JPH07131036A - Semiconductor acceleration sensor - Google Patents

Abstract

(57) [Abstract] [Purpose] In a semiconductor acceleration sensor, the influence of thermal stress generated by the difference in the linear expansion coefficient between the base material and the pedestal is eliminated to prevent fluctuations in the output temperature characteristics of the semiconductor acceleration sensor, The object of the present invention is not to damage the cantilever beam even if an excessive impact load is applied in the detection direction, and further to reduce the number of parts, the number of assembly steps, the time, and the cost. [Structure] Arm 11 is installed on pedestal 3, and arm 11
Is a cantilever beam 4 having a semiconductor strain gauge 6 and a weight 5 attached at a position opposite to the position of the pedestal 3.
Install. Further, the weight 13 joined to the tip of the cantilever beam 4 has a trapezoidal shape or the like, and the cross-sectional shape of the pedestal 14 has an L-shaped shape or the like, so that a gap between the pedestal 14 and the weight 13 and a gap between the arm 11 and the weight 13 are formed. The configuration is such that the displacement of the weight 13 can be controlled. The pedestal 16 and the weight 15 are made of the same material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the structure of a semiconductor acceleration sensor having a semiconductor strain gauge used in a device for measuring physical vibration.

[0002]

2. Description of the Related Art FIG. 13 (a) shows, for example, JP-A-62-22.
FIG. 13 (b) is a side sectional view taken along line XX of FIG. 13 (a), and FIG. 13 (c) is a front sectional view taken along line YY of FIG. 13 (a). It is a figure. In the figure, 1 is a base made of metal or the like and having a welded portion 1a formed on the outer peripheral portion thereof, and 2 is a welded portion 2a made of metal or the like on the outer peripheral portion.
The cap is formed to form a package with the base 1. Reference numeral 3 denotes a pedestal fixed on the base 1, and 4 denotes a cantilever beam having one end bonded to the pedestal 3 and the other end bonded to a weight 5 made of a metal material used to enhance output sensitivity. Thin portion 4a
Are formed. Reference numeral 6 is a detection element formed on the thin portion 4a, which is electrically connected by a wiring formed by a semiconductor strain gauge formed by thermal diffusion or ion implantation and formed by aluminum vapor deposition to form a full bridge circuit. ing. 7 is a lead terminal that penetrates through the base 1 and is exposed to the outside, 8 is hard glass that is filled between the outer periphery of the lead terminal and the through hole, and 9 is wire bonding between the lead terminal 7 and the semiconductor strain gauge 6. The wire 10 made of gold wire or aluminum wire is a damping liquid made of silicon oil enclosed in the package.

[0003]

In the conventional semiconductor acceleration sensor as described above, as the metal material of the normal base,
A metal material having a linear expansion coefficient close to that of a silicon single crystal is common. However, for example, the thermal stress generated by the difference in the linear expansion coefficient between the base material made of metal and the glass or the pedestal made of silicon is affected by the thermal stress because the position of the semiconductor strain gauge is relatively close to the pedestal part. However, there is a problem that the output temperature characteristic of the semiconductor acceleration sensor is changed. Further, the conventional semiconductor acceleration sensor has a problem that the cantilever beam is damaged when an excessive impact load is applied in the acceleration detection direction and the allowable stress is exceeded in the sectional shape of the thin portion of the cantilever beam. Further, in the conventional semiconductor acceleration sensor, in order to increase the output sensitivity of the sensor, a weight made of metal is joined to the tip of the cantilever beam, which increases the number of parts and requires many steps and time in the assembly process. There was a problem of high cost.

[0004]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and can prevent thermal stress caused by a difference in linear expansion coefficient between a base material or glass and silicon from a cantilever beam, especially from a cantilever beam. The purpose of the present invention is to obtain a semiconductor acceleration sensor having an accurate output temperature characteristic without being transmitted to the semiconductor strain gauge portion. Also, when an excessive impact load is applied in the acceleration detection direction, the thin-walled cantilever beam cross-sectional shape limits the stress displacement within the permissible stress, and the cantilever beam is not damaged. The purpose is to get a sensor. Furthermore, it aims at obtaining an inexpensive semiconductor acceleration sensor by reducing the number of parts and the number of assembly steps.

[0005]

A semiconductor acceleration sensor according to the present invention is provided with an arm for supporting a cantilever beam, and a semiconductor strain gauge portion of the cantilever beam is arranged at a position opposite from a pedestal holding the arm. .

In addition, the weight joined to the tip of the cantilever beam is attached from the back surface of the cantilever beam, and the cross section of the weight is substantially trapezoidal, and the pedestal for holding the arm is L-shaped. is there.

Further, the weight joined to the tip of the cantilever beam and the pedestal for holding the arm are both made of glass of the same material.

[0008]

In the semiconductor acceleration sensor according to the present invention, the arm for supporting the cantilever beam is provided, and the semiconductor strain gauge portion of the cantilever beam is arranged at the position opposite to the pedestal holding the arm. The thermal stress generated due to the difference in the linear expansion coefficient of the pedestal made of glass and glass or silicon is arranged so as not to be transmitted to the semiconductor strain gauge part through the pedestal, and the arm part can absorb and relax the thermal stress, and output With respect to temperature characteristics, accuracy is improved.

Further, the weight joined to the tip of the cantilever beam is attached from the rear surface of the cantilever beam, the cross section of the weight is substantially trapezoidal, and the pedestal for holding the arm is L-shaped. Even if an excessive impact load is applied in the acceleration detection direction, the cross-sectional shape of the thin portion of the cantilever beam can limit the stress displacement within the allowable stress, improving the impact resistance without damaging the cantilever beam. Done.

Further, since the weight joined to the tip of the cantilever beam and the pedestal for holding the arm are made of a pair of glasses, the weight made of a metal material is unnecessary, the number of parts is reduced and the number of assembling steps is reduced. The cost can be reduced and the manufacturing cost can be reduced. In addition, even if an excessive impact load is applied in the acceleration detection direction, the cross-sectional shape of the thin portion of the cantilever beam can limit the stress displacement within the allowable stress, improving the impact resistance without damaging the cantilever beam. Is done.

[0011]

EXAMPLES Example 1. Hereinafter, a semiconductor acceleration sensor according to a first embodiment of the present invention will be described with reference to the drawings. 1 is a plan view showing a semiconductor acceleration sensor according to a first embodiment of the present invention, FIG. 2 is a side sectional view taken along the line AA in FIG. 1, and FIG. 3 is an overall perspective view. In the figure, the same parts as those in the prior art will be described with the same reference numerals. Reference numeral 11 denotes an arm connected to the pedestal 3, and the cantilever beam 4 is arranged integrally with the arm 11 and at a position opposite to the pedestal 3 holding the arm 11, and a weight 5 is joined to the tip thereof. There is. Reference numeral 6 denotes a semiconductor strain gauge arranged at the projecting root portion of the cantilever beam, and 12 denotes a convex portion of a stopper provided on the base 1 for controlling the downward displacement of the weight 5.

Next, the operation will be described. As shown in the figure, since the position of the semiconductor strain gauge 6 is far from the pedestal 3, the semiconductor acceleration is unlikely to be affected by the thermal stress generated by the difference in the linear expansion coefficient between the base material made of metal and the pedestal made of glass or silicon. It becomes difficult to change the output temperature characteristic of the sensor. Further, since the downward displacement of the weight 5 can be controlled by the stopper convex portion 12, the cantilever beam 4 will not be damaged even if an excessive impact load is applied in the acceleration detection direction.

Example 2. Next, a semiconductor acceleration sensor according to a second embodiment of the present invention will be described with reference to the drawings. 4 is a plan view showing a semiconductor acceleration sensor according to a second embodiment, FIG. 5 is a side sectional view taken along the line BB in FIG. 4, FIG. 6 is a front sectional view taken along the line CC in FIG. 5, and FIG. Is. In the figure, reference numeral 13 is a weight having a substantially trapezoidal cross section, which is attached from the back surface of the cantilever beam 4 and is joined to the tip of the cantilever beam 4. Again 1
Reference numeral 4 denotes a pedestal having an L-shaped cross section.

Next, the operation will be described. As shown in the figure, since the position of the semiconductor strain gauge 6 is far from the pedestal 14, it is hard to be affected by the thermal stress generated by the difference in the linear expansion coefficient between the base material made of metal and the pedestal made of glass or silicon. It becomes difficult to change the output temperature characteristic of the sensor. Further, the displacement of the weight 13 joined to the tip of the cantilever beam 4 is caused by the gap d1 between the arm 11 and the weight 13 and the gap d2 between the pedestal 14 and the weight 13.
By adopting the stopper structure for limiting the displacement by the above, the vertical displacement of the weight 13 can be controlled, so that the cantilever beam 4 will not be damaged even if an excessive impact load is applied in the acceleration detection direction.

In the above embodiment, the weight 13 has a substantially trapezoidal cross section, but the shape shown in FIG. 8 can achieve the same purpose.
Any shape may be used as long as the displacement limiting structure is formed by the gap between the weight 13 and the weight 13 and the gap between the pedestal 14 and the weight 13.

Embodiment 3. Next, a semiconductor acceleration sensor according to a third embodiment of the present invention will be described with reference to the drawings. FIG. 9 is a plan view showing a semiconductor acceleration sensor according to the third embodiment, and FIG.
Is a side sectional view taken along the line DD in FIG. 9, and FIG. 11 is an overall perspective view. In the figure, 15 is a cantilever beam 4.
A weight having an L-shaped cross section joined to the tip of the, 16 is a pedestal having a L-shaped cross section, the weight 15, the pedestal 16
Are made of the same glass material. Reference numeral 17 is a convex portion formed on the base 1.

Next, the operation will be described. As shown in the figure, since the position of the semiconductor strain gauge 6 is far from the pedestal 16 portion, it is hard to be affected by the thermal stress generated by the difference in linear expansion coefficient between the base material made of metal and the pedestal made of glass or silicon. It becomes difficult to change the output characteristics of the sensor. In addition, the weight 15 joined to the tip of the cantilever beam 4 has a stopper structure that limits the displacement of the weight 15 by the gap d3 between the arm 11 and the weight 15 and the gap d4 between the base 1 and the weight 15. Therefore, the cantilever beam 4 will not be damaged even if an excessive impact load is applied in the acceleration detection direction. Furthermore, since the weight 15 joined to the tip of the cantilever beam 4 and the pedestal 16 holding the arm 11 are both made of the same glass material,
It is possible to reduce the number of parts and the man-hours and time in the assembly process, and it is possible to reduce the cost.

Next, the manufacturing process of the weight 15 and the pedestal 16 will be described with reference to FIG. First, a glass material 18 processed into a specific shape (concave shape) is joined to the cantilever beam 4 as shown in FIGS. Then Fig. 12 (c)
As shown in, the weight 15 and the pedestal 16 are formed by cutting and separating the middle portion of the glass material 18 by etching or the like.

[0019]

As described above, according to the semiconductor acceleration sensor of the present invention, the thermal stress caused by the difference in linear expansion coefficient between the base material or glass and silicon can be absorbed and relaxed in the arm portion, and the cantilever beam can be obtained. In particular, a semiconductor acceleration sensor having high output temperature characteristics can be obtained without thermal stress being transmitted to the semiconductor strain gauge portion. Further, even if an excessive impact load is applied in the acceleration detection direction, the stress displacement can be limited within the allowable stress of the cantilever beam, the cantilever beam is not damaged, and a semiconductor acceleration sensor with high impact tolerance can be obtained. it can. Further, since the weight joined to the cantilever beam and the pedestal for holding the arm are made of the same material, the number of parts and the number of assembly steps can be reduced, and an inexpensive semiconductor acceleration sensor can be obtained. There is.

[Brief description of drawings]

FIG. 1 is a plan sectional view showing a semiconductor acceleration sensor according to a first embodiment of the present invention.

FIG. 2 is a side sectional view showing the semiconductor acceleration sensor according to the first embodiment of the present invention.

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

FIG. 4 is a plan sectional view showing a semiconductor acceleration sensor according to a second embodiment of the present invention.

FIG. 5 is a side sectional view showing a semiconductor acceleration sensor according to a second embodiment of the present invention.

FIG. 6 is a front sectional view showing a semiconductor acceleration sensor according to a second embodiment of the present invention.

FIG. 7 is a perspective view showing a semiconductor acceleration sensor according to a second embodiment of the present invention.

FIG. 8 is a front cross-sectional view showing a second embodiment in which the shape of the weight is changed.

FIG. 9 is a plan sectional view showing a semiconductor acceleration sensor according to a third embodiment of the present invention.

FIG. 10 is a side sectional view showing a semiconductor acceleration sensor according to a third embodiment of the present invention.

FIG. 11 is a perspective view showing a semiconductor acceleration sensor according to a third embodiment of the present invention.

FIG. 12 is a side view showing the manufacturing process of the semiconductor acceleration sensor according to the third embodiment of the present invention.

FIG. 13 is a plan sectional view showing a conventional semiconductor acceleration sensor.
(a), side sectional view (b), front sectional view (c).

[Explanation of symbols]

 1 base 3 pedestal 4 cantilever beam 5 weight 6 semiconductor strain gauge 11 arm 12,17 convex portion 13,15 weight 14,16 pedestal 18 glass material

Claims (3)

[Claims] 1. In a semiconductor acceleration sensor in which a cantilever beam is installed on a base via a pedestal, and a semiconductor strain gauge and a weight are attached to the cantilever beam, an arm is installed on the pedestal and the arm is installed. The semiconductor acceleration sensor is characterized in that the cantilever beam is attached in a cantilever structure at a position opposite to the position of the pedestal, and a semiconductor strain gauge portion is arranged at a position opposite to the pedestal. 2. The semiconductor acceleration according to claim 1, wherein the weight is attached to an upper portion or a lower portion of the cantilever beam, and a stopper member for limiting displacement of a gap between the pedestal and the weight and a gap between the arm and the weight is formed. Sensor. 3. The semiconductor acceleration sensor according to claim 1, wherein the pedestal and the weight are made of the same material.