JP2583615B2 - Touch sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention detects, for example, a force applied to a finger surface of a hand from a grasped object by being attached to a hand of a robot, particularly a finger, in three directions. The present invention relates to a touch sensor.

[Conventional technology]

In recent years, the robot industry has achieved dramatic growth both qualitatively and quantitatively. In particular, in terms of quality, efforts have been made to mount a tactile sensor on the robot hand and to make the robot more intelligent.

The performance and conditions required for the contact sensor are as follows.

High sensitivity: High sensitivity for detecting force. It is desirable to be able to detect several grams with one element.

High resolution: The sensor element is desired to be small and dense.

Wide dynamic range: The detection range must be as wide as possible.

High reliability and high durability: To withstand long-time use even in harsh environments.

Linearity and hysteresis: Pressure and output are proportional and there is no hysteresis.

Response speed: The signal when the object is grasped is transmitted quickly to the control unit.

Flexibility: Soft as human skin is desirable.

Slip sensation: detecting not only pressure but also slip.

Inexpensive: Simple structure and inexpensive.

Various tactile sensors satisfying some of these conditions have been proposed or developed. A touch sensor of a push button type or a conductive rubber type is a representative example. In the former push-button type touch sensor, the metal push button supported by the coil spring is normally electrically OFF when there is no pressurization, but when pressurized, the contact closes and turns ON. It becomes. However, this method has a drawback that only the ON and OFF states are known, and is not suitable for continuous force detection.

On the other hand, the latter conductive rubber type touch sensor utilizes the fact that the electric resistance (conductivity) of the conductive rubber decreases when both sides of the conductive rubber sheet are sandwiched between electrodes and a force is applied to the sensor surface. is there. However, this method also has a problem that non-linearity and hysteresis occur between force and conductivity.

In addition to these, the various types of tactile sensors that have been proposed also have advantages and disadvantages, and not only do they not have sufficient performance, but also sense only one direction of pressure, that is, only the direction perpendicular to the contact surface. At present, very few sensors detect a force parallel to the contact surface.

[Problems to be solved by the invention]

Recently, there has been a tendency to develop tactile sensors that detect forces in three directions. For example, Japanese Patent Application No. 62-049996 and Japanese Patent Application No. 63-186959, which are proposed by the present applicant, are mentioned. However, such a conventional touch sensor uses a rigid wiring board or the like, so that it can be easily mounted on a flat surface of the robot hand, but a plurality of elements are arranged in a matrix on a curved surface such as a finger of the robot hand. No consideration has been given to mounting them side by side.

SUMMARY OF THE INVENTION An object of the present invention is to provide a thin and flexible structure (flexible structure) three-component force detection type touch sensor that solves the above-mentioned conventional disadvantages and can be attached to a finger of a robot hand. It is in.

[Means for solving the problem]

In order to achieve such an object, a first embodiment of the present invention provides:
In a contact sensor that detects an applied force by resolving it in three directions, three sets of strain gauges are formed integrally from a silicon wafer and correspond to the three directions of forces applied to the surface of the pressure receiving portion. A plurality of sensor cells, a flexible silicon oxide film connecting each of the plurality of sensor cells, and a flexible wiring board for mounting the plurality of sensor cells connected by the silicon oxide film. It is characterized by.

A second embodiment of the present invention is characterized in that a lattice-shaped groove is formed between a plurality of sensor cells while leaving a flexible silicon oxide film.

According to a third embodiment of the present invention, a plurality of sensor cells are arranged in a matrix, and each of the sensor cells has a pair of switches for individually selecting and operating the sensor cells. And the wiring for row selection are separately provided on the front surface and the back surface of the flexible wiring board.

Further, the fourth embodiment of the present invention is configured such that three sets of strain gauges are each formed of a high-resistance silicon layer, and the wirings of the three sets of strain gauges provided in the sensor cell do not overlap each other and rise. It is characterized by having been done.

(Operation)

The present invention, as described above, 3 component force _{(F X, F Y, F} Z) of the sensor cell can detect formed on a silicon wafer or integral with oxide film of a flexible, these the silicon oxide film sensor cells Is connected to a flexible wiring board while being connected, so that an array of contact sensors having a flexible structure can be realized. This is extremely effective in achieving the goal.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

A. Overview of Embodiment First, an overview of the entire touch sensor according to an embodiment of the present invention will be described.

The contact sensor according to the embodiment of the present invention uses a plurality of diaphragm-type three-component force detecting sensor cells (silicon sensor elements), and connects these sensor cells with a flexible oxide film to form a matrix. In addition, these are mounted on a flexible wiring board by soldering or the like, and can be wound around a curved surface such as a finger of a robot hand.

As described above, the structure is such that a plurality of three-component-force detection type sensor cells are connected by a flexible oxide film, so that they can be bent. Further, since a flexible wiring board is used, this wiring Naturally, a touch sensor in which silicon sensor elements as sensor cells are arranged in a matrix on a substrate and electrically and physically connected to each other can be naturally bent. As shown in FIG. 1 (A), when such a touch sensor 2 is mounted so as to be wound around the finger 1 of the robot hand, pressure, slip, moment, etc. applied to the surface of the robot hand can be detected. It can be detected by the sensor 2.

FIG. 1B schematically shows a cross-sectional state of one contact sensor 2 in the contact sensor group attached to the finger 1 of the robot hand. When a force is applied in the direction of the arrow in FIG. 3, each silicon sensor element 6 of the contact sensor 2 can detect the force in that direction.

B. Configuration of Embodiment Next, a specific configuration of the touch sensor according to the embodiment of the present invention will be described.

2 (A) and 2 (B) show the appearance of individual three-component force detecting type silicon sensor elements constituting the touch sensor of one embodiment of the present invention, and FIG. 2 (A) shows the front side and FIG. B) shows the back side.

Here, reference numeral 6 denotes a silicon sensor element, which has a square outer shape, and has a columnar pressure receiving column 7 integrally formed at the center thereof. Reference numeral 4 denotes a fixing portion protruding along the entire outer edge of the silicon sensor element 6, and reference numeral 5 denotes an annular groove-shaped thin portion formed between the pressure receiving column 7 and the fixing portion 4. In the thin portion 5, strain gauges 9 are formed at a plurality of positions in the diametrical direction and the like as shown in the figure (B) by a predetermined method such as a semiconductor wafer process. 8 is a solder terminal (solder bump). The pressure receiving column 7 at the center of the silicon sensor element 6 receives forces F _X , F _Y , and F _Z in three directions, and receives the silicon sensor element 6.
The force in the three directions is detected by the strain gauge 9 on the back surface of.

FIG. 3A shows an arrangement of the wiring of the strain gauge 9 and the arrangement of the solder terminals 8 in the silicon sensor element 6 described above.

The silicon sensor element 6 is formed from a semiconductor silicon wafer, and X ₁ , X ₂ , Y ₁ , Y ₂ , Z _{1 to} Z ₄ are formed by a semiconductor process.
Is formed. Also, the solder terminals 8 for connecting the aluminum wiring 14 and the electrodes can be formed in the plating step of the semiconductor process. Furthermore, in the wiring pattern of the present embodiment, two sets of half bridges and one set of full bridges coexist as shown in FIG. 4, the bridge voltage E and the ground G are shared, and V _X , V _Y , V _Z can be taken out as an output voltage. Further, the wirings 14 are arranged so as not to cross over each other while wrapping around these electrodes, thereby eliminating a decrease in the reliability of the electrical characteristics when crossing over.

The above configuration is based on the prior application proposed by the present applicant (Japanese Patent Application
-186959), except that a switch 15 of a semiconductor FET (field effect transistor), a horizontal address terminal M and a vertical address terminal N in a matrix arrangement are newly added thereto. And

The switch 15 switches ON and OFF of the voltage E, and two switches are connected in series to the voltage E. The gate of the switch 15 is connected to the horizontal address terminal M, and the switch 15 is turned on (closed) by a signal for selecting a row when a plurality of silicon sensor elements 6 are arranged in a matrix. , Conduction). The other switch 15 has its gate connected to the vertical address terminal N, and this switch 15 is turned on by a signal for selecting a column when a plurality of silicon sensor elements 6 are arranged in a grid.

Therefore, when a selection signal (for example, a voltage) is simultaneously applied to both of these address terminals M and N from the outside, the two switches 15 and 15 are simultaneously turned on, so that the switches 15 and 15 in the silicon sensor element 6 are turned on. subsequent three pairs of strain gauge bridge (F _X and F _Y of detection half-bridge, the detection of F _Z full bridge) so that the voltage E is applied to. On the other hand, if the signal is not applied to both the horizontal address terminal M and the vertical address terminal N, the voltage E is not applied to the strain gauge bridge, so that the output from the strain gauge bridge cannot be obtained.

The embodiment of the present invention is characterized in that the two switches 15, 15 and the address terminals M and N are provided. Further, as the switches 15, 15, for example, an FET (field effect transistor) well known as a semiconductor element can be used.

FIG. 3 (B) shows the silicon sensor element 6 of FIG. 3 (A).
2 shows a cross-sectional structure in which is mounted on a flexible wiring substrate 12. In FIG. 2B, a strain gauge 9 and a solder terminal 8 are formed on the silicon sensor element 6. The surface of the external fixing portion 4 of the silicon sensor element 6 is covered with a skin 10 for protecting the silicon sensor element 6. Each of the solder terminals 8 protruding on the back surface of the silicon sensor element 6 and each of the electrodes 11 protruding on the wiring board are connected to each other by a flip chip bonder, and an adhesive is provided between the back surface of the silicon sensor element 6 and the flexible wiring board 12. 13 firmly fixed.

In FIG. 3 (A), a ground terminal indicated by reference numeral 19 However, this is not a solder terminal, but it is used to supply electricity to the lower conductive part of the silicon sensor element 6 as ground and to connect to the ground terminal 8 without crossover with the aluminum wiring 14. It is a solderless earth. That is, the internal structure between the two ground terminals is as shown in FIG. In the figure, a silicon wafer 20 is a component of the silicon sensor element 6 and has a p
It is composed of a layer, an n layer and a p layer. The uppermost p layer inside the n layer is the strain gauge 9. The wiring 14 is formed above the p-layer and the n-layer. The lower part of the solderless ground terminal 19 is a p-layer and has high conductivity. On the other hand, the lower part of the solder terminal 8 which is ground is also the same p-layer. Therefore, the solderless ground terminal 19 (this is the ) Flows along the broken line as shown by the arrow, reaches the solder terminal 8, and is grounded outside the contact sensor via the solder terminal 8.

C. Manufacturing Method of Embodiment Next, an example of a manufacturing method of the touch sensor of the embodiment of the present invention will be described.

FIG. 6A shows two silicon sensor elements 6 for example.
One of the processing steps of a silicon sensor element group (hereinafter, referred to as a sensor array) when three are arranged in a matrix is shown. First, in the first step of processing, a strain gauge 9 is formed on the front surface of a silicon wafer by a semiconductor wafer process.
, Switch 15, solder terminal (solder bump) 8, wiring 14
And a silicon oxide film 21 as a flexible oxide film
The pattern shown in FIG. 6A is formed, and a pattern which can be processed as shown in FIG. 6A is formed on the back surface of the silicon wafer by etching.

Next, the process moves to the back surface of the silicon wafer.
In the state of the wafer, an annular groove 5 shown in FIG. 6A is formed by electric discharge machining.

After that, lattice grooves 24 are formed on the back surface of the silicon wafer by a dicing saw. At this time, the silicon oxide film
One of the important points of the present invention is to process the lattice-shaped groove 24 while leaving 21.

In this way, a series of 2 ×
When three sensor arrays are cut out, the result is as shown in FIG. 6A, and the cross section at that time is shown in FIG. 6B. FIG. 6B shows a structure in which a plurality of the silicon sensor elements 6 shown in FIG. 3B are connected by a silicon oxide film 21.

D. Wiring Method of Embodiment As described above, a wiring method of how to arrange the wiring 14 in the sensor array connected by the flexible silicon oxide film 21 will be described below.

FIG. 7 shows an example of a wiring method to the vertical address terminal N, and FIG. 8 shows a wiring method to the horizontal address terminal M.

First, the wiring method for the vertical addresses in FIG. 7 will be described. In a plan view A in the figure, the wiring connecting the vertical address terminal N of the three silicon sensor element 6 are arranged in the longitudinal direction of the left side of the drawing in parallel to N _1. When a vertical address signal (selection signal) is applied to this wiring N1, _one switch 15 (see FIG. 3A) of each left silicon sensor element 6 is turned on. Further, when the wire connecting the vertical address terminal N of the three silicon sensor element 6 are arranged on the right side of the longitudinal direction of the drawing in parallel and N _2, the wiring
Given a vertical address signal to the N _2, 1 a switch 15 of the right silicon sensor element 6 is turned ON. However, as described above, each of the silicon sensor elements 6 has two switches 15 for the vertical address and the horizontal address, and if both the switches 15 and 15 are not simultaneously turned on, the output from the bridge is output. Cannot be obtained (see FIG. 3 (A)). Therefore, the other switch 15 needs a wiring for supplying a horizontal address signal (selection signal) to the horizontal address terminal M.

The plan view A of FIG. 8 shows the wiring M ₁ , M ₂ , M ₃ of the above-mentioned horizontal address signal.
If, another wiring put out taken parallel to the transverse direction _{(V Y, V Z1, V} X, E,
G, V _Z2 ) Wiring method is shown. Also, as shown in the sectional views B and C of FIG. 8, these wirings are flexible double-sided printed wiring boards, that is, through-holes of the flexible wiring board 12.
22 and is formed below the flexible wiring board 12. On the other hand, vertical address signal wirings N ₁ and N ₂ are cross-sectional views in FIG.
As shown in FIGS. 8B and 8C, the wiring is formed on the surface of the flexible wiring board 12, so that there is no crossover between the upper wiring circuit in FIG. 7 and the lower wiring circuit in FIG. Furthermore, since a flexible material is used as the material of the flexible wiring board 12, it can be bent. At this time, the silicon sensor element 6 itself is not bent, but the silicon oxide film 21 is flexible and can be bent.

Since the silicon oxide film 21 firmly connects the silicon sensor elements 6, the terminals can be accurately positioned on the flexible wiring board 12 and connected and assembled at once. That is, the silicon oxide film 21
Therefore, there is an advantage that a cumbersome connection / assembly process, which is difficult to obtain the accuracy of assembling the silicon sensor elements 6 separately, is not required.

FIG. 9 shows a state in which the touch sensor of the embodiment of the present invention manufactured as follows is wound around the finger 1 of the robot hand. In this example, the silicon sensor elements 6 are arranged in five rows, but can be arranged in any desired column in the longitudinal direction. Signal lines from the sensor array are collected by a cable 25 and connected to an external device (not shown).

(Effect of the Invention) As described above, according to the present invention, the three components (F _X , F
Sensor cells capable of detecting _Y , F _Z ) are formed integrally with a silicon wafer together with a flexible oxide film, and these sensor cells are connected to a flexible wiring substrate while being connected by the silicon oxide film. Therefore, a plurality of sensor cells connected by a flexible silicon oxide film are collectively mounted on a flexible wiring board, and an array of contact sensors having a flexible structure can be easily realized. Can also be wound and attached, which is extremely effective in improving the intelligence of the robot.

[Brief description of the drawings]

FIG. 1 (A) is a perspective view showing a group of touch sensors of the embodiment of the present invention mounted on a finger of a robot hand. FIG. 1 (B) is a schematic cross-sectional view showing one cross-sectional state of the touch sensor. 2 (A) is a perspective view showing the front side appearance of one sensor cell of the touch sensor according to the embodiment of the present invention, FIG. 2 (B) is a perspective view showing the back side appearance of the sensor cell, FIG. 3 (A) ) Is the strain gauge of the sensor cell of the embodiment of the present invention,
FIG. 3 (B) is a cross-sectional view showing a cross section of the sensor cell, FIG. 4 is a circuit diagram showing an equivalent circuit of the embodiment of FIG. 3 (A), FIG. FIG. 5 is a cross-sectional view showing the internal structure of the sensor cell of FIG. 3 (A), FIG. 6 (A) is a perspective view showing one of the processing steps of the touch sensor of the embodiment of the present invention, FIG. 6 (B) ) Is a cross-sectional view showing the state after the processing, FIG. 7 is a plan view and a cross-sectional view showing the wiring state of the vertical address of the contact sensor in the 2 × 3 sensor cell array according to the embodiment of the present invention, FIG. FIG. 9 is a plan view and a cross-sectional view showing the wiring at the horizontal address of the contact sensor of FIG. 7 and the wiring circuit of the other input / output terminals. FIG. 9 is a diagram showing the contact sensor of the present invention mounted on the finger of the robot hand. It is sectional drawing which shows the detail. DESCRIPTION OF SYMBOLS 1 ... Finger, 2 ... Contact sensor, 4 ... Fixed part, 5 ... Annular groove part, 6 ... Sensor cell (silicon sensor element), 7 ... Pressure receiving column, 8 ... Solder terminal, 9 ... Distortion Gauge, 10 ... skin, 11 ... electrode, 12 ... flexible wiring board, 13 ... adhesive, 14 ... wiring, 15 ... switch, 18 ... n-layer, 19 ... solderless earth terminal, 20 ... silicon wafer, 21 ... silicon oxide film, 22 ... through-hole, 24 ... latticed groove, 25 ... cable.

Claims (4)

(57) [Claims] 1. A contact sensor for detecting an applied force by resolving it in three directions, wherein three sets of strain gauges are formed integrally from a silicon wafer and correspond to the three directions of forces applied to the surface of the pressure receiving portion. Are disposed, a flexible silicon oxide film connecting each of the plurality of sensor cells, and a flexible flexible wiring board mounting the plurality of sensor cells connected by the silicon oxide film And a touch sensor comprising: 2. The touch sensor according to claim 1, wherein a lattice-like groove is formed between the plurality of sensor cells while leaving a flexible silicon oxide film. 3. A plurality of sensor cells are arranged in a matrix. Each of the sensor cells has a pair of switches for individually selecting and operating the sensor cells, and a column selection wiring and a row connected to the switches respectively. The touch sensor according to claim 1, wherein the selection wiring is separately provided on a front surface and a back surface of the flexible wiring board. 4. The three sets of strain gauges are each formed of a high-resistance silicon layer, and are configured such that the wires of the three sets of strain gauges provided in the sensor cell do not overlap and cross each other. The touch sensor according to claim 1, wherein: