Abstract:
An acceleration switch has a frame fixed to a first substrate, a beam positioned inside the frame and supported by the frame, and a mass body supported by the beam and having a hole portion at substantially a center thereof. A central body is positioned inside the hole portion and fixed to the first substrate. The hole portion or the central body are suitably configured, or the position of the hole portion or the position of the center body is suitably selected, so that the acceleration switch is capable of detecting a predetermined acceleration irrespective of the influence of gravity acceleration.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an acceleration switch and an electronic device. 
     2. Description of the Related Art 
     As a conventional acceleration switch, there is used an omnidirectional acceleration switch as described in Japanese Patent Application Laid-open No. Hei 09-145740, in which a counter electrode (central body) is provided inside a mass body and the mass body is supported by a beam. Such an acceleration switch is described below with reference to  FIG. 1 . 
       FIG. 1  is a cross-sectional view of the conventional acceleration switch. This acceleration switch  001  includes a peripheral portion (frame)  101 , a beam  102 , a mass body (weight)  103 , and a counter electrode  104 . One end of the beam  102  is fixed to the mass body  103  and the other end of the beam  102  is fixed to the peripheral portion  101 . In this manner, the peripheral portion  101  supports the mass body  103  with the use of the beam  102 . 
     In accordance with acceleration applied to the acceleration switch  001 , the mass body  103  and the counter electrode  104  disposed inside the mass body  103  are brought into contact with each other. In this manner, an external device connected to the acceleration switch  001  detects vibration. In other words, when acceleration is applied to the acceleration switch  001 , the mass body  103  moves to contact with the counter electrode  104 , and the acceleration switch is turned ON. This acceleration switch has various advantages such as being available as a normally-off and omnidirectional switch and being relatively compact and mass-producible because monocrystalline silicon can be used as a base for production with the use of semiconductor manufacturing technology. 
     An acceleration switch to be mounted on an electronic device is highly required to be more compact, and hence a smaller external dimension of the acceleration switch is more advantageous. Cost of the acceleration switch is also highly required to be lower, and it is therefore further advantageous to use the semiconductor manufacturing technology to reduce the external dimension of the acceleration switch and thereby produce a large number of acceleration switches on a single wafer. 
     However, this is effective when the acceleration switch is placed horizontally, but the omnidirectional sensitivity is not effective depending on the usage of the acceleration switch, and a predetermined sensitivity may not be obtained. 
     For example, it is supposed that the acceleration switch is held perpendicularly (in the vertical direction) with respect to a horizontal plane (including a plane perpendicular to the vertical direction, a substantially horizontal plane, and a plane equivalent thereto). In the case where the acceleration switch is produced to have a sensitivity of, for example, 1 G or less, the switch becomes the ON state in response to the gravity of 1 G.  FIG. 2A  illustrates the case where the acceleration switch is held in parallel to the horizontal plane.  FIG. 2B  illustrates the case where the acceleration switch is held perpendicularly to the horizontal plane. In  FIG. 2A , the horizontal plane is the XY plane, and the direction of gravity is the Z direction. In  FIG. 2B , the horizontal plane is the XZ plane, and the direction of gravity is the Y direction (to be exact, the −Y direction). In the case where the acceleration switch is produced to have a sensitivity of 1 G or less, such as 1 G, when the switch is turned upright, the switch becomes the ON state because the gravity acceleration of 1 G has already been applied. 
     A specific description is now given. In the following, for simplification, a mass body and a counter electrode corresponding to the mass body  103  and the counter electrode  104  are only illustrated. In  FIGS. 2A and 2B , the line AA′ represents a center line of a counter electrode  202  in the X direction (second direction), the line BB′ represents a center line of a mass body  201  in the X direction, and the line CC′ represents center lines of the counter electrode  202  and the mass body  201  in the Y direction (first direction) orthogonal to the thickness direction of a first substrate to be described later. The direction of gravity (vertical direction) in  FIG. 2A  is the Z direction, and the direction of gravity in  FIG. 2B  is the Y direction. Note that, in  FIG. 2A , the line AA′ and the line BB′ are aligned with each other. 
       FIGS. 2A and 2B  illustrate the case of an acceleration switch  002  having a sensitivity of, for example, 1 G.  FIG. 2A  illustrates the case where the acceleration switch  002  is placed horizontally. A distance “a” as an electrode interval between the counter electrode  202  and the mass body  201  is equal to a distance by which the mass body  201  displaces when an acceleration of 1 G is applied to the acceleration switch  002 . Note that, a gap between the counter electrode  202  and the mass body  201  is uniformly the same as the distance “a” on the whole circumference. In this case, when the acceleration switch  002  is turned upright with respect to the horizontal plane, the mass body  201  displaces in the direction of gravity (vertical direction) in response to the gravity of 1 G. 
     As illustrated in  FIG. 2B , the counter electrode  202  is brought into contact with a side wall of a through hole (hole portion)  205  on the C side, with the Y direction being the direction of gravity (vertical direction). The displacement amount in response to 1 G is equal to the distance “a” between the electrode of the mass body  201  and the counter electrode  202 , and hence the mass body  201  is brought into contact with the counter electrode  202 . In other words, the conventional technology has a problem in that a predetermined acceleration cannot be detected when acceleration other than an acceleration intended to be detected, such as the gravity acceleration, is applied. Note that, the electrodes to be electrically conductive by this contact are formed on opposing side walls of the mass body  201  and the counter electrode  202 . 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to improve the above-mentioned acceleration switch so that a predetermined acceleration can be detected even when acceleration other than an acceleration intended to be detected, such as the gravity acceleration, is applied. 
     In order to solve these problems, an acceleration switch of the present invention is configured as follows. 
     According to an exemplary embodiment of the present invention, there is provided an acceleration switch, including: a first substrate made of an insulating material; a frame fixed to the first substrate; a beam which is positioned inside the frame and is supported by the frame; a mass body which is supported by the beam and has a hole portion at substantially a center thereof; and a central body which is positioned inside the hole portion and is fixed to the first substrate, in which, under a state where the first substrate is placed substantially horizontally, center positions of at least one of a combination of the mass body and the hole portion, a combination of the mass body and the central body, and a combination of the hole portion and the central body are not aligned with each other in a first direction. 
     The acceleration switch according to the exemplary embodiment of the present invention further includes a second substrate which is positioned on an opposite side of the first substrate and is made of an insulating material, and the frame and the central body are fixed to the second substrate. 
     Further, in the acceleration switch according to the exemplary embodiment of the present invention, the second substrate includes: a first through electrode for electrically connecting the frame and an external circuit to each other; and a second through electrode for electrically connecting the central body and the external circuit to each other. 
     Further, in the acceleration switch according to the exemplary embodiment of the present invention, the beam is a single beam. 
     Further, in the acceleration switch according to the exemplary embodiment of the present invention, the beam is an arc-like beam. 
     Further, in the acceleration switch according to the exemplary embodiment of the present invention, a distance between a side surface of the hole portion and a side surface of the central body is 1 μm or more and 20 μm or less. 
     Further, in the acceleration switch according to the exemplary embodiment of the present invention, the hole portion includes: a straight portion which is parallel to the first direction; and an arc portion which warps with respect to a second direction orthogonal to the first direction and a thickness direction. 
     According to an exemplary embodiment of the present invention, there is provided an electronic device, including: the above-mentioned acceleration switch; and a circuit for detecting a detection signal output from the acceleration switch to perform a predetermined operation in accordance with the detection signal. 
     According to the present invention, a predetermined acceleration intended to be detected can be detected even when another acceleration than the acceleration intended to be detected is applied. 
     With this configuration, when the acceleration switch is mounted in, for example, an electronic device which can incorporate only a small capacity battery to save power, the device can stop its operation when a human vibration is not detected, that is, when the device is not used, and the device can automatically start its operation upon detection of vibration, that is, when the device is used. Thus, it is possible to realize an electronic device in which the wasted use of a battery is avoided. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the accompanying drawings: 
         FIG. 1  is a schematic front view of a conventionally known acceleration switch; 
         FIGS. 2A and 2B  are front views illustrating an operation of the conventionally known acceleration switch; 
         FIGS. 3A to 3D  are front views illustrating an operation of an acceleration switch according to a first embodiment of the present invention; 
         FIGS. 4A and 4B  are front views illustrating an operation of a conventionally known acceleration switch; 
         FIGS. 5A and 5B  are front views illustrating an operation of an acceleration switch according to a second embodiment of the present invention; 
         FIGS. 6A and 6B  are front views illustrating an operation of an acceleration switch according to a third embodiment of the present invention; 
         FIGS. 7A and 7B  are front views illustrating an operation of an acceleration switch according to a fourth embodiment of the present invention; and 
         FIG. 8  is a schematic horizontal cross-sectional view illustrating the acceleration switch according to the embodiments of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to the accompanying drawings, exemplary embodiments of the present invention are described below. 
     (First Embodiment) 
     As described in the description of the related art illustrated in  FIGS. 2A and 2B , in the case where the acceleration switch  002  is turned upright with respect to the horizontal plane, as long as the distance between the mass body  201  and the counter electrode  202  is sufficiently large so that the mass body  201  and the counter electrode  202  may not contact with each other, the mass body  201  and the counter electrode  202  are prevented from contacting with each other even when the acceleration switch  002  is turned upright with respect to the horizontal plane. The details of a first embodiment of the present invention are described below with reference to  FIGS. 3A to 3D . 
     In  FIGS. 3A to 3D , the line DD′ represents a center line of a counter electrode  302  in the X direction (second direction), the line EE′ represents a center line of a mass body  301  in the X direction, and the line FF′ represents center lines of the counter electrode  302  and the mass body  301  in the Y direction (first direction). In  FIG. 3A , the horizontal plane is the XY plane, and the direction of gravity (vertical direction) is the Z direction. In  FIG. 3B , the horizontal plane is the XZ plane, and the direction of gravity is the Y direction. Note that, in  FIG. 3A , the line DD′ and the line EE′ are aligned with each other. 
       FIG. 3A  illustrates the case where an acceleration switch  003  is placed horizontally, in which the distance between the mass body  301  and the counter electrode  302  is sufficiently large in the Y direction of  FIG. 3A . A distance between an electrode of the mass body  301  and the counter electrode  302  on the F side is represented by “ 3   a ”. When the acceleration switch  003  is turned upright with respect to the horizontal plane, because “a” corresponds to 1 G, the mass body  301  displaces by the distance “a” in response to the gravity of 1 G applied to the acceleration switch  003 . Thus, the distance between the mass body  301  and the counter electrode  302  becomes “ 2   a ”, which is the difference between “ 3   a ” and “a”. This state is illustrated in  FIG. 3B . In this manner, even when the acceleration switch  003  is turned upright with respect to the horizontal plane, the acceleration switch  003  can maintain a sensitivity of 2 G in the Y direction and a sensitivity of 1 G in the X direction of  FIG. 3B , though the sensitivity is improved in one direction (Y direction of  FIG. 3B ). 
     In other words, under the state where a first substrate to be described later is placed substantially horizontally in  FIG. 3A , the center of the through hole  305  is shifted from the center of the mass body  301  to the F side by the distance “a”, and hence the counter electrode  302  is decentered. That is, the acceleration switch of  FIG. 3A  has a shape in which the centers of the mass body  301  and the counter electrode  302  are aligned and coincide with each other, but the centers of the mass body  301  and the counter electrode (central body)  302  do not coincide with and are shifted from the center of the through hole (hole portion)  305  by the distance “a”.  
     In other words, under the state where a first substrate to be described later is placed substantially horizontally in  FIG. 3A , the center of the through hole  305  is shifted from the center of the mass body  301  to the F side by the distance “a”, and hence the counter electrode  302  is decentered. That is, the acceleration switch of  FIG. 3A  has a shape in which the centers of the mass body  301  and the counter electrode  302  are aligned with each other, but the centers of the mass body  301  and the counter electrode (central body)  302  are shifted from the center of the through hole (hole portion)  305  by the distance “a”. 
     In this embodiment, the thorough hole  305  of the mass body  302  is formed of the straight portion  305   a  and the arc portion  305   b,  but the thorough hole  305  may have an oval shape formed by an arc portion as a whole. The oval shape in this case can have the minor direction corresponding to the second direction and the major direction corresponding to the first direction. 
     (Modified Example of First Embodiment) 
     As described above, in the acceleration switch according to the first embodiment, the center of the through hole  305  is shifted from the center of the mass body  301  to the F side by the distance “a”, and hence the counter electrode  302  is apparently decentered. A modified example thereof is described below.  FIGS. 3C and 3D  illustrate the modified example of the first embodiment. Referring to  FIGS. 3C and 3D , the difference between the first embodiment and the modified example is clearly described, but the common description of the first embodiment and the modified example is omitted. 
     The modified example is different from the first embodiment in that the mechanism of decentering the counter electrode  302  is changed. Specifically, as is understood from the comparison between  FIG. 3C  and  FIG. 3A , an acceleration switch of  FIG. 3C  has a shape in which, under the state where the first substrate to be described later is placed substantially horizontally, the centers of the mass body  301  and the through hole (hole portion)  305  are aligned and coincide with each other, but the centers of the mass body  301  and the through hole (hole portion)  305  do not coincide with and are shifted from the center of the counter electrode (central body)  302  by the distance “a”.  
     Note that, the distances between the counter electrode  302  and the through hole  305  in the respective directions are the same as those in the first embodiment. In  FIG. 3C , the distance between the counter electrode  302  and the straight portion  305   a  is the distance “a”. In  FIG. 3C , the distance between the counter electrode  302  and the arc portion  305   b  is the distance “ 3   a ” on the F side and the distance “a” on the F′ side. 
     Even in the case where such a modified example is employed, when the substrate of the acceleration switch  003  is turned upright with respect to the horizontal plane, the counter electrode  302  and the through hole  305  are prevented from contacting with each other in the Y direction, and the acceleration switch  003  can maintain a sensitivity of 2 G in the Y direction and a sensitivity of 1 G in the X direction of  FIG. 3D . Note that,  FIG. 3D  illustrates the state of the acceleration switch  003  where all the centers of the mass body  301 , the through hole  305 , and the counter electrode  302  are aligned with one another. 
     (Second Embodiment) 
     Next, a description is given of the case of an acceleration switch having a sensitivity of more than 1 G.  FIGS. 4A and 4B  illustrate an acceleration switch  004  having a sensitivity of, for example, 2 G. In  FIGS. 4A and 4B , the line GG′ represents a center line of a counter electrode  402  in the X direction (second direction), the line HH′ represents a center line of a mass body  401  in the X direction, and the line II′ represents center lines of the counter electrode  402  and the mass body  401  in the Y direction (first direction). In  FIG. 4A , the horizontal plane is the XY plane, and the direction of gravity (vertical direction) is the Z direction. In  FIG. 4B , the horizontal plane is the XZ plane, and the direction of gravity is the Y direction. Note that, in  FIG. 4A , the line GG′ and the line HH′ are aligned with each other. 
       FIG. 4A  illustrates the case where the acceleration switch  004  is placed horizontally. A distance “ 2   b ” between the counter electrode  402  and an electrode of the mass body  401  is equal to a distance by which the mass body  401  displaces when an acceleration of 2 G is applied to the acceleration switch  004 . Note that, a gap between the counter electrode  402  and the mass body  401  is uniformly the same as the distance “ 2   b ” on the whole circumference. Symbol “b” as used herein is a distance by which the mass body  401  displaces in response to the acceleration of 1 G. 
     In this case, when the acceleration switch  004  is turned upright with respect to the horizontal plane, the mass body  401  displaces in the direction of gravity (vertical direction) in response to the gravity of 1 G. For example, as illustrated in  FIG. 4B , the counter electrode  402  becomes closer to a side wall of a through hole (hole portion)  405  on the I side, with the Y direction being the direction of gravity (vertical direction). Accordingly, a distance between an electrode of the mass body  401  and the counter electrode  402  is changed from “ 2   b ” to “b”, with the result that the sensitivity in the longitudinal direction (on the I side, the upward direction of gravity, the upward vertical direction) becomes 1 G. In this case, the acceleration switch  004  is designed so as to be switched ON or OFF when an acceleration of 2 G is applied, and hence it is difficult to realize a desired operation satisfactorily. 
     In view of this, the following second embodiment of the present invention discusses a configuration of an acceleration switch which is designed so that the counter electrode may have an offset amount “b” in the downward direction of gravity (downward vertical direction), and the center of the counter electrode becomes closer to the mass body by the offset amount “b” with respect to the center of the through hole under the state where the acceleration switch is held horizontally. 
     The details of the second embodiment of the present invention are described below with reference to  FIGS. 5A and 5B . In  FIGS. 5A and 5B , the line JJ′ represents a center line of a counter electrode  502  in the X direction (second direction), the line KK′ represents a center line of a mass body  501  in the X direction, and the line LL′ represents center lines of the counter electrode  502  and the mass body  501  in the Y direction (first direction). In  FIG. 5A , the horizontal plane is the XY plane, and the direction of gravity (vertical direction) is the Z direction. In  FIG. 5B , the horizontal plane is the XZ plane, and the direction of gravity is the Y direction. Note that, in  FIG. 5B , the line JJ′ and the line KK′ are aligned with each other.  FIG. 5A  illustrates the case where an acceleration switch  005  as a target of this embodiment is placed horizontally. A space between the mass body  501  and the counter electrode  502  is shifted by 1 G, and hence a distance between the counter electrode  502  and the mass body  501  on the L side is the distance “ 3   b ”, and a distance therebetween on the L′ side is the distance “b”. 
     In this case, when the acceleration switch  005  is turned upright with respect to the horizontal plane, the distance between the mass body and the counter electrode is reduced by 1 G in the L direction to be “ 2   b ”. This state is illustrated in  FIG. 5B . In this manner, a predetermined sensitivity of 2 G can be maintained even when the acceleration switch is turned upright with respect to the horizontal plane. Note that, in this case, the distance between the counter electrode  502  and the mass body  501  is uniformly the same as the distance “ 2   b ” on the whole circumference. 
     In this manner, in the second embodiment, as described in the modified example of the first embodiment, the acceleration switch of  FIG. 5A  has a shape in which, under the state where the first substrate to be described later is placed substantially horizontally, the centers of the mass body  501  and the through hole (hole portion)  505  are aligned with each other, but the centers of the mass body  501  and the through hole (hole portion)  505  are shifted from the center of the counter electrode (central body)  502  by the distance “b”. 
     (Third Embodiment) 
     Next, a description is given of the case of offsetting the position of the counter electrode instead of offsetting the position of the mass body. In a third embodiment of the present invention, as a modified example of the second embodiment, the offset amount can be provided as appropriate similarly to the first embodiment. Specifically, an acceleration switch in this embodiment has a shape in which, under the state where the first substrate to be described later is placed substantially horizontally, the centers of a mass body  601  and a counter electrode  602  are aligned with each other, but the centers of the mass body  601  and the counter electrode (central body)  602  are shifted from the center of a through hole (hole portion)  605  by the distance “b”. 
     This state is illustrated in  FIGS. 6A and 6B . In  FIGS. 6A and 6B , the line MM′ represents a center line of the counter electrode  602  in the X direction (second direction), the line NN′ represents a center line of the mass body  601  in the X direction, and the line OO′ represents center lines of the counter electrode  602  and the mass body  601  in the Y direction (first direction). In  FIG. 6A , the horizontal plane is the XY plane, and the direction of gravity (vertical direction) is the Z direction. In  FIG. 6B , the horizontal plane is the XZ plane, and the direction of gravity is the Y direction. Note that, in  FIG. 6B , the line MM′ and the line NN′ are aligned with each other. 
     In this manner, when an acceleration switch  006  in this embodiment is turned upright with respect to the horizontal plane, the mass body displaces by the distance “b” in response to the gravity of 1 G, and the distance between the mass body and the counter electrode can be maintained to “ 2   b ”. This state is illustrated in  FIG. 6B . Note that, in this case, the distance between the counter electrode  602  and the mass body  601  is uniformly the same as the distance “ 2   b ” on the whole circumference. 
     (Fourth Embodiment) 
     Next, a description is given of the case of changing the shape of the counter electrode.  FIGS. 7A and 7B  illustrate another method for maintaining a sensitivity of 2 G in the longitudinal direction even when an acceleration switch is turned upright with respect to the horizontal plane. In  FIGS. 7A and 7B , the line PP′ represents a center line of a mass body  701  in the X direction (second direction), the line RR′ represents a center line of a counter electrode  702  in the X direction, and the line QQ′ represents center lines of the counter electrode  702  and the mass body  701  in the Y direction (first direction). In  FIG. 7A , the horizontal plane is the XY plane, and the direction of gravity (vertical direction) is the Z direction. In  FIG. 7B , the horizontal plane is the XZ plane, and the direction of gravity is the Y direction. Note that, in  FIG. 7B , the line PP′ and the line RR′ are aligned with each other. 
     The shape of the counter electrode is changed so as to have the distance “ 3   b ” between the counter electrode  702  and a wall surface of a through hole  705  of the mass body  701  on the Q side and have the distance “b” between the counter electrode  702  and a wall surface of the through hole  705  of the mass body  701  on the Q′ side. This state is illustrated in  FIG. 7A . 
     When this acceleration switch  007  is turned upright with respect to the horizontal plane, the mass body  701  displaces by 1 G, and hence the distance “ 2   b ” can be obtained both in the upward and downward longitudinal directions. Thus, a sensitivity of 2 G can be maintained in the longitudinal direction. This state is illustrated in  FIG. 7B . 
     As described above, according to the present invention, a predetermined acceleration can be detected even when a load other than an acceleration intended to be detected, such as the gravity acceleration, is applied. In particular, by recognizing in advance which direction the acceleration switch will be supported with respect to the direction of gravity (vertical direction), the detection of acceleration in any direction can be dealt with in design as in the above-mentioned first to fourth embodiments. Note that, it is assumed in those embodiments that the up-down direction or sheet direction of the drawings is the direction of gravity (vertical direction) for convenience sake, but the present invention is not limited to the embodiments illustrated in the drawings. 
     Note that, the acceleration switch of the present invention described above is effective not only for the example described above alone but also for a combination of the examples. Further, in the case where the acceleration switch is placed horizontally for use, the acceleration switch of the present invention is effective as an acceleration switch for obtaining different sensitivities depending on directions. Such an acceleration switch can be supported to a desired device in accordance with the directivity of vibration or acceleration recognizable in advance, for example, in the case where the frequency of application of vibration or acceleration differs depending on directions. 
     In particular, the embodiments of the present invention have discussed the case where the position of the mass body of the acceleration switch moves when the mass body is affected by the gravity acceleration as compared to the state where the mass body is not affected by the gravity acceleration. An electronic device including an acceleration switch often vibrates in the vertical direction, which is the direction of gravity acceleration. Therefore, as illustrated in  FIGS. 3B ,  5 B,  6 B, and  7 B regarding the vertical direction, the acceleration switch is configured so that the distance between the counter electrode and the through hole may be uniform both in the positive and negative Y directions even in such a case. In this manner, the acceleration switch can have the same sensitivity both in the positive and negative vertical directions of the electronic device with respect to a uniform external vibration in the vertical direction. 
     Now, the configuration of the acceleration switch is described below with reference to  FIGS. 1 and 8 . First, a second substrate of the acceleration switch  001  includes a substrate peripheral portion (frame)  101 , a beam  102 , a mass body  103 , and a counter electrode  104  in this order from the outside to the inside of  FIG. 1 . A distance between a side surface of a hole portion of the mass body  103  and a side surface of the counter electrode is 1 μm or more and 20 μm or less. 
     The substrate peripheral portion or frame  101  except for a bonding portion with the beam  102  to be described later has an inner circumferential shape (substrate inner surface  101   a ) obtained by hollowing out substantially the center in  FIG. 1  into a cylindrical shape. The substrate peripheral portion  101  is sandwiched by a first substrate  105  and a third substrate  106  of  FIG. 8  from the upper side and the lower side of  FIG. 8 . The first substrate  105  and the third substrate  106  are formed of an insulating material. How to sandwich the substrate peripheral portion  101  is not particularly limited, but in this embodiment, the substrate peripheral portion  101  is sandwiched by the first substrate  105  and the third substrate  106  over the full width of the shaded region of the substrate peripheral portion  101  illustrated in  FIG. 1 . 
     The mass body  103  is formed into a ring shape (tubular shape) having a mass body inner surface  103   a  and a mass body outer surface  103   b  illustrated in  FIG. 1 , and is positioned inside the substrate inner surface  101   a  of the substrate peripheral portion  101  hollowed out into the cylindrical shape. In addition, the mass body  103  is not in contact with the first substrate  105  and the third substrate  106  illustrated in  FIG. 8  but is positioned between the first substrate  105  and the third substrate  106  via air gaps. 
     The beam  102  connects the substrate peripheral portion  101  and the mass body  103  to each other. The beam  102  is elastic and is formed so as to substantially go around inside a gap between the substrate peripheral portion  101  and the mass body  103 . Specifically, one end of the beam  102  is connected to the substrate peripheral portion  101  at the substrate inner surface  101   a  on the lower side of  FIG. 1 , and the other end of the beam  102  is connected to the mass body  103  at the mass body outer surface  103   b  on the lower side of  FIG. 1 . In addition, similarly to the mass body  103 , the beam  102  is not in contact with the first substrate  105  and the third substrate  106  illustrated in  FIG. 8  but is positioned between the first substrate  105  and the third substrate  106  via air gaps. Note that, the top surface of the beam  102  in  FIG. 8  is flush with the top surface of the mass body  103 , but the top surface of the beam  102  may be flush with a connection surface between the substrate peripheral portion  101  and the first substrate  105 . The beam  102  in  FIG. 8  is formed so that the vertical width is smaller than the vertical width of the mass body  103 . 
     The counter electrode  104  has a cylindrical shape, and is positioned inside the mass body inner surface  103   a  and at substantially the center of the acceleration switch  001 . The center of the counter electrode  104  substantially matches with the centers of the substrate peripheral portion  101  and the mass body  103 . In addition, the counter electrode  104  is sandwiched by the first substrate  105  and the third substrate  106  of  FIG. 8  from the upper side and the lower side of  FIG. 8 . Note that, the above-mentioned “thickness direction of the first substrate” is a direction orthogonal to the line SS′ of  FIG. 8  in plan view. 
     The through electrodes  107  and  108  in this embodiment have a tapered shape or a conical shape in the depth direction from the top surface of the first substrate  105  in  FIG. 8 . The through electrodes  107  and  108  are not in contact with each other, and are formed to pass through the first substrate  105  to the depths reaching the substrate peripheral portion  101  and the counter electrode  104  of  FIG. 8 , respectively. In order to reliably connect the through electrodes  107  and  108  to the substrate peripheral portion  101  and the counter electrode  104 , concave portions  101   b  and  104   b  are formed in the substrate peripheral portion  101  and the counter electrode  104 , respectively, so that the distal ends of the through electrodes  107  and  108  may enter the concave portions  101   b  and  104   b . Note that, the purpose of the through electrodes is to establish electrical conduction of the substrate peripheral portion  101  and the counter electrode  104 , respectively, and hence the shape is not limited as long as the through electrodes are in contact with the substrate peripheral portion  101  and the counter electrode  104 , respectively. 
     In this case, the substrate peripheral portion  101  and the counter electrode  104  are sandwiched by the first substrate  105  and the third substrate  106  illustrated in  FIG. 8 . As described above, the first substrate  105  and the third substrate  106  are formed of an insulating material, and hence electrical conduction between the substrate peripheral portion  101  and the counter electrode  104  is not established. 
     Note that, in this embodiment, the surface at which the first substrate  105  and the substrate peripheral portion  101  are in contact with each other and the surface at which the first substrate  105  and the counter electrode  104  are in contact with each other are formed so as to protrude toward the substrate peripheral portion  101  side and the counter electrode  104  side, respectively. This is for the purpose of providing air gaps between the above-mentioned beam  102  and mass body  103  and the first substrate  105  with ease. Therefore, on the surface at which the third substrate  106  and the substrate peripheral portion  101  are in contact with each other and the surface at which the third substrate  106  and the counter electrode  104  are in contact with each other, the third substrate  106  maybe formed so as to protrude toward the substrate peripheral portion  101  side and the counter electrode  104  side. 
     In this case, when acceleration is applied, the overall acceleration switch  001  moves, but the mass body  103  supported by the beam  102  does not move, and hence the counter electrode  104  provided in the space inside the mass body is brought into contact with the mass body  103 . As a result, the electrical conduction is established from the counter electrode  104  via the mass body  103 , the beam  102 , the substrate peripheral portion  101 , and the through electrode  107  to an external contact. The counter electrode  104  is also connected to an external contact via the other through electrode  108 . Note that, the distance between the side surface of the through hole (hole portion) of the mass body  103  and the side surface of the counter electrode  104  (central body) is 1 μm or more and 20 μm or less. 
     In this manner, this acceleration switch is turned ON (the state where electrical conduction between the through electrodes  107  and  108  is established) when the level of vibration becomes a certain value or more, and is turned OFF (the state where electrical conduction between the through electrodes  107  and  108  is not established) when the level of vibration becomes less than the certain value.