JP2009068936A - Physical quantity detecting apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a physical quantity detecting apparatus enabling detection of an accurate physical quantity by suppressing displacement of a weight part affected by electrostatic force. <P>SOLUTION: A physical quantity detecting apparatus 20 is configured so that a sensor part 19 is mounted on a substrate 7. The sensor part 19 comprises a frame part 3, a weight part 4, and a beam part 5. The weight part 4 is connected to the frame part 3 through the beam part 5 and suspended in an opening part of the frame part 3. The physical quantity detecting apparatus 20 has, as shield members, an upper lid 1 and a lower lid 2 composed of an electroconductive material above and below the weight part 4. The upper lid 1 and the lower lid 2 are electrically connected with a ground on the substrate 7 or a power supply pattern 8 to which power supply voltage is applied. In such a configuration as above, the upper lid 1 and the lower lid 2 as shield members cover the weight part 4, efficiently blocks an external electrostatic field from the weight part 4 and suppresses displacement of the weight part 4 affected by the electrostatic force, thereby enabling accurate detection of a physical quantity by the physical quantity detecting apparatus 20. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a physical quantity detection device that detects a physical quantity such as acceleration or tilt angle in a two-dimensional or three-dimensional direction applied to a measurement object.

  The physical quantity detection device is a general term for converters that convert mechanical physical quantities into electrical signals. An inclination sensor that outputs an electrical signal according to an inclination angle and an acceleration sensor that outputs an electrical signal according to acceleration. It has been known. The tilt sensor is also used as an input means for inputting different information depending on the tilt angle, and the acceleration sensor is also used as a detection means for an airbag operating means of an automobile.

  Many types of physical quantity detection devices have been proposed. Among them, a resistance type physical quantity detection device that has a weight part suspended by a beam or the like and detects a physical quantity based on a change in resistance value due to a strain of a gauge resistance as a means for detecting displacement of the weight part according to the applied physical quantity. In addition, a capacitive physical quantity detection device that detects a physical quantity based on a change in electrical capacitance between electrodes is known, and many proposals are seen (for example, see Patent Document 1).

  The configuration and function of the conventional physical quantity detection device described in Patent Document 1 will be described with reference to the drawings. FIG. 4 is a cross-sectional view rewritten within a range that does not depart from the gist of the physical quantity detection device described in Patent Document 1 so as to facilitate explanation.

  The physical quantity detection device 106 of the prior art includes an upper lid 101, a lower lid 102, a movable electrode 103, and a fixed electrode 104. The movable electrode 103 is not illustrated so as to be separated from the left and right fixed electrodes between the fixed electrodes 104. It is suspended by a thin and flexible beam. Further, the upper lid 101 and the lower lid 102 located above and below the movable electrode are fixed to the fixed electrode 104 portion, and a concave portion is provided to face the movable electrode 103, and a metal film 105 is provided in the concave portion.

  The physical quantity detection device 106 of the prior art is the above-described capacitive physical quantity detection device. When the physical quantity detection device 106 receives acceleration from the outside, the movable electrode 103 which is a weight portion having an appropriate mass is displaced, and the interval between the movable electrode 103 and the fixed electrode 104 changes. At this time, the acceleration applied to the physical quantity detection device 106 can be known by detecting the electric capacitance between the movable electrode 103 and the fixed electrode 104.

JP 2002-151703 A (4th to 5th pages, FIG. 1)

  However, the conventional physical quantity detection device has the following problems. When friction occurs between the physical detection device and another member, or when the physical detection device comes into contact with another charged member, the members constituting the physical detection device are charged. In particular, when the lid covering the periphery of the weight portion is formed of a dielectric such as silicon or glass, or when the periphery of the sensor is sealed with a resin that is a dielectric, these dielectrics are easily charged. .

Thus, when a member around the weight portion is charged, the weight portion is displaced due to the influence of electrostatic force, and there is a problem that the displacement of the weight portion due to an angle, acceleration, or the like cannot be accurately detected.
In particular, in the resistance-type physical quantity detection device described above, even if the weight is slightly attracted by the electrostatic force, the point on the electrical characteristics at which the output signal becomes zero shifts, and the displacement of the weight due to the angle, acceleration, etc. It cannot be detected accurately.

A physical quantity detection device 106 described in Patent Document 1 is a metal film 105 provided on an upper lid 101 and a lower lid 102, and sticks to an upper lid 101 and a lower lid 102 of a weight portion that is a movable electrode 103 by electrostatic force. Is to prevent.
However, in the physical quantity detection device 106 described in Patent Document 1, since the metal film 105 is not connected to an electric wiring to which a predetermined voltage such as a ground is applied, the electrostatic field is not sufficiently blocked by the metal film 105. The displacement due to the electrostatic force of the weight portion that is the movable electrode 103 cannot be sufficiently prevented. As a result, there is a problem that the weight portion is displaced in a predetermined direction due to electrostatic force, and an accurate physical quantity cannot be detected.

  Therefore, an object of the present invention is to provide a physical quantity detection device that solves the above-described problems and suppresses the displacement of the weight due to the influence of electrostatic force and enables accurate physical quantity detection.

  In order to solve the above problems, the physical quantity detection device of the present invention adopts the following configuration.

  A physical quantity detection device according to the present invention includes a weight part suspended so as to be displaceable with respect to a support part, and detects a displacement of the weight part according to an applied physical quantity, and a substrate on which the sensor is mounted. And a shield member that covers the weight part from at least one direction, and the shield member is an electric element to which a predetermined voltage is applied on the sensor or the substrate. It is connected to wiring.

  In addition, the physical quantity detection device according to the present invention includes a cover member that is formed of a conductive material and that covers the weight portion by being joined to the support portion as a shield member.

  Furthermore, the physical quantity detection device according to the present invention is characterized in that a metal film formed on a surface facing the weight part of the cover member that joins the support part and covers the weight part is provided as a shield member. .

  Furthermore, the physical quantity detection device according to the present invention is characterized in that a cover member is provided on each of the sensor-mounted surface and the opposite surface of the sensor.

  Furthermore, the physical quantity detection device according to the present invention is characterized in that the sensor and the substrate are fixed with a conductive adhesive, and the shield member and the electrical wiring are electrically connected with the conductive adhesive. Is.

  Furthermore, the physical quantity detection device according to the present invention is characterized in that the weight portion is suspended by the beam portion with respect to the support portion, and the sensor detects the displacement of the weight portion from the deflection of the beam portion.

  Furthermore, in the physical quantity detection device according to the present invention, the sensor detects the displacement of the weight part from the electric capacitance between the first electrode provided on the weight part and the second electrode provided on the support part. It is characterized by detecting.

  The physical quantity detection device of the present invention includes a shield member that is electrically joined to an electric wiring to which a predetermined potential is applied and covers the weight portion from at least one direction. Accordingly, it is possible to efficiently block the external electrostatic field to the weight part, suppress the displacement of the weight part due to the influence of electrostatic force, and detect an accurate physical quantity.

  Hereinafter, a physical quantity detection device according to an optimal embodiment of the present invention will be described in detail with reference to the drawings.

<Example 1>
FIG. 1 is a cross-sectional view schematically showing the structure of the physical quantity detection device according to the first embodiment of the present invention.

As illustrated in FIG. 1, the physical quantity detection device 20 according to the first embodiment of the present invention includes a configuration in which a sensor unit 19 is mounted on a substrate 7. The sensor portion 19 includes a frame portion 3 having an opening at the center, a substantially cubic weight portion 4, and a thin and flexible beam portion 5. The weight portion 4 is joined to the frame portion 3 via a pair of beam portions 5, and is suspended substantially at the center of the opening portion of the frame portion 3.
Further, in the physical quantity detection device 20 according to the first embodiment of the present invention, the upper lid 1 and the lower lid, which are configured to have a conductive material apart from the weight portion 4 and the beam portion 5 above and below the weight portion 4. The lid 2 is provided as a shield member. Both ends of the upper lid 1 and the lower lid 2 are joined to the frame portion 3, so that a space surrounded by the frame portion 3, the upper lid 1 and the lower lid 2 is airtight. Further, a concave portion is provided on the lower surface of the upper lid 1 facing the weight portion 4 and the beam portion 5.

As a material for the frame part 3, the weight part 4, and the beam part 5, for example, a silicon single crystal plate or a glass plate can be used. When such a material is used, the small physical quantity detection device 20 can be formed by a known processing means such as a photolithography technique or anisotropic dry etching (RIE). In addition to the silicon single crystal or glass, a flexible material such as silicon nitride, silicon oxide, polyimide resin, or epoxy resin can be used as the member of the beam portion 5.
As materials for the upper lid 1 and the lower lid 2, in addition to metal materials often used as electronic component materials such as Au and Cu, conductive materials such as conductive plastic materials containing carbon and metal powder can be used.

As shown in FIG. 1, in the physical quantity detection device 20 according to the first embodiment of the present invention, the lower lid 2 of the sensor unit 19 is fixed to the substrate 7 with a conductive adhesive 10. The conductive adhesive 10 electrically connects the power supply pattern 8 provided on the substrate 7 and applied to the ground or power supply voltage to the lower lid 2.
Furthermore, in the physical quantity detection device 20 of the first embodiment of the present invention, the upper lid 1 is electrically connected to the power supply pattern 8 provided on the substrate 7 by the connection wire 6.

Since the physical quantity detection device 20 has the above-described configuration, when the acceleration is received, the weight part 4 suspended inside is displaced according to the magnitude and direction of the applied acceleration, and the beam part 5 is bent. Will occur. As already known, if, for example, a piezoresistive element is formed on the beam portion 5 and a Wheatstone bridge including the piezoresistive element is formed, the physical quantity detection device 20 is added due to fluctuations in the bridge equilibrium voltage. It is possible to detect physical quantities such as acceleration.
Further, when a pair of beams are provided in a direction perpendicular to the beam portion 5 in addition to the beam portion 5 shown in FIG. 1, a biaxial or triaxial physical quantity detection device can be configured.

  Further, in the physical quantity detection device 20 of the first embodiment of the present invention, as described above, the upper lid 1 and the lower lid 2 that cover the weight portion 4 are configured to have a conductive material. The lid 2 is electrically connected to a power supply pattern 8 provided on the substrate 7 to which a ground or power supply voltage is applied. Therefore, the potentials of the upper lid 1 and the lower lid 2 are held at the same potential as that of the power supply pattern 8, that is, the ground or the power supply voltage, and the static electricity is not charged.

Thereby, the upper lid 1 and the lower lid 2 cover the weight portion 4 as a shield member, efficiently shuts off the electrostatic field from the outside to the weight portion 4, and suppresses the displacement of the weight portion 4 due to the influence of electrostatic force. That is, in the physical quantity detection device 20 of the first embodiment, the physical quantity can be accurately detected by accurately detecting the displacement of the weight part 4 due to the acceleration.
Even in the configuration of a resistance-type acceleration sensor including a piezoresistive element and a Wheatstone bridge detection means, the displacement of the weight portion 4 due to the influence of electrostatic force is suppressed, and an offset is prevented from being generated in the bridge equilibrium voltage, so that physical quantities such as acceleration are accurately determined It becomes possible to detect.

  In FIG. 1, the lower lid 2 is connected to the power supply pattern 8 on the substrate 7 via the conductive adhesive 10, and the upper lid 1 is connected to the power supply pattern 8 via the connection wire 6. However, the present invention is not limited to this, and the upper lid 1 and the lower lid 2 are electrically connected to the power supply pattern 8 by a metal bonding means such as solder in addition to the conductive adhesive and wire connection. It is good also as a structure.

In FIG. 1, both the upper lid 1 and the lower lid 2 are configured to have a conductive material and serve as a shield member that is electrically connected to the power supply pattern 8 to which a ground or power supply voltage is applied. However, it is good also as a structure which uses either the upper cover 1 or the lower cover 2 as a shield member.
Even in a configuration in which either the upper lid 1 or the lower lid 2 is a shield member, the electrostatic field to the weight portion from the direction in which the shield member is provided is cut off, and the displacement of the weight portion due to the influence of electrostatic force is prevented. It is possible to suppress and improve the accuracy of detection of the physical quantity.

<Example 2>
Next, a physical quantity detection apparatus according to Embodiment 2 of the present invention will be described with reference to the drawings. The same reference numerals are given to the same components that have already been described, and descriptions thereof are omitted. The physical quantity detection device according to the second embodiment is different from the physical quantity detection device according to the first embodiment in the configuration of the shield member. FIG. 2 is a cross-sectional view schematically showing the structure of the physical quantity detection device according to the second embodiment of the present invention.

  As illustrated in FIG. 2, the physical quantity detection device 21 according to the second embodiment includes a configuration in which the sensor unit 22 is mounted on the substrate 7 in the same manner as the physical quantity detection device 20 according to the first embodiment. The sensor portion 22 includes a frame portion 3 having an opening at the center, a substantially cubic weight portion 4, and a thin and flexible beam portion 5. The weight portion 4 is joined to the frame portion 3 via a pair of beam portions 5, and is suspended substantially at the center of the opening portion of the frame portion 3.

Further, in the physical quantity measuring device 21 of the second embodiment, an upper lid 23 and a lower lid 24 made of an insulating material are provided above and below the weight portion 4 so as to be separated from the weight portion 4 and the beam portion 5. A metal film 11 is provided as a shield member on the surface of the upper lid 23 and the lower lid 24 facing the weight portion 4. Both ends of the upper lid 23 are fixed to the connection pattern 12 provided on the frame portion 3 to electrically connect the metal film 11 and the connection pattern 12.
Further, the lower lid 24 is fixed to the lower part of the frame part 3 so that a part of the metal film 11 is exposed to the outside of the frame part 3. Thereby, the space surrounded by the frame portion 3, the upper lid 23, and the lower lid 24 is made airtight. The sensor unit 22 is fixed to the substrate 7 on the surface of the lower lid 24 where the metal film 11 is not formed.

In the physical quantity detection device 21 according to the second embodiment, the upper lid 23 and the lower lid 24 are formed using an insulating material, and the metal film 11 including a metal material is provided. With such a configuration, there is an advantage that a glass substrate, a silicon substrate, or the like often used in a semiconductor process can be used as a material for the upper lid 23 and the lower lid 24. Further, as a material for the upper lid 23 and the lower lid 24, a resin material such as an epoxy resin or a polyimide resin may be used in addition to a glass plate or a silicon plate.

  As the material of the metal film 11, a metal material used in a semiconductor process such as Au, Cu, Al, Cr, or Sn can be used, and it can be formed by a known film forming means such as vapor deposition, sputtering, or plating. . Further, as the material of the metal film 11, a conductive adhesive in which conductive particles are dispersed in a resin material such as epoxy, polyimide, or silicon may be used in addition to the metal material described above. When forming the metal film 11 with a conductive adhesive, known film forming means such as printing and coating can be used.

As shown in FIG. 2, in the physical detection device 21 according to the second embodiment, the metal film 11 provided on the upper lid 23 is provided on the substrate 7 via the connection pattern 12 and the connection wire 6. The power supply pattern 8 applied to the ground or the power supply voltage is electrically connected. Here, as the material of the connection pattern 12, a metal material used in a semiconductor process such as Au, Cu, Al, Cr, or Sn can be used. Desirable is a metal material such as Au or Al, which can easily adopt a wire connecting means.
Furthermore, in the physical quantity detection device 21 according to the second embodiment, the power supply pattern 8 described above is connected via the connection wire 6 in a portion where the metal film 11 provided on the lower lid 24 is exposed to the outside of the frame portion 3. And is electrically connected.

  Since the physical quantity detection device 21 has the above-described configuration, like the physical quantity detection device 20, the physical weight detection device 21 is displaced according to the magnitude and direction of the applied acceleration when the weight portion 4 suspended therein is applied. Then, the beam portion 5 is bent. For example, if a piezoresistive element is formed on the beam portion 5 and a Wheatstone bridge including the piezoresistive element is configured, a physical quantity such as acceleration applied to the physical quantity detection device 21 can be detected from a change in the bridge equilibrium voltage. it can. Further, when a pair of beams are provided in a direction perpendicular to the beam portion 5 in addition to the beam portion 5 shown in FIG. 2, a biaxial or triaxial physical quantity detection device can be configured.

  In the physical quantity detection device 21 according to the second embodiment of the present invention, the metal film 11 provided on the upper lid 23 and the lower lid 24 and covering the weight portion 4 is electrically connected to the power supply pattern 8 applied to the ground or the power supply voltage. It is connected to the. For this reason, the potential of each metal film 11 provided on the upper lid 23 and the lower lid 24 is held at the same potential as the power supply pattern 8, that is, the ground or the power supply voltage, and does not charge static electricity.

  As a result, each metal film 11 provided on the upper lid 23 and the lower lid 24 covers the weight portion 4 as a shield member, effectively blocks an electrostatic field from the outside to the weight portion 4, and the weight portion due to the influence of electrostatic force 4 is suppressed. That is, in the physical quantity detection device 21 according to the second embodiment, as in the physical quantity detection device 20 according to the first embodiment, the physical quantity can be accurately detected by accurately detecting the displacement of the weight portion 4 due to the acceleration. It becomes possible.

  FIG. 3 is a plan view showing a configuration example of the metal film 11 provided on the upper lid 23 and the lower lid 24. As shown in FIG. 3, the metal film 11 does not need to cover the entire surface of the upper lid 23 and the lower lid 24, and the object of the present invention can be achieved even if it is formed in a mesh shape having openings.

  In FIG. 2, the connection pattern 12 connected to the metal film 11 provided on the upper lid 23 is connected to the power supply pattern 8 via the connection wire 6, and the metal film 11 provided on the lower lid 24 is connected to the power supply pattern 8 via the connection wire 6. An example of connection with is shown. However, the present invention is not limited to this, and the metal film 11 provided on the upper lid 23 and the lower lid 24 is electrically connected to the power supply pattern 8 by a metal bonding means such as a conductive adhesive or solder. It is good also as a structure connected to.

In FIG. 2, both the upper lid 23 and the lower lid 24 are configured to include the metal film 11 that is electrically connected to the power supply pattern 8 to which a ground or power supply voltage is applied and serves as a shield member. However, a configuration in which either one of the upper lid 23 and the lower lid 24 is provided with a shield member may be adopted.
Even if the shield member is provided on either the upper lid 23 or the lower lid 24, the electrostatic field to the weight portion from the direction in which the shield member is provided is blocked, and the displacement of the weight portion due to the influence of electrostatic force is prevented. It is possible to suppress and improve the accuracy of detection of the physical quantity.

  In the first embodiment and the second embodiment described above, the present invention is provided with a shield member in a resistance type physical quantity detection device in which a detection element such as a piezoresistive element is provided in a beam portion and the deflection of the beam portion due to displacement of the weight portion is detected. An example of However, the present invention is not limited to the resistance type physical quantity detection device. The first electrode is provided in the weight portion and the second electrode is provided in the support portion, and the first electrode and the second electrode due to the displacement of the weight portion. The present invention is also applicable to a capacitive physical quantity detection device that detects an electrical capacitance between the two.

  Also in the capacitive physical quantity detection device, as shown in the first and second embodiments, the shield member is provided with a shield member that covers the weight portion and is connected to an electric pattern to which a predetermined voltage is applied. The external electrostatic field to the part is effectively cut off, and the displacement of the weight part due to the influence of electrostatic force is suppressed. Accordingly, it is possible to accurately detect the physical quantity by accurately detecting the displacement of the weight portion due to the acceleration.

It is sectional drawing which shows the structure of the physical quantity detection apparatus in Example 1 of this invention. It is sectional drawing which shows the structure of the physical quantity detection apparatus in Example 2 of this invention. It is a top view which shows the structural example of the metal film in Example 2 of this invention. It is sectional drawing which shows the structure of the physical quantity detection apparatus of a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 23 Upper lid 2, 24 Lower lid 3 Frame part 4 Weight part 5 Beam part 6 Connection wire 7 Substrate 8 Power supply pattern 10 Conductive adhesive 11 Metal film 12 Connection pattern 19, 22 Sensor part 20, 21 Physical quantity detection apparatus

Claims (7)

A sensor that has a weight part suspended so as to be displaceable with respect to the support part, and detects a displacement of the weight part according to an applied physical quantity;
In a physical quantity detection device comprising a substrate on which the sensor is mounted,
A shield member that is formed with a conductive material and covers the weight portion from at least one direction,
The shield member is connected to an electrical wiring to which a predetermined voltage is applied on the sensor or the substrate. The physical quantity detection device according to claim 1, further comprising a cover member that is formed of a conductive material and that covers the weight portion by joining to the support portion as the shield member. The physical quantity detection device according to claim 1, wherein a metal film formed on a surface facing the weight portion of a cover member that joins the support portion and covers the weight portion is provided as the shield member. 4. The physical quantity detection device according to claim 2, wherein the cover member is provided on each of a surface of the sensor mounted on the substrate and a surface on the opposite side. 5. While fixing the sensor and the substrate with a conductive adhesive,
The physical quantity detection device according to claim 2, wherein the shield member and the electric wiring are electrically connected by the conductive adhesive. The weight portion is suspended by a beam portion with respect to the support portion,
The physical quantity detection device according to any one of claims 1 to 5, wherein the sensor detects a displacement of the weight portion from a deflection of the beam portion. The sensor detects displacement of the weight part from an electric capacity between a first electrode provided on the weight part and a second electrode provided on the support part. The physical quantity detection device according to claim 1.

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