JP4104961B2 - Stress sensor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a stress sensor, and more particularly to a stress sensor that can be used for a pointing device for a personal computer, a multifunction switch for various electronic devices, and the like.
[0002]
[Prior art]
The applied stress deforms a resistance element having a pair of electrodes and a resistor connected to the electrode, thereby changing the resistance value of the resistance element, and the direction and magnitude of the stress by the resistance value change. The stress sensor for grasping the above is disclosed in International Publication No. WO 02/064487.
[0003]
Such disclosure includes a technique for lowering a pair of electrodes by press working or the like. By adopting this technique, for example, when a resistor is formed so as to straddle both electrodes by a screen printing method, there is an advantage that variation in the shape of the resistor can be kept low.
[0004]
[Problems to be solved by the invention]
However, according to the study by the present inventors (including those other than the inventor, the same applies hereinafter), the adoption of the above technique can surely suppress the variation in the resistor shape and the resulting variation in the resistance value of the resistance element. It was found that the rate of change in value could not be increased. If the resistance value change rate cannot be increased, the output of the stress sensor cannot be increased. By increasing the output of the stress sensor, the S / N ratio can be improved and the noise margin can be increased.
[0005]
Therefore, the problem to be solved by the present invention is to increase the resistance value change rate of the resistance element without extremely increasing the height of the electrode constituting the resistance element.
[0006]
[Means for Solving the Problems]
First stress sensor of the present invention for solving the above problems, granted stress, by modifying resistance element having a resistor connected to both of the paired conductive Goku及 beauty the electrodes , changing the resistance value of the resistor element, the stress sensor to obtain an output by the change in resistance value, the paired electric machining gap, while apart from that of the electrode in contact with the resistor, the resistor wherein the one or more electrically conductive surface forming member for forming a Tonokai surface is disposed. In addition, the second stress sensor changes the resistance value of the resistance element by deforming the resistance element having the applied stress and the resistor connected to both the electrode and the electrode, In the stress sensor that obtains an output by the change in the resistance value, the resistance element is formed on the substrate surface, and the deformation of the resistance element includes the extension due to the bending of the substrate, and contacts the resistor between the pair of electrodes, And having at least one conductive interface forming member that forms an interface with the resistor, and the interface forming surface of the interface forming member has a portion that is substantially perpendicular to the substrate surface. Features.
[0007]
Generally, a stress sensor functions as a stress sensor only when there is a control unit that detects and calculates the electrical signal. However, in this specification, the part excluding the control unit is referred to as a “stress sensor” for convenience.
[0008]
The "interface" refers to the interface of the two phases in contact with each other, the interfacial forming member composed mainly resistor 3 and the conductive member when the, by example, by melting together, a new phase Say what does not form. Needless to say, the present invention is configured even when a new phase is formed and as a result, the interface between the new phase and the resistor is in electrical contact.
[0009]
The degree of conductivity of the interface forming member 1 is not particularly limited. However, the condition is that the conductive state at the interface changes due to the deformation of the resistive element 5 in the energized state of the resistive element 5 during the stress sensor operation and affects the stress sensor characteristics and the like. Therefore, when the conductivity of the interface forming member 1 is low enough to prevent such influence, it does not correspond to the interface forming member 1 according to the present invention.
[0010]
The present invention has been made paying attention to the influence of the deformation of the resistance element 5 on the conductivity at the interface between the interface forming member 1 and the resistor 3. When the adhesion between the interface forming member 1 and the resistor 3 decreases due to the deformation of the resistance element 5, the transfer of electrons at the interface is hindered, and the inventors increase the resistance value of the resistance element 5 detected thereby. Thought. Therefore, it was concluded that increasing the inhibition factor can increase the rate of change in resistance value of the resistance element 5.
[0011]
According to this idea, the reason why the resistance value change rate of the resistance element 5 is reduced by lowering the conventional pair of electrodes 2 can be explained. This is because the inhibition factor is reduced by reducing the height of the electrode 2 and reducing the area of the interface formed by the electrode 2 and the resistor 3.
[0012]
The configuration of the present invention has an effect of increasing the rate of change in resistance value of the resistance element 5 according to the present invention. This is because the presence / absence of the interface forming member 1 can increase the factors that inhibit the electron transfer at the interface. In order to obtain the effect, it is not necessary to extremely increase the height of the electrode 2 constituting the resistance element 5. This is because the interface forming member 1 plays the role of hindering the effect obtained when the height of the electrode 2 is increased, that is, the electron transfer at the interface.
[0013]
Specific examples of the present invention will be described with reference to the drawings. FIG. 1A is a plan view of the resistance element 5 constituting the stress sensor of the present invention, and FIG. 1B is a cross-sectional view taken along line AA ′ of the plan view. In the figure, the resistance element 5 is formed on the surface of the substrate 4. In addition, one interface forming member 1 that contacts the resistor 3 between the paired electrodes 2 and forms an interface with the resistor 3 is disposed on the surface of the substrate 4.
[0014]
A post 7 as a stress receiving member is fixed or integrated on the surface of the substrate 4 shown in FIG. 1, and the resistance element 5 is arranged at a position corresponding to the contour of the bottom surface of the post 7 on the other surface of the substrate 4. FIG. 2 shows a state in which stress is applied to the post 7 after fixing the end of the post. 2A shows the case where stress is applied to the post 7 in an arbitrary lateral direction, that is, the x-axis and y-axis directions, and FIG. 2B shows the case where the top surface of the post 7 is pressed, ie, the z-axis. The case where stress is applied in the direction is shown. In either case, it can be seen that the resistive element 5 is deformed by the application of stress. It can also be seen that the deformation of the resistance element 5 is accompanied by expansion / contraction due to the bending of the substrate 4.
[0015]
A second stress sensor according to the present invention, comprising a configuration of a first stress sensor, wherein the resistance element 5 is formed on the surface of the substrate 4, and the deformation of the resistance element 5 includes expansion due to bending of the substrate 4; In the stress sensor having a preferable configuration based on the stress sensor of the present invention, the interface is preferably formed obliquely or perpendicularly with respect to the expansion / contraction direction of the resistance element 5. This is because it is efficient to inhibit the exchange of electrons at the interface. Specifically, for example, the energizing direction of the resistance element 5 in FIG.
[0016]
Further, in the configuration of the second stress sensor according to the present invention and a preferable configuration based on the second stress sensor, a portion in which the interface forming surface of the interface forming member 1 is substantially perpendicular to the surface of the substrate 4 It is preferable to have. This is because the adhesion between the interface forming member 1 and the resistor 3 is most likely to decrease due to deformation such as expansion of the resistance element 5. The reason is that the area of the vertical surface is small, and the stress converted into the extension of the resistance element 5 tends to concentrate.
[0017]
Further, in the configuration of the second stress sensor of the present invention and a preferable configuration based on the configuration, as shown in FIG. 2, the post 7 receives the applied stress, and the bottom surface of the post 7 is a substrate. It is preferable that the resistance element 5 is arranged at a position corresponding to the outline of the bottom surface of the post 7 on the other surface of the substrate 4. When stress is applied to the post 7, the largest stress is transmitted to the portion of the substrate 4 located at the contour of the bottom surface of the post 7. Therefore, the stress transmission to the resistance element 5 is also highly efficient and a large output can be obtained. In this case, it is further preferable that the interface is located at or near the position corresponding to the contour of the bottom surface of the post 7. As described above, since the largest stress is transmitted to the portion of the substrate 4 located at the contour of the bottom surface of the post 7, it is possible to expect a larger output when the interface is located at the position.
[0018]
In the configuration of the second stress sensor of the present invention and a preferable configuration based on the second sensor, the electrode 2 and the interface forming member 1 are obtained by removing a part of the conductor layer on the surface of the substrate 4 and obtaining the remainder thereof. Or it is preferable to obtain by an additive method. This is because the electrode 2 and the interface forming member 1 can be formed at the same time, which is advantageous in that the production can be simplified. Further, the interface forming member 1 is obtained by removing a part of the conductor layer on the surface of the substrate 4 and obtaining it as a remaining part or by an additive method. This is because it is easy to form a vertical surface.
[0019]
In the configuration of the second stress sensor of the present invention and a preferable configuration based on the second stress sensor, the plurality of conductive protrusions on the surface of the substrate 4 in which the interface forming member 1 is interspersed between the paired electrodes 2 It may be. For example, the use of a large number of such protrusions is advantageous in that the total area of the interface between the resistor 3 and the interface forming member 1 can be increased.
[0020]
In the configuration of the second stress sensor of the present invention and the preferable configuration based on the second stress sensor, the interface includes a plurality of oblique components and / or vertical components and / or curved components having different angles with respect to the extending direction of the resistance element 5. It is preferable to have. For example, the interface forming member 1 in FIG. Also by doing this, the total area of the interface between the resistor 3 and the interface forming member 1 can be increased, which is advantageous in that respect.
[0021]
In the configuration of the second stress sensor of the present invention and a preferable configuration based on the second stress sensor, the resistor 3 is formed on the surface of the substrate 4 in a thick film, and the resistor 3 covers part or all of the interface forming member 1. It is preferable. This is one form of interface formation between the resistor 3 and the interface forming member 1. Here, for example, the screen printing is employed as a thick film technique, and the technique of printing the resistor 3 paste on the interface forming member 1 has an advantage of facilitating the interface formation between the resistor 3 and the interface forming member 1. . At this time, the contact between the electrode 2 and the resistor 3 can be easily realized at the same time. Therefore, it is very advantageous in that the production can be simplified.
[0022]
In the configurations of the first and second stress sensors according to the present invention and the preferable configurations based on them, it is preferable that the resistor 3 is composed of a conductive material and a non-conductive material, and the two are not fused. . The resistor 3 corresponding to this is, for example, a material made of carbon material such as amorphous carbon or graphite as a conductive material, and an epoxy resin material as a main non-conductive material. Further, instead of the carbon material powder, a metal powder such as silver may be applicable. This is because the carbon material or metal does not fuse with the resin material. On the other hand, what does not correspond to this is a so-called metal glaze type in which ruthenium oxide is dissolved (fused) in the glass frit and almost the entire resistor 3 has conductivity.
[0023]
In the resistor 3 made of a conductive substance and a non-conductive substance and in a state where the two do not merge, the non-conductive substance and the conductive substance exist independently. The electrical connection between the resistor 3 and the interface forming member 1 at the interface is made on condition that the conductive material near the interface actually contacts the interface. Therefore, it can be seen that the resistance value of the resistance element 5 using the resistor 3 varies greatly depending on the presence or absence of the contact. When the resistance element 5 is deformed with a decrease in adhesion between the interface forming member 1 and the electrode 2 and the resistor 3 with respect to the resistance element 5, the resistance value change of the resistance element 5 increases.
[0024]
On the other hand, the resistance element 5 using the resistor 3 such as the metal glaze system in which almost the entire resistor 3 has conductivity has no concept of the presence or absence of the contact. Therefore, when the resistance element 5 is deformed with a decrease in adhesion between the interface forming member 1 and the electrode 2 and the resistor 3 with respect to the resistance element 5, the resistance value change of the resistance element 5 is relatively moderate. It is thought that.
[0025]
Of course, even the resistor 3 such as the above metal glaze type is not excluded from the resistor 3 constituting the present invention because the resistance value changes if there is a decrease in adhesion with the interface forming member 1. Needless to say.
[0026]
DETAILED DESCRIPTION OF THE INVENTION
First, a glass fiber-mixed epoxy resin plate is prepared by laminating a plurality of prepregs and heating and pressing them. The plate becomes the substrate 4. Then, after applying a copper foil having a thickness of 18 μm on both surfaces of the substrate 4 and performing a known etching process (removal process) except for the necessary part of the copper foil, the wiring 6, the electrode 2 and the interface forming member 1 are shown in FIG. Formed as shown.
[0027]
Next, a conductive material is disposed on the inner wall of a through hole provided in advance in the substrate 4 by drilling, thereby electrically connecting the wirings 6 on the front and back surfaces of the substrate 4 . At this time, the conductive substance (copper) deposited by electroless plating is also deposited on the surfaces of the wiring 6, the electrode 2 and the interface forming member 1. As a result, the height of each of the wiring 6, the electrode 2, and the interface forming member 1 becomes a substantially constant value of 30 to 50 μm. If the height of the electrode 2 is about this level, the height of the electrode 2 constituting the resistance element 5 is not extremely high. Therefore, the resistance element 5 is caused by variations in the shape of the resistor 3 arranged by screen printing described later. Variation in resistance value can be suppressed.
[0028]
Next, the resistor 3 is disposed on the surface of the substrate 4 on which the electrode 2 is formed by screen printing technology, and is cured by heating. Thus, four resistance elements 5 as shown in FIG. 1 were formed per stress sensor. Here, the resistor 3 is made of amorphous carbon powder as a conductive material and epoxy resin material as a non-conductive material. The four resistance elements 5 are subjected to a known laser trimming process in order to make their resistance values substantially equal.
[0029]
Thereafter, the substrate 4 is cut into the shape shown in FIG. 3 and a fixing hole 8 is provided. Then, an alumina ceramic post 7 is fixed to the surface opposite to the surface of the substrate 4 on which the resistance element 5 is formed, which is substantially the center of the substrate 4 (FIG. 3A). An epoxy adhesive was used for such fixing. Further, as shown in FIG. 3B, the fixing position is such that the contour of the bottom surface of the post 7 is in a corresponding position with all the resistance elements 5 through the substrate 4.
[0030]
Through the above steps, the stress sensor of the present invention can be obtained. This stress sensor is attached to an electronic device or the like by inserting a screw into the fixing hole 8 or the like. Then, by applying stress to the post 7, the resistance element 5 is extended as described in FIG. At this time, patterning is performed during the above-described etching process so that the interface forming member 1 is positioned in a direction substantially perpendicular to the extending direction of all the resistance elements 5. Further, although not shown in FIG. 3 by the patterning, the wiring 6 is formed across the front and back of the substrate 4 and, as a result, is patterned so as to configure the bridge circuit shown in FIG.
[0031]
Such a stress sensor cannot operate alone, and can control an electronic device via a signal control unit. FIG. 4 shows an outline of the state of electric signal input / output of the bridge circuit in the stress sensor of the present invention. A predetermined voltage is applied between the voltage application terminals (Vcc) and (GND) of the bridge circuit. Further, a stress sensor in the Y-axis direction is constituted by the resistance element 5 and the Y terminal (Yout) on the left side of the figure, and a stress sensor in the X-axis direction is constituted by the resistance element 5 and the X terminal (Xout) on the right side of the figure. . Thus, as shown in FIG. 2A, it is possible to grasp that the stress is applied in arbitrary x and y directions and the direction and magnitude of the stress at that time. Further, as shown in FIG. 2B, when the top surface of the post 7 is pressed, that is, the stress is applied in the z-axis direction, and the magnitude of the stress at that time can be grasped. By applying stress in the z-axis direction, all four resistance elements 5 are stretched, and each resistance value is increased to substantially the same level. Such electrical characteristics are different from those when stress is applied in an arbitrary lateral direction (x, y direction), and can be distinguished from those.
[0032]
When sensing the application of stress in the z-axis direction, for example, when using the stress sensor of the present invention as a pointing device of a computer and assigning the application of stress in the z-axis direction to a so-called mouse click signal. is there. In addition, for example, the stress sensor of the present invention is used as a multi-function / multi-directional switch for small portable devices such as so-called mobile phones. In this case, when a downward stress is applied for a predetermined time, it is possible to respond to a command to turn on / off the power of the portable device. In these two cases, there is little need to accurately detect the magnitude of applied stress. It is only necessary to be able to sense that a certain level of stress has been applied. However, even in these cases, there is no change in grasping the magnitude of the applied stress. In the latter case, even when stress is applied in an arbitrary lateral direction (x, y direction), it is only necessary to detect that a certain level of stress is applied.
[0033]
In this example, the substrate 4 material is glass fiber mixed epoxy resin, and the post 7 is alumina ceramic. However, it goes without saying that the combination is not limited to this. For example, both the post 7 and the substrate 4 can be made of a ceramic material. However, it is preferable to make the post 7 material more rigid than the substrate 4 material as in this example. This is because the substrate 4 can be easily deformed and the resistance value change rate of the resistance element 5 can be increased. However, when the deformation of the substrate 4 is made too easy, there is a possibility that the deformation may be plastic deformation that loses reversibility. The glass fiber-mixed epoxy resin, which is the substrate 4 material used in this example, is made of a material mixed with fibers having a higher tension than the main resin material, and can effectively prevent plastic deformation. In the case of using a fiber-mixed resin material for the substrate 4, one or more fibers such as an aramid resin fiber, a nylon fiber, and a polyolefin resin are available in addition to the glass fiber.
[0034]
Further, in this example, the interface forming member 1 is made of a material made of copper, the number thereof is 1, and the shape thereof is a rod shape shown in FIG. 1, but it goes without saying that the present invention is not limited to this. FIG. 5 shows an example in which the resistance element 5 is configured using another interface forming member 1 instead of the interface forming member 1 of this example.
[0035]
5A shows that the interface forming member 1 meanders so that an interface is formed from a straight line having an oblique component and a straight line in a vertical direction with respect to the extending direction of the resistance element 5 (a direction parallel to the wiring 6 in FIG. 5). It shows the case. By meandering, the area of the interface can be increased.
[0036]
FIG. 5B shows a case where two interface forming members 1 (FIG. 1) of this example shown in FIG. 1 are used. Also in this case, the area of the interface can be increased.
[0037]
FIG.5 (c) has shown the case where many interface formation members 1 shorter than what was used in this example are arrange | positioned in zigzag form. Also in this case, the area of the interface can be increased.
[0038]
【The invention's effect】
According to the present invention, it is possible to increase the resistance value change rate of the resistance element without extremely increasing the height of the electrode constituting the resistance element.
[Brief description of the drawings]
FIG. 1A is a plan view of a resistance element constituting a stress sensor according to an example of an embodiment of the present invention, and FIG.
FIG. 2A is a state in which stress is applied in an arbitrary x and y direction to a stress sensor according to an embodiment of the present invention, and FIG. 2B is a diagram illustrating the stress sensor illustrated in FIG. It is a state that stress is applied in the z direction.
FIG. 3A is a plan view of a stress sensor as an example of an embodiment of the present invention, and FIG. 3B is a bottom view of FIG.
FIG. 4 is a diagram showing an example of a signal input / output state of the stress sensor of the present invention.
FIG. 5 is a diagram showing various shapes of an interface forming member constituting the stress sensor of the present invention.
[Explanation of symbols]
1. 1. Interface forming member Electrode 3. Resistor 4. Substrate 5. Resistance element 6. Wiring 7 Post 8. Fixing hole

Claims (11)

The applied stress changes the resistance value of the resistance element by deforming the resistance element having a resistor connected to both the pair of electrodes and the electrode, and obtains an output by changing the resistance value. In the sensor
Between the electrodes forming a pair, while away from that of the electrode, characterized in that the resistor and in contact, one or more electrically conductive surface forming member for forming an interface between the resistor is located A stress sensor. The stress sensor according to claim 1, wherein the resistance element is formed on a substrate surface, and the deformation of the resistance element includes expansion due to bending of the substrate. The applied stress changes the resistance value of the resistance element by deforming the resistance element having a resistor connected to both the pair of electrodes and the electrode, and obtains an output by changing the resistance value. In the sensor
A resistive element is formed on the substrate surface, and the deformation of the resistive element includes stretching due to bending of the substrate;
In contact with the resistor between the electrodes serving as the pair has one or more electrically conductive surface forming member for forming an interface with the resistor, the interface forming surface of the interface member is substantially above stress sensor characterized by having a portion constituted by a plane perpendicular to the substrate surface. The interface is primarily the stress sensor according to claim 2 or 3, wherein the formed obliquely or perpendicularly to the stretching direction of the resistive element. Has a post for receiving said applied stresses, the post bottom secured or integrated with one surface of the substrate, wherein the resistive element distribution in the contour position corresponding to the post bottom at the other surface of the substrate stress sensor according to any one of claims 2-4, characterized in that the. Stress sensor of claim 5 wherein said interface is located at or near corresponding to the contour of the post bottom. The said electrode and the said interface formation member remove | eliminate a part of conductor layer on the surface of the said board | substrate , and are obtained as the remainder, or are obtained by an additive method, The any one of Claims 2-6 characterized by the above-mentioned. The stress sensor according to item 1 . Stress sensor according to any one of claims 1-7, wherein the interface forming member is a pair with electrodes interspersed with multiple conductive protrusions Ru disposed between made. The interface, according to any one of claims 1-8, characterized in that it comprises a plurality of oblique components and / or vertical component and / or curved components of different angles with respect to the extension direction of the resistive element Stress sensor. The resistor is a thick film formed, the stress sensor according to any one of claims 1-9 in which the resistor, characterized in that the covering part or all of the interface member. The resistor consists of a conductive material and a non-conductive material, the stress sensor according to any one of claims 1 to 10, both are characterized in that a state which is not fused.

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