Abstract:
Disclosed herein is an accelerator sensor, including: a mass body; a flexible beam that is provided with a piezoresistive element configured of an X-axis resistive element, a Y-axis resistive element, and a Z-axis resistive element having both ends connected with contact pads and is connected with the mass body; and a support portion that is connected with the flexible beam and supports the flexible beam so as to float the mass body, wherein the flexible beam has a slit provided between one-axis resistive element and the other axis resistive element adjacent to each other and the slit is extendedly formed from the contact pads connected with ends of the one axis resistive element and the other axis resistive element to the contact pads connected with the other ends thereof.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the benefit of Korean Patent Application No. 10-2012-0133840, filed on Nov. 23, 2012, entitled “Acceleration Sensor” which is hereby incorporated by reference in its entirety into this application. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Technical Field 
         [0003]    The present invention relates to an acceleration sensor. 
         [0004]    2. Description of the Related Art 
         [0005]    Generally, an acceleration sensor has been variously used for a car, an airplane, a mobile communication terminal, a toy, and the like. Meanwhile, a high-performance and small tri-axial acceleration sensor capable of measuring an X axis, a Y axis, and a Z axis has been developed so as to measure fine acceleration. 
         [0006]    Further, the acceleration sensor according to the related art has technical features of converting a motion of a mass body and a flexible portion into an electrical signal and uses a piezoresistive type that detects a motion of a mass body using a change in resistance of a piezoresistive element disposed in a flexible portion, a capacitive type that detects a motion of a mass body using a change in capacitance between fixed electrodes, and the like. 
         [0007]    Here, the piezoresistive type uses an element of which the resistance value is changed due to stress and, for example, increases a resistance value at a place where tensile stress is distributed and reduces a resistance value at a place where a compressive stress is distributed. 
         [0008]    However, the acceleration sensor based on the piezoresistive type according to the related art including the following Citation List has direction dependency since acceleration is a vector quantity, such that the acceleration sensor has a problem in that other-axis sensitivity appears. That is, the acceleration sensor based on the piezoresistive type may be difficult to accurately and efficiently sense acceleration and may generate short between resistors due to an effect of two axis components other than a required axis among three components of X, Y, and Z. 
       RELATED ART DOCUMENT 
     Patent Document 
       [0000]    
       
         (Patent Document 1) US 20060156818 A 
       
     
       SUMMARY OF THE INVENTION 
       [0010]    The present invention has been made in an effort to provide an acceleration sensor capable of improving sensitivity by having slits provided between piezoresistive elements disposed on a beam, preventing short from being generated between contact pads by extending the slits to the contact pads of the piezoresistive elements, and improving a stress concentration effect by additionally forming notches in the slits. 
         [0011]    According to a preferred embodiment of the present invention, there is provided an acceleration sensor, including: a mass body; a flexible beam that is provided with a piezoresistive element configured of an X-axis resistive element, a Y-axis resistive element, and a Z-axis resistive element having both ends connected with contact pads and is connected with the mass body; and a support portion that is connected with the flexible beam and supports the flexible beam so as to float the mass body, wherein the flexible beam has a slit provided between one-axis resistive element and the other axis resistive element adjacent to each other and the slit is extendedly formed from the contact pads connected with ends of the one axis resistive element and the other axis resistive element to the contact pads connected with the other ends thereof. 
         [0012]    The flexible beam may be configured of a first flexible beam, a second flexible beam, a third flexible beam, and a fourth flexible beam that are connected with all sides of the mass body at an equal distance, and the first flexible beam and the second flexible beam may be disposed to face each other based on the mass body and the third flexible beam and the fourth flexible beam may be disposed so as to face each other based on the mass body. 
         [0013]    The first flexible beam and the second flexible beam may be provided with the X-axis resistive element and the Z-axis resistive element and the third flexible beam and the fourth flexible beam may be provided with the Y-axis resistive element. 
         [0014]    A width center of the first flexible beam that is an orthogonal direction to a direction in which the support portion is connected with the mass body may be provided with the X-axis resistive element and a width edge of the first flexible beam may be provided with the Z-axis resistive element so as to be parallel with the X-axis resistive element, and a width center of the second flexible beam that is an orthogonal direction to a direction in which the support portion is connected with the mass body may be provided with the X-axis resistive element and a width edge of the second flexible beam may be provided with the Z-axis resistive element so as to be parallel with the X-axis resistive element. 
         [0015]    The first and second flexible beams may have a first slit provided between the X-axis resistive element and the Z-axis resistive element and has a second slit provided at an opposite side of the X-axis resistive element with respect to the first slit and a third slit at an opposite side of the Z-axis resistive element with respect to the first slit. 
         [0016]    The first slit may be provided with notches each protruded so as to be opposite to the X-axis resistive element and the Z-axis resistive element. 
         [0017]    The second slit may be provided with a notch protruded so as to be opposite to the X-axis resistive element. 
         [0018]    The third slit may be provided with a notch protruded so as to be opposite to the Z-axis resistive element. 
         [0019]    The Z-axis resistive elements formed on the first flexible beam and the second flexible beam may be disposed at one side on one beam and the other side on another beam, based on the X-axis resistive element. 
         [0020]    According to another preferred embodiment of the present invention, there is provided an acceleration sensor, including: a mass body; a flexible beam that is provided with a piezoresistive element configured of an X-axis resistive element, a Y-axis resistive element, and a Z-axis resistive element having both ends connected with contact pads and is connected with the mass body; and a support portion that is connected with the flexible beam and supports the flexible beam so as to float the mass body, wherein the flexible beam has slits provided between one axis resistive element and the other axis resistive element that are adjacent to each other and the slit is provided between a contact pad of the one axis resistive element and a contact pad of the other axis resistive element opposite to the one axis resistive element. 
         [0021]    The flexible beam may be configured of a first flexible beam, a second flexible beam, a third flexible beam, and a fourth flexible beam that are connected with all sides of the mass body at an equal distance and the first flexible beam and the second flexible beam may be disposed to face each other based on the mass body and the third flexible beam and the fourth flexible beam are disposed so as to face each other based on the mass body. 
         [0022]    The first flexible beam and the second flexible beam may be provided with the X-axis resistive element and the Z-axis resistive element and the third flexible beam and the fourth flexible beam may be provided with the Y-axis resistive element. 
         [0023]    A width center of the first flexible beam that is an orthogonal direction to a direction in which the support portion is connected with the mass body may be provided with the X-axis resistive element and a width edge of the first flexible beam may be provided with the Z-axis resistive element so as to be parallel with the X-axis resistive element and a width center of the second flexible beam that is an orthogonal direction to a direction in which the support portion is connected with the mass body may be provided with the X-axis resistive element and a width edge of the second flexible beam may be provided with the Z-axis resistive element so as to be parallel with the X-axis resistive element. 
         [0024]    The Z-axis resistive elements formed on the first flexible beam and the second flexible beam may be disposed at one side on one beam and the other side on another beam, based on the X-axis resistive element. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0025]    The above and other objects, features and advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which: 
           [0026]      FIG. 1  is a configuration diagram schematically illustrating an acceleration sensor according to a preferred embodiment of the present invention; 
           [0027]      FIG. 2  is a partial configuration diagram schematically illustrating an acceleration sensor according to another preferred embodiment of the present invention; and 
           [0028]      FIG. 3  is a partial configuration diagram schematically illustrating an acceleration sensor according to still another preferred embodiment of the present invention. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0029]    The objects, features and advantages of the present invention will be more clearly understood from the following detailed description of the preferred embodiments taken in conjunction with the accompanying drawings. Throughout the accompanying drawings, the same reference numerals are used to designate the same or similar components, and redundant descriptions thereof are omitted. Further, in the following description, the terms “first,” “second,” “one side,” “the other side” and the like are used to differentiate a certain component from other components, but the configuration of such components should not be construed to be limited by the terms. Further, in the description of the present invention, when it is determined that the detailed description of the related art would obscure the gist of the present invention, the description thereof will be omitted. 
         [0030]    Hereinafter, preferred embodiments of the present invention are described in detail with reference to the accompanying drawings. 
         [0031]      FIG. 1  is a configuration diagram schematically illustrating an acceleration sensor according to a preferred embodiment of the present invention. As illustrated in  FIG. 1 , an acceleration sensor  100  is a tri-axial piezoresistive acceleration sensor and includes a mass body  110 , a flexible beam  120 , a piezoresistive element (resistor)  130 , and a support portion  140 . 
         [0032]    In more detail, when external force is generated, the mass body  110  moves due to a moment generated by the external force and a resistance value of the piezoresistive element  130  of the flexible beam  120  formed of a flexible substrate is changed due to a displacement of the mass body  110 . 
         [0033]    To this end, the mass body  110  is connected with the flexible beam  120 , the piezoresistive element is disposed on the flexible beam  120 , and the support portion  140  is connected with the flexible beam  120  to support the flexible beam  120  so as to float the mass body  110 . 
         [0034]    Further, the flexible beam  120  is configured of a first flexible beam  121 , a second flexible beam  122 , a third flexible beam  123 , and a fourth flexible beam  124  that are each connected with all sides of the mass body  110  at an equal distance. Further, the first flexible beam  121  and the second flexible beam  122  are disposed to face each other based on the mass body  110  and the third flexible beam  123  and the fourth flexible beam  124  are disposed to face each other based on the mass body  110 . 
         [0035]    In addition, the piezoresistive element includes an X-axis resistive element  131 , a Y-axis resistive element  132 , and a Z-axis resistive element  133 . 
         [0036]    In more detail, the first flexible beam  121  and the second flexible beam  122  are provided with the X-axis resistive element  131  and the Z-axis resistive element  133  and the third flexible beam  123  and the fourth flexible beam  124  are provided with the Y-axis resistive element  132 . 
         [0037]    In addition, a width center of the first flexible beam  121  that is an orthogonal direction to a direction in which the support portion is connected with the mass body is provided with the X-axis resistive element  131  and a width edge of the first flexible beam is provided with a Z-axis resistive element  133  so as to be parallel with the X-axis resistive element  131 . That is, the first flexible beam  121  is provided with two pairs of X-axis resistive elements  131  and Z-axis resistive elements  133  that are parallel with each other. 
         [0038]    In addition, a width center of the second flexible beam  122  that is an orthogonal direction to a direction in which the support portion is connected with the mass body is provided with the X-axis resistive element  131  and a width edge of the second flexible beam is provided with a Z-axis resistive element  133  so as to be parallel with the X-axis resistive element  131 . That is, the second flexible beam  122  is provided with two pairs of X-axis resistive elements  131  and Z-axis resistive elements  133  that are parallel with each other. 
         [0039]    Further, in connection with the Z-axis resistive elements  133  disposed on the first flexible beam  121  and the second flexible beam  122  that are disposed so as to face each other based on the mass body  110 , the Z-axis resistive element  133  is disposed at one side on one beam and is disposed at the other side on another beam, based on the X-axis resistive element  131 . 
         [0040]    Further, the first and second flexible beams  121  and  122  of the acceleration sensor according to the preferred embodiment of the present invention are each provided with slits  121   a ,  121   b ,  121   c ,  122   a ,  122   b , and  122   c  so as to prevent short and crosstalk of the X-axis resistive element  131  and the Z-axis resistive element  133  that are adjacent to each other and improve sensitivity. 
         [0041]    Further, one end and the other end of the X-axis resistive element  131  and the Z-axis resistive element  133  are each connected with contact pads  131   a ,  131   b ,  133   a , and  133   b.    
         [0042]    That is, one end of the X-axis resistive element  131  is connected with a contact pad  131   a  of the first X-axis resistive element and the other end thereof is connected with a contact pad  131   b  of the second X-axis resistive element and one end of the Z-axis resistive element  133  is connected with a contact pad  133   a  of the first Z-axis resistive element and the other end thereof is connected with a contact pad  133   b  of the second Z-axis resistive element. 
         [0043]    In addition, the slits  121   a ,  121   b , and  121   c  are formed to extend over the contact pad  131   b  of the second X-axis resistive element from the contact pad  131   a  of the first X-axis resistive element and the contact pad  133   b  of the second Z-axis resistive element from the contact pad  133   a  of the first Z-axis resistive element. 
         [0044]    Further, the slits  121   a ,  121   b ,  121   c ,  122   a ,  122   b , and  122   c  are configured of the first slits  121   a  and  122   a , the second slits  121   b  and  122   b , and the third slits  121   c  and  122   c  and the first slits  121   a  and  122   a  are formed between the X-axis resistive element  131  and the Z-axis resistive element  133 , the second slits  121   b  and  122   b  are formed at an opposite side of the X-axis resistive element  131  with respect to the first slits  121   a  and  122   a , and the third slits  121   c  and  122   c  are formed at an opposite side of the Z-axis resistive element  133  with respect to the first slits  121   a  and  122   a.    
         [0045]    Next, the third flexible beam  123  is provided with two Y-axis resistive elements  132  toward the support portion  140  from an adjacent portion of the mass body  110 . 
         [0046]    Further, the Y-axis resistive elements  132  are disposed, in a row, at the width center of the flexible beam that is an orthogonal direction to the direction in which the support portion  140  is connected with the mass body  110 . 
         [0047]    Further, like the third flexible beam  123 , the fourth flexible beam  124  is provided with two Y-axis resistive elements  132  that are toward the support portion  140  from an adjacent portion of the mass body  110  and are disposed, in a row, at the width center of the flexible beam that is an orthogonal direction to the direction in which the support portion  140  is connected with the mass body  110 . 
         [0048]    In addition to this, the third flexible beam  123  and the fourth flexible beam  124  are provided with the Y-axis resistive elements  132  that are symmetrical with each other based on the mass body  110 . 
         [0049]    As described above, the acceleration sensor according to the preferred embodiment of the present invention has the slits provided between the X-axis resistive element and the Z-axis resistive element that are the piezoresistive elements on the flexible beams and at the other side opposite thereto, thereby improving the sensitivity and preventing the short of the contact pads. 
         [0050]      FIG. 2  is a partial configuration diagram schematically illustrating an acceleration sensor according to another preferred embodiment of the present invention. As illustrated, the acceleration sensor according to another preferred embodiment of the present invention is different from the acceleration sensor according to the preferred embodiment illustrated in  FIG. 1 , in terms of only the formation position and the size of the slit. That is, the acceleration sensor according to another preferred embodiment of the present invention has slits provided at an adjacent portion of the pad portion between different axis piezoresistive elements. 
         [0051]    In more detail, a width center of a first flexible beam  221  that is an orthogonal direction to a direction in which the support portion is connected with the mass body is provided with an X-axis resistive element  231  and a width edge of the first flexible beam  221  is provided with a Z-axis resistive element  233  so as to be parallel with the X-axis resistive element  231 . That is, the first flexible beam  221  is provided with two pairs of X-axis resistive elements  231  and Z-axis resistive elements  233  that are parallel with each other. 
         [0052]    Further, the third flexible beam and the fourth flexible beam and the X-axis and Y-axis resistive elements and the Z-axis resistive element disposed thereon are implemented so as to be the same as the acceleration sensor according to the preferred embodiment illustrated in  FIG. 1 , and therefore the overlapping description thereof will be omitted. 
         [0053]    Further, the piezoresistive element according to another preferred embodiment of the present invention has slits provided between the contact pads connected with other axis resistive elements so as to prevent the short and crosstalk of the other axis resistive elements adjacent to each other and improve the sensitivity. 
         [0054]    In more detail, one end and the other end of the X-axis resistive element  231  and the Z-axis resistive element  233  are each connected with contact pads  231   a ,  231   b ,  233   a , and  233   b.    
         [0055]    That is, one end of the X-axis resistive element  231  is connected with a contact pad  231   a  of the first X-axis resistive element and the other end thereof is connected with a contact pad  231   b  of the second X-axis resistive element and one end of the Z-axis resistive element  233  is connected with a contact pad  233   a  of the first Z-axis resistive element and the other end thereof is connected with a contact pad  233   b  of the second Z-axis resistive element. 
         [0056]    Further, the contact pad  233   a  of the first Z-axis resistive element is disposed to face the contact pad  231   a  of the first X-axis resistive element and the contact pad  233   b  of the second Z-axis resistive element is disposed to face the contact pad  231   b  of the second X-axis resistive element. 
         [0057]    In addition, the slits  221  and  221   b  are configured of the first slit  221   a  and the second slit  221   b  and the first slit  221   a  is disposed between the contact pad  231   a  of the first resistive element and the contact pad  233   a  of the first Z-axis resistive element and the second slit  221   b  is disposed between the contact pad  231   b  of the second X-axis resistive element and the contact pad  233   b  of the second Z-axis resistive element. 
         [0058]    In addition, the first slit  221   a  and the second slit  221   b  may be more extendedly formed than the contact pads  231   a ,  233   a ,  231   b , and  233   b  opposite thereto. 
         [0059]    Further, the piezoresistive element according to another preferred embodiment of the present invention has the slits provided between the contact pads even in the X-axis resistive element and the Z-axis resistive element that are disposed on the second flexible beam and is implemented to be the same as the foregoing first flexible beam, therefore the detailed description thereof will be omitted. 
         [0060]    According to the configuration as described above, the piezoresistive element according to another preferred embodiment of the present invention has the slits oppositely provided only in the contact pads of different axis resistive elements, thereby improving a problem in that the beam width is increased due to a diffusion length. 
         [0061]      FIG. 3  is a partial configuration diagram schematically illustrating an acceleration sensor according to still another preferred embodiment of the present invention. As illustrated, the acceleration sensor according to still another preferred embodiment of the present invention is different from the acceleration sensor according to the preferred embodiment illustrated in  FIG. 1 , in terms of only the shape of the slit. That is, the acceleration sensor according to still another embodiment of the present invention has notches further provided in the slits that are formed on the flexible beams. 
         [0062]    In more detail, a width center of a first flexible beam  321  that is an orthogonal direction to a direction in which the support portion is connected with the mass body is provided with an X-axis resistive element  331  and a width edge of the first flexible beam  321  is provided with a Z-axis resistive element  331  so as to be parallel with the X-axis resistive element  333 . That is, the first flexible beam  321  is provided with two pairs of X-axis resistive elements  331  and Z-axis resistive elements  333  that are parallel with each other. 
         [0063]    Further, the third flexible beam and the fourth flexible beam and the X-axis and Y-axis resistive elements and the Z-axis resistive element disposed thereon are implemented so as to be the same as the acceleration sensor according to the preferred embodiment illustrated in  FIG. 1 , and therefore the overlapping description thereof will be omitted. 
         [0064]    Further, the piezoresistive element according to another preferred embodiment of the present invention has slits provided between the contact pads connected with the other axis resistive element so as to prevent the short and crosstalk of the other axis resistive element adjacent to each other and improve the sensitivity. 
         [0065]    In addition, the slits  321   a ,  321   b , and  321   c  are each provided so as to prevent the short and crosstalk of the X-axis resistive element  331  and the Z-axis resistive element  333  and improve the sensitivity. 
         [0066]    Further, one end and the other end of the X-axis resistive element  331  and the Z-axis resistive element  333  are each connected with contact pads  331   a ,  331   b ,  333   a , and  333   b.    
         [0067]    That is, one end of the X-axis resistive element  331  is connected with the contact pad  331   a  of the first X-axis resistive element and the other end thereof is connected with the contact pad  331   b  of the second X-axis resistive element and one end of the Z-axis resistive element  333  is connected with the contact pad  333   a  of the first Z-axis resistive element and the other end thereof is connected with the contact pad  333   b  of the second Z-axis resistive element. 
         [0068]    In addition, the slits  321   a ,  321   b , and  321   c  are formed to extend over the contact pad  331   b  of the second X-axis resistive element from the contact pad  331   a  of the first X-axis resistive element and the contact pad  333   b  of the second Z-axis resistive element from the contact pad  333   a  of the first Z-axis resistive element. 
         [0069]    Further, the slits  321   a ,  321   b , and  321   c  are configured of the first slits  321   a , the second slit  321   b , and the third slit  321   c , the first slit  321   a  is formed between the X-axis resistive element  331  and the Z-axis resistive element  333 , the second slit  321   b  is formed at an opposite side of the X-axis resistive element  331  with respect to the first slit  321   a , and the third slit  321   c  is formed at an opposite side of the Z-axis resistive element  333  with respect to the first slit  121   a.    
         [0070]    In addition, the first slit  321   a  is provided with notches  321   a ′ and  321   a ″ that are each protruded so as to be opposite to the X-axis resistive element  331  and the Z-axis resistive element  333 . 
         [0071]    Further, the second slit  321   b  is provided with a notch  321   b ′ that is protruded to be opposite to the X-axis resistive element  331 . 
         [0072]    Further, the third slit  321   c  is provided with a notch  312   c ′ that is protruded to be opposite to the Z-axis resistive element  333 . 
         [0073]    Further, the acceleration sensor according to still another preferred embodiment of the present invention has the slits provided even in the X-axis resistive element and the Z-axis resistive element that are disposed on the second flexible beam and is implemented to be the same as the foregoing first flexible beam, therefore the detailed description thereof will be omitted. 
         [0074]    According to the configuration as described above, the acceleration sensor according to still another preferred embodiment of the present invention is provided with the notches in addition to the slits, thereby implementing more effective stress concentration. 
         [0075]    According to the preferred embodiments of the present invention, it is possible to obtain the acceleration sensor capable of improving sensitivity by having the slits provided between the piezoresistive elements disposed on the beam, preventing the short from being generated between the contact pads by extending the slits to the contact pads of the piezoresistive elements, and improving the stress concentration effect by additionally forming the notches in the slits. 
         [0076]    Although the embodiments of the present invention have been disclosed for illustrative purposes, it will be appreciated that the present invention is not limited thereto, and those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention. 
         [0077]    Accordingly, any and all modifications, variations or equivalent arrangements should be considered to be within the scope of the invention, and the detailed scope of the invention will be disclosed by the accompanying claims.