WO2003074986A1

WO2003074986A1 - Stress sensor

Info

Publication number: WO2003074986A1
Application number: PCT/JP2003/002096
Authority: WO
Inventors: Hideyuki Teraoka
Original assignee: K-Tech Devices Corp.
Priority date: 2002-03-07
Filing date: 2003-02-26
Publication date: 2003-09-12
Also published as: JPWO2003074986A1; AU2003211715A1

Abstract

A stress sensor capable of irritating strain gauges (5) disposed on the surface of a substrate (3), wherein the strain gauges (5) are disposed on the surface of the substrate (3) having a plurality of piece-like parts (1) with free tips or semi-free tips and a support part for supporting the piece-like parts and irritated by a stress added to the piece-like parts (1) to vary the electric characteristics of the strain gauges (5) so as to detect the stress from a variation in the electric characteristics, for example, such a structure that the plurality of piece-like parts (1) are led from the peripheral edges of the frame-like substrate (3) toward the inside of a frame and the peripheral edges of the frame-like substrate (3) form support parts is adopted, whereby the stress sensor can be downsized by deflecting the substrate (3).

Description

6 Description

Stress sensor technical field

The present invention relates to a stress sensor using a resistance element or the like as a strain gauge, and more particularly to a stress sensor that can be used for a pointing device for a personal convenience or a multifunctional switch for various electronic devices such as a mobile phone. . Background art

Regarding a stress sensor using a resistance element as a strain gauge, see Japanese Patent Application Laid-Open No. 2000-28073, Japanese Patent Application Laid-Open No. 8-873735, Japanese Patent Application Laid-Open No. 7-209104 The official gazette has its disclosure.

The outline of the stress sensor disclosed in Japanese Patent Application Laid-Open No. 2000-260783 is that a post 30 as a stress transmitting member is provided at a central portion, and a middle portion between an outer peripheral portion and a central portion. In addition, a thin polygonal or circular ceramic substrate 20 having four resistive elements 22 radially centered on the post 30 is used as a component thereof, and the substrate 20 is pressed by the post 30. The flexure is caused by using the outer peripheral portion as a fulcrum, and the resistance element 22 is distorted to detect the pressing of the boss 30 (FIGS. 14 and 15).

The outline of the stress sensor disclosed in Japanese Patent Application Laid-Open No. 8-87375 is that a lower surface of a flat substrate 3 is integrally formed with the substrate 3 at positions shifted by 90 degrees from each other. The strain gauge 5 is connected to a central portion of the upper surface of the substrate 3, extends perpendicular to the upper surface, and has a tip as a stress transmitting member capable of being displaced in an arbitrary direction. It comprises a stick portion 40 and detects the displacement direction and the displacement amount of the tip of the stick portion 40 from the output of the strain gauge 5 (FIG. 16).

The outline of the stress sensor disclosed in Japanese Patent Application Laid-Open No. 7-209104 is as follows: a reper-arm 41 as a stress transmitting member, a central portion to which the lever-arm 41 is attached, and A substantially flat tab area protruding outward from the central portion along the force detection axis When the external force is applied to the free end of the lever arm 4 1, the substrate 3 receives concentrated strain at almost the joint between the tab area 4 2 and the central portion. A strain gauge 5 is provided at the joint (Fig. 17).

In the stress sensor disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 2000-266783, the pressure applied to a post 30 disposed at the center of the polygonal or circular substrate 20 is increased. This is the driving force for bending the substrate 20. The deflection stimulates the resistance element 22 which is a strain gauge. In order to obtain the stimulus sufficiently, it is necessary to obtain a sufficient amount of substrate 20 bending. However, when the substrate 20 made of ceramic is used, it is difficult to obtain a sufficient amount of deflection from its rigidity. Therefore, it is necessary to increase the distance from the center of the substrate 20 as a point of emphasis to the outer end of the substrate 20 as a fulcrum, and to promote the bending of the substrate 20 by applying the leverage principle. For that purpose, it is necessary to enlarge the shape of the substrate 20. Therefore, it is difficult to reduce the size of the entire stress sensor (Figs. 14 and 15).

Here, if a flexible material is selected as the substrate 20 material, the above problem may be solved, but a new problem arises. A new problem is that the plastic deformation of the substrate 20 is likely to occur. That is, when the flexible substrate 20 is repeatedly bent, the shape of the substrate 20 becomes difficult to be restored. In other words, there is a problem that the plastic deformation may occur beyond the range of the natural deformation of the substrate 20. When the substrate 20 is plastically deformed, the output resistance value from the strain gauge (resistance element 22) for the subsequent application of stress becomes inaccurate. The reason is that plastic deformation loses reversibility and does not recover even if stress is removed.Strain gauges on such a substrate 20 always receive the stress due to the plastic deformation of the substrate 20. (Stimulation). Therefore, in a stress sensor that stimulates a strain gauge disposed on the substrate 20 by bending the substrate 20, the substrate 20 material has a certain degree of rigidity and elasticity like ceramic or fiber-reinforced plastic. It is thought that it is required to have.

In addition, it is theoretically possible to promote the bending of the substrate 20 by making the bent portion of the substrate 20 extremely narrow. However, the narrow portion may be brittlely broken due to excessive stress concentration on the narrow portion via the stress transmitting member. In addition, it is difficult to form the strain gauge 5 in the narrow portion with high positional accuracy and uniformity due to the manufacturing process in mass production. It is.

The stress sensor disclosed in JP-A-8-87375 also has the same problem as the stress sensor disclosed in JP-A-2000-76803. . The reason for this is that the stick portion 40 as the stress transmitting member is connected to the central portion of the substrate 3 and employs a configuration that extends perpendicular to the upper surface. That is, since the force point is located at the center of the substrate 3 and the fulcrum is located at the outer end of the substrate 3, it is necessary to enlarge the outer shape of the substrate 3 to promote the bending of the substrate 3 by applying the leverage principle. It is difficult to miniaturize the whole (Figure 16).

Further, the stress sensor disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 7-209104 is also disclosed in Japanese Patent Application Laid-Open No. 2000-26873 and Japanese Patent Application Laid-Open No. 8-87375. It has the same problem as the stress sensor disclosed in the gazette. The reason is that the lever arm 4 1 is attached to the central portion of the substrate 3 and has the substrate 3 having a substantially flat tab area 4 2 protruding outward from the central portion. When it is applied to the free end of 4 1, the substrate 3 is subjected to concentrated strain at almost the joint between the tab area 4 2 and the central part, and the strain gauge 5 is arranged at the joint. That's why. Therefore, it is necessary to increase the distance between the center portion, which is the above-mentioned point of force, and the outer end of the tab region 42, which is the fulcrum, and it is difficult to reduce the size of the entire stress sensor (FIG. 17).

An object of the present invention is to reduce the size of a stress sensor that functions by deflecting a substrate and stimulating a strain gauge disposed on the substrate surface. Disclosure of the invention

In order to solve the above-mentioned problems, a first stress sensor of the present invention provides a strain gauge on a surface of a substrate 3 having a plurality of strips 1 each having a free end or a semi-free end, and a support that supports them. 5 are arranged, and the strain gauge 5 is stimulated by applying a direct stress to the piece-shaped portion 1 to change the electrical characteristics of the strain gauge 5, and the stress is grasped from the change in the electrical characteristics. (Figs. 1 and 2).

The above “free end” is defined as the state where the stress sensor does not operate and the other state Refers to the end of the strip 1 that is not substantially fixed. The term “semi-free end” means that the stress sensor is temporarily fixed by other members in a state in which the stress sensor does not operate and in an operating state, but even in the fixed state, the degree of freedom of movement and deformation is small. The end of a flaky part 1

. Another meaning of the “free end” and the “semi-free end” is that the end of the flaky portion 1 which is not fixed by the support portion but can move and deform independently of the support portion is also included. Including.

The state in which “the support portion supports the flaky portion 1” means that the support portion and the flaky portion 1 are integrated, or that the support portion and the flaky portion 1 are initially separate members and are bonded together. State with both agents <Includes both. Here, the supporting portion in FIGS. 1 and 2 corresponds to the frame portion 2. In addition, `` strain gauge 5 '' is applied with a thick film resistance element by screen printing, thin film resistance element by sputtering technology, commercially available chip resistor, piezoelectric element, thick film capacitor element, and other stress. It is a circuit element whose electrical characteristics can change due to It is preferable that the material of the “substrate 3” has a certain degree of rigidity and elasticity as described above. For example, a resin molded article in which ceramics such as alumina, reinforcing fibers such as glass fibers are mixed, and a material in which the surface of a metal plate is coated with glass are suitable. However, it goes without saying that a flexible material having a lower rigidity than the above can be suitably used as long as it does not easily undergo plastic deformation under repeated stress application.

“Direct stress application to the flaky portion 1” refers to the application of stress to the flaky portion 1 without substantially attenuating the transmission of stress. For example, as in the stress sensor disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 7-209104, the stress applied to the central portion by the lever / arm 41 attached to the central portion of the substrate 3 is applied to the tab region. 4 2 (corresponding to the strip 1), the stress applied to the strip 1, which takes the transmission path of the stress transmitted as a result (FIG. 17), is such that the stress is applied to the substrate 3 Since it also contributes to the deformation of the part, the transmission of stress to the flank 1 involves substantial stress attenuation, and is not “direct stress application to the flank 1”.

By “directly applying a stress to each of the plurality of piece-shaped portions 1”, the substrate 3 can be bent with a smaller stress than in the related art. In the three types of stress sensors (Figs. 14 to 17) shown as conventional technologies, the substrate 3 is located in the direction in which the substrate 3 is to be bent. , Therefore, the stress transmitting member 4 is arranged at the center of the substrate 3. Therefore, even if a stress is applied to the stress transmitting member 4, the bending of the substrate 3 is hindered as a whole.

On the other hand, the first stress sensor according to the present invention described above “applies a stress directly to each of the plurality of strips 1”. The tip of the piece-shaped portion 1 is a free end or a semi-free end. Therefore, it is possible to remove a factor that hinders the conventional bending of the substrate 3 and to flex the piece-like portion 1 while minimizing the loss of the stress applied to the stress transmitting member 4. This eliminates the need to lengthen the flaky portion 1 as in the conventional case. That is, by bending the substrate 3, the size of the stress sensor that stimulates the strain gauges 5 arranged on the surface of the substrate 3 can be reduced.

In the second stress sensor of the present invention, a plate-like member 51 having a strain gauge 5 on a plate-like surface has a flaky portion 1 fixed or integrated with a central region 52 thereof. A mechanism is provided for applying stress to the flaky portion 1 in a state where 52 is fixed to the support member 16, and the strain gauge 5 is stimulated by the direct application of stress to the flaky portion 1. Thus, the electrical characteristics of the strain gauge 5 are changed, and the stress is grasped from the change in the electrical characteristics.

FIG. 10 shows an example of the configuration of the second stress sensor, and FIG. 11 shows the operation state of the stress sensor. It can be seen that the stress transmitting member 4 is configured to directly apply a stress to the flaky portion 1. Therefore, for the same reason that the size of the stress sensor can be reduced by the configuration of the first stress sensor, the size of the stress sensor can also be reduced by the configuration of the second stress sensor. The terms used in the description of the second stress sensor are synonymous with the terms used in the description of the first stress sensor.

Further, in the third stress sensor of the present invention, the strain gauge 5 is arranged on the surface of the substrate 3, and the central region 52 of the substrate 3 is fixed, and the strain gauge 5 is directly connected to the substantial outer end region of the substrate 3. When the strain gauge 5 is stimulated due to the application of a large stress, the electrical characteristics of the strain gauge 5 are changed, and the stress is grasped from the change in the electrical characteristics. Here, the “substrate 3 outer edge region” refers to a region other than the substrate 3 central region 52.

The third stress sensor is different from the first stress sensor and the second stress sensor in that the third stress sensor does not have the flaky portion 1. Even if there is no flaky portion 1, by applying a direct stress to the outer end region of the substrate 3, the substrate 3 is bent and the strain gauges 5 arranged on the surface of the substrate 3 are stimulated, Such stress can be grasped. Therefore, for the same reason that the stress sensor can be downsized by the configuration of the first stress sensor, the stress sensor can be downsized by the configuration of the third stress sensor. The meanings of the terms used in the description of the third stress sensor are the same as those used in the description of the first stress sensor.

Here, the above-mentioned "piece-like portion 1" refers to a portion provided so as to easily bend a specific region of the substrate 3 or the plate-like member 51 and integrated with or fixed to the substrate 3 or the plate-like member 51. . It does not matter whether the flaky portion 1 exists along the surface of the substrate 3 or the surface of the plate-like member 51. However, if the structure of the substrate 3 and the plate-like member 51 is simplified by integrating it with the central area 52 described later by integral molding, etc. It preferably exists along the three faces.

The “central region 52” is a portion that constitutes a part of the substrate 3 or the plate-like member 51. For example, in the substrate 3 shown in FIG. Say the area. In the frame-shaped substrate 3 shown in FIGS. 1, 2, and 9, the “central region 52” does not exist. Here, the stress sensor generally functions as a stress sensor only when there is a control unit that detects and calculates the electrical characteristics such as the resistance value. However, in this specification, a portion excluding the control unit is referred to as a “stress sensor” for convenience. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a diagram illustrating an outline of a structure of a stress sensor according to a first embodiment of the present invention. FIG. 2 is a diagram illustrating an outline of a structure of a stress sensor according to a second embodiment of the present invention. FIG. 3 is a diagram showing an operation state of the stress sensor according to the first embodiment of the present invention. FIG. 4 is a diagram illustrating an operation state of the stress sensor according to the second embodiment of the present invention. FIG. 5 is a diagram showing an example of an outline of an electric signal input / output state in the stress sensor of the present invention. FIG. 6 is a plan view of a large-sized substrate used for manufacturing the stress sensor according to the first embodiment of the present invention. FIG. 7 is a diagram showing an example of an outline of an electric signal input / output state in the stress sensor of the present invention. FIG. 8 is a plan view of a large-sized substrate used for manufacturing the stress sensor according to the second embodiment of the present invention. FIG. 9 shows the deformation of the stress sensor according to the first or second embodiment of the present invention. It is a figure showing an important section of an example. FIG. 10 is a diagram showing an outline of the structure of the stress sensor according to the third embodiment of the present invention. FIG. 11 is a diagram showing an operation state of the stress sensor according to the third embodiment of the present invention. FIG. 12 is a diagram showing an outline of the structure of the stress sensor according to the fourth embodiment of the present invention. FIG. 13 is a diagram illustrating an operation state of the stress sensor according to the fourth embodiment of the present invention. FIG. 14 is a diagram showing the structure of a conventional stress sensor. FIG. 15 is a diagram showing an operation state of a conventional stress sensor. FIG. 16 is a diagram showing the structure of a conventional stress sensor. FIG. 17 is a diagram showing the structure of a conventional stress sensor.

The reference numerals attached to these drawings are: 1 ... piece-like portion, 2 ... frame-like portion, 3 ... substrate 4 ... stress transmission member, 5 ... strain gauge, 6 ... resistive element, 7 ... substrate terminal portion, 8 ... trimaple Chip resistor, 9 ... adhesive, 10 ... notch, 1 1 ... fitting member, 1 2 ... hole, 13 ... large board, 14 ... dividing groove, 15 ... dividing line, 1 6 ... support member, 17 ... terminal, 20 ... board, 21 ... trimming groove, 22 ... resistor element, 23 ... post operation part, 24 ... conductor, 30 ... post, 3 Ob ... post Bottom contour, 3 1… Circuit board, 3 2… Solder, 40… Stick part, 4 1… Lever arm, 4 2… Tab area, 50… Hole, 5 1… Plate member, 5 2 ... the central area, 53 ... conductors. BEST MODE FOR CARRYING OUT THE INVENTION

(First Embodiment)

FIG. 1 schematically shows the structure of a stress sensor according to the first embodiment of the present invention (corresponding to the above “first stress sensor”). Four pieces 1 are led out from the periphery (frame 2) of the frame substrate 3 made of alumina ceramic toward the inside of the frame. The frame 2 and the piece 1 are integrally formed, and the frame 2 is a support for the piece 1. Further, in the boundary region between the frame-shaped part 2 and the strip-shaped part 1, a thick film of a resistance element 6 as a strain gauge 5 is formed by a screen printing technique. These resistance elements 6 are realized by forming conductors by the same screen printing technique so as to obtain the connection state as shown in FIG. Although this conductor is not shown in FIG. 1, it is considered that it is preferable to form the conductor mainly in the frame portion 2 from the viewpoint of easy layout design of the conductor (wiring). FIG. 5 shows an outline of an electric signal input / output state in the stress sensor of the present invention. Four resistance elements 6 constitute a bridge circuit. A predetermined voltage is applied between the voltage application terminals (Vcc) and (GND) of this bridge circuit. A stress sensor in the Y-axis direction is constituted by the resistance element 6 and the Y terminal (, Y out) on the left side of the figure, and the stress in the X axis direction is formed by the resistance element 6 and the X terminal (X out) on the side of the figure. A sensor is configured. Thereby, the direction and magnitude of the stress application can be grasped.

The screen printing described above can be performed on a large substrate 13 in which a large number of the frame-shaped substrates 3 are arranged vertically and horizontally, so that printing can be performed on a large number of substrates 3 with a single operation, which is excellent in mass productivity. preferable. Specifically, for example, a large substrate 13 shown in FIG. 6 can be suitably used. The large-sized substrate 13 shown here has dividing grooves 14 formed vertically and horizontally. By applying a force in the direction to open the dividing grooves 14 after forming the resistive element 6 and the conductor by screen printing. The substrate is divided into individual substrates 3.

In the above screen printing, a silver-based metal glaze was used as a conductor paste, and a ruthenium oxide-based metal powder with the smallest possible individual ruthenium oxide particles was used as a resistor paste. Such a resistor paste has a large change in resistance value even with slight strain, and has good sensitivity as the strain gauge 5, so that it can be suitably used. A glass paste for protecting the resistance element 6 was also used. These pastes can be selected from commercially available ones.

The resistive elements 6 are subjected to a trimming step using a laser trimmer so that each of the resistive elements 6 has substantially the same resistance value. In the case where the above-mentioned large-sized substrate 13 is used, it is preferable to perform this step before the dividing step, since it improves work efficiency and is excellent in mass productivity.

The notch 10 formed in each of the stress transmission member 4 and the fitting member 11 made of alumina ceramic sandwiches the flaky portion 1, and the inner circumference of the stress transmission member 4 is slightly smaller than the outer circumference thereof. '1 大きな大きな大きな大きな大きな大きな大きな. No other member such as an adhesive was used for the fixing, and the fixing was realized by contact between the stress transmitting member 4 and the fitting member 11. The flaky portion 1 can slide with the notch portion 10, the lower surface of the stress transmitting member 4, and the fitting member 11 without strongly contacting them, and the ends thereof are substantially free ends. It became. As described above, the stress sensor according to the first embodiment of the present invention was obtained. Fig. 3 shows the operating state of the stress sensor according to the first embodiment. FIG. 3A shows a state in which no stress is applied to the stress transmitting member 4. FIG. 3B shows a state in which the stress is applied to the stress transmitting member 4 in any of the x and y planes (arbitrary lateral direction). FIG. 3C shows a state in which the stress is applied to the stress transmitting member 4 in the z direction (downward). In these cases, a region corresponding to the frame portion 2 shown in FIG. 1 is fixed by a housing or the like of the electronic device, and is not substantially deformed.

'In Fig. 3 (a), no deformation of the substrate 3 and the strain gauge 5 is observed. In FIG. 3 (b), the free end of the piece 1 is pressed by the lower surface of the stress transmitting member 4 and the bottom surface of the fitting member 11 or the notch 10 shown in FIG. 1, and the piece 1 is bent. You can see that As a result of this bending, significant deformation of the substrate 3 occurs at the boundary between the frame-shaped portion 2 and the piece-shaped portion 1, and the strain gauges 5 disposed at the boundary also deform to follow the deformation. In the figure, the strain gauge 5 existing in the direction in which the stress is applied (left side in the figure) is deformed so as to expand, and the strain gauge 5 on the opposite side (right side in the figure) is deformed so as to contract. However, when the stress sensor is used, for example, as a pointing device of a personal computer, a stress is applied in the lateral direction while pressing the top surface of the stress transmitting member 4 downward. In such a usage form, it is considered that all the strain gauges 5 are deformed so as to extend, and the degree of elongation is different in each case. In the first embodiment, the strain gauge 5 is a resistance element, and its resistance increases as the resistance element 6 expands, and decreases as the resistance element 6 contracts.

In FIG. 3 (c), the free end of the piece 1 is pressed by the lower surface of the stress transmitting member 4 or the notch 10 shown in FIG. 1, and the piece 1 is bent downward. Understand. As a result of this bending, the strain gauge 5 is deformed so as to follow the deformation, as in FIG. 3 (b). The detection that the stress transmitting member 4 is pressed in the downward direction (Z direction) in this manner detects that the four resistance elements 6 that are the strain gauges 5 are expanded by the pressing, and the respective resistance values are made substantially equal. Recognizing that it will grow up to. Such stress sensor characteristics are different from those obtained when a stress is applied in an arbitrary lateral direction, and can be distinguished therefrom. Immediately That is, changes in the electrical characteristics of the strain gauge that change in response to external force can be output as coordinate data in three orthogonal directions.

(Second embodiment)

FIG. 2 schematically shows the structure of a stress sensor (corresponding to the first stress sensor) according to the second embodiment of the present invention. Four flaky portions 1 are led out from the periphery of the frame-shaped substrate 3 made of an epoxy resin plate mixed with glass fibers into the frame. The flaky portion 1 is integrated with the frame-shaped substrate 3 by excavating the substrate 3, and the frame-shaped portion 2 is a support portion of the flaky portion 1. Further, in the boundary region between the frame-shaped part 2 and the piece-shaped part 1, a resistor constituting the resistance element 6 serving as the strain gauge 5 is formed as a thick film by screen printing technology. These resistance elements 6 (R1 to R4) are set to be connected as shown in FIG. The trimmable chip resistor 8 (R1trim to R4trrim) shown here will be described later.

Further, the formation of the conductor and the electrode for the resistance element 6 constituting the resistance element 6 in the second embodiment does not depend on the screen printing technique, but may be performed by a conductor on a normal printed circuit board such as a so-called subtract method or an additive method. This is achieved by employing a forming technique. Although this conductor is not shown in FIG. 1, it is considered that it is preferable to form the conductor mainly in the frame portion 2 from the viewpoint of easiness of layout design of the conductor.

In addition, screen printing of the resistor can be performed on a large substrate 13 in which a large number of the frame-shaped substrates 3 are arranged vertically and horizontally. It is preferable because it is excellent. Specifically, for example, a large-sized substrate 13 shown in FIG. 8 can be suitably used. The large-sized substrate 13 shown here has dividing lines 15 formed vertically and horizontally. After forming the resistor by screen printing, it is cut along these dividing lines 15 by a rotating disk cutter or the like. Then, the substrate is divided into individual frame-shaped substrates 3.

Here, prior to screen printing of the resistor on the large-sized substrate 13, it is preferable that the substrate 3 is subjected to the above-mentioned excavation processing to form holes 12 shown in FIG. The reason for this is that the excavation gives vibration to the entire substrate 3 and adversely affects the printed thick film resistor, such as peeling off from the substrate 3 surface. In addition, the cutting process by the above-mentioned rotary disc is usually applied to the substrate 3 in comparison with the excavation process mentioned here. Vibration is very small and hardly affects other components.

In the screen printing, a carbon resin based paste was used as the paste for the resistor. Such a resistor paste is preferable because it can be cured at a temperature that does not deteriorate the substrate 3 containing a resin material as a main component. Also, a polyethylene terephthalate resin paste for protecting the resistor was used. These can be selected from commercially available products.

A trimmable chip resistor 8 (R1 trim to R4 trim) is connected in series for each of the resistor elements 6 (R1 to R4), and the resistor element 6 and the trimmable chip resistor 8 are shown in FIG. In such a connection state. FIG. 7 also shows an outline of an electric signal input / output state in the stress sensor of the present invention. The four sets of resistance elements 6 and the trimmable chip resistors 8 constitute a bridge circuit. A predetermined voltage is applied between the voltage application terminals (V c c) and (G N D) of this bridge circuit. A stress sensor in the Y-axis direction is constituted by the resistance element 6 on the left side of the drawing, the trimmable chip resistor 8 and the Y terminal (Y out), and the resistance element 6 on the right side of the drawing, the trimmable chip resistor 8 and the X The terminal (X out) constitutes a stress sensor in the X-axis direction.

Laser trimming is performed only on the trimmer chip resistor 8 using a laser trimmer so that the sum of the resistance values of the above four sets of resistance elements 6 and the trimmer chip resistor 8 becomes approximately the same. In the case where the large-sized substrate 13 is used, this step is preferably performed before the above-described cutting step, since working efficiency is improved and mass productivity is excellent. The reason that the resistor element 6 was not trimmed by the laser trimmer was that the resistance due to the laser irradiation on the resin-based substrate 3 on which the resin-containing resistive antibody and resistor were disposed This is because the instability of the value was considered. It is thought that these resins tend to exhibit unstable behavior against very high temperature treatment such as laser irradiation. However, such trimming is possible when using laser irradiation such as excimer laser, which can adjust the temperature during irradiation in a relatively low temperature range, or when using a resin material (epoxy, etc.) that is relatively stable even when irradiated with YAG laser. . In such a case, it is advantageous in that the number of components of the stress sensor can be reduced as compared with the case where the trimmable chip resistor 8 is used. Note that the trimmable chip resistor 8 was disposed on the substrate terminal section 7 shown in FIG. This arrangement is performed through a known chip component mounting technique and a known reflow process. The reason for disposing the trimable chip resistor 8 at the substrate terminal portion 7 is that the region (substrate terminal portion 7 region) which is not easily affected by the bending of the substrate 3 due to the operation of the stress sensor is the trimmable chip resistor 8 by the bending. This is because the resistance value does not easily change. When stress is applied to the trimmable chip resistor 8 due to the influence of the bending, the resistance value of the trimmable chip resistor 8 changes, and the output value of the stress sensor may be deviated.

The substrate terminal section 7 is provided with input / output terminals 17 of the stress sensor at equal intervals. The terminal 17 is formed at the same time when the conductor, the electrode for the resistor element 6, and the like are formed. A land for the trimmable chip resistor 8 is also formed at the same time. The pattern of the conductor and the like is formed such that each trimmable chip resistor 8 is connected to each terminal 17.

Next, the lower surface of the stress transmitting member 4 made of alumina ceramic and all the tips of the flaky portions 1 are fixed using an epoxy adhesive 9 as a connecting member. Even in the fixed state, the end of the flaky portion 1 has some freedom of movement and deformation due to the presence of the adhesive 9, and the end of the flaky portion 1 substantially has the “semi-free end” described above. " As described above, one way to make the “semi-free end” is that the connecting member is more flexible than the material of the flaky portion 1. The second embodiment satisfies this.

In the second embodiment, the adhesive 9 is used for the connection member. However, the present invention is not limited to this, and a panel material or the like can be used. The spring material referred to here is a material that is more easily deformable than the material of the substrate 3 and is `` softer than the material of the flaky portion 1 '', and is suitably used as a component of the stress sensor of the present invention. can do. Needless to say, even when the adhesive 9 is used for the connection member, a material other than the epoxy resin can be used. For example, it is considered that a more flexible rubber adhesive can be selected, so that it is preferable. In addition, an acryl resin adhesive can be used.

The surplus adhesive shown in FIG. 2 wraps around to the back side of the piece-shaped portion 1, but it is considered that this does not adversely affect the characteristics of the stress sensor. However, due to the relative positional relationship between other stress sensor components and the stress sensor and other members in the vicinity, the free deflection of the flaky portion 1 It is preferable that such surplus is small, or it is preferable to remove it by a technique such as scraping, because it may possibly hinder the reaction somewhat.

As described above, the stress sensor according to the second embodiment of the present invention was obtained. Fig. 4 shows the operating state of the stress sensor according to the second embodiment. FIG. 4A shows a state in which no stress is applied to the stress transmitting member 4. FIG. 4 () shows a state in which a stress is applied to the stress transmitting member 4 in any of the x and y planes (arbitrary lateral direction). FIG. 4C shows a state in which the stress is applied to the stress transmitting member 4 in the z direction (downward). In these cases, a region corresponding to the frame portion 2 shown in FIG. 2 is fixed by a housing or the like of the electronic device, and is not substantially deformed.

In FIG. 4 (a), no deformation of the strain gauge 5 is observed. In FIG. 4B, it can be seen that the free end of the piece 1 is pressed by the lower surface of the stress transmitting member 4 via the adhesive 9 and the piece 1 is bent. As a result of this bending, significant deformation of the substrate 3 occurs at the boundary between the frame-shaped portion 2 and the piece-shaped portion 1, and the strain gauge 5 disposed at the boundary also deforms so as to follow the deformation. . In this figure, as in FIG. 3 (b), the strain gauge 5 existing in the direction in which the stress is applied is deformed so as to expand, and the strain gauge 5 on the opposite side is deformed so as to contract. This is considered to be caused by the elasticity of the material used for the adhesive 9. Since the resistance element 6 is used as the strain gauge 5 in the second embodiment as in the first embodiment, the characteristic value changes due to the deformation.

In FIG. 4 (c), it can be seen that the semi-free end of the strip 1 is pressed by the lower surface of the stress transmitting member 4 via the adhesive 9, and the strip 1 is bent downward. As a result of this bending, it is possible to obtain a stress sensor characteristic similar to the stress sensor characteristic in FIG. 3C of the first embodiment. .

In the stress sensor according to the second embodiment, a trimmable chip resistor 8 is used as a constituent member. However, if the same resistance value adjusting function can be achieved, a trimming resistance element or a variable resistor using a thick film technique or a thin film technique directly formed on the surface of the substrate 3 ′ can be used. In this example, laser trimming is described as a trimming method. However, other methods, for example, other trimming methods such as a sand blast method are used. Can be selected.

FIG. 9 shows the stress sensor according to the first or second embodiment of the present invention, in which a set of other shapes of the substrate 3, arrangement positions of the strain gauges 5, and arrangement positions of the stress transmission members 4, which can constitute the stress sensor, are shown. An example of matching is shown. FIG. 9 (a) shows a configuration in which the length of the strip 1 is less than or equal to the width of the strip 1. The advantages of this configuration are: (1) the large area of the substrate 1 around the strain gauge 5 increases the degree of freedom in the layout of conductors, etc., and (2) the accuracy of the stress sensor characteristic (3) The area of the strain gauge 5 can be increased, and the variation in the characteristics of the strain gauge 5 can be reduced. The reason that the advantage (2) can be obtained is that it is generally difficult to excavate so as to leave the elongated strip 1 particularly in the excavation processing in the second embodiment, and the shape of the strip 1 is difficult. This is because variation easily occurs.

FIG. 9 (b) shows a configuration in which the flaky portions 1 are led out from the four corners of the substrate 3. In this configuration, when only the four corners of the frame 2 are fixed to the electronic device housing or the like, the frame 2 (the four corners) serves as a fulcrum in the principle of leverage. When the flaky portion 1 is the force point and the strain gauge 5 is located at the action point, the distance between the fulcrum and the action point can be made very short, and the sensitivity of the stress sensor accompanying the application of stress to the stress transmitting member 4 can be kept high. There are advantages. Since the four corners of the frame portion 2 are relatively large regions that do not affect the sensor characteristics, they are easily selected as portions to be fixed to an electronic device housing or the like. .

FIG. 9C shows a configuration in which the outer shape of the substrate 3 is circular. The advantage of this configuration is that the area of the mounting board for electronic devices, etc., occupied by the four corners of the frame-shaped portion 2 that is not involved in the function or operation of the stress sensor can be utilized for other components.

An advantage common to the stress sensors of the first and second embodiments is that the strain gauge 5 and the stress transmitting member 4 can be arranged on the same substrate 3 surface. Conversely, there is no need to dispose any stress sensor components on the opposite surface of the substrate 3. This makes it possible to make contact with the opposite surface during the screen printing of the conductor 5 and the resistor 3 constituting the resistance element 6 on one surface of the substrate 3 and the fixing work using the adhesive or the like of the stress transmission member 4. No strict conditions are imposed, such as cleanliness and softness of the place where the work is performed. That is, manufacturing workability is improved. Especially When the resin molded body mixed with glass fiber is used as the substrate 3, there is an advantage that it is not necessary to perform a process of forming a through hole for wiring on both surfaces thereof and converting the inner wall surface into a conductor. Similarly, the ceramic substrate 3 also has an advantage in that wiring is performed on both surfaces thereof, so that a step of realizing conduction between both surfaces of the substrate 3 by so-called through-hole printing or the like is not required. ·

Third Embodiment FIG. 10 schematically shows the structure of a stress sensor (corresponding to the second stress sensor) according to a third embodiment of the present invention. The substrate 3 made of alumina ceramic has a cross shape, and the lower surface of the intersection area and a support member 16 made of alumina ceramic are fixed and supported by an adhesive 9. The supporting member 16 has its end positioned so as to correspond to the resistance element 6 which is the strain gauge 5 disposed at the junction between the flaky portion 1 on the upper surface of the substrate 3 and the intersection region. An adhesive 9 is provided at the tip of the flaky portion 1 on the upper surface of the substrate 3, and is fixed to the lower surface of the stress transmitting member 4. Here, the end of the flaky portion 1 is not fixed by the support member 16 and can be moved and deformed independently of the support member 16. Corresponds to the “semi-free end”. The stress transmitting member 4 is a hollow body having an opening on the lower surface.

FIG. 11 shows an operation state of the stress sensor according to the third embodiment of the present invention. FIG. 11A shows a state in which no stress is applied to the stress transmitting member 4. FIG. 11 (b) shows a state in which a stress is applied to the stress transmitting member 4 in any of the x and y planes (arbitrary lateral direction). Fig. 11 (c) shows a state in which the stress is applied to the stress transmitting member 4 in the z direction (downward). In these cases, it is assumed that the bottom of the support member 16 is fixed to a mounting board or the like of the electronic device.

In FIG. 11A, no deformation of the substrate 3 and the strain gauge 5 is observed. In FIG. 11 (b), it can be seen that the end of the strip 1 is pressed by the edge of the lower surface of the stress transmitting member 4 and the strip 1 is bent. As a result of this bending, significant deformation of the substrate 3 occurs at the boundary between the support member 16 and the flaky portion 1, and the strain gauge 5 disposed at the boundary also deforms so as to follow the deformation. . In the figure, the strain gauge 5 existing in the direction of applying stress (left side) 'expands. The strain gauge 5 on the opposite side (right side) is deformed to shrink. In the third embodiment, the resistance element 6 is used as the strain gauge 5 as in the first and second embodiments, so that the characteristic value changes due to the deformation. -In Fig. 11 (c), it can be seen that the free end of the piece 1 is pressed by the edge of the lower surface of the stress transmitting member 4 via the adhesive 9, and the piece 1 is bent downward. As a result of this bending, a stress sensor characteristic similar to the stress sensor characteristic in FIG. 3 (c) of the first embodiment can be obtained.

In the stress sensor according to the third embodiment of the present invention, the means for transmitting the change in the characteristic value of the strain gauge 5 to the electronic device includes, for example, forming four terminals on the lower surface of the intersection area of the substrate 3 in a rectangular shape, Means can be considered such as transmission to the electronic device mounting substrate on the lower surface through the support member 16 made of a conductive material. In this case, only the anisotropic conductive material portion that is locally strongly compressed by the presence of the projections conducts, so that conduction to the mounting board is possible while maintaining insulation between adjacent projections. In addition, for example, a method in which the support member 16 is hollow (cylindrical) and a conducting wire is passed therethrough is also conceivable, but is not particularly limited thereto.

The change in the characteristic value of the strain gauge 5 transmitted to the mounting substrate is caused by realizing the electrical signal input / output state shown in FIGS. 5 and 7 by the control means provided on the mounting substrate. The sensor can be activated.

In the stress sensors according to the second and third embodiments of the present invention, the adhesive 9 is used for fixing the stress transmitting member 4 and the substrate 3. At this time, if the positional relationship between the two deviates, the sensitivity balance of the stress sensor may be lost. Therefore, in order to realize a predetermined positional relationship, it is preferable to devise the shape of the portion where the two come into contact. For example, the contact portion of the flaky portion 1 is formed in a concave shape, the contact portion of the stress transmitting member 4 is formed in a convex shape, and a shape in which the unevenness can be fitted is adopted.

(Fourth embodiment)

FIG. 12A schematically shows the structure of a stress sensor (corresponding to the second stress sensor) according to the fourth embodiment of the present invention. This structure is the same as the structure of the third embodiment, except that the support member 16 has a plate shape, and the plate member 51 is fixed or integrated with the plate surface, and This is a structure having a hole 50 or a concave portion that allows the strip-shaped portion 1 to bend. In FIGS. 12 and 13, the plate-shaped member 51 has a hole 50 that allows the one-piece portion 1 to bend, but may be a concave portion instead of the hole 50.

The plate-shaped member 51 made of an epoxy resin mixed with glass fiber has a cross shape. Similarly, a supporting member 16 made of an epoxy resin mixed with glass fiber and a central region 52 of the plate-like member 51 are fixed with an adhesive 9 (not shown). The supporting member 16 is provided with a hole 50, and the bending of the piece portion 1 in the plane direction of the plate member 51 is allowed. On the upper surface of the plate-shaped member 51 in the figure, a strain gauge 5 composed of a resistance element 6 and a conductor (not shown) are arranged. The method of forming the strain gauge 5 and the conductor was the same as the method of forming the second embodiment described above. Further, the electrical characteristics of the strain gauge 5 are transmitted from a conductor (not shown) arranged on the surface of the support member 16 to the board terminal portion 7 via the conductor 53 on the side surface of the plate member 51, and Is sent to the control unit. '

The conductor 53 on the side surface of the plate-shaped member 51 is formed by means of applying a conductor paste, drilling through holes, or printing through holes. The connection between the conductor 53 on the side surface of the plate-like member 51 and the surface of the support member 16 is made by solder, conductive adhesive or the like. If the strength of the connection between the conductor 53 on the side surface of the plate member 51 and the surface of the support member 16 is sufficient, the above-mentioned “central region” can be used without the need for the “fixing by the adhesive 9 (not shown)”. 52 is fixed to the support member 16 ". In this case, it is advantageous in that the number of steps can be reduced without going through the fixing step. Also, by forming the strain gauge 5 such as the resistance element 6 and the conductor around it on the lower surface of the plate-like member 51 in FIG. 12 (a), that is, the surface facing the support member 16 surface, Conduction between the plate member 51 and the indicating member 16 is possible without the need for the conductor 53. If the conductor 53 on the side surface is not formed as described above, it is advantageous in that the number of steps can be reduced.

Further, similarly to the third embodiment, a stress transmitting member 4 made of ceramic or the like, which is a hollow body having an opening on the lower surface, is fixed to the plate-shaped member 1 on the upper surface of the plate-shaped member 51. For such fixation, an adhesive 9 or the like is used.

FIG. 12 (b) is a plan view of the stress sensor of FIG. 12 (a). In the figure, the support member 16, the plate-like member 51, the stress transmitting member 4, and the strain gauge 5 indicate a positional relationship among each other. The strain gauge 5 exists over the central region 52 of the plate-like member 51 and the flared portion 1 or the plate-like member 5 1 that straddles the hole 50 or the end of the concave portion that allows the buckle 1 to bend. It is a positional relationship that exists on the surface.

It can be seen that the positional relationship is such that the plate-like member 51 can be inserted into the hole 50 formed in the support member 16 in a bent state. Further, all the strain gauges 5 are arranged over the central region 52 of the plate-like member 51 and the flaky portion 1 and have a hole 50 formed in the support member 16 and a periphery of the hole 50. Is located at a position corresponding to the boundary of. Arranging the strain gauge 5 at such a position is advantageous in that a stress sensor with the highest sensitivity can be obtained.

FIG. 13 shows an operation state of the stress sensor according to the fourth embodiment of the present invention. FIG. 13A shows a state in which no stress is applied to the stress transmitting member 4. FIG. 13B shows a state in which stress is applied to the stress transmitting member 4 in any of the x and y planes (arbitrary lateral direction). FIG. 13 (c) shows a state in which the stress is applied to the stress transmitting member 4 in the z direction (downward). In these cases, it is assumed that the bottom of the support member 16 is fixed to a mounting board or the like of the electronic device.

In FIG. 13 (a), no deformation of the plate member 51 and the strain gauge 5 is observed. In FIG. 13 (b), it can be seen that the end of the flaky portion 1 is pressed by 緣 on the lower surface of the stress transmitting member 4 and the flaky portion 1 is bent. As a result of this bending, significant deformation of the plate-like member 51 occurs at the boundary between the support member 16 and the flaky portion 1, and the strain gauge 5 disposed at the boundary also follows the deformation. It is deformed as follows. In the figure, the strain gauge 5 existing in the direction in which the stress is applied (left side in the figure) is deformed so as to expand, and the strain gauge 5 on the opposite side (right side in the figure) is deformed so as to contract. Since the stress sensor of the fourth embodiment uses the resistance element 6 as the strain gauge 5 similarly to the first, second, and third embodiments, the characteristic value changes similarly due to the deformation. .

In FIG. 13 (c), the free end of the plate-like portion 1 of the plate-like member 51 is pressed by the edge of the lower surface of the stress transmitting member 4 via the adhesive 9, and the plate-like portion 1 bends downward. You can see that This As a result, the same stress sensor characteristics as those in FIG. 3C of the first embodiment can be obtained.

In the state shown in Fig. 13 (b) and Fig. 13 (c), if any excessive stress is applied in the horizontal or downward direction, the stress transmission that is not fixed to the piece 1 The member 4 portion and the support member 16 collide with each other, and there is an effect of preventing further bending of the plate-shaped member 51. Thus, by adjusting the shape of the lower end of the stress transmitting member .4 and the shape of the support member 16, there is an advantage that the upper limit of the amount of deflection of the plate member 51 can be determined. Further, by forming the plate-shaped member 51 as a concave portion instead of the hole 50 allowing the bending of the piece-shaped portion 1, an upper limit of the amount of bending of the same plate-shaped member 51 can be advantageously determined. Has an effect.

The stress sensor according to the fourth embodiment has an advantage that the entire stress sensor can be reduced in thickness as compared with the stress sensor according to the third embodiment. This is because the supporting member 16 has a plate shape. Further, the stress sensor according to the fourth embodiment has an advantage that it is easy to manufacture as compared with the stress sensor according to the third embodiment. This is because the transmission path of the characteristic value of the strain gauge 5 is simplified similarly to the transmission path of a normal surface mount electronic component.

In the stress sensors according to the second to fourth embodiments of the present invention, when the stress transmitting member 4 is placed and fixed on the piece 1, the placement is facilitated, and the stress transmitting member 4 and the piece 1 In order to maintain high positional accuracy between the two, it is preferable that the mounting position of the flaky portion 1 be a concave portion (thin portion) so that the stress transmitting member 4 can be fitted into the concave portion. For the same reason, in the third or fourth embodiment, a concave portion is provided in one or both of the support member 16 and the substrate 3 or in one or both of the plate member 51 and the support member 16. It is preferable that both can be fitted together.

The stress transmitting member 4 used in the stress sensors according to the first to fourth embodiments of the present invention is preferably made of a rigid body such as ceramic or metal. This is because there is almost no absorption and attenuation of stress, and the stress can be transmitted accurately. Here, when resin is used as the material for the stress transmitting member 4 for reasons such as reduction in manufacturing cost and ease of molding, polyvinyl terephthalate (PVT) or polybutylene terephthalate (PBT) is particularly preferably used. it can. The PVT and PBT are particularly excellent in rigidity among resin-based materials. Also, because the heat resistance is good, This has the advantage that the rigidity can be maintained even when the boundary is slightly higher than room temperature.

In the stress sensors according to the first to fourth embodiments of the present invention, an example has been described in which the strain gauge 5 is disposed at the joint between the support portion and the piece-shaped portion 1, but the present invention is not limited to such an arrangement position. . It is most preferable to dispose the support portion and the flaky portion 1 in a region that is most likely to be deflected by stress application. For this purpose, it is possible to adopt a configuration in which only one flank is arranged. Further, a part of the flaky portion 1 may be made thinner or narrower so that the thinner portion or the narrow portion is particularly easily bent, and the strain gauge 5 may be disposed there. By forming the thin portion or the narrow portion, there is an advantage in manufacturing that an optimum position for disposing the strain gauge 5 can be specified in advance, and a forming position shift at the time of forming the strain gauge 5 can be prevented. .

In the stress sensors according to the first to fourth embodiments of the present invention, one stress transmitting member 4 is used, but it goes without saying that a plurality of stress transmitting members 4 may be present. For example, it is attached to each piece 1. Further, in the stress sensor in which the stress is applied directly to the flaky portion 1, the stress transmitting member 4 is unnecessary. Industrial applicability

According to the present invention, it is possible to reduce the size of a stress sensor that stimulates a strain gauge disposed on a substrate surface by bending the substrate. The miniaturized stress sensor is particularly suitable as a component for operating a small electronic device such as a personal computer or a mobile phone.

Claims

The scope of the claims

1. A strain gauge is arranged on the surface of a substrate having a plurality of strips having free or semi-free ends and a support section for supporting the strips, and is caused by direct stress applied to the strips. A stress sensor comprising: changing the electrical characteristics of the strain gauge by stimulating the strain gauge; and obtaining the stress from the change in the electrical characteristics.

2. The stress sensor according to claim 1, wherein a plurality of piece-shaped portions are led out from a peripheral edge of the frame-shaped substrate into the frame, and the peripheral edge of the frame-shaped substrate is a support portion.

3. A plate-like member having a strain gauge on a plate-like surface has a piece that is fixed or integrated in the central area, and is directly attached to the piece in a state where it is fixed to the central area support member. The strain gauge is stimulated by applying a stress to the flaky portion, thereby changing the electrical characteristics of the strain gauge. A stress sensor characterized by grasping.

4. The stress sensor according to any one of claims 1 to 3, further comprising a stress transmitting member that transmits stress to the flaky portion.

5. The piece-shaped portion and the stress transmitting member are connected by a connecting member, and the connecting member is also flexible in the piece-shaped portion and the stress transmitting member. The stress sensor according to any one of the above items.

6. The stress sensor according to any one of claims 1, 2, 4, and 5, wherein the strain gauge is disposed at a joint between the supporting portion and the piece-shaped portion.

7. Changes in the electrical characteristics of the strain gauge that change in response to external force are coordinate data in 3 orthogonal directions. The stress sensor according to any one of claims 1 to 6, wherein the stress sensor is capable of outputting as a force.

8. The first, second, or fourth to seventh aspects of the present invention, wherein a trimming resistance element is provided on the support portion, and the trimming resistance element and a strain gauge made of the resistance element are connected in series. The stress sensor according to any one of the above.

9. The stress sensor according to any one of claims 1 to 8, wherein a length of the flank is less than or equal to a width of the flank.

10. The stress according to any one of claims 1 to 9, wherein the direct application of stress to the strip is performed at a substantially outer end of the strip. Sensor.

11. The support member is plate-shaped, and the plate-shaped member is fixed or integrated with the plate-shaped surface, and has a hole or a concave portion that allows bending of the piece-shaped portion. 3rd to 5th

10. The stress sensor according to any one of claims 7, 9, 9, and 10.

1 2. The strain gauge must be present over the central region of the plate-like member and the flaky portion, or be present on the surface of the plate-like member straddling the end of the hole or recess that allows the flaky portion to bend. The stress sensor according to claim 11, characterized in that:

1 3. A strain gauge is arranged on the substrate surface, and the strain gauge is stimulated by applying a direct stress to the substantial outer edge region of the substrate in a state where the substrate central region is fixed. A stress sensor that changes the electrical characteristics of the strain gauge to determine the stress from the change in the electrical characteristics.