Physical quantity sensor device and method for producing the same

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.

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. 8is 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, a circuit board1300is mounted on a package1100and fixed thereto. A sensor element1200is stacked on the circuit board1300via an adhesive film1400as the elastic member. The sensor element1200and the circuit board1300are wired with bonding wires1500to 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-elasticity adhesive film1400is used as the adhesion portion thereof. In the structure, the low-elasticity adhesive film1400is used to fix the sensor element1200located thereon for an anti-vibration purpose. As a result, the upper portion of the adhesive film1400is low in rigidity.

Wire bonding may be performed relative to the mounted component, i.e., sensor element1200on the adhesive film1400, or another component may be mounted in addition to the sensor element1200. In this case, the holding of the sensor element1200becomes unstable so that assembly such as bonding or mounting becomes difficult.

In contrast, to design the structure to be stable during the assembly, the adhesive film1400as the elastic member should be hardened. This causes a problem that the elastic function of the adhesive film1400is not performed, the amount of attenuation is reduced, and the external acceleration is more likely to be transmitted to the sensor element1200.PATENT DOCUMENT 1JP-H11-218424APATENT DOCUMENT 2JP-H11-264731 APATENT DOCUMENT 3JP-2002-195834 APATENT DOCUMENT 4JP-2002-250627 APATENT DOCUMENT 5JP-2003-21515 APATENT DOCUMENT 6JP-2003-28647 APATENT DOCUMENT 7JP-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.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1is a view showing a schematic cross-sectional structure of an angular velocity sensor device S1as a physical quantity sensor device according to a first example embodiment of the present invention.

As shown inFIG. 1, the angular velocity sensor device S1broadly includes the following: a package100; a circuit board300held on the package100via an adhesive agent400as an elastic member; a sensor element200stacked on the circuit board300and adhered thereto via an adhesive film600, for sensing an angular velocity; and bonding wires500for coupling the foregoing components to each other.

The package100contains the sensor element200and the circuit 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 S1to contact a proper position of a subject to measure.

In an example shown inFIG. 1, the package100is a multilayer substrate including multiple stacked ceramic layers110made of, e.g., alumina or the like. Wires (not shown) are formed on a surface of each of the layers110and in through holes formed in the individual layers110. The angular velocity sensor device S1can be electrically coupled to an outside via the wires.

The package100also has a depressed portion120in the bottom portion thereof, to contain the circuit board300. The circuit board300contained in the depressed portion120is mounted on the bottom portion of the package100and fixed thereto via the adhesive agent400as the elastic member.

The adhesive agent400is an elastic member having elasticity and made of, e.g., a resin such as a silicone gel. The adhesive agent400functions herein as an anti-vibration member to attenuate an external acceleration applied from the package100to the sensor element200as an angular velocity sensing element.

A lid140made of a metal, resin, ceramic, or the like is attached to an opening of the package100. The lid140seals an inside of the package100. The lid140is made of a metal herein and bonded to the package100by welding such as seam welding or brazing.

The sensor element200is stacked on an upper surface of the circuit board300via the adhesive member600. The adhesive member600is harder than the adhesive agent400as the elastic member and has rigidity. As the adhesive member600, an adhesive film made of, e.g., a silicone-based resin or the like can be adopted.

The sensor element200is an angular velocity sensing element for sensing an angular velocity. The sensor element200can 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. The sensor element200senses 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 the sensor element200.FIG. 2is a view showing a schematic plan structure of the sensor element200in the angular velocity sensor device S1shown inFIG. 1.

The sensor element200has a substrate10such as a semiconductor substrate and is formed by performing a well-known micromachining process with respect to the substrate10. The substrate10can 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 structures20to60are defined by trenches, as shown inFIG. 2. The beam structures20to60are formed by performing trench etching, release etching, and the like with respect to a surface layer of the substrate10, e.g., the second silicon layer of the SOI substrate. The beam structures20to60include a vibrator20, beam portions23and40, and electrodes50and60, which will be described later.

The vibrator20is formed at a center portion of the substrate10and capable of vibrating within a plane horizontal to the substrate10, i.e., in the plane inFIG. 2. In this example embodiment, the vibrator20includes a first vibrating portion21having a generally rectangular configuration positioned at the center portion; a second vibrating portion22configured as a rectangular frame positioned around the outer periphery of the first vibrating portion21; and a driving beam portion23coupling the first and second vibrating portions21and22to each other.

The vibrator20is coupled to an anchor portion30provided on a peripheral portion of the substrate10via the sensing beam portion40. The anchor portion30is fixed to and supported by the portion of the substrate10which is located below the surface layer formed with the beam structure20, i.e., the supporting substrate portion of the substrate10. The vibrator20is floating from the supporting substrate portion.

As shown inFIG. 2, the driving beam portion23is 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, the sensing beam portion40is configured to extend in, e.g., the x-direction such that it is elastically deformable substantially only in the y-direction.

Of the vibrator20, the first vibrating portion21is allowed to vibrate in the x-direction (driving vibration direction) in a plane horizontal to the substrate10by the driving beam portion23. On the other hand, the whole vibrator20is allowed to vibrate in the y-direction (sensing vibration direction) in a plane horizontal to the substrate10by the sensing beam portion40.

Between the first and second vibrating portions21and22, driving electrodes50are provided for causing the driving vibration of the first vibrating portion21in the x-direction. The driving electrodes50are fixed to the supporting substrate portion mentioned above, similarly to the anchor portion30. The driving electrodes50are disposed to oppose a comb-tooth portion (comb-tooth portion for driving)21aprojecting from the first vibrating portion21such that the comb teeth thereof and those of the comb-tooth portion21ainterdigitate.

On the other hand, sensing electrodes60are provided in an outer periphery of the second vibrating portion22. The sensing electrodes60sense an angular velocity around a z-axis perpendicular to the substrate10based on the vibration of the vibrator20and are fixed to the supporting substrate portion, similarly to the anchor portion30. The sensing electrodes60are disposed to oppose a comb-tooth portion (comb-tooth portion for sensing)22aprojecting from the second vibrating portion22such that the comb teeth thereof and those of the comb-tooth portion22ainterdigitate.

Additionally, in the present sensor element200, pads made of aluminum or the like are provided at appropriate positions on the substrate10to apply voltages to the vibrator20, driving electrodes50, sensing electrodes60, and the like mentioned above or to retrieve signals therefrom.

These pads are provided on, e.g., the peripheral portion of the substrate10. To these pads, the above-mentioned bonding wires500made of Au (gold), aluminum, or the like are connected, as shown inFIG. 1. The sensor element200according to this example embodiment has a structure as described above.

The circuit board300used 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. The circuit board300can be also a signal processing chip having functions of sending a voltage to the sensor element200, processing an electric signal from the sensor element200, outputting the processed electric signal to the outside, and the like.

As shown inFIG. 1, the sensor element200and the circuit board300are electrically coupled via the above-mentioned bonding wires500made of gold, aluminum, or the like, while the circuit board300and the package100are also electrically coupled via the bonding wires500.

Thus, the individual components of the sensor element200, the circuit board300, and the package100are electrically connected via the bonding wires500. It is to be noted that the sensor element200and the circuit board300need not be connected directly via the bonding wires500, as shown inFIG. 1.

For example, the sensor element200can be coupled to the package100via the bonding wires500, while the package100is coupled to the circuit board300via the bonding wires500. In this case, the sensor element200and the circuit board300can be similarly coupled to each other via the bonding wires500, though with intervention of the package100.

In this manner, an electric signal (capacitance change) from the sensor element200is sent to the circuit board300, converted to a voltage signal by a C/V conversion circuit or the like provided on the circuit board300, and outputted as an angular velocity signal.

Thus, the angular velocity sensor device S1according to this example embodiment is constructed by successively stacking the circuit board300and the sensor element200on the package100via the adhesive agent400as the elastic member.

Further, as a structure peculiar to this example embodiment, a magnetic member700made of a ferromagnetic material is provided at a given portion. Here, to define the given portion, explanation will be added. As explained above, the adhesive agent400is disposed between the sensor element200and the bottom portion of the package100. The adhesive agent400has (i) a first side facing a first space in which the sensor element200is 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 the adhesive agent400. The magnetic member700is thus disposed at the given portion included in the sensor-element-side space which the adhesive agent400faces via the first side. For instance, in this example embodiment, the magnetic member700is disposed or interposed between the adhesive agent400and the sensor element200.

For instance, in this example embodiment, the circuit board300is mounted on the package100via the adhesive agent400as the elastic member and the sensor element200is stacked in fixed relation onto the circuit board300, while the magnetic member700is interposed between the adhesive agent400and the circuit board300.

The magnetic member700is configured as a plate in this example embodiment and bonded to the circuit board300via 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 the circuit board300can be used for the magnetic 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 S1according 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 the magnetic member700.

A method for fabricating the angular velocity sensor device S1thus constructed according to this example embodiment will be described with reference toFIGS. 3A to 3FandFIGS. 4A to 4C. 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, the magnetic member700is adhered to the surface of the circuit board300to be mounted on the package100.

In this example embodiment, a method has been adopted which preliminarily processes the magnetic member700into the size of the circuit board300, i.e., into the chip size and then bonds the magnetic member700to the circuit board300. However, it is also possible to bond the wafer-size magnetic member700to a wafer of the circuit boards300at a stage before it is cut into individual chips and then form the circuit boards300as the chips with the magnetic members700through simultaneous dicing.

Next, as shown inFIG. 3B, the adhesive member600for fixing the sensor element200is placed on the circuit board300. Then, as shown inFIG. 3C, the sensor element200is aligned on the circuit board300. Then, as shown inFIG. 3D, the sensor element200is mounted on the circuit board300via the adhesive member600and adhesively fixed thereto.

The sensor element200may be also formed as a chip with the adhesive member600by bonding the adhesive member600composed of an adhesive film to a wafer of the sensor elements200at a stage before it is cut into individual chips and then perform simultaneous dicing. The resulting sensor element200may be also stacked on the circuit board300and adhered thereto.

These process steps result in completing a sensor module in which the sensor element200is stacked in fixed relation onto the circuit board300with the magnetic member700. Subsequently, the sensor module is mounted on the package100.

First, as shown inFIG. 3E, the adhesive agent400as the elastic member described above is applied onto the bottom portion of the depressed portion120of the package100. Then, as shown inFIG. 3F, the sensor module is mounted on the adhesive agent400with the magnetic member700opposing the bottom portion of the package100.

Then, by curing the adhesive agent400, the magnetic member700of the sensor module is bonded to the package100. In a currently reached state, the sensor module, i.e., the circuit board300and the sensor element200are held by the soft adhesive agent400as the elastic member and wire bonding is difficult to perform in this state.

When wire bonding is performed, a magnet800is provided herein below the package100, as shown inFIG. 4A. The magnet800can be incorporated into a bonding apparatus or a fixing jig810for the package100to act as a magnet chuck.

By the magnet800, a magnetic force is generated to press the magnetic member700against the package100via the adhesive agent400. As a result, the movement of the magnetic member700is suppressed and the movement of the sensor module during bonding can be suppressed. In short, the magnet800is constructed as a magnetic member fixing means for solidly fixing the magnetic member700by using a magnetic force.

As shown inFIGS. 4A to 4B, wire bonding is performed in the state in which the sensor module described above is solidly fixed to the package100by thus using the magnetic force of each of the magnet800below the package100and the magnetic member700. As a result, the package100and the circuit board300are wired with the bonding wires500, while the sensor element200and the circuit board300are wired with the bonding wires500.

After wire bonding is completed, the package100is detached from above the magnet800as shown inFIG. 4Cso that the magnetic force is removed. Then, by welding or brazing the lid140to the package100, the inside of the package100is sealed, thereby completing the angular velocity sensor device S1described above.

It is also possible to use a magnet such as ferrite to compose the magnetic member700and use a ferromagnetic material such as iron to compose the magnetic member fixing means below the package100in place of the magnet800. The arrangement also allows the same effect to be obtained. To obtain a fixing strength, each of the magnetic member700and the magnetic member fixing means can also be composed of a magnet.

The foregoing example shown inFIGS. 3A to 3FandFIGS. 4A to 4Cmounts the sensor module described above on the package100via the adhesive agent400, cures the adhesive agent400, and then performs wire bonding. The curing of the adhesive agent400may be also performed after wire bonding.

In this case, wire bonding is performed with the sensor module temporarily bonded using the uncured adhesive agent400having fluidity. However, during wire bonding, a solidly fixed structure can be implemented by using the magnetic force of the magnetic member700irrespective of the adhesive agent and a sufficient bonding property can be obtained.

In this case, the adhesive agent400is cured after wire bonding. At this time, when the magnetic member700and the magnetic member fixing means are composed of magnets each having the same polarity, a repelling force acts between the magnetic member700and the package100. This allows the suppression of the thinning of the adhesive agent400under the weight of the sensor module and allows the adhesive400to retain a sufficient thickness.

In the foregoing example shown inFIGS. 3A to 3FandFIGS. 4A to 4C, the magnetic member700, the circuit board300, and the sensor element200have been incorporated to produce the sensor module; then, the sensor module is mounted on the package100via the adhesive agent400. This order in which the individual components are mounted on the package100is not limited thereto.

For example, it is also possible to mount the magnetic member700on the package100via the adhesive agent400, adhesively mount the circuit board300and the sensor element200in succession thereon in the state in which the magnetic member700is solidly held by using a magnetic force, and then further perform wire bonding.

Alternatively, it is also possible to mount the circuit board300with the magnetic member700on the package100via the adhesive agent400, adhesively mount the sensor element200thereon in the state in which the magnetic member700and the circuit board300are 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 S1is in a normal use state with no magnetic force applied thereto so that the movement of the sensor element200is not suppressed. Accordingly, the anti-vibration performance of the adhesive agent400is sufficiently exerted as designed.

Referring primarily toFIG. 2, the sensing operation in such an angular velocity sensor device S1will be described.

A driving signal (sinusoidal voltage or the like) is applied from the circuit board300to the driving electrodes50of the sensor element200via the bonding wires500to generate an electrostatic force between the comb-tooth portion21aof the first vibrating portion21mentioned above and the driving electrodes50. As a result, the elastic force of the driving beam portion23causes the driving vibration of the first vibrating portion21in the x-direction.

When an angular velocity Ω is applied around the z-axis as a result of the driving vibration of the first vibrating portion21, a Coriolis force is applied in the y-direction to the first vibrating portion21so that the elastic force of the sensing beam portion40causes the sensing vibration of the whole vibrator20in the y-direction.

As a result, the sensing vibration causes a change in the capacitance between the respective comb teeth of the sensing electrodes60and the comb-tooth portion22afor sensing. By sensing the capacitance change, the magnitude of the angular velocity Ω can be determined.

For instance, when the vibrator20is displaced unilaterally in the y-direction, capacitance changes in opposite directions occur in the left and right sensing electrodes60inFIG. 2. The capacitance changes in the left and right sensing electrodes60are individually converted to voltages and the two voltage values are differentially amplified and outputted so that the angular velocity Ω is determined.

In the angular velocity sensor device S1as a physical quantity sensor device, the sensor element200for sensing an angular velocity as a physical quantity is mounted on the package100and held thereby via the adhesive agent400as an elastic member having elasticity. The angular velocity sensor device S1is characterized in that the magnetic member700made of a ferromagnetic material is provided in the sensor-element-side space with respect to the adhesive agent400, as shown inFIG. 1.

The arrangement allows a magnetic force to act from outside the package100such that the magnetic member700is pressed against the package100, as described above. By the magnetic force, the sensor element200on the elastic member400is more solidly fixed to the package100than when it is merely held by the adhesive agent400as the elastic member400.

Thus, the foregoing magnetic force is caused to act during the assembly or the like and to solidly hold components including the sensor element200mounted on the package100via the adhesive agent400. It becomes possible to properly mount them on the adhesive agent400and/or perform bonding relative to the components mounted on the adhesive 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 the adhesive agent400as the elastic member. This is because the magnetic force stabilizes the supporting of the members to be bonded.

Subject components mounted on the adhesive agent400as the elastic member are not limited to the sensor element200and the circuit board300. For example, a component (not shown) mounted as necessary on the sensor element200can be also included in one of the subject components. When such a component is mounted on the adhesive agent400, fixation using the magnetic force as described above is effective.

When the angular velocity sensor device S1is used, the adhesive agent400is 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 S1to properly balance the trade-off between the elastic function and the efficiency in assembly.

The angular velocity sensor device S1according to this example embodiment is characterized in that the magnetic member700is interposed between the adhesive agent400and the sensor element200. The arrangement can properly provide the magnetic member700in the sensor-element-side space with respect to the adhesive agent400.

The angular velocity sensor device S1according to this example embodiment is also characterized in that the circuit board300is mounted on the package100via the adhesive agent400as the elastic member and the sensor element200is stacked in fixed relation onto the circuit board300, while the magnetic member700is interposed between the adhesive agent400and the circuit board300.

FIG. 5is a view showing a schematic cross-sectional structure of an angular velocity sensor device S2as a physical quantity sensor device according to a second example embodiment of the present invention.

The angular velocity sensor device S2according to this example embodiment is also the angular velocity sensor device, in which the sensor element200is mounted on the package100and held thereby via the adhesive agent400as the elastic member. In addition, the angular velocity sensor device S2is also characterized in that the magnetic member700is provided in the sensor-element-side space with respect to the adhesive 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, the circuit board300and the sensor element200are successively stacked on the package100and the magnetic member700is interposed between the circuit board300and the adhesive agent400.

The present example embodiment is the same as the first example embodiment described above in the structure in which the sensor element200is stacked on the circuit board300. In this example embodiment, however, the circuit board300is solidly held on the package100by using a highly rigid adhesive agent not shown and the adhesive agent400as the elastic member is provided between the circuit board300and the sensor element200. The arrangement prevents the vibration of the sensor element200in the angular velocity sensor device S2according to this example embodiment.

As shown inFIG. 5, this example embodiment has interposed the magnetic member700between the adhesive agent400and the sensor element200in the structure in which the sensor element200is stacked on the circuit board300via the adhesive agent400. The magnetic member700is solidly bonded to the sensor element200via 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 S2according to this example embodiment can be implemented as follows. First, the circuit board300, the adhesive agent400, the magnetic member700, and the sensor element200are stacked in layers and integrated by curing the adhesive agent400. The integrated body is mounted on the package100and adhesively fixed.

It is also possible to, e.g., mount the circuit board300first in fixed relation onto the package100, stack the adhesive agent400and the sensor element200with the magnetic member700thereon, and then integrate them by curing the adhesive agent400.

In a currently reached state, the sensor element200is held by the soft adhesive agent400as the elastic member on the circuit board300. Accordingly, when wire bonding is performed, it is accomplished in the state in which the sensor element200is solidly fixed to the package100by using the magnetic force of each of the magnetic member fixing means and magnetic member700described above. The bonding wires500are thus formed, in the same manner as in the example embodiment described above.

In this example embodiment also, the curing of the adhesive agent400may be also performed after wire bonding. Before wire bonding, the circuit board300and the sensor element200are integrated in the state in which they are temporarily bonded to each other with the adhesive agent400having fluidity. During wire bonding, however, a sufficient bonding property can be obtained by using the magnetic force of the magnetic member700.

Thereafter, the removal of the magnetic force, the attachment of the lid140to the package100, and the like are performed in the same manner as in the example embodiment described above, whereby the angular velocity sensor device S2according to this example embodiment is completed.

It will be easily understood that, in this example embodiment also, the magnetic member700and the like can be variously modified as shown in the example embodiment described above.

FIG. 6shows a schematic cross-sectional structure of an angular velocity sensor device S3as a physical quantity sensor device according to a third example embodiment of the present invention.

The angular velocity sensor device S3according to this example embodiment is also the angular velocity sensor device in which the sensor element200is mounted on the package100and held thereby via the adhesive agent400as the elastic member. In addition, the angular velocity sensor device S3is also characterized in that the magnetic member700is provided in the sensor-element-side space with respect to the adhesive 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, the magnetic member700according to this example embodiment includes (i) a first magnetic member710located in a first space and (ii) a second magnetic member720located in a second space. The first and second spaces are defined with respect to the adhesive agent400as the elastic member, similarly in the first example embodiment. The adhesive agent400faces the first space (sensor-element-side space) that includes the sensor element200, while the adhesive agent400faces 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 first magnetic member710is closer to the sensor element200than the adhesive agent400; the second magnetic member720is closer to the bottom of the package100than the adhesive agent400. The first and second magnetic members710and720are opposing each other via the adhesive agent400; namely, the adhesive agent400is disposed or interposed between the first and second magnetic members710and720.

For instance, the circuit board300is mounted on the package100and the sensor element200is 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, the magnetic member700including the first and second magnetic members710and720is interposed between the circuit board300and the package100.

InFIG. 6, the upper first magnetic member710is solidly fixed to the circuit board300, while the lower second magnetic member720is solidly fixed to the package100, each by using a hard adhesive agent or the like which is not shown.

The adhesive agent400as the elastic member is interposed between the first and second magnetic members710and720to provide adhesion between the two magnetic members710and720. Thus, the angular velocity sensor device S3according 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 the package100with respect to the adhesive agent400. In this case also, elasticity is exerted by the adhesive agent400and vibration is restricted.

By disposing the two magnetic members710and720in opposing relation with the adhesive agent400interposed therebetween as in this example embodiment, a magnetic circuit can be formed between the two magnetic members710and720.

The sensor element200and the circuit board300may 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 the circuit board300and the sensor element200through the formation of the magnetic circuit mentioned above. Thus, this example embodiment allows the minimization of the magnetic influence of the magnetic member700.

In addition, in the angular velocity sensor device S3according to this example embodiment, a protruding portion730is provided by an embossing finish or the like at a portion of the second magnetic member720of the mutually opposing portions of the first and second magnetic opposing members710and720, as shown inFIG. 6.

The protruding portion730allows the adhesive agent400as the elastic member to retain a thickness between the two magnetic members710and720. When the two magnetic members710and720are caused to approach each other within a given distance by the magnetic force, the protruding portion730functions as a stopper to prevent the adhesive agent400from sinking under the magnetic force. This allows the adhesive agent400to retain a proper thickness.

Although the protruding portion730is provided only at the second magnetic member720in the example shown inFIG. 6, the protruding portion may be also provided only at the first magnetic member710or at each of the first and second magnetic members710and720.

In other words, the protruding portion may be provided appropriately at at least one of the mutually opposing portions of the first and second magnetic members710and720so long as it functions as a stopper to prevent the adhesive agent400from sinking under the magnetic force and allows the adhesive agent400to retain a proper thickness. Alternatively, multiple protruding portions may be also provided.

FIG. 7is a view showing a schematic cross-sectional structure of an angular velocity sensor device S4according 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 second magnetic members710and720according to the third example embodiment described above.

The angular velocity sensor device S4according to this example embodiment also allows the trade-off between the elastic function and the assemblability to be properly balanced by providing the magnetic member700in the sensor-element-side space facing the sensor element200with respect to the adhesive agent400. Furthermore, similarly to the third example embodiment, the magnetic member700includes two mutually opposing first and second magnetic members710and720. The first magnetic member710is in the first space with respect to the adhesive agent400, while the second magnetic member720, in the second space. The first space includes the sensor element200, while the second space includes the bottom of the package100, as shown inFIG. 7.

Accordingly, in the angular velocity sensor device S4according this example embodiment also, a magnetic circuit can be formed between the two magnetic members710and720and the magnetic influence of the magnetic member710can be minimized.

In this example embodiment, an end portion of the first magnetic member710is provided with a protruding (or projecting) portion740that overhangs from an end portion of the second magnetic member720to project toward the package100, as shown inFIG. 7.

The projecting portion740is configured as a bent portion formed by bending the end portion of the first magnetic member710. To allow the adhesive agent400to retain a thickness between the two magnetic members710and720, the projecting length of the projecting portion740is adjusted to be larger than a thickness of the adhesive agent400.

In the arrangement, when the first magnetic member710is caused to approach the package100within a given distance by the magnetic force, the projecting portion740comes in contact with the package100to function as a stopper. Accordingly, this example embodiment can also prevent the adhesive agent400from sinking under the magnetic force and allows the adhesive agent400to retain a proper thickness. Furthermore, the projecting portion740can be alternatively provided at a portion of the first magnetic member710instead of the end portion of the first magnetic member710. For instance, the projecting portion740can be provided in any portion of the first magnetic member710as long as the projecting portion740comes in contact with the package100without being intervened by the second magnetic member720, e.g., through a through-hole provided in the second magnetic member720.

Other Example Embodiments

Although the magnetic members710and720are interposed between the circuit board300and the package100in each of the angular velocity sensor devices which uses the magnetic member700composed of the first and second magnetic members710and720described above, the magnetic members710and720may be also interposed between the circuit board300and the sensor element200.

In each of the angular velocity sensor devices which uses the magnetic member700composed of the first and second magnetic members710and720, at least one of the mutually opposing portions of the first and second magnetic members710and720may have the foregoing protruding portion730. In addition, the projecting portion740may be also provided at the end portion of the first magnetic member710. In other words, it is also possible to prevent the adhesive agent400from sinking under the magnetic force and allow the adhesive agent400to retain a thickness by making effective use of each of the functions of the protruding and projecting portions described above.

When the vibrator20of the sensor element200is electro-magnetically driven in each of the example embodiments described above, the magnetic member700can 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 the magnetic member700as 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 foregoing sensor element200may 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.