KR101829215B1 - Force sensor and method of manufacturing the same - Google Patents

Abstract

A pressure sensor comprises: a first electrode and a second electrode provided to face each other; and a dielectric layer interposed between the first and second electrodes, and composed of a foaming elastic body formed with pores therein, wherein the second electrode has a core-cell structure having cores respectively composed of conductive fabrics, and a plurality of woven core-cells composed of cells made of metal layers provided to surround the core. Thus, the pressure sensor can secure improved sensitivity.

Description

TECHNICAL FIELD [0001] The present invention relates to a pressure sensor and a method of manufacturing the pressure sensor.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure sensor and a method of manufacturing the same. More particularly, the present invention relates to a pressure sensor for sensing a pressure applied from the outside and a method for manufacturing the pressure sensor.

The touch screen, which is one of the input devices, can be used for a variety of portable terminals such as a mobile phone, an MP3 player, a PDA, a PMP, a PSP, a portable game machine, and a DMB receiver from various monitors such as a navigation device, an industrial terminal, Of course, it is widely used as an input device for various electric and electronic devices ranging from a refrigerator, a microwave oven, and a washing machine to various home appliances.

The touch screen has been developed in various ways such as a resistance film type and a capacitance type according to its structure and operation principle, and recently, a capacitance type is widely applied in a smart phone.

The capacitive touch screen includes a capacitive pressure sensor that generates an input signal corresponding to a touch pressure and a position from a magnitude of a capacitance change that varies depending on a magnitude of a touch pressure of a finger.
As a prior art of the present invention, Japanese Unexamined Patent Application Publication No. 2009-103531 (published May 21, 2009) is disclosed.

1 is a cross-sectional view illustrating a conventional capacitive pressure sensor.

1, a conventional capacitive pressure sensor 100 includes an elastic spacer 130, which elastically changes a predetermined distance d between a lower electrode 110 and an upper electrode 120, Elastic layer) is essential. That is, when the touch pressure is not applied, the elastic spacer 130 keeps the lower electrode 110 and the upper electrode 120 at the distance d, and when the touch pressure is applied, the upper and lower electrodes 110 and 120, The input signal is generated corresponding to the capacitance change by varying (increasing) the capacitance d between the upper and lower whole stations by varying the distance d between the upper and lower electrodes. When the touch pressure disappears, the distance d between the upper and lower electrodes is Restore to original distance. Therefore, in the conventional capacitive pressure sensor 100, the performance of the elastic spacer 130 is a major factor determining the performance of the sensor.

In the case of the capacitance displacement type pressure sensor including the elastic spacer, air may be discharged through the elastic spacers or air may be drawn in, thereby sensing the applied pressure as the capacitance value changes.

However, there is a problem that the sensitivity of the pressure sensor deteriorates as the airflow for the inflow and outflow of the air is not smoothly performed.

It is an object of the present invention to provide a pressure sensor having an improved sensitivity by smoothly flowing the air inside.

It is an object of the present invention to provide a method of manufacturing a pressure sensor capable of easily manufacturing a pressure sensor having an improved sensitivity.

The pressure sensor according to embodiments of the present invention includes a first electrode and a second electrode provided to face each other, and a dielectric layer interposed between the first and second electrodes, the dielectric layer being made of a foamable elastic body having pores formed therein And the second electrode has a core cell structure having a plurality of woven core cells each made of a cell made of a conductive fabric and a metal layer provided to surround the core.

In one embodiment of the present invention, the dielectric layer may be coated on the second electrode.

In one embodiment of the present invention, if the second electrode corresponds to a common electrode, the first electrode may correspond to a sensing electrode provided in each of a plurality of regions.

In an embodiment of the present invention, the second electrode may have a thickness of 10 to 50 탆.

In one embodiment of the present invention, air may be introduced into or out of the pores through the interface between the core cells.

The pressure sensor according to an embodiment of the present invention may further include a double-sided tape interposed between the dielectric layer and the first electrode.

In a method of manufacturing a pressure sensor according to embodiments of the present invention, a common electrode having a core cell structure including a plurality of core cells each made of a cell made of a conductive fabric and a metal layer surrounding the core, Prepare. Next, a dielectric layer made of a foamable elastic body having pores formed therein is formed on the common electrode. Then, a sensing electrode is formed on the dielectric layer.

In one embodiment of the present invention, the common electrode may be provided by forming a metal layer on a surface of the core through a plating process.

In one embodiment of the present invention, a coating process may be performed to form a dielectric layer on the common electrode.

In one embodiment of the present invention, a double-sided tape may be used to form the sensing electrode on the dielectric layer.

According to embodiments of the present invention, since the second electrode has a core cell structure having a plurality of core cells formed of a cell made of a conductive fabric and a metal layer provided to surround the core, And air flows along the interface between the core cells and the core cells, so that the flow of air can be smooth. Thus, the pressure sensor including the first and second electrodes and the dielectric layer can secure excellent sensitivity. Further, the thinness of the pressure sensor can be realized.

On the other hand, the dielectric layer can be formed on the second electrode through a coating process. Thus, a bonding step of forming a separate bonding layer on the dielectric layer and the second electrode or a bonding step using a double-sided tape may be omitted. As a result, the dielectric layer can be easily formed on the common electrode through a simplified coating process.

Further, in the case of a bonding process or an adhering process for attaching an existing dielectric layer to an electrode, a process of patterning the bonding layer or cutting the double-sided tape according to the shape of the elastic body is required, so that the process is complicated and its degree of freedom is limited The dielectric layer is formed through a coating process as in the present invention, thereby simplifying the process.

1 is a cross-sectional view illustrating a conventional capacitive pressure sensor.
2 is a cross-sectional view illustrating a capacitive pressure sensor according to the present invention.
3 is a cross-sectional view illustrating the first electrode of FIG. 2. FIG.
FIG. 4 is a graph for explaining a change in capacitance versus applied pressure of the capacitive pressure sensor according to the present invention shown in FIG. 2;

Hereinafter, a pressure device according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings. The present invention is capable of various modifications and various forms, and specific embodiments are illustrated in the drawings and described in detail in the text. It should be understood, however, that the invention is not intended to be limited to the particular forms disclosed, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention. Like reference numerals are used for like elements in describing each drawing. In the accompanying drawings, the dimensions of the structures are enlarged to illustrate the present invention in order to clarify the present invention.

The terms first, second, etc. may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be referred to as a second component, and similarly, the second component may also be referred to as a first component.

The terminology used in this application is used only to describe a specific embodiment and is not intended to limit the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. In this application, the terms "comprises", "having", and the like are used to specify that a feature, a number, a step, an operation, an element, a part or a combination thereof is described in the specification, But do not preclude the presence or addition of one or more other features, integers, steps, operations, components, parts, or combinations thereof.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms such as those defined in commonly used dictionaries are to be interpreted as having a meaning consistent with the contextual meaning of the related art and are to be interpreted as either ideal or overly formal in the sense of the present application Do not.

Capacitive Pressure Sensor

2 is a cross-sectional view illustrating a capacitive pressure sensor according to the present invention. 3 is a cross-sectional view illustrating the first electrode of FIG. 2. FIG.

2 and 3, a capacitive pressure sensor 100 according to the present invention includes a first electrode 110, a second electrode 120, and a dielectric layer 130. When the capacitive pressure sensor is applied to a display device, it may be disposed under the display module.

The first electrode 110 may be driven as a sensing electrode. The first electrode 110 may be formed of a conductive metal such as ITO, copper, or silver.

The first electrode 110 is located, for example, on the inner base surface of the housing (not shown). The first electrode 110 may be fixed to the housing using a bonding layer, a double-sided tape, or the like between the housings.

The second electrode 120 is disposed to face the first electrode 110. The second electrode 120 is spaced apart from the first electrode 110 at a previous interval. In addition, the second electrode 120 may be directly laminated and bonded to the bottom surface of the display module, for example. The second electrode 120 may be vertically displaced by applying pressure to the second electrode 120 from the outside. Accordingly, the distance between the first and second electrodes 110 and 120 can be varied by the external pressure.

The second electrode 120 has a core cell structure composed of woven core cells. That is, each of the core cells is composed of a cell made of a conductive fabric and a cell made of a metal layer provided to surround the core. Thus, the second electrode 120 has a woven core cell structure, so that air can smoothly flow from the pores 135 in the dielectric layer 130 along the interface between the core cells. As the flow of air into or out of the dielectric layer 130 is smooth, the thickness of the dielectric layer 130, that is, the distance between the first and second electrodes 110 and 120 Can be changed quickly. Thus, the sensitivity of the pressure sensor according to the change in the separation distance can be improved.

The dielectric layer 130 is interposed between the first and second electrodes 110 and 120. As the second electrode 120 is displaced in the vertical direction, the distance between the first and second electrodes 110, 120 changes. Accordingly, the capacitance of the pressure sensor can be changed according to the change in the separation distance. Thereby, the pressure applied to the pressure sensor can be measured according to the change of the capacitance.

That is, when the external rotor pressure is applied, the position of the second electrode 120 is displaced downward. At this time, the distance d between the first electrode 110 and the second electrode 120 varies (decreases), and the distance between the first electrode 110 and the second electrode 120 The capacitance change corresponding to the formula of C = μA / d (where C is the capacitance, μ is the permittivity, A is the area, and d is the distance between the electrodes) The capacitance type pressure sensor 100 can determine the magnitude of the applied pressure because it depends on the magnitude of the change in the distance d between the two electrodes proportional to the size.

The dielectric layer 130 is made of an elastic material having a plurality of pores distributed therein. As the dielectric layer 130 is made of an elastic material, the dielectric layer 130 can be compressed and further restored by applying or releasing a pressure applied to the outside. Further, as a plurality of pores are distributed in the dielectric layer 130, air can be introduced into or discharged from the dielectric layer 130 through the pores. Examples of the material constituting the dielectric layer v include foamed urethane, silicone and the like.

The dielectric layer 130 may be formed on the second electrode 120 through a coating process.

In an embodiment of the present invention, the second electrode 120 may be used as a common electrode covering the dielectric layer 130 as a whole. Meanwhile, the first electrode 110 may be used as a sensing electrode in the region where the entire area of the dielectric layer 130 is evenly divided.

In an embodiment of the present invention, the second electrode 120 may have a thickness of about 10 to 50 μm. When the second electrode 120 has a thickness of less than 10 μm, the electrical conductivity of the second electrode 120 may not be sufficient, while the second electrode 120 may have a thickness of more than 50 μm The pressure applied from the outside may be excessively absorbed by the second electrode 120 and may be detrimental to the thickness reduction of the pressure sensor.

In addition, when the second electrode 120 has a single-layered structure of metal, the dielectric layer 130 must have a relatively large thickness in order to smoothly move the pores distributed in the dielectric layer 130 The pressure sensor 100 must have a relatively thin thickness as the second electrode 120 has a core cell structure to form an air flow path as in the present invention, .

The pressure sensor 100 according to an embodiment of the present invention may further include a double-sided tape 140. The double-sided tape 140 is interposed between the dielectric layer 130 and the first electrode 110. The double-sided tape 140 may include an anisotropic conductive material having conductivity.

Manufacturing Method of Capacitive Pressure Sensor

According to the method of manufacturing a capacitive pressure sensor according to an embodiment of the present invention, a common electrode is first prepared. The common electrode is formed to have a core cell structure having a plurality of core cells each made of a cell made of a conductive fabric and a metal layer surrounding the core.

The common electrode may have a core cell structure in which a plurality of core cells are woven by forming a metal layer through a plating process on a conductive fabric. Thereby, a common electrode of a core cell structure having a plurality of core cells is formed. And a ground potential may be applied to the common electrode.

Next, a dielectric layer made of a foamable elastic body having pores formed therein is formed on the common electrode.

The dielectric layer may be formed on the common electrode through a coating process. That is, according to the coating process, a dielectric layer can be formed on the common electrode by spraying a solution containing a foamable elastic material onto the common electrode. Alternatively, the common electrode may be immersed in a solution containing the foamable elastic body to form a dielectric layer on the common electrode. Thus, a bonding process of forming a separate bonding layer on the dielectric layer and the common electrode or a bonding process using a double-sided tape may be omitted. As a result, the dielectric layer can be easily formed on the common electrode through a simplified coating process.

Further, in the case of a bonding process or an adhering process for attaching an existing dielectric layer to an electrode, a process of patterning the bonding layer or cutting the double-sided tape according to the shape of the elastic body is required, so that the process is complicated and its degree of freedom is limited The dielectric layer is formed through a coating process as in the present invention, thereby simplifying the process.

Subsequently, a sensing electrode is formed on the dielectric layer. The sensing electrode is formed on the dielectric layer using a double-sided tape between the dielectric layers.

FIG. 4 is a graph for explaining a change in capacitance versus applied pressure of the capacitive pressure sensor according to the present invention shown in FIG. 2;

Referring to FIG. 4, when the applied pressure is in the range of 0.5 to 2.0 kgf, the capacitance type pressure sensor according to the present invention can detect the change amount of the capacitance within the range of 3,200 to 17,700. On the other hand, in the case of a pressure sensor having a dielectric layer made of first and second electrodes having a single thin film structure and an elastic body having pores distributed therein as in the prior art, the change in the capacitance within the range of 850 to 4,600 As shown in Fig.

100: pressure sensor 110: first electrode
120: second electrode 130: dielectric layer
140: Double-sided tape

Claims (10)

A first electrode and a second electrode arranged to face each other; And
And a dielectric layer interposed between the first and second electrodes and made of a foamable elastic body having pores formed therein,
The second electrode has a woven core cell structure having a plurality of core cells each made of a cell made of a conductive fabric and a metal layer surrounding the core,
And a path of air is formed along the interface between the pores and the core cells. The pressure sensor according to claim 1, wherein the dielectric layer is coated on the second electrode. The pressure sensor according to claim 1, wherein when the second electrode corresponds to a common electrode, the first electrode is provided in each of the plurality of regions. The pressure sensor according to claim 1, wherein the second electrode has a thickness of 10 to 50 占 퐉. The pressure sensor according to claim 1, wherein air is introduced into or out of the pores through the interface between the core cells. The pressure sensor according to claim 1, further comprising a double-sided tape interposed between the dielectric layer and the first electrode. Preparing a common electrode having a woven core cell structure having a plurality of core cells each made of a cell made of a conductive fabric and a metal layer provided to surround the core;
Forming a dielectric layer made of a foamable elastic body having pores therein on the common electrode; and
And forming a sensing electrode on the dielectric layer,
And a path of air is formed along the interface between the pores and the core cells. The method of manufacturing a pressure sensor according to claim 7, wherein preparing the common electrode includes forming a metal layer on a surface of the core through a plating process. 8. The method of claim 7, wherein forming the dielectric layer on the common electrode is performed through a coating process. The method of manufacturing a pressure sensor according to claim 7, wherein the step of forming the sensing electrode on the dielectric layer uses a double-sided tape.

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