US20060255441A1 - Physical quantity sensor device - Google Patents

Abstract

A circuit board is mounted on a package via an adhesive agent as an elastic member. A sensor element is stacked in fixed relation onto the circuit board. The sensor element, the circuit board, and the package are wired with bonding wires. A magnetic member made of a ferromagnetic material is disposed between the adhesive agent and the circuit board.

Description

CROSS REFERENCE TO RELATED APPLICATIONS
• This application is based on and incorporates herein by reference Japanese Patent Application No. 2005-141066 filed on May 13, 2005.
FIELD OF THE INVENTION
• The present invention relates to a physical quantity sensor device including a sensor element for sensing a physical quantity; the sensor element is mounted on a package and held thereby via an elastic member having elasticity.
BACKGROUND OF THE INVENTION
• A physical quantity sensor device of this type typically includes a sensor element for sensing a physical quantity such as an angular velocity or acceleration; the sensor element is mounted on a package. This type of physical quantity sensor device has an application as an angular velocity sensor device or acceleration sensor device.
• In such a physical quantity sensor device, a problem occurs in sensor characteristics when an impact from the outside, i.e., an external acceleration is applied thereto.
• For example, an angular velocity sensor device senses an angular velocity based on a Coriolis force generated in a sensing direction. However, an acceleration in the sensing direction may be transmitted to a sensor element from the outside via a package even when an angular velocity is not actually applied thereto. Here, an output is produced as though an angular velocity occurred.
• With respect to such a physical quantity sensor device, a structure has been conventionally proposed in which a sensor element is held on a package via an elastic member having elasticity such as an adhesive agent or rubber. Here, the elastic member functions as an anti-vibration member to absorb unnecessary vibration resulting from an external acceleration (see, e.g., PATENT DOCUMENTs 1 to 7).
• In such a structure, the external acceleration is attenuated by the elastic function of the elastic member in a path in which the external acceleration is transmitted to the sensor element via the package. The attenuated external acceleration is thus transmitted to the sensor element. Accordingly, this structure may reduce the unnecessary vibration to the sensor element.
• In this structure of the physical quantity sensor device, however, it may be difficult to properly perform bonding relative to a component (e.g., sensor element) mounted on the elastic member, or to properly mount the component on the elastic member. This may cause a problem that sufficient assembly cannot be obtained.
• FIG. 8 is a view showing a schematic cross-sectional structure of a conventional physical quantity sensor device when, e.g., a low-elasticity adhesive film is used as an elastic member.
• InFIG. 8, acircuit board1300 is mounted on apackage1100 and fixed thereto. Asensor element1200 is stacked on thecircuit board1300 via anadhesive film1400 as the elastic member. Thesensor element1200 and thecircuit board1300 are wired withbonding wires1500 to be electrically connected.
• In the conventional physical quantity sensor device, to form a soft adhesion structure for serving as an anti-vibration structure, the low-elasticityadhesive film1400 is used as the adhesion portion thereof. In the structure, the low-elasticityadhesive film1400 is used to fix thesensor element1200 located thereon for an anti-vibration purpose. As a result, the upper portion of theadhesive film1400 is low in rigidity.
• Wire bonding may be performed relative to the mounted component, i.e.,sensor element1200 on theadhesive film1400, or another component may be mounted in addition to thesensor element1200. In this case, the holding of thesensor element1200 becomes unstable so that assembly such as bonding or mounting becomes difficult.
• In contrast, to design the structure to be stable during the assembly, theadhesive film1400 as the elastic member should be hardened. This causes a problem that the elastic function of theadhesive film1400 is not performed, the amount of attenuation is reduced, and the external acceleration is more likely to be transmitted to thesensor element1200.
• Patent Document 1
• JP-H11-218424 A
• Patent Document 2
• JP-H11-264731 A
• Patent Document 3
• JP-2002-195834 A
• Patent Document 4
• JP-2002-250627 A
• Patent Document 5
• JP-2003-21515 A
• Patent Document 6
• JP-2003-28647 A
• Patent Document 7
• JP-2003-21647 A
SUMMARY OF THE INVENTION
• An object of the present invention is to provide a physical quantity sensor device capable of addressing the foregoing problem. This physical quantity sensor device includes a sensor element for sensing a physical quantity: the sensor element is mounted on a package and held thereby via an elastic member having elasticity. This physical quantity sensor device is to properly balance the trade-off between the elastic function and efficient assembly.
• As an aspect of the present invention, a physical quantity sensor device is provided as follows. A sensor element is included for sensing a physical quantity. A package to which the sensor element is mounted is included. An elastic member having elasticity is included to be disposed between the sensor element and the package for holing the sensor element to the package. The elastic member faces (i) a first space including the sensor element and (ii) a second space opposing to the first space. A magnetic member made of a ferromagnetic material is included in the first space.
BRIEF DESCRIPTION OF THE DRAWINGS
• FIG. 1 is a schematic cross-sectional view of an angular velocity sensor device as a physical quantity sensor device according to a first example embodiment of the present invention;
• FIG. 2 is a schematic plan view of a sensor element in the angular velocity sensor device shown inFIG. 1.
• FIGS. 3A to3F are process step diagrams each illustrating a method for fabricating the angular velocity sensor device shown inFIG. 1;
• FIGS. 4A to4C are process step diagrams each illustrating the fabrication method, which are subsequent toFIGS. 3A to3F;
• FIG. 5 is a schematic cross-sectional view of an angular velocity sensor device as a physical quantity sensor device according to a second example embodiment of the present invention;
• FIG. 6 is a schematic cross-sectional view of an angular velocity sensor device as a physical quantity sensor device according to a third example embodiment of the present invention;
• FIG. 7 is a schematic cross-sectional view of an angular velocity sensor device as a physical quantity sensor device according to a fourth example embodiment of the present invention; and
• FIG. 8 is a schematic cross-sectional view of a physical quantity sensor device when a low-elasticity adhesive film is used as an elastic member, in a prior art.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTSExample Embodiment 1
• FIG. 1 is a view showing a schematic cross-sectional structure of an angular velocity sensor device S1 as a physical quantity sensor device according to a first example embodiment of the present invention.
• Structure, Etc.
• As shown inFIG. 1, the angular velocity sensor device S1 broadly includes the following: apackage100; acircuit board300 held on thepackage100 via anadhesive agent400 as an elastic member; asensor element200 stacked on thecircuit board300 and adhered thereto via anadhesive film600, for sensing an angular velocity; andbonding wires500 for coupling the foregoing components to each other.
• Thepackage100 contains thesensor element200 and thecircuit board300, serves as a base portion for defining a main body of the angular velocity sensor device S1, and allows the angular velocity sensor device S1 to contact a proper position of a subject to measure.
• In an example shown inFIG. 1, thepackage100 is a multilayer substrate including multiple stackedceramic layers110 made of, e.g., alumina or the like. Wires (not shown) are formed on a surface of each of thelayers110 and in through holes formed in the individual layers110. The angular velocity sensor device S1 can be electrically coupled to an outside via the wires.
• Thepackage100 also has adepressed portion120 in the bottom portion thereof, to contain thecircuit board300. Thecircuit board300 contained in thedepressed portion120 is mounted on the bottom portion of thepackage100 and fixed thereto via theadhesive agent400 as the elastic member.
• Theadhesive agent400 is an elastic member having elasticity and made of, e.g., a resin such as a silicone gel. Theadhesive agent400 functions herein as an anti-vibration member to attenuate an external acceleration applied from thepackage100 to thesensor element200 as an angular velocity sensing element.
• Alid140 made of a metal, resin, ceramic, or the like is attached to an opening of thepackage100. Thelid140 seals an inside of thepackage100. Thelid140 is made of a metal herein and bonded to thepackage100 by welding such as seam welding or brazing.
• Thesensor element200 is stacked on an upper surface of thecircuit board300 via theadhesive member600. Theadhesive member600 is harder than theadhesive agent400 as the elastic member and has rigidity. As theadhesive member600, an adhesive film made of, e.g., a silicone-based resin or the like can be adopted.
• Thesensor element200 is an angular velocity sensing element for sensing an angular velocity. Thesensor element200 can be formed as a semiconductor chip that forms a beam structure having a commonly known comb-tooth structure relative to a silicon substrate or the like. Thesensor element200 senses a change in electrostatic capacitance (electric signal) between a movable electrode and a fixed electrode; the electrostatic capacitance is responsive to an applied angular velocity.
• Referring primarily toFIG. 2, a description will be given to a detailed structure of thesensor element200.FIG. 2 is a view showing a schematic plan structure of thesensor element200 in the angular velocity sensor device S1 shown inFIG. 1.
• Thesensor element200 has asubstrate10 such as a semiconductor substrate and is formed by performing a well-known micromachining process with respect to thesubstrate10. Thesubstrate10 can adopt, e.g., a rectangular SOI (silicon-on-insulator) substrate. The SOI substrate is formed by laminating a second silicon layer (second semiconductor layer) on a first silicon layer (first semiconductor layer) via an oxide film (insulating layer).
• Beam structures20 to60 are defined by trenches, as shown inFIG. 2. Thebeam structures20 to60 are formed by performing trench etching, release etching, and the like with respect to a surface layer of thesubstrate10, e.g., the second silicon layer of the SOI substrate. Thebeam structures20 to60 include avibrator20,beam portions23 and40, andelectrodes50 and60, which will be described later.
• Thevibrator20 is formed at a center portion of thesubstrate10 and capable of vibrating within a plane horizontal to thesubstrate10, i.e., in the plane inFIG. 2. In this example embodiment, thevibrator20 includes a first vibratingportion21 having a generally rectangular configuration positioned at the center portion; a second vibratingportion22 configured as a rectangular frame positioned around the outer periphery of the first vibratingportion21; and adriving beam portion23 coupling the first and second vibratingportions21 and22 to each other.
• Thevibrator20 is coupled to ananchor portion30 provided on a peripheral portion of thesubstrate10 via thesensing beam portion40. Theanchor portion30 is fixed to and supported by the portion of thesubstrate10 which is located below the surface layer formed with thebeam structure20, i.e., the supporting substrate portion of thesubstrate10. Thevibrator20 is floating from the supporting substrate portion.
• As shown inFIG. 2, thedriving beam portion23 is configured to extend in, e.g., a y-direction such that it is elastically deformable substantially only in an x-direction. On the other hand, thesensing beam portion40 is configured to extend in, e.g., the x-direction such that it is elastically deformable substantially only in the y-direction.
• Of thevibrator20, the first vibratingportion21 is allowed to vibrate in the x-direction (driving vibration direction) in a plane horizontal to thesubstrate10 by thedriving beam portion23. On the other hand, thewhole vibrator20 is allowed to vibrate in the y-direction (sensing vibration direction) in a plane horizontal to thesubstrate10 by thesensing beam portion40.
• Between the first and second vibratingportions21 and22, drivingelectrodes50 are provided for causing the driving vibration of the first vibratingportion21 in the x-direction. The drivingelectrodes50 are fixed to the supporting substrate portion mentioned above, similarly to theanchor portion30. The drivingelectrodes50 are disposed to oppose a comb-tooth portion (comb-tooth portion for driving)21aprojecting from the first vibratingportion21 such that the comb teeth thereof and those of the comb-tooth portion21ainterdigitate.
• On the other hand, sensingelectrodes60 are provided in an outer periphery of the second vibratingportion22. Thesensing electrodes60 sense an angular velocity around a z-axis perpendicular to thesubstrate10 based on the vibration of thevibrator20 and are fixed to the supporting substrate portion, similarly to theanchor portion30. Thesensing electrodes60 are disposed to oppose a comb-tooth portion (comb-tooth portion for sensing)22aprojecting from the second vibratingportion22 such that the comb teeth thereof and those of the comb-tooth portion22ainterdigitate.
• Additionally, in thepresent sensor element200, pads made of aluminum or the like are provided at appropriate positions on thesubstrate10 to apply voltages to thevibrator20, drivingelectrodes50,sensing electrodes60, and the like mentioned above or to retrieve signals therefrom.
• These pads are provided on, e.g., the peripheral portion of thesubstrate10. To these pads, the above-mentionedbonding wires500 made of Au (gold), aluminum, or the like are connected, as shown inFIG. 1. Thesensor element200 according to this example embodiment has a structure as described above.
• Thecircuit board300 used herein is an IC chip or the like in which, e.g., a MOS transistor, a bipolar transistor, or the like has been formed by using a well-known semiconductor process on a silicon substrate or the like. Thecircuit board300 can be also a signal processing chip having functions of sending a voltage to thesensor element200, processing an electric signal from thesensor element200, outputting the processed electric signal to the outside, and the like.
• As shown inFIG. 1, thesensor element200 and thecircuit board300 are electrically coupled via the above-mentionedbonding wires500 made of gold, aluminum, or the like, while thecircuit board300 and thepackage100 are also electrically coupled via thebonding wires500.
• Thus, the individual components of thesensor element200, thecircuit board300, and thepackage100 are electrically connected via thebonding wires500. It is to be noted that thesensor element200 and thecircuit board300 need not be connected directly via thebonding wires500, as shown inFIG. 1.
• For example, thesensor element200 can be coupled to thepackage100 via thebonding wires500, while thepackage100 is coupled to thecircuit board300 via thebonding wires500. In this case, thesensor element200 and thecircuit board300 can be similarly coupled to each other via thebonding wires500, though with intervention of thepackage100.
• In this manner, an electric signal (capacitance change) from thesensor element200 is sent to thecircuit board300, converted to a voltage signal by a CN conversion circuit or the like provided on thecircuit board300, and outputted as an angular velocity signal.
• Thus, the angular velocity sensor device S1 according to this example embodiment is constructed by successively stacking thecircuit board300 and thesensor element200 on thepackage100 via theadhesive agent400 as the elastic member.
• Further, as a structure peculiar to this example embodiment, amagnetic member700 made of a ferromagnetic material is provided at a given portion. Here, to define the given portion, explanation will be added. As explained above, theadhesive agent400 is disposed between thesensor element200 and the bottom portion of thepackage100. Theadhesive agent400 has (i) a first side facing a first space in which thesensor element200 is included and (ii) a second side facing a second space that opposes the first space (in the example inFIG. 1, the second space includes the bottom portion of the package100). In other words, the elastic member faces (i) the first space (also called sensor-element-side space) including the sensor element and (ii) the second space (also called package-side space) not including the sensor element200 (in the example inFIG. 1, the second space includes the bottom portion of the package100). The given portion is defined to be included in this first space or the sensor-element-side space with respect to theadhesive agent400. Themagnetic member700 is thus disposed at the given portion included in the sensor-element-side space which theadhesive agent400 faces via the first side. For instance, in this example embodiment, themagnetic member700 is disposed or interposed between theadhesive agent400 and thesensor element200.
• For instance, in this example embodiment, thecircuit board300 is mounted on thepackage100 via theadhesive agent400 as the elastic member and thesensor element200 is stacked in fixed relation onto thecircuit board300, while themagnetic member700 is interposed between theadhesive agent400 and thecircuit board300.
• Themagnetic member700 is configured as a plate in this example embodiment and bonded to thecircuit board300 via a hard adhesive agent not shown, e.g., an adhesive agent made of a silicone-based resin or the like. The magnetic member700A includes magnetic material with ferromagnetism such as iron, nickel, cobalt, or an alloy thereof.
• For instance, 42 alloy, Kovar™, or the like having a linear expansion coefficient close to that of the Si chip composing thecircuit board300 can be used for themagnetic member700. However, any material having ferromagnetism at the working temperature thereof may be appropriately used, provided that it meets the object of allowing fixation using a magnetic force and there is no requirement concerning other characteristics.
• In the angular velocity sensor device S1 according to this example embodiment, it is also possible to preliminarily magnetize a material such as ferrite, which is a ferromagnetic material, and use the resulting magnet as themagnetic member700.
• Fabrication Method, Operation, Etc.
• A method for fabricating the angular velocity sensor device S1 thus constructed according to this example embodiment will be described with reference toFIGS. 3A to3F andFIGS. 4A to4C. These figures are process step diagrams for illustrating the fabrication method according to this example embodiment and are schematic cross-sectional views obtained by viewing work in the individual fabrication process steps from the same viewpoint as inFIG. 1.
• First, as shown inFIG. 3A, themagnetic member700 is adhered to the surface of thecircuit board300 to be mounted on thepackage100.
• In this example embodiment, a method has been adopted which preliminarily processes themagnetic member700 into the size of thecircuit board300, i.e., into the chip size and then bonds themagnetic member700 to thecircuit board300. However, it is also possible to bond the wafer-sizemagnetic member700 to a wafer of thecircuit boards300 at a stage before it is cut into individual chips and then form thecircuit boards300 as the chips with themagnetic members700 through simultaneous dicing.
• Next, as shown inFIG. 3B, theadhesive member600 for fixing thesensor element200 is placed on thecircuit board300. Then, as shown inFIG. 3C, thesensor element200 is aligned on thecircuit board300. Then, as shown inFIG. 3D, thesensor element200 is mounted on thecircuit board300 via theadhesive member600 and adhesively fixed thereto.
• Thesensor element200 may be also formed as a chip with theadhesive member600 by bonding theadhesive member600 composed of an adhesive film to a wafer of thesensor elements200 at a stage before it is cut into individual chips and then perform simultaneous dicing. The resultingsensor element200 may be also stacked on thecircuit board300 and adhered thereto.
• These process steps result in completing a sensor module in which thesensor element200 is stacked in fixed relation onto thecircuit board300 with themagnetic member700. Subsequently, the sensor module is mounted on thepackage100.
• First, as shown inFIG. 3E, theadhesive agent400 as the elastic member described above is applied onto the bottom portion of thedepressed portion120 of thepackage100. Then, as shown inFIG. 3F, the sensor module is mounted on theadhesive agent400 with themagnetic member700 opposing the bottom portion of thepackage100.
• Then, by curing theadhesive agent400, themagnetic member700 of the sensor module is bonded to thepackage100. In a currently reached state, the sensor module, i.e., thecircuit board300 and thesensor element200 are held by the softadhesive agent400 as the elastic member and wire bonding is difficult to perform in this state.
• When wire bonding is performed, amagnet800 is provided herein below thepackage100, as shown inFIG. 4A. Themagnet800 can be incorporated into a bonding apparatus or a fixingjig810 for thepackage100 to act as a magnet chuck.
• By themagnet800, a magnetic force is generated to press themagnetic member700 against thepackage100 via theadhesive agent400. As a result, the movement of themagnetic member700 is suppressed and the movement of the sensor module during bonding can be suppressed. In short, themagnet800 is constructed as a magnetic member fixing means for solidly fixing themagnetic member700 by using a magnetic force.
• As shown inFIGS. 4A to4B, wire bonding is performed in the state in which the sensor module described above is solidly fixed to thepackage100 by thus using the magnetic force of each of themagnet800 below thepackage100 and themagnetic member700. As a result, thepackage100 and thecircuit board300 are wired with thebonding wires500, while thesensor element200 and thecircuit board300 are wired with thebonding wires500.
• After wire bonding is completed, thepackage100 is detached from above themagnet800 as shown inFIG. 4C so that the magnetic force is removed. Then, by welding or brazing thelid140 to thepackage100, the inside of thepackage100 is sealed, thereby completing the angular velocity sensor device S1 described above.
• It is also possible to use a magnet such as ferrite to compose themagnetic member700 and use a ferromagnetic material such as iron to compose the magnetic member fixing means below thepackage100 in place of themagnet800. The arrangement also allows the same effect to be obtained. To obtain a fixing strength, each of themagnetic member700 and the magnetic member fixing means can also be composed of a magnet.
• The foregoing example shown inFIGS. 3A to3F andFIGS. 4A to4C mounts the sensor module described above on thepackage100 via theadhesive agent400, cures theadhesive agent400, and then performs wire bonding. The curing of theadhesive agent400 may be also performed after wire bonding.
• In this case, wire bonding is performed with the sensor module temporarily bonded using the uncuredadhesive agent400 having fluidity. However, during wire bonding, a solidly fixed structure can be implemented by using the magnetic force of themagnetic member700 irrespective of the adhesive agent and a sufficient bonding property can be obtained.
• In this case, theadhesive agent400 is cured after wire bonding. At this time, when themagnetic member700 and the magnetic member fixing means are composed of magnets each having the same polarity, a repelling force acts between themagnetic member700 and thepackage100. This allows the suppression of the thinning of theadhesive agent400 under the weight of the sensor module and allows the adhesive400 to retain a sufficient thickness.
• In the foregoing example shown inFIGS. 3A to3F andFIGS. 4A to4C, themagnetic member700, thecircuit board300, and thesensor element200 have been incorporated to produce the sensor module; then, the sensor module is mounted on thepackage100 via theadhesive agent400. This order in which the individual components are mounted on thepackage100 is not limited thereto.
• For example, it is also possible to mount themagnetic member700 on thepackage100 via theadhesive agent400, adhesively mount thecircuit board300 and thesensor element200 in succession thereon in the state in which themagnetic member700 is solidly held by using a magnetic force, and then further perform wire bonding.
• Alternatively, it is also possible to mount thecircuit board300 with themagnetic member700 on thepackage100 via theadhesive agent400, adhesively mount thesensor element200 thereon in the state in which themagnetic member700 and thecircuit board300 are solidly held by using a magnetic force, and then further perform wire bonding.
• It is to be noted that the completed angular velocity sensor device S1 is in a normal use state with no magnetic force applied thereto so that the movement of thesensor element200 is not suppressed. Accordingly, the anti-vibration performance of theadhesive agent400 is sufficiently exerted as designed.
• Referring primarily toFIG. 2, the sensing operation in such an angular velocity sensor device S1 will be described.
• A driving signal (sinusoidal voltage or the like) is applied from thecircuit board300 to the drivingelectrodes50 of thesensor element200 via thebonding wires500 to generate an electrostatic force between the comb-tooth portion21aof the first vibratingportion21 mentioned above and the drivingelectrodes50. As a result, the elastic force of thedriving beam portion23 causes the driving vibration of the first vibratingportion21 in the x-direction.
• When an angular velocity Q is applied around the z-axis as a result of the driving vibration of the first vibratingportion21, a Coriolis force is applied in the y-direction to the first vibratingportion21 so that the elastic force of thesensing beam portion40 causes the sensing vibration of thewhole vibrator20 in the y-direction.
• As a result, the sensing vibration causes a change in the capacitance between the respective comb teeth of thesensing electrodes60 and the comb-tooth portion22afor sensing. By sensing the capacitance change, the magnitude of the angular velocity Ω can be determined.
• For instance, when thevibrator20 is displaced unilaterally in the y-direction, capacitance changes in opposite directions occur in the left andright sensing electrodes60 inFIG. 2. The capacitance changes in the left andright sensing electrodes60 are individually converted to voltages and the two voltage values are differentially amplified and outputted so that the angular velocity Ω is determined.
• Effect, Etc.
• In the angular velocity sensor device S1 as a physical quantity sensor device, thesensor element200 for sensing an angular velocity as a physical quantity is mounted on thepackage100 and held thereby via theadhesive agent400 as an elastic member having elasticity. The angular velocity sensor device S1 is characterized in that themagnetic member700 made of a ferromagnetic material is provided in the sensor-element-side space with respect to theadhesive agent400, as shown inFIG. 1.
• The arrangement allows a magnetic force to act from outside thepackage100 such that themagnetic member700 is pressed against thepackage100, as described above. By the magnetic force, thesensor element200 on theelastic member400 is more solidly fixed to thepackage100 than when it is merely held by theadhesive agent400 as theelastic member400.
• Thus, the foregoing magnetic force is caused to act during the assembly or the like and to solidly hold components including thesensor element200 mounted on thepackage100 via theadhesive agent400. It becomes possible to properly mount them on theadhesive agent400 and/or perform bonding relative to the components mounted on theadhesive agent400. This allows efficient assembly.
• For instance, the arrangement is effective when wire bonding is performed relative to the components (including the sensor element200) mounted on theadhesive agent400 as the elastic member. This is because the magnetic force stabilizes the supporting of the members to be bonded.
• Subject components mounted on theadhesive agent400 as the elastic member are not limited to thesensor element200 and thecircuit board300. For example, a component (not shown) mounted as necessary on thesensor element200 can be also included in one of the subject components. When such a component is mounted on theadhesive agent400, fixation using the magnetic force as described above is effective.
• When the angular velocity sensor device S1 is used, theadhesive agent400 is allowed to exert the elastic function as exerted conventionally by removing the magnetic force in the angular velocity sensor device S1. This allows the anti-vibration function or the like to be performed and unnecessary vibration resulting from an external acceleration to be absorbed.
• Thus, this example embodiment allows the angular velocity sensor device S1 to properly balance the trade-off between the elastic function and the efficiency in assembly.
• The angular velocity sensor device S1 according to this example embodiment is characterized in that themagnetic member700 is interposed between theadhesive agent400 and thesensor element200. The arrangement can properly provide themagnetic member700 in the sensor-element-side space with respect to theadhesive agent400.
• The angular velocity sensor device S1 according to this example embodiment is also characterized in that thecircuit board300 is mounted on thepackage100 via theadhesive agent400 as the elastic member and thesensor element200 is stacked in fixed relation onto thecircuit board300, while themagnetic member700 is interposed between theadhesive agent400 and thecircuit board300.
Example Embodiment 2
• FIG. 5 is a view showing a schematic cross-sectional structure of an angular velocity sensor device S2 as a physical quantity sensor device according to a second example embodiment of the present invention.
• The angular velocity sensor device S2 according to this example embodiment is also the angular velocity sensor device, in which thesensor element200 is mounted on thepackage100 and held thereby via theadhesive agent400 as the elastic member. In addition, the angular velocity sensor device S2 is also characterized in that themagnetic member700 is provided in the sensor-element-side space with respect to theadhesive agent400, in the same manner as in the first example embodiment described above. This arrangement can properly balance the trade-off between the elastic function and the efficiency in assembly.
• In the first example embodiment described above, thecircuit board300 and thesensor element200 are successively stacked on thepackage100 and themagnetic member700 is interposed between thecircuit board300 and theadhesive agent400.
• The present example embodiment is the same as the first example embodiment described above in the structure in which thesensor element200 is stacked on thecircuit board300. In this example embodiment, however, thecircuit board300 is solidly held on thepackage100 by using a highly rigid adhesive agent not shown and theadhesive agent400 as the elastic member is provided between thecircuit board300 and thesensor element200. The arrangement prevents the vibration of thesensor element200 in the angular velocity sensor device S2 according to this example embodiment.
• As shown inFIG. 5, this example embodiment has interposed themagnetic member700 between theadhesive agent400 and thesensor element200 in the structure in which thesensor element200 is stacked on thecircuit board300 via theadhesive agent400. Themagnetic member700 is solidly bonded to thesensor element200 via the same adhesive agent as used in the example embodiment described above or the like.
• For example, a method for fabricating the angular velocity sensor device S2 according to this example embodiment can be implemented as follows. First, thecircuit board300, theadhesive agent400, themagnetic member700, and thesensor element200 are stacked in layers and integrated by curing theadhesive agent400. The integrated body is mounted on thepackage100 and adhesively fixed.
• It is also possible to, e.g., mount thecircuit board300 first in fixed relation onto thepackage100, stack theadhesive agent400 and thesensor element200 with themagnetic member700 thereon, and then integrate them by curing theadhesive agent400.
• In a currently reached state, thesensor element200 is held by the softadhesive agent400 as the elastic member on thecircuit board300. Accordingly, when wire bonding is performed, it is accomplished in the state in which thesensor element200 is solidly fixed to thepackage100 by using the magnetic force of each of the magnetic member fixing means andmagnetic member700 described above. Thebonding wires500 are thus formed, in the same manner as in the example embodiment described above.
• In this example embodiment also, the curing of theadhesive agent400 may be also performed after wire bonding. Before wire bonding, thecircuit board300 and thesensor element200 are integrated in the state in which they are temporarily bonded to each other with theadhesive agent400 having fluidity. During wire bonding, however, a sufficient bonding property can be obtained by using the magnetic force of themagnetic member700.
• Thereafter, the removal of the magnetic force, the attachment of thelid140 to thepackage100, and the like are performed in the same manner as in the example embodiment described above, whereby the angular velocity sensor device S2 according to this example embodiment is completed.
• It will be easily understood that, in this example embodiment also, themagnetic member700 and the like can be variously modified as shown in the example embodiment described above.
Example Embodiment 3
• FIG. 6 shows a schematic cross-sectional structure of an angular velocity sensor device S3 as a physical quantity sensor device according to a third example embodiment of the present invention.
• The angular velocity sensor device S3 according to this example embodiment is also the angular velocity sensor device in which thesensor element200 is mounted on thepackage100 and held thereby via theadhesive agent400 as the elastic member. In addition, the angular velocity sensor device S3 is also characterized in that themagnetic member700 is provided in the sensor-element-side space with respect to theadhesive agent400, similarly to the first example embodiment. The arrangement can properly balance the trade-off between the elastic function and the efficiency in assembly.
• As shown inFIG. 6, themagnetic member700 according to this example embodiment includes (i) a firstmagnetic member710 located in a first space and (ii) a secondmagnetic member720 located in a second space. The first and second spaces are defined with respect to theadhesive agent400 as the elastic member, similarly in the first example embodiment. Theadhesive agent400 faces the first space (sensor-element-side space) that includes thesensor element200, while theadhesive agent400 faces the second space that does not include the sensor element200 (e.g., inFIG. 6, the second space (package-side space) includes the bottom of the package100). In other words, the firstmagnetic member710 is closer to thesensor element200 than theadhesive agent400; the secondmagnetic member720 is closer to the bottom of thepackage100 than theadhesive agent400. The first and secondmagnetic members710 and720 are opposing each other via theadhesive agent400; namely, theadhesive agent400 is disposed or interposed between the first and secondmagnetic members710 and720.
• For instance, thecircuit board300 is mounted on thepackage100 and thesensor element200 is fixed to an upper surface thereof by using a hard adhesive agent, an adhesive film, or the like which is not shown. On the other hand, themagnetic member700 including the first and secondmagnetic members710 and720 is interposed between thecircuit board300 and thepackage100.
• InFIG. 6, the upper firstmagnetic member710 is solidly fixed to thecircuit board300, while the lower secondmagnetic member720 is solidly fixed to thepackage100, each by using a hard adhesive agent or the like which is not shown.
• Theadhesive agent400 as the elastic member is interposed between the first and secondmagnetic members710 and720 to provide adhesion between the twomagnetic members710 and720. Thus, the angular velocity sensor device S3 according to this example embodiment has a structure obtained by adding, in the foregoing structure shown inFIG. 1, another magnetic member in the second space facing thepackage100 with respect to theadhesive agent400. In this case also, elasticity is exerted by theadhesive agent400 and vibration is restricted.
• By disposing the twomagnetic members710 and720 in opposing relation with theadhesive agent400 interposed therebetween as in this example embodiment, a magnetic circuit can be formed between the twomagnetic members710 and720.
• Thesensor element200 and thecircuit board300 may be influenced by an electromagnetic force resulting from residual magnetism after processing. However, the structure makes it possible to suppress the leakage of a magnetic field toward thecircuit board300 and thesensor element200 through the formation of the magnetic circuit mentioned above. Thus, this example embodiment allows the minimization of the magnetic influence of themagnetic member700.
• In addition, in the angular velocity sensor device S3 according to this example embodiment, a protrudingportion730 is provided by an embossing finish or the like at a portion of the secondmagnetic member720 of the mutually opposing portions of the first and second magnetic opposingmembers710 and720, as shown inFIG. 6.
• The protrudingportion730 allows theadhesive agent400 as the elastic member to retain a thickness between the twomagnetic members710 and720. When the twomagnetic members710 and720 are caused to approach each other within a given distance by the magnetic force, the protrudingportion730 functions as a stopper to prevent theadhesive agent400 from sinking under the magnetic force. This allows theadhesive agent400 to retain a proper thickness.
• Although the protrudingportion730 is provided only at the secondmagnetic member720 in the example shown inFIG. 6, the protruding portion may be also provided only at the firstmagnetic member710 or at each of the first and secondmagnetic members710 and720.
• In other words, the protruding portion may be provided appropriately at at least one of the mutually opposing portions of the first and secondmagnetic members710 and720 so long as it functions as a stopper to prevent theadhesive agent400 from sinking under the magnetic force and allows theadhesive agent400 to retain a proper thickness. Alternatively, multiple protruding portions may be also provided.
Example Embodiment 4
• FIG. 7 is a view showing a schematic cross-sectional structure of an angular velocity sensor device S4 according to a fourth example embodiment of the present invention. The present example embodiment has been obtained by partly modifying the device having the first and secondmagnetic members710 and720 according to the third example embodiment described above.
• The angular velocity sensor device S4 according to this example embodiment also allows the trade-off between the elastic function and the assemblability to be properly balanced by providing themagnetic member700 in the sensor-element-side space facing thesensor element200 with respect to theadhesive agent400. Furthermore, similarly to the third example embodiment, themagnetic member700 includes two mutually opposing first and secondmagnetic members710 and720. The firstmagnetic member710 is in the first space with respect to theadhesive agent400, while the secondmagnetic member720, in the second space. The first space includes thesensor element200, while the second space includes the bottom of thepackage100, as shown inFIG. 7.
• Accordingly, in the angular velocity sensor device S4 according this example embodiment also, a magnetic circuit can be formed between the twomagnetic members710 and720 and the magnetic influence of themagnetic member710 can be minimized.
• In this example embodiment, an end portion of the firstmagnetic member710 is provided with a protruding (or projecting)portion740 that overhangs from an end portion of the secondmagnetic member720 to project toward thepackage100, as shown inFIG. 7.
• The projectingportion740 is configured as a bent portion formed by bending the end portion of the firstmagnetic member710. To allow theadhesive agent400 to retain a thickness between the twomagnetic members710 and720, the projecting length of the projectingportion740 is adjusted to be larger than a thickness of theadhesive agent400.
• In the arrangement, when the firstmagnetic member710 is caused to approach thepackage100 within a given distance by the magnetic force, the projectingportion740 comes in contact with thepackage100 to function as a stopper. Accordingly, this example embodiment can also prevent theadhesive agent400 from sinking under the magnetic force and allows theadhesive agent400 to retain a proper thickness. Furthermore, the projectingportion740 can be alternatively provided at a portion of the firstmagnetic member710 instead of the end portion of the firstmagnetic member710. For instance, the projectingportion740 can be provided in any portion of the firstmagnetic member710 as long as the projectingportion740 comes in contact with thepackage100 without being intervened by the secondmagnetic member720, e.g., through a through-hole provided in the secondmagnetic member720.
Other Example Embodiments
• Although themagnetic members710 and720 are interposed between thecircuit board300 and thepackage100 in each of the angular velocity sensor devices which uses themagnetic member700 composed of the first and secondmagnetic members710 and720 described above, themagnetic members710 and720 may be also interposed between thecircuit board300 and thesensor element200.
• In each of the angular velocity sensor devices which uses themagnetic member700 composed of the first and secondmagnetic members710 and720, at least one of the mutually opposing portions of the first and secondmagnetic members710 and720 may have the foregoing protrudingportion730. In addition, the projectingportion740 may be also provided at the end portion of the firstmagnetic member710. In other words, it is also possible to prevent theadhesive agent400 from sinking under the magnetic force and allow theadhesive agent400 to retain a thickness by making effective use of each of the functions of the protruding and projecting portions described above.
• When thevibrator20 of thesensor element200 is electro-magnetically driven in each of the example embodiments described above, themagnetic member700 can be used as a source for generating a magnetic field therefor. In this case, since the magnetic field should be positively generated, the structure can be made more compact by mounting themagnetic member700 as a magnet.
• A package is not limited to the ceramic package described above. The configuration of the package is not limited to the foregoing examples shown in the drawings.
• Although the angular velocity sensor device has been described heretofore as an example of the physical quantity sensor device according to the present invention, the present invention is not limited to an angular velocity sensor and is also applicable to an acceleration sensor, a pressure sensor, a temperature sensor, a humidity sensor, an optical sensor, an image sensor, or the like.
• In other words, in each of the example embodiments described above, the foregoingsensor element200 may be also an acceleration sensing element, a pressure sensing element, a temperature sensing element, a humidity sensing element, an optical sensing element, or an image sensing element.
• As the circuit board, any circuit such as a circuit using a MOS transistor, a bipolar transistor, or the like, a memory circuit, or the like may be used. In the physical quantity sensor device according to the present invention, the circuit board need not be provided and the sensor element may be attached directly to the package via the adhesive agent as the elastic member.
• In this case, the magnetic member may be provided appropriately between the adhesive agent and the sensor element. The elastic member is not limited to the adhesive agent made of a resin described above. Otherwise, the elastic member may be also composed of, e.g., rubber, a low-elasticity adhesive film, or the like.
• It will be obvious to those skilled in the art that various changes may be made in the above-described embodiments of the present invention. However, the scope of the present invention should be determined by the following claims.

Claims (9)

1. A physical quantity sensor device comprising:

a sensor element for sensing a physical quantity;

a package to which the sensor element is mounted;

an elastic member having elasticity, disposed between the sensor element and the package for holing the sensor element to the package, the elastic member facing (i) a first space including the sensor element and (ii) a second space opposing the first space; and

a magnetic member, which is made of a ferromagnetic material and included in the first space.

2. The physical quantity sensor device ofclaim 1, wherein

the magnetic member is disposed between the elastic member and the sensor element.

3. The physical quantity sensor device ofclaim 2, further comprising:

a circuit board mounted to the package via the elastic member, wherein

the sensor element is stacked in fixed relation to the circuit board, and

the magnetic member is disposed between the elastic member and the circuit board.

4. The physical quantity sensor device ofclaim 2, further comprising:

a circuit board fixed to the package, wherein

the sensor element is stacked to the circuit board via the elastic member, and

the magnetic member is disposed between the elastic member and the sensor element.

5. The physical quantity sensor device ofclaim 1, further comprising:

a second magnetic member, which is made of a ferromagnetic material and included in the second space with respect to the elastic member, wherein

the magnetic member included in the first space with respect to the elastic member is referred to as a first magnetic member,

the first magnetic member and the second magnetic member oppose each other, and

the elastic member is disposed between the first magnetic member and the second magnetic member.

6. The physical quantity sensor device ofclaim 5, further comprising:

a protruding portion provided to at least one of opposing portions of the first magnetic member and the second magnetic member for allowing the elastic member to retain a thickness between the first magnetic member and second magnetic member.

7. The physical quantity sensor device ofclaim 5, further comprising:

a protruding portion provided to an end portion of the first magnetic member to oppose the package, for allowing the elastic member to retain a thickness between the first magnetic member and second magnetic member.

8. The physical quantity sensor device ofclaim 5, further comprising:

a protruding portion provided to the first magnetic member to oppose the package without being intervened by the second magnetic member, for allowing the elastic member to retain a thickness between the first magnetic member and second magnetic member.

9. The physical quantity sensor device ofclaim 1, wherein

the elastic member includes an adhesive agent made of a resin.

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