JPH01312433A - Contact force sensor - Google Patents

Abstract

PURPOSE:To detect the deflection of a silicon cell highly sensitively by supporting both ends of the lower surface of the square silicon cell on which a bridge circuit and the like, wherein a strain gage is assembled, are arranged with the supporting parts of the frame of a supporting stage. CONSTITUTION:A supporting stage 4 has a frame part 5 and supporting parts 6 which support both end parts of a silicon cell 1 that is coupled into the frame part 5. The stage is constituted with an insulating material. An insulating layer 7 is formed on the surface of a conductive part 1A on the cell 1. A strain gage 8 is formed on the insulating layer 7. A wiring pattern 9 is further formed. The cell 1 is supported on the supporting parts 6, with the surface on which the gage 8 and the like are formed facing downward. A conductive rubber sheet 11 is brought into close contact with the upper surface of the cell 1. A solder bump 3 for each terminal which is provided on the lower surface side of the cell 1 is connected to an electrode on a printed wiring board 13. Such contact force sensors are used as an array wherein a plurality of the sensors are arranged in a matrix pattern.

Description

[Detailed Description of the Invention] [Industrial Application Field 1] The present invention relates to a pressure sensor, and more specifically, it is often attached to a robot's hand, etc., and works in a fixed place to receive force from an object to be grasped. Therefore, there are limits to their work scope and functionality.For example, welding robots for the vehicle industry are installed at a specific location on the production line, and weld the vehicle body by moving the welding arm, so the robot itself does not make decisions on its own. It is not intended for welding.

However, in recent years, so-called intelligent robots with sensory and cognitive functions comparable to the five human senses have been developed and are gradually being put into practical use.

By the way, these intelligent robots need to be equipped with sensors to detect various senses.

Typical sensors are visual sensors and pressure (tactile) sensors, and pressure sensors in particular can be said to be indispensable for tasks such as grasping objects.

The following functions are required for pressure sensors for intelligent robots.

(1) High sensitivity High sensitivity for detecting a single force, for example, it is possible to detect a load of several grams with a negative element.

(2) Wide dynamic range 2. The operating range should be as wide as possible.

(3) High reliability and durability = A. To withstand harsh environments.

(4) Linearity/low hysteresis: Pressure and output are proportional,
Less hysteresis.

(5) Response speed: The response speed of signal processing is high.

(6) Flexibility Maintains flexibility like the skin of two people's hands and allows objects to be gripped softly.

(7) It should be possible to detect not only slip sensation and pressure, but also slip if possible.

(8) Compact and inexpensive: Thin and compact with low manufacturing and material costs.

Pressure sensors that meet some of these requirements have been proposed or put into practical use, such as those that use on/off microswitches, those that use pressure-sensitive rubber sheets (conductive rubber sheets), Alternatively, a sensor that uses changes in the amount of reflected light turns on when it receives a force, but this only detects the presence or absence of a force, and continuously detects the magnitude of that force. I haven't gotten into that.

In addition, those that use pressure-sensitive rubber sheets utilize the fact that a conductive rubber sheet is sandwiched between two electrodes and the sheet resistance changes by applying force to the electrodes. There are problems in that linearity cannot be obtained between the force and the senna signal output, hysteresis tends to occur, and heat resistance is low because a rubber sheet is used.

Furthermore, a device that utilizes changes in the amount of light reflection involves placing a rubber sheet with many conical protrusions on the surface of a transparent acrylic plate, and placing a mirror or light-receiving element on the back side of the acrylic plate. When light is irradiated into the acrylic board from the lateral direction of the acrylic board, the protrusions of the rubber sheet mentioned above change depending on the magnitude of the external force, and the extent of the dents can be detected using a mirror or a light-receiving element. be. However, although various types of pressure sensors have been proposed or prototyped, none of them fully satisfy the above-mentioned functions. Therefore, there is a strong desire to develop a highly sensitive and truly practical pressure sensor. .

In view of the above problems, it is an object of the present invention to provide a pressure sensor that has high practical performance, has a simple structure, is easy to manufacture, and can be thin and arranged in high density.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a support base in which a window wall frame portion is formed in a matrix shape, a bridge circuit incorporating a semiconductor strain gauge, and a bridge circuit. Common to a plurality of rectangular silicon cells whose both ends are supported by support parts of a window wall frame section with the surface on which switch means and terminals for the The device is characterized by comprising a conductive rubber sheet disposed in the terminal and electrically connected to a predetermined terminal of the terminals.

A flexible printed wiring board is bonded to the bottom side of the silicon cell where a ground terminal is formed together with a solder bump and a switch means 5 via its electrode, and the ground terminal provided on the bottom side of the silicon cell is conductive. Since we were able to obtain grounding by electrically connecting the conductive rubber sheet placed on the top side of the silicon cell itself through the silicon cell itself, we installed a ground terminal on each silicon cell and connected it from each ground terminal. There is no need to draw out the ground wire, and the signal lines in the printed circuit board that span multiple silicon cells can be simplified, contributing to cost reduction and making it highly practical and thin and high-density. It is possible to provide a pressure sensor that can be arrayed.

[Examples] Examples of the present invention will be described below in detail and specifically based on the drawings.

First, we will discuss the principle of bending of the silicon cell according to the present invention, which has both end support beams as shown in FIGS. 6A and 6B. If a force is applied to the center of the upper surface of the silicon cell 1 while it is supported by the support base 2, the silicon cell 1 will bend as shown in FIG. 6B, and tensile stress will be generated on the lower surface of the silicon cell 1.

Therefore, four strain gauges R1, R2, R3, and R4 are arranged on the lower surface side of the silicon cell 1 as described above, as shown in FIG. 7A, and these strain gauges R, -R4 are arranged as shown in FIG. 7C. Incorporate it into a bridge circuit as shown, apply a voltage V between opposing vertices and ground one end (G), and connect switching elements Sl and S2 to each of the output lines drawn out from between the other opposing vertices. By arranging the strain gauges R and -R4, the resistance change caused by the above-described deflection can be taken out as an output signal from the terminals T and t by turning on the switching elements 51 and S2. Note that E is a voltmeter.

In FIG. 7A, a silicon cell 1 is formed from a semiconductor silicon material in this way, and strain gauges R0 to R4 and switching elements Sl and S2 are connected to the output line from the bridge circuit, and furthermore, an output terminal T and a silicon cell 1 are formed on the silicon cell 1. The reason why semiconductor silicon was used for the beam members shown in FIGS. 6A and 6B is that semiconductor silicon can be used for strain gauges R, -R4, switching elements 51°S2, wiring, and This is because the solder bumps 3 formed on the T, t, s, and V terminals can be formed in a consistent process using a film forming technology. Furthermore, by forming such a silicon cell, it is possible to make the beam member smaller and thinner. Also, the switching element Sl formed here.

S2 is, for example, a field effect transistor.

FIG. 1 is a diagram showing the basic configuration of the present invention, where:
Reference numeral 4 denotes a support stand, and the support stand 4 includes a frame portion 5 of the form, and support portions 6 that support both ends of the silicon cell 1 fitted into the frame portion 5.
and is composed of an insulating member. In addition, as shown in FIG. 2, the silicon cell 1 has an insulating layer 7 formed by a so-called PN junction on the surface of the conductive part IA (P layer) that forms the base thereof.
A strain gauge 8 is formed as a P layer on the insulating layer 7, and a wiring pattern 9 made of aluminum or the like is further formed, and a grounding terminal 10 is made conductive by a semiconductor process. The part IA is left intact and formed thereon.

Therefore, the silicon cell 1 constructed in this way is supported by the support part 6 with the surface on which the strain gauge 8 etc. are formed facing downward, as shown in FIG. 1 top surface (corresponds to the bottom side in the M2 diagram)
For example, a conductive adhesive 21 is used to adhere the conductive rubber sheet 11, and a flexible protective film 12 made of, for example, an insulating rubber sheet is provided thereon to electrically and thermally protect the conductive rubber sheet 11. In other words, by configuring like this,
The grounding terminal 10 shown in FIG. 2 is electrically connected to the conductive rubber sheet 11 via the conductive part IA of the silicon cell 1, so there is no need to provide a through hole in the silicon cell 1 itself. The conductive rubber sheet 11 plays the role of grounding wiring.

Reference numeral 13 denotes a flexible printed wiring board disposed on the lower surface side of the silicon cell 1. The flexible printed wiring board 13 has printed wiring as described later on both sides thereof. The solder bumps 3 of each terminal are connected to the flexible printed wiring board 1
It is connected to an electrode (not shown) on 3 by soldering.

Although the configuration of a single pressure sensor has been described above, such a pressure sensor is generally used as an array in which a plurality of the above-mentioned single units are arranged in a matrix. Therefore, below, we will discuss configuring pressure sensors in an array.

FIGS. 3A to 3C are diagrams showing a case in which three individual pressure sensors are arranged in three rows. In FIG. 3A, the support base 4 is formed of an electrically insulating rigid body, and has grooves 14 formed in the column direction on its lower surface side, for example, as shown in FIG. 3B. FIG. 3C shows a state in which the silicon cells 1 are fitted into the support parts 6 of the individual frames of the support stand 4, and the flexible printed wiring boards 13 are attached in the column direction to the grooves 14 on the lower surface of the support stand. 15 is a conductor circuit formed on both sides of the flexible printed wiring board 13.

Next, when considering the signal lines to be drawn out from one silicon cell 1 with reference to FIGS. 4A to 4C, it is found that on one silicon cell 1 there is a For the bridge circuit, the terminals V, S, T,
t and G, a fourth
As shown in Figure B and Figure 4C, electrodes v, s, , T, , t corresponding to the above terminals and lead wires LV, LS, LT, and Lt from each of the electrodes must be provided. . However, as mentioned above, there is no need for electrodes and wiring for the grounding terminal G, and one piece of wiring can be saved.

However, when the silicon cells 1 are arranged in a matrix instead of just one, the number of wires increases in the column direction as well, so the flexible printed wiring board 13 as shown in FIGS. 4B and 4C It becomes impossible to use only one side. Therefore, the case where five silicon cells 1 are arranged in the column direction will now be described with reference to FIGS. 5A and 5B.

5A and 5B show the installation state of the electrodes and lead-out wiring on the flexible printed wiring board 13 in this case, where 1-1 to 1-5 are connected to the flexible printed wiring board 13. The positions of five silicon cells 1 in the column direction are shown. That is, since the five silicon cells must be turned on and off in this way, the through holes 20 are provided in the electrodes S6 corresponding to the silicon cells 1-1 to 1-4. Wiring lines LSI to LS4 for driving the switches are arranged on the back surface side via the -rule 20. LV, Lt, and LT are lead wirings for V, t, and T provided on the upper surface side, respectively.

To describe signal processing in a pressure sensor configured in a matrix in this way, first, by transmitting a signal to the switch signal terminal S provided in one silicon cell, two signals are transmitted from this silicon cell L to terminals T and t. However, it is difficult to process the signals if the signals are obtained from five silicon cells 1-1 to 1-5 at the same time as shown in FIGS. 5A and 5B. Therefore, first, when taking out a signal from the silicon cell 1-1, the signal line LSI
The switching element is turned "on" via the signal lines LS2 to LS5, but in this case no signals are sent to the other signal lines LS2 to LS5. In this way, the switching elements in each silicon cell may be turned on sequentially via the signal line.

Note that in the example of FIGS. 5A and 5B, silicon cell 1
An example in which five circuit boards are arranged has been described, but this is because a maximum of five circuits can be processed by wiring in four rows on the double-sided flexible printed wiring board 13. Therefore, the number of silicon cells 1 arranged in the column direction is 4 or 3.
It is even easier to make them individual. In this way, by fitting the silicon cells 1 into the frames formed on the support base 4 in the row and column directions, an array of pressure sensors can be obtained.

[Effects of the Invention] As described above, according to the present invention, the lower surface of a rectangular silicon cell in which a bridge circuit incorporating a semiconductor strain gauge, its switch means, and various terminals are arranged is arranged in a matrix shape. Since both ends of the silicon cell are supported by the support parts of the frame of the support stand equipped with a frame part, and the deflection of the silicon cell is detected, the detection sensitivity can be kept high. The wiring board is bonded to supply electrical signals to the switch means and to take out signals from the strain gauges, and a conductive rubber sheet is connected to the upper surface of the silicon cell over the entire surface of the support base. Since the conductive rubber sheet is electrically connected to the ground terminal provided on the bottom side through the conductive silicon cell itself, there is no need to arrange the ground wire on the flexible printed wiring board, and that is all. This makes wiring on the flexible printed wiring board easier, making it possible to provide a pressure sensor that is thin overall and has excellent detection accuracy.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing the basic structure of the pressure sensor of the present invention, FIG. 2 is a partial cross-sectional view of its silicon cell, and FIGS. 3A, 3B, and 3C are examples of the support base according to the present invention. FIG. 4A is a wiring diagram on the silicon cell, and FIGS. 4B and 4C are a flexible printed wiring board according to the present invention. 5A and 5B are a plan view and a side view showing an example of the basic wiring state, and FIGS. 5A and 5B are a plan view and a side view showing an example of wiring on a flexible printed wiring board according to the present invention, respectively The sectional view, FIGS. 6A and 6B are schematic diagrams 7A and 7 showing the supporting state and load state of the silicon cell, respectively.
Figure B is a block diagram of a circuit arranged on the silicon cell and a cross-sectional view of the silicon cell, and Figure 7C is a block diagram of a bridge circuit on the silicon cell. 1.1-1 to 1-5... Silicon cell, l^... Conductive part, 3... Solder bump, Sl, S2... Switching element, R0 to R4, 8... Strain gauge, 4... Support stand, 5... Frame part, 6... Support part, 7... Insulating layer, 9... Wiring pattern, io... Grounding terminal, 11... Conductive rubber sheet , 12... Film, 13... Flexible printed wiring board, 14...
Groove, 15... Conductor circuit, V, S, T, t, G... Terminal, V,, S,, TE, tI knee... Electrode, 1, V, LS,
LSI ~LS4. LT, Lt...Wiring, 20...
・Through hole. Patent applicant 7-? Figure 2 Figure 3C Figure 4B Figure 4A Figure 4C Figure 5B Figure 5A

Claims (4)

[Claims] (1) A supporting base in which a window frame portion is formed in a matrix, a bridge circuit incorporating a semiconductor strain gauge, and a surface on which switch means and terminals for the bridge circuit are arranged are placed downward, and the above-mentioned A plurality of rectangular silicon cells whose both ends are supported by the supporting portions of the window frame portion; A pressure sensor comprising: a conductive rubber sheet connected to a conductive rubber sheet; (2) The pressure sensor according to claim 1, wherein the conductive rubber sheet covers the plurality of rectangular silicon cells over the entire surface of the support base. (3) The pressure sensor according to claim 1 or 2, wherein the predetermined terminal is a grounding terminal, and grounding wiring is provided by the conductive rubber sheet. (4) In the pressure sensor according to any one of claims 1 to 3, a flexible printed wiring board is arranged on the lower surface side of the rectangular silicon cell,
A pressure sensor characterized in that an electrode of the flexible printed wiring board is electrically connected to a terminal other than the predetermined terminal.