped weight 20 having a conical opening 30 is attached. Aperture
30 is located near the center of the opening surface 31 of the weight 20, and the sensor element
In the longitudinal direction of 10, the weight 20 is opened perpendicularly to the opening surface 31 up to the center of the weight 20. In order to further restrict the movement of the sensor element 10, a conical rod 40 having a vertex angle equal to the vertex angle of the cone of the opening 30 is attached to the rod support 50, and inserted into the opening 30.

The weight 20 is subjected to acceleration, whereby the sensor element 10 bends and a bending stress is generated in the strain-sensitive portion 60. The change in resistance value ΔR of the diffusion resistance due to bending is proportional to the bending stress σ as follows. ΔR∝σ σ: bending stress Also, the bending stress that occurs differs depending on the position where the diffusion resistance is mounted on the sensor element 10, so that according to the above equation, the resistance value changes depending on the position where the diffusion resistance is mounted, and the sensor element 10 bends. As a result, the bridge circuit breaks down, thereby detecting acceleration.

Next, a method of manufacturing the acceleration sensor according to the present invention will be described. The silicon sensor element 10 is provided with a strain-sensitive portion 60 by forming a diffusion resistor by injecting impurities in a normal semiconductor process, and is processed into a predetermined shape by dicing or the like. The weight 20 can be formed by piercing the opening 30 from a rectangular parallelepiped metal, or can be manufactured by injection molding of plastic. The rod 40 can be manufactured by shaving a metal, or a plastic or the like can be used to reduce an impact at the time of contact with the weight 20. The support part 50 and the rod 40 may be processed integrally,
It may be processed separately and bonded or welded.

Next, the function of the acceleration sensor will be described. For example, if brass is used for the weight 20, the shape is 2.8 mm
In the case of × 3.0 mm × 1.0 mm, the weight is 60 mg, the length of the sensor element 10 is 1 mm, and the cross section is w: 150 μm × h: 525 μm, the breaking stress due to bending is 3.0 × 108 [N / m2]
This is the value of the stress applied to the sensor element when an impact acceleration of about 200 G in the h direction and about 700 G in the w direction is applied to the sensor element, and at this value, the sensor element 10 is h
Deflection is about 300 μm in the direction and about 500 μm in the direction w. for that reason,
It is necessary to keep the distance t between the opening 30 and the bar 40 below this value.

When the rod 40 is made of brass, in the acceleration sensor as described above, the apex angle is 30 degrees and the bottom of the cone is φ0.5 m.
The length of m is about 1.5 mm, so that the movement of the sensor element 10 can be sufficiently regulated. Next, a method of adjusting the gap t will be described in detail with reference to FIG. 2, t represents the distance between the opening 30 and the inner and outer surfaces of the rod 40, and a represents the distance between the bottom of the opening 30 and the top of the rod 40. Θ represents the apex angle of the cone of the opening 30 and the rod 40.

In FIG. 2, the gap t is expressed as t = a × sin (θ / 2) using the apex angle θ and the distance a between the vertices. Therefore, from the state where the valley bottom of the opening 30 and the apex of the rod 40 are in contact with each other, the rod support 50 is moved by a feed mechanism with a screw such as a micrometer or a parallel guide feed mechanism to accurately control a. For example, it is possible to easily set t to a predetermined value. Further, since the opening 30 and the rod 40 have a conical shape, t set as described above is set not only in the vertical direction on the paper surface of FIG. It is possible to prevent destruction due to excessive acceleration in all directions around the sensor element 10 only by accurately controlling the value of.

For example, if θ is 30 degrees and a is 1 mm, t = 0.259 m
m, and a can be adjusted accurately. Thereby, the gap t can be adjusted within the breaking displacement of the sensor element 10. In the above structure, if a voltage of about 5 V is applied to the bridge circuit, 2.5 m
A sensitivity of about V can be obtained. Further, as a result of a drop impact test, it was confirmed that the device could withstand a drop test of 1 m.

(Embodiment 2) FIG. 3 is a perspective view of Embodiment 2. In the second embodiment, as shown in FIG. 3, the acceleration sensor of the first embodiment has the opening 30 formed into a quadrangular pyramid and the rod 40 formed into a quadrangular pyramid. Other configurations and a manufacturing method are the same as those in the first embodiment. In this manner, by forming the pyramid into a quadrangular pyramid, the twist around the sensor element 10 is less likely to occur than in the case of the first embodiment on the conical shape.

(Embodiment 3) FIG. 4 is a perspective view showing Embodiment 3 in which two openings 30 and two rods 40 are arranged. By arranging two or more openings 30 and rods 40 in this way, it is possible to regulate the torsional movement around the sensor element 10 as shown by the arrow A in the figure, and prevent damage due to the torsion of the sensor element 10 be able to.

(Embodiment 4) FIG. 5 is a perspective view of Embodiment 4. In the fourth embodiment, the acceleration sensor of the first embodiment is replaced with the opening 30.
Is a hemisphere, and the rod 40 is also a hemisphere. Other configurations and a manufacturing method are the same as those in the first embodiment. in this way,
By making it hemispherical, manufacturing becomes easier.

[0023]

As described above, according to the present invention, the semiconductor acceleration sensor element is provided with a weight having an opening, a rod is inserted into the opening, and the movement of the sensor element is regulated to facilitate manufacture. In addition, there is an effect of preventing damage to the sensor element due to dropping or the like. In addition, by making the shape of the opening and the rod inserted therein conical, etc., the distance between the sensor element and the regulating member of the sensor element, which was difficult with the conventional technology, can be accurately controlled, and it is easy. This has the effect of improving the shock resistance of the acceleration sensor.

The arrangement of a plurality of openings and bars as described above has an effect of preventing the sensor element from being damaged by twisting.

[Brief description of the drawings]

FIG. 1 is a perspective view showing one embodiment of a semiconductor acceleration sensor of the present invention.

FIG. 2 is a plan view of one embodiment of the semiconductor acceleration sensor of the present invention.

FIG. 3 is a perspective view showing one embodiment of the semiconductor acceleration sensor of the present invention.

FIG. 4 is a perspective view showing one embodiment of the semiconductor acceleration sensor of the present invention.

FIG. 5 is a perspective view showing one embodiment of the semiconductor acceleration sensor of the present invention.

FIG. 6 is a plan view showing an example of a conventional semiconductor acceleration sensor.

FIG. 7 is a plan view showing an example of a conventional semiconductor acceleration sensor.

[Explanation of symbols]

 Reference Signs List 10: Sensor element 20: Weight 30: Opening 31: Opening surface 40: Bar 50: Bar support 60: Strain-sensitive part 70: Element support 200: Pedestal 210: Regulator 300: Package 310: Regulator a: Opening Distance between the vertices of the part 30 and the rod 40 t: Clearance between the opening 30 and the rod 40 θ: Apex angle of the cone

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masataka Shinoggi 1-8-1 Nakase, Mihama-ku, Chiba-shi, Chiba SIIR Corporation

Claims (5)

[Claims] A cantilever element having a strain-sensitive portion and having a function of detecting acceleration, a support for fixing and supporting one end of the element, and a semiconductor acceleration sensor having a weight at the other end of the element In the above, an opening is provided in the weight, and a rod having a portion that fits in the opening is arranged such that a distance between the surface of the opening and the surface of the rod that fits each other is uniform. Semiconductor acceleration sensor. 2. The semiconductor acceleration sensor according to claim 1, wherein said opening and said rod are conical. 3. The semiconductor acceleration sensor according to claim 1, wherein said opening is a quadrangular pyramid, and said rod is also a quadrangular pyramid. 4. The semiconductor acceleration sensor according to claim 1, wherein the opening is a hemisphere, and the rod is a hemisphere. 5. The semiconductor acceleration sensor according to claim 1, further comprising at least two of said opening and said rod.