JPH04329328A - Contact pressure sensor and its measurement method - Google Patents

Abstract

PURPOSE:To enable detection of load stabilized with high sensitivity and high precision by using a single body sensor based on a variety of contact pressure measurement conditions. CONSTITUTION:A contact pressure sensor 15 is formed by a semiconductor strain gauge 2 and multiple terminals 5, a load detection element 10 composed of a silicon chip having a pressure receiving cylinder 4 in a central part and a flexible print wiring board 6 connected to chip 1 is supported by an elastic floor 11. A pressure receiving plate 13 is provided corresponding to the size of elastic floor 11 on the upper surface of pressure receiving cylinder 4, a space between pressure receiving plate 13 and elastic floor 11 is filled with an elastic adhesive agent 14.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a contact pressure sensor, and more particularly to a single-element contact pressure sensor suitable for measuring the distribution of pressure exerted by an object in contact within an arbitrary plane.

0002

2. Description of the Related Art FIG. 6 shows an example of a conventional strain gauge type contact pressure sensor. In this example, as shown in (A), Cu-Ni, Ni-
A strain gauge 27 constructed by bonding a resistance element 26 made of Cr or other alloy and having a resistance of usually 120 to 1000Ω is attached to a structure 2 made of a metal material such as stainless steel.
(B) shows a conventional contact pressure sensor 29 constructed in this way. Note that the signal detected by this sensor 29 is taken out by the wiring 31 soldered to the terminal 30 of the strain gauge 27, but the sensitivity of such a contact pressure sensor 29 is 1 to 1. 6mV/kgf is common, usually 1000-200
Usually, it is amplified and used by a 0x amplifier circuit.

FIG. 7 shows another conventional example of a semiconductor strain gauge type contact pressure sensor. Here, 32 is a silicon chip, 33 is a pressure receiving column 33 formed by grinding the load receiving side of the chip 32, and on the back side thereof is a semiconductor strain gauge 34, its detection circuit 35, and a driving circuit 35. A signal terminal 36 necessary for this purpose is formed. Then, the load detection element 37 configured in this manner is mounted on the circuit board 38, and the terminal 39 formed on the board 38 and the signal terminal 36 are connected with wiring 40 by wire bonding. The above signal is taken out from 38 through wiring 31.

0004

However, the first problem with the conventional strain gauge type contact pressure sensor as shown in FIG. 6 is that the manufacturing process is complicated. In particular, the task of attaching the strain gauge 27 to a specific part of the structure 25 that causes strain is a difficult task that has the greatest impact on the sensitivity and various characteristics of the sensor depending on the location and bonding conditions. Therefore, it is necessary to rely on the skill of the operator, and there is a problem in that sensor characteristics vary.

The second problem is that the resistance of the resistance element is 12
Since it is small (0 to 1000Ω), it is easy for inductive noise to occur.

The third problem is that because the ratio of resistance change to length change due to strain in the strain gauge (referred to as gauge factor) is small, only a low sensitivity of about 1 to 6 mV/kgf can be obtained.

[0007] The fourth problem is that shielded wires are normally used for the wiring for extracting signals from the contact pressure sensor to prevent noise, but the diameter of the wiring becomes large and the contact pressure sensor can be constructed to be more compact. This feature will be lost.

On the other hand, the conventional semiconductor strain gauge contact pressure sensor shown in FIG. 7 has solved the first to third problems, but the fifth problem is that the wire bonding used for wiring has Poor mechanical strength and reliability.

A sixth problem is that the silicon chip forming the semiconductor strain gauge is made of a hard and brittle material and is therefore susceptible to impact.

Furthermore, the seventh problem is that in such a conventional structure, the pressure receiving area of the pressure receiving column 33 is small, so when measuring the contact pressure received from a soft object, the pressure receiving column 33 tends to sink into the object. Because of this, when a load is applied to the contact pressure sensor, the detected load does not exhibit linear characteristics.

The object of the present invention is to solve such conventional problems, and to provide a contact pressure sensor and its measurement capable of stably detecting a load with high sensitivity and high precision using a single sensor under all contact pressure measurement conditions. The purpose is to provide a method.

0012

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a semiconductor strain gauge, a Wheatstone bridge circuit incorporating the semiconductor strain gauge, and a power supply, ground, and element selection circuit for the circuit. A load detecting element having a pressure receiving column for receiving a load in the center of a silicon cell in which a switch for output signals and terminals for supplying output signals are formed, and a flexible print connected to each terminal of the load detecting element. a wiring board, an elastic floor that supports the silicon cell of the load detection element substantially in the center, and a pressure receiving plate that is fixed to the upper surface of the pressure receiving column in parallel with the silicon cell and that is formed to have approximately the same diameter as the elastic floor. and an elastic adhesive filled in a gap between the pressure receiving plate and the elastic bed.

[0013]

[Operation] According to the present invention, a pressure-receiving pillar and a semiconductor strain gauge formed by semiconductor process technology are provided in the central part of the silicon chip where strain is likely to occur, and the ends of the flexible printed wiring board are connected to this. In addition to configuring a load detection element, such an element is supported almost at the center of the elastic floor, and a pressure receiving plate with a size corresponding to the elastic floor is provided on the top surface of the pressure receiving column, and the pressure receiving plate and the elastic This technology fills the space between the floor and the floor with an elastic adhesive, which increases the gauge factor compared to conventional methods and buffers the impact on the silicon cell.Furthermore, it can be installed alone on a support, resulting in high precision. contact pressure can be detected.

[0014]

Embodiments Hereinafter, embodiments of the present invention will be described in detail and specifically based on the drawings.

FIG. 1 shows a first embodiment of the invention. Figure 1
(A) shows the structure of a single contact pressure sensor, where 1 is a silicon chip, and 2 is a semiconductor strain gauge formed near the center of the silicon chip 1 as shown in (B). These semiconductor strain gauges 2 are incorporated into a Wheatstone bridge circuit 3 as shown in FIG. 1(C). 4 is a pressure receiving column soldered to the center of the silicon chip 1; 5 is a terminal formed by a solder bump formed at the end of the silicon chip 1; and 6 is connected to these terminals 5 through the terminal 5. This is a flexible printed wiring board for extracting signals.

The flexible printed wiring board 6 has a base film 7 with a thickness of several tens of micrometers, and has signal wiring 8 on the bottom side and a metal foil 9 as a shield layer on the top side. After connecting the wiring board 6 to the terminal 5, the load detection element 10 having such a structure is placed in the recess 11A of the elastic floor 11 and fixed with adhesive. 12 is a holding plate provided to hold the wiring board 6 on the elastic floor 11;
This holding plate 12 protects the connection portion of the wiring board 6 to the terminal 5 from being subjected to excessive force. Also, 13
is a pressure receiving plate attached to the upper part of the pressure receiving column 4, and here, the elastic floor 11 and the pressure receiving plate 13 are both formed in the shape of a disk with the same diameter, and the elastic floor 11, which surrounds the pressure receiving column 4, The space between the pressure receiving plates 13 is filled with a relatively flexible adhesive 14. In this example, the adhesive 14 has a Young's modulus of 0.
Epoxy resin of 35 kgf/mm2 was used.

FIG. 2 shows an example in which a load is detected by the contact pressure sensor 15 constructed in this manner. This is an example in which the sensor 15 detects the applied load. Note that (A) in FIG. 2 is a detection measurement example according to this embodiment, and (B) in FIG. 2 is an example in which a conventional contact pressure sensor 15F having the form shown in FIG. 7 was used for comparison with this embodiment. This is an example. Further, a gap H is maintained between the leather body 16 and the support body 17 that supports both the sensors 15 and 15F. In other words, the upper surfaces that receive the loads of the sensors 15 and 15F are designed to protrude from the upper surface 17A of the support body 17 by the above-mentioned dimension H.

FIG. 3 shows the load P15 detected by the sensor 15 of the present invention and the load P15F detected by the conventional sensor 15F with respect to the load P applied through the leather body 16 in such a state. A comparison is shown. That is, as is clear from this figure, the sensor 1 of the present invention
5 can accurately detect the load in a linear line as shown on P15 in response to the applied load P, whereas the conventional sensor 15F can detect the load linearly as shown on P15F. The detected load becomes inaccurate because the area of the pressure receiving part is small and the applied load P is not properly transmitted to the sensor 15F via the leather body 16.

Next, another embodiment in which the load is detected using the sensor 15 of the present invention will be described with reference to FIG.

In this example, a leather body 16 is placed above the contact pressure sensor 15 which is supported by a support 17 in the same manner as shown in FIG. , a solid body 18 is placed on the sensor 15 so that a load is evenly applied thereto, and a pressure F is applied from above. At this time, the leather body 16
FIG. 5 shows the relationship in which G of Pv/Ps=G changes with respect to the protrusion amount H of the sensor 15 described above, where Pv is the load detected corresponding to the shared load Ps of the sensor received from the sensor.

As is clear from this figure, in this embodiment, H
It can be seen that when = 0.1 mm, the contact pressure sensor 15 accurately detects a load corresponding to the sensor shared load Ps. That is, in this example, H is 0.1
This shows that by keeping the value at mm, the same detection accuracy can be obtained whether the surface of the support 17 in which the sensor 15 is embedded is a flat or curved surface.

[0022]

As explained above, according to the present invention, there is provided a semiconductor strain gauge, a Wheatstone bridge circuit incorporating the semiconductor strain gauge, a power supply to the circuit, a ground, an element selection switch, and a Wheatstone bridge circuit incorporating the semiconductor strain gauge. A load detection element having a pressure receiving column for receiving a load in the center of a silicon cell in which terminals for supplying output signals are formed, and a flexible printed wiring board connected to each of the terminals of the load detection element. , an elastic floor supporting the silicon cell of the load sensing element substantially in the center; a pressure receiving plate fixed to the upper surface of the pressure receiving column in parallel with the silicon cell and formed to have substantially the same diameter as the elastic bed; An elastic adhesive is filled in the gap between the pressure receiving plate and the elastic floor, and the load transmitted to the element through the pressure receiving plate while being protected by the surrounding adhesive layer is detected. Therefore, it is possible to reduce the variation in sensor sensitivity, and at the same time, it is expected that the sensitivity will be improved, and the prototype sensor was able to confirm a sensitivity of about 70 mV/kgf.

Furthermore, by forming a flexible printed wiring board as described in claims 2 and 3, the space required to support the contact pressure sensor can be reduced, and furthermore, the bending resistance of the wiring can be improved. Moreover, the reliability of the wiring connection portion against external mechanical forces can be improved.

Furthermore, the impact resistance of the sensor is improved by filling the sensor with an elastic adhesive. Furthermore, linear load detection characteristics can be obtained even for loads applied via soft objects.

Furthermore, by applying the measuring method according to claim 5, it is possible to minimize the decrease in sensor sensitivity due to the provision of the pressure receiving plate, and the Young's modulus is 0.35.
kgf/mm2: 91 → 72mV/kgf, about 20
It was confirmed that the decrease in sensitivity could be suppressed to .

[0026] In addition, when applying such a measurement method, since the detected value can be freely corrected, it is necessary to precisely set the height H at which the pressure receiving plate protrudes from the surrounding surface when installing the contact pressure sensor. None.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing an example of the configuration of the present invention.

FIG. 2 is an explanatory diagram showing a comparison of specific examples of contact pressure measurement according to the present invention and a conventional example.

FIG. 3 is an output characteristic curve diagram of the measurement results shown in FIG. 2;

FIG. 4 is an explanatory diagram showing another measurement example according to the present invention.

FIG. 5 is a characteristic curve diagram related to sensor installation conditions obtained from the measurement results shown in FIG. 4;

FIG. 6 is a perspective view showing the configuration of a conventional example.

FIG. 7 is a sectional view showing the configuration of a conventional semiconductor strain gauge type.

[Explanation of symbols]

1 Silicon chip 2 Semiconductor strain gauge 3 Wheatstone bridge circuit 4 Pressure receiving column 5 Terminal 6 Flexible printed wiring board 7 Base film 8 Wiring 9 Metal foil 10 Load detection element 11 Elastic floor 12 Presser plate 13 Pressure receiving plate 14 Adhesive 15 Contact pressure sensor 16 Leather body 17 Support

Claims (5)

[Claims] [Claim 1] A semiconductor strain gauge, a Wheatstone bridge circuit incorporating the semiconductor strain gauge, and a silicon substrate in which a power supply to the circuit, a ground, a switch for selecting an element, and terminals for supplying an output signal are formed. A load sensing element having a pressure receiving column for receiving a load in the center of the cell, a flexible printed wiring board connected to each terminal of the load sensing element, and a silicon cell of the load sensing element approximately in the center. a supporting elastic bed; a pressure receiving plate fixed to the upper surface of the pressure receiving column in parallel with the silicon cell and formed to have approximately the same diameter as the elastic bed; and filling a gap between the pressure receiving plate and the elastic bed. A contact pressure sensor comprising: an elastic adhesive; 2. The flexible printed wiring board comprises:
2. The contact pressure sensor according to claim 1, wherein an end portion of the contact pressure sensor is fixed to the elastic floor by a holding plate that is thinner than a gap between the pressure receiving plate and the elastic floor. 3. The flexible printed wiring board comprises:
Wiring formed on one side of a base film with a thickness of 25 μm or less, metal foil for shielding formed on the entire surface of the other side, and a metal foil with a thickness of 25 to 100 μm covered on both sides of the base film. The contact pressure sensor according to claim 1, wherein the contact pressure sensor has a membrane body, and the wiring is disposed approximately at the center of the entire thickness. 4. The elastic adhesive has a Young's modulus of 1 kgf/mm2 or less.
Contact pressure sensor described in . 5. The contact pressure sensor according to claim 1 is supported by a support, and the upper surface of the pressure receiving plate is made to protrude from the top surface of the support by a height H. , correcting the load detected by the contact pressure sensor based on a relationship with a value G obtained by dividing the load detected by the load carried by the pressure plate out of the load applied to the upper surface of the pressure plate; A measuring method for a contact pressure sensor characterized by: