JPH11201982A - Semiconductor acceleration sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor acceleration sensor capable of preventing breakage by excessive acceleration at the time of a falling impact or the like and being easily manufactured. SOLUTION: The sensor element 10 of the cantilever needle of a silicon rectangular parallelepiped is provided with a distortion sensitive part 60 for detecting acceleration near a fixed end. To the free end part of the sensor element 10, a rectangular parallelepiped weight 20 provided with a rectangular parallelepiped opening part 30 is attached. A bar 40 for controlling the movement of the sensor element 10 is attached to a supporting part 50 and inserted to the opening part 30 of the weight 20 and formation is performed. By the abutting of the opening part 30 and the bar 40, the breakage of the sensor element 10 is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an acceleration sensor mounted on an automobile, a robot, or the like, for measuring acceleration such as impact, inclination, and the like by changing the resistance value of a piezo resistor provided on a beam.

[0002]

2. Description of the Related Art A conventional semiconductor acceleration sensor is disclosed, for example, in Japanese Patent Laid-Open No. 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 10 is regulated by regulating members 21 and 22. In FIG. 6, the acceleration in the vertical direction on the paper is detected. If an excessive acceleration is applied to the sensor element 10 at the time of a drop impact or the like, the inclined surface 21a is used so that the displacement of the silicon sensor element 10 does not reach the breaking displacement.
The movement of the sensor element 10 in the vertical direction on the paper is regulated by the regulating members 21 and 22 provided with
Is not excessively displaced, thereby preventing the sensor element 10 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. In FIG. 7, a package 300 is attached to a silicon sensor element 10 having a strain-sensitive portion 60.
Further, regulating members 310 and 210 for regulating the movement of the sensor element 10 are attached to the pedestal 200.
The structure restricts the displacement of the sensor element 10 so that the sensor element 10 does not undergo 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. For example, in the example of FIG. 6, the length of the silicon sensor element 10 is 1 mm, the weight of the weight 20 is 40 mg, and the sensor element 1
When the cross-section of is approximately 300 μm × 300 μm, when a breaking limit stress is applied to the sensor element 10 at the time of a drop impact or the like, the sensor element 10 bends 200 to 300 μm in the vertical direction on the paper, and thus the sensor element 1 and the stopper 21a, It is necessary to keep the distance from 22a to this value or less.
Since the gap between the joint surfaces 21a and 22a of 22 must be controlled to about 200 μm, the processing becomes complicated, and there is a problem that the manufacturing cost increases.

[0005] 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.
When excessive acceleration is applied to 0 and the sensor element 10 is deformed beyond the breaking displacement, the sensor element 10 and the regulating members 210 and 310
By restricting the movement of the sensor element 10 within the breaking displacement by contact with the sensor element 10, the sensor element 10 is not broken. When manufacturing by assembling parts as shown in FIG. 7, the package 300, the pedestal 200, and the sensor element
There is a problem that it is necessary to accurately perform the positioning of 10 and the above-described parts processing, the number of parts is large, and the manufacturing is difficult.

[0006] In both cases of FIGS. 6 and 7, damage due to bending in the vertical direction of the paper due to excessive acceleration of the sensor element 10 at the time of a drop impact or the like is prevented.
Unless a similar structure is provided in the direction perpendicular to the paper surface, there is a problem that damage in the direction perpendicular to the paper surface cannot be prevented. Further, this method is effective only when the sensor element is broken by simple bending, and there is a problem that no measure is taken when the sensor element is broken by twisting around the sensor element.

[0007]

According to the semiconductor acceleration sensor of the present invention, a rod is attached to an opening provided in a weight attached to one end of the sensor element so that the sensor element is not greatly displaced in the direction of applied acceleration at the time of a drop impact or the like. With a simple structure in which a certain gap is provided and inserted, the movement of the sensor element is restricted by the contact between the opening and the rod, and an acceleration sensor having high shock resistance can be easily manufactured. Further, by arranging two or more structures of the opening and the rod as described above, it becomes possible to prevent the sensor element from being broken due to a twist around the sensor element at the time of a drop impact or the like.

[0008]

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

[0009]

Embodiment 1 FIG. 1 is a perspective view showing the structure of a semiconductor acceleration sensor according to one embodiment of the present invention. FIG. 2 is a sectional view of the embodiment 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. A rectangular parallelepiped weight 20 having a rectangular parallelepiped opening 30 is attached to the free end of the sensor element 10. Opening 30 is weight 20
It is located near the center of the opening surface 31 of the sensor element 10 and opens perpendicularly to the opening surface 31 up to the center of the weight 20 in the longitudinal direction of the sensor element 10.

Further, a rod 40 for regulating the movement of the sensor element 10
Is attached to the rod support 50, and is inserted into the opening 30 of the weight 20 to form. The outer diameter of the rod 40 is slightly smaller than the inner diameter of the opening 30. When the rod 40 is inserted into a predetermined position with respect to the opening 30, a constant gap is formed. The weight 20 and the sensor element 10 are 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 The bending stress that occurs differs depending on the position where the diffusion resistance is mounted on the sensor element 10. Therefore, 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 collapses, and thereby the acceleration is detected.

Next, a method of manufacturing each element of the acceleration sensor according to the present embodiment will be described. Silicon sensor element 10
In the conventional semiconductor process, a strain-sensitive portion 60 is formed by forming a diffusion resistor by an impurity implantation method in an ordinary semiconductor process, and is processed into a predetermined shape by a processing method such as etching and dicing. Weight 20
Can be formed from a rectangular parallelepiped metal through the opening 30, 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 rod support 50 and the rod 40 may be integrally processed, or may be separately processed and bonded or welded.

Next, a method of assembling the acceleration sensor according to this embodiment will be described. In FIG. 2, t is the opening 30 and the rod 4
Indicates a gap with 0. As described above, it is necessary to provide a constant gap t between the opening 30 and the rod 40. To prevent damage to the sensor element 10, the sensor element 10 with the weight 20 attached and the rod 40
The manufacturing is performed with the gap t between the opening 30 and the rod 40 kept within the breaking limit of the sensor element 10 by positioning. Alternatively, a plate-shaped metal or the like having a known thickness is inserted between the opening 30 and the rod 40, and the sensor element 10 having the weight 20 attached thereto while keeping the gap t constant, and the rod support 50 are fixed. Thereafter, by removing the plate-like metal or the like, it is possible to manufacture the semiconductor device while keeping the gap t constant. Further, a film-shaped object is inserted into the gap between the opening 30 and the rod 40, and the sensor element 10 having the weight 20 attached thereto, and
After fixing the rod supporting portion 50 of the rod 40, the film can be dissolved with a solvent or the like to assemble with the gap t kept constant.

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]
When an impact acceleration of about 200 G is applied to the sensor element 10 in the h direction and about 700 G in the w direction, the sensor element 10
This is the value of the stress applied to the sensor element 10.
Deflects about 300 μm in the h direction and about 500 μm in the w direction.

Therefore, it is necessary to keep the distance t between the opening 30 and the bar 40 below this value. With the above-described manufacturing method, the acceleration sensor is manufactured by limiting the gap t to within the breaking limit. When the rod 40 is made of brass, in the above-described acceleration sensor, the cross section is about 0.5 mm × 0.5 mm and the length is about 1.5 mm, so that the movement of the sensor element 10 can be sufficiently regulated. In the above-described structure, when a voltage of about 5 V is applied to the bridge circuit, a sensitivity of about 2.5 mV can be obtained with respect to 1 G of acceleration.
Furthermore, the acceleration sensor of this embodiment was attached to a dedicated jig and electrically connected, and a drop impact test was performed while measuring the output of the sensor at the time of impact. However, it was confirmed that the one with the rod 40 attached as in this example can withstand a drop test of about 1 m.

[0015]

Second Embodiment FIG. 3 is a perspective view of a second embodiment. In FIG. 3, the element support is omitted. In the second embodiment, as shown in FIG. 3, the acceleration sensor of the first embodiment is different from the acceleration sensor of the first embodiment in that the weight 20 has a cylindrical shape, and a thin portion 80 for reducing stress concentration is provided on the sensor element 10. The strain-sensitive part 60 is formed by combining the sensor element 10 provided on the back surface of the sensor element 10 with respect to the thin part 80 at the position of the thin part 80 on the sensor element 10 in the longitudinal direction. Other configurations and a manufacturing method are the same as those in the first embodiment.

In the case of such a structure, the processing of the sensor element 10 becomes complicated. However, even when a large stress is applied to the sensor element 10 at the time of a drop impact or the like and the breaking limit displacement amount in the first embodiment is reached, the thin-walled portion is not formed. Since 80 is provided, stress concentration does not occur and it is hard to break. Therefore, the gap t is the sensor element as in the first embodiment.
10 can be set larger than a structure like a rectangular parallelepiped, and assembling becomes easy. Furthermore, since the opening can be cut through and the bar can be manufactured by a relatively simple processing method such as a lathe,
It can be manufactured at low cost.

[0017]

Third Embodiment FIG. 4 is a perspective view of a third embodiment. In FIG. 4, the element support is omitted. FIG. 4 shows the acceleration sensor according to the first embodiment in which the opening 30 and the rod 40 are changed into a cylindrical shape. Other configurations and the manufacturing method are the same as those of the first embodiment. The function will be described in detail with reference to FIGS. 4, 8, and 9. FIG. 9 is a plan view of FIG. 4, as viewed from the direction A in FIG.
In FIG. 9, the rod supporting portion 50 of the rod 40 is not shown. Similarly, FIG. 8 is a plan view of the case where the opening 30 and the bar 40 are rectangular parallelepipeds (Example 1), similarly viewed from the A direction. As shown in FIG. 8, the sensor element 10
When the tilt is generated around the sensor element 10 when the rod 40 and the rod 40 are fixed, the gap t is not constant, but as shown in FIG.
If the rod 40 and the rod 40 are cylindrical, the weight 20 and the rod 4
Even if the mounting angle of 0 is shifted, the gap t is constant,
When the sensor element 10 and the rod 40 are fixed, the accuracy of the mounting angle around the sensor 10 is not required, and the manufacture becomes easy.

[0018]

Embodiment 4 FIG. 5 is a perspective view showing an embodiment in which two openings 30 and two bars 40 are arranged. In FIG. 5, the element support is omitted. By arranging two or more openings 30 and two or more rods 40 in this manner, it is possible to regulate the torsional movement around the sensor element 10 as shown by the arrow a in the figure, and prevent the sensor element 10 from being damaged due to torsion. be able to.

[0019]

As described above, according to the present invention, the semiconductor acceleration sensor element can be easily manufactured by attaching a weight having an opening, inserting a rod into the opening, and regulating the movement of the sensor element. This has the effect of preventing damage to the sensor element due to dropping or the like. Furthermore, it was difficult in the past,
The vertical and horizontal movements of the sensor element can be restricted, so that the sensor element can be prevented from being damaged in two directions and the shock resistance can be improved. In addition, arranging a plurality of openings and bars 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 sectional view showing 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 sectional view showing an example of a conventional semiconductor acceleration sensor.

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

FIG. 8 is a plan view according to an embodiment of the present invention.

FIG. 9 is a plan view according to an embodiment of the present invention.

[Explanation of symbols]

 10 Sensor element 20 Weight 21 Restriction member 21a Inclined surface 22 Restriction member 22a Inclined surface 30 Opening 31 Opening surface 40 Rod 50 Bar support 60 Strain-sensitive part 70 Element support 80 Thin part 200 Base 210 Restriction member 300 Package 310 Restriction member 400 Lead t Clearance between opening and rod

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

Claims (6)

[Claims] 1. A semiconductor acceleration sensor having a cantilever element having a strain-sensitive part and having a function of detecting acceleration, a support for fixing and supporting one end of the element, and a weight at the other end. An opening is provided in the weight, and a rod in which the positional relationship with the element for restricting displacement of the element does not change in the opening is inserted with a certain gap with the inner wall of the opening. Semiconductor acceleration sensor. 2. The semiconductor acceleration sensor according to claim 1, wherein the opening and the rod are cuboids. 3. The semiconductor acceleration sensor according to claim 1, wherein the opening is a cylinder, and the rod is also a cylinder. 4. The semiconductor acceleration sensor according to claim 1, wherein the opening has a conical shape and the rod has a conical shape. 5. The semiconductor acceleration sensor according to claim 1, wherein the semiconductor acceleration sensor has two or more openings and two or more rods. 6. The semiconductor acceleration sensor according to claim 1, wherein a film-shaped object is inserted between the opening and the rod, and the element and the rod are fixed. A method for manufacturing a semiconductor acceleration sensor, wherein the semiconductor acceleration sensor is manufactured by dissolving with a solvent or the like so as to keep the gap between the opening and the rod constant.