JPH0473629B2 - - Google Patents

Description

[Detailed description of the invention] [Technical field to which the invention pertains] This invention relates to a pressure sensor that uses a strain gauge to detect a force applied to a pressure-receiving surface. This invention relates to a small pressure sensor suitable for detecting the distribution of

[Prior Art and its Problems] Fig. 1 shows a conventionally used sensor (octagonal stress ring) that detects three-directional components of force. This sensor has strain gauges 41 to 41 on six outer peripheral surfaces of a metal octagonal ring 1 excluding the pressure receiving surface 2 and the substrate surface 3, and on both side surfaces and the inner peripheral surface.
44, 51 to 54, and 61 to 64 are pasted, and the three directional components are separated from each other and detected respectively depending on the pasting position. The above-mentioned strain gauges 41 to 44 are attached to the outer peripheral surface of the octagonal ring perpendicular to the pressure receiving surface 2 and to the inner peripheral surface of the ring, and detect the force component Fz perpendicular to the pressure receiving surface 2. Further, the strain gauges 51 to 54 are attached to four oblique outer peripheral surfaces of the octagonal ring, and detect the x-direction component Fx of the horizontal force component applied to the pressure receiving surface 2. Furthermore, the strain gauges 61 to 64 are attached to both sides of the ring at the same angle as the diagonal surface of the octagonal ring and approximately at the center of the wall thickness of the ring, so that the strain gauges 61 to 64 are affixed to both sides of the ring at the same angle as the diagonal surface of the octagonal ring and approximately at the center of the wall thickness of the ring. Detect the component Fy in the y direction.

In this way, the three-direction force sensor shown in the figure decomposes force into the basic orthogonal coordinate system and detects it as three-direction component forces, so by combining these three component forces using an arithmetic expression, , the magnitude and direction of force can be determined. Furthermore, force in any direction can be determined.

A major feature of the three-directional force sensor is that force can be easily decomposed and combined in this way.

However, although the conventional octagonal stress ring shown in the figure is well-known as a sensor for detecting force components in three directions, it has the following drawbacks, especially when arranged in a planar array. It is inappropriate to detect the load distribution of a load distributed over a surface. The drawbacks are listed below.

Since it has a structure in which a large number of strain gauges are attached in each direction of the ring body, it is difficult to downsize it.

Since the strain gauge is attached, creep occurs due to the attached layer, resulting in poor stability.

Depending on where the strain gauge is attached, a large interference output is generated.

It is relatively difficult to manufacture. In particular, it is difficult to attach the strain gauge to the inner peripheral surface of the ring.

It is not suitable for mass production and is expensive.

On the other hand, in order to realize a robot hand with an advanced pressure sensing function as close as possible to the pressure sensing function of the human palm, the pressure sensor must have the function of a three-directional force sensor, and a large number of such sensors must be used. Arranged in a high-density surface array, the distribution state of the applied force and the center of force (center of gravity)
It is necessary to be able to accurately determine the resultant force acting on it. Therefore, such a pressure sensor is required to be able to accurately separate and accurately detect the component forces of a load without mutual interference, and to be able to minimize dimensions and integrate at high density. The size is several mm square, preferably 1 mm.
It is desirable to make it less than a corner.

[Objective of the Invention] The object of the present invention is to overcome the drawbacks of the above-mentioned prior art, to provide a compact and high-density integration system that is highly stable and capable of accurate detection of three-direction components of force. It is an object of the present invention to provide a pressure sensor that can be easily mass-produced, can be manufactured at low cost, and has little interference between components of force in three directions.

[Summary of the Invention] In order to achieve the above object, the present invention uses single crystal silicon as a pressure sensitive structure, and forms a plurality of diffusion type strain gauges on a surface perpendicular to the pressure receiving surface of the pressure sensitive structure. , a support that detects three components of force applied to the pressure-receiving surface by changes in resistance values of these strain gauges, wherein the pressure-sensitive structure has a support surface parallel to the pressure-receiving surface. in which a terminal formed on the strain gauge forming surface of the pressure sensitive structure and a terminal formed on the supporting surface of the support are connected by a flexible wiring film. It is characterized by

[Embodiments of the Invention] Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 2 shows the basic configuration of the present invention, in which a plurality of P Diffusion type strain gauge 101
104, 111-114, 121-124 are formed by planar technology. The strain gauges 101 to 104 described above detect the force component Fz perpendicular to the pressure receiving surface 8, and the strain gauges 111
114 detect one component Fx of the force parallel to the pressure receiving surface 8, and strain gauges 121 to 124 detect another component Fy of the force parallel to the pressure receiving surface 8.
As will be described later, these strain gauges are arranged in locations that are highly sensitive and are theoretically unaffected by component forces in other two directions.

The pressure-sensitive structure 7 is fixed on a substrate (not shown) at a substrate surface 9 and receives the force applied to the pressure-receiving surface 8 .
The above-mentioned strain gauge groups that detect each component of this force are each connected to a bridge, as shown in FIGS. 3A to C, for example, and output electric signals Ez, Ex, and Ey according to the force component. do. In addition, the second
In the figure, wiring for bridge connection is omitted to avoid complexity. Further, in this embodiment, the P-type diffusion type strain gauge is formed on the N-type silicon single crystal surface, but it is also possible to form the strain gauge of the N-type diffusion layer on the P-type silicon. However, the former method provides higher sensitivity.

FIG. 4 shows an example of the gauge arrangement and wiring on the strain gauge forming surface (plane) 13 of FIG. 2. FIG.
As shown, strain gauge 10 for Fz detection
1 to 104 are arranged on the line A-A' passing through the center of the pressure-sensitive structure 7 and parallel to the upper pressure-receiving surface 8, on the strain gauge forming surface 13 near the left and right outer edges and inner edge, A bridge connection is made using a wiring 141, and an input/output is performed through a bonding pad section 15 connected to this wiring 141. In addition, a total of four strain gauges 111 to 114 for Fx detection are placed on the strain gauge forming surface 13 near the outer edge on two lines tilted at an angle α° both upward and downward from the above-mentioned line A-A'.
They are arranged and bridge-connected by wiring 142, and input/output is performed by bonding pad section 15 connected to this wiring 142. Furthermore, the strain gauges 121 to 124 for Fy detection are formed on a strain gauge forming surface located on a material mechanical neutral axis near the center of the ring on a line tilted at an angle α° both upward and downward from the above-mentioned line A-A'. A total of 4 pieces are placed in 13,
And bridge-connected with wiring 143, this wiring 1
Input/output is performed by the bonding pad section 15 connected to the terminal 43. The above-mentioned angle α° is selected at a position that does not cause distortion when only a force perpendicular to the pressure receiving surface 8 is applied to the pressure receiving surface. For example, in the case of a circular ring as shown in the figure, the angle α° is 50.4 Become a neighborhood.

Next, an example of a method for manufacturing the pressure sensor configured as described above will be briefly described with reference to FIGS. 5A and 5B. First, a given thickness (e.g. 0.6mm)
Pressure sensation of a single crystal silicon wafer 16 having a predetermined conductivity type (e.g. N-type), specific resistance (e.g. 1 to 10 Ωcm), and a predetermined crystal orientation (e.g. formation plane in the 111 direction). A group of diffusion type strain gauges 101 to 124 arranged as shown in FIG. 4 and metal wiring are formed in the sensor unit cell corresponding area 17 by IC manufacturing technology (planar technology) such as maskless ion beam processing and Al vapor deposition. do. this
According to the IC manufacturing method, a large number of pressure sensor unit cells can be fabricated on one wafer 16. By accurately cutting out pressure sensor unit cells from this wafer 16 by wire saw cutting, laser machining, or machining such as etching, a small size (for example, several
A planar pressure sensor unit cell having a size of 1 mm to 1 mm is obtained. Although the above description has been made regarding a ring-shaped pressure sensor, it goes without saying that the planar structure of the present invention can also be applied to pressure sensors other than ring-shaped.

FIG. 6 shows an example of the cross-sectional configuration of a pressure sensor to which the present invention having the above-described structure is applied. ~10
Metal thin film wirings 141 to 143 and bonding pad portions 15 are formed on the substrate 7 with an SiO ₂ insulating film 201 interposed therebetween by vapor deposition.

FIG. 7 shows an example of a distributed load cell in which pressure sensors, which are the basis of the present invention, are arranged in a planar array so that the load distribution of a load distributed in a planar manner can be detected. First, the pressure sensor 202 of the present invention configured as described above is inserted into the parallel groove 202 on the common substrate 203.
4 are vertically fitted to each other, and are arranged and fixed in a multi-plane array in both the horizontal x and y directions, and a pressure receiving plate 205 is fixed on top of these pressure sensors 202 to form a distributed load cell 206. In this example, a case is shown in which one pressure-receiving fine module is formed with two pressure sensors 202 as one set, but these pressure-receiving fine modules are arranged in an array at a density of, for example, about 25 to 100 pieces per ¹ cm2. The material accumulated on the body is attached to the gripping surface of a robot hand, making it possible to measure three-dimensional pressure distribution.

FIG. 8 shows an embodiment of the present invention having connection means for measurement wiring from each pressure sensor 202 described above, where 207 is a flexible wiring film as a connection means, and 208 is a connection on the board 203 side. The wiring film 207 serves as a terminal part as a means, and the wiring film 207 connects the bonding pad part 15 of the sensor 202 and the terminal part 2.
Connect with 08. Further, 209 is a wiring as a connection means, and 210 is a mount part. On this mount part 210, a semiconductor chip (not shown) which internally integrates the signal processing circuits such as the aforementioned bridge circuit and an attached amplifier is mounted. After completing the signal processing, only the net detection signal that needs to be output to the outside can be taken out via the connection pin 211. As a means suitable for mounting such a semiconductor chip, for example, a known thick film circuit may be provided on the upper surface of the uppermost layer 212, and a part or all of the signal processing circuit may be formed in the silicon single crystal constituting the sensor 202 by known means. It is also possible to build it in.

As mentioned above, the strain gauges are highly sensitive and are placed in locations that are theoretically unaffected by other two-directional force components, so it is possible to compensate for unevenness in the resistance values of the eight gauges, and to compensate for temperature Compensation enables highly accurate measurement of three-dimensional pressure distribution. In addition, since the pressure in the pressure-receiving micro-module is expressed by a change in the resistance of the semiconductor strain gauge, the resistance of the strain gauge in each pressure-receiving micro-module is scanned by a scanner, passed through an amplifier, an A/D converter, and then
It is loaded into the μ-CPU and calculates the three-direction component force, resultant force, three-direction moment, etc. at each point using a basic calculation algorithm, and the results of this calculation can be stored in a memory file. In addition, by appropriately selecting the material distribution of the pressure-receiving surface pad, it is possible to calculate the elasticity of the object.
It enables soft handling of objects without deforming or damaging them, and can also be used as an auxiliary input for determining the object's material and recognizing its shape. In addition, slippage due to insufficient gripping force is calculated from temporal changes in the pressure distribution on the pressure-receiving surface.
The gripping force control calculation algorithm enables soft handling without slippage. In addition, it is possible to perform supervisory control or autonomous local control from a host computer with high speed, high response, and high precision using basic operation calculation algorithms such as grasping, lifting, insertion, and rotation for hand drive mechanism control. It becomes possible. Furthermore, by attaching the pressure sensor of the present invention to the sole of the robot's foot for controlling the robot's walking, highly accurate walking control becomes possible.

[Effects of the Invention] As explained above, according to the present invention, a large number of single crystal silicon, which is excellent as an elastic material, is used as a pressure-sensitive structure in the form of a wafer using planar technology used in IC manufacturing. By forming a diffusion type strain gauge group and a wiring group corresponding to a pressure sensor unit cell, and making it possible to cut out a large number of pressure sensor unit cells from this wafer, it is extremely small.
It is possible to obtain a pressure sensor (pressure sensor unit cell) suitable for detecting load distribution for detecting three components of force, which has well-matched characteristics, good safety, high precision, good mass production, and low cost. can.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing a pressure sensor unit cell (octagonal stress ring) according to the prior art, FIG. 2 is a perspective view showing the configuration of the pressure sensor unit cell that is the basis of the present invention, and FIGS. A circuit diagram showing the connection state of the strain gauge of the pressure sensor shown in Fig. 4.
The figure is a schematic diagram of an example of the arrangement of strain gauges and wiring of a pressure sensor unit cell which is the basis of this invention, FIG. FIG. 6 is a cross-sectional view showing an example of the cross-sectional structure of a pressure sensor unit cell to which the present invention is applied;
FIG. 7 is a perspective view showing an example of a load cell formed by arranging pressure sensor unit cells in a planar array according to the present invention, and FIG. 8 is an embodiment of the present invention having connection means for connecting the unit cells and a substrate. FIG. DESCRIPTION OF SYMBOLS 1... Metal octagonal ring, 7... Silicon pressure sensitive structure, 8... Pressure receiving surface, 9... Substrate surface, 13...
...Strain gauge forming surface, 15... Bonding pad portion, 16... Silicon wafer, 17... Area corresponding to pressure sensor unit cell, 101 to 104, 1
11-114, 121-124... Diffusion type strain gauge, 141-143... Wiring.

Claims (1)

[Claims] 1. A pressure-sensitive structure made of single crystal silicon, a plurality of diffusion strain gauges formed on a surface perpendicular to the pressure-receiving surface of the pressure-sensitive structure, and a change in the resistance value of these strain gauges causes the pressure-receiving The strain gauge of the pressure-sensitive structure detects three components of force applied to a surface, and the pressure-sensitive structure is fixed to a support having a support surface parallel to the pressure-receiving surface. A pressure sensor characterized in that a terminal formed on a forming surface and a terminal formed on the supporting surface of the support body are connected by a flexible wiring film.