Small vibration sensor

Abstract

The invention relates to a vibration sensor comprising a carrier substrate with a first surface and a second surface, a suspension member and a mobile mass fixed thereto, where at least a part of the mobile mass and / or the suspension member is adapted to vibrate when the vibration sensor is exposed to external vibrations, a readout mechanism for detecting vibrations of the mobile mass and / or at least a part of the suspension member, and a signal processor for processing at least an electrical signal from the readout mechanism, where the mobile mass forms a first projected area in a plane defined by the carrier substrate and the signal processor forms a second projected area in the plane defined by the carrier substrate, the first and second projected areas at least partially spatially overlapping in the plane defined by the carrier substrate. The invention further relates to a hearing device comprising such a vibration sensor and to a use of the vibration sensor for voice recognition in a hearing device.

Description

[Technical field]

[0001] The present invention relates to a vibration sensor comprising a carrier substrate with a first surface and a second surface, a suspension member and a mobile mass fixed thereto, where at least a portion of the mobile mass and / or the suspension member is adapted to vibrate when the vibration sensor is exposed to external vibrations. The vibration sensor further comprises a readout mechanism for detecting vibrations of the mobile mass and / or at least a portion of the suspension member, and a signal processor for processing at least an electrical signal from the readout mechanism. The mobile mass forms a first projected area on the carrier substrate, and the signal processor forms a second projected area on the carrier substrate. [Background technology]

[0002] Vibration sensors are used in devices where the available space is very limited. Hence, there is a need for the various elements to fit within the package in an optimal manner to meet the stringent space-related requirements. At the same time, if for example the vibration sensor is to be integrated into a hearing device, where it is intended to detect sound-induced vibrations within the skull of the user of the hearing device, the vibration sensor requires a moving mass of a certain size and shape to provide the required sensitivity.

[0003] An example of a prior art sensor is proposed, for example, in US Patent Application Publication No. 2020 / 136586. The sensor proposed in US Patent Application Publication No. 2020 / 136586 comprises, among other elements, a piezoelectric element / resonator and a temperature-sensitive component. The temperature-sensitive component converts the measured temperature into an electrical signal. Although the piezoelectric element / resonator and the temperature-sensitive component are arranged in a stacked arrangement, i.e., on opposite sides of the substrate, the sensor proposed in US Patent Application Publication No. 2020 / 136586 is disadvantageous in that it lacks a signal processor, for example, for processing the signal from the temperature-sensitive component. Adding a signal processor to the sensor proposed in US Patent Application Publication No. 2020 / 136586 would increase the footprint of the sensor. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] US Patent Application Publication No. 2020 / 136586 Summary of the Invention [Problem to be solved by the invention]

[0005] It may be seen as an objective of embodiments of the present invention to provide a miniature vibration sensor with a small footprint.

[0006] It may be seen as a further object of embodiments of the present invention to provide a miniature vibration sensor having a reduced surface area without compromising the sensitivity, and therefore performance, of the vibration sensor. [Means for solving the problem]

[0007] The above object is achieved in a first aspect by a vibration sensor, comprising: a) a carrier substrate having a first surface and a second surface; b) a suspension member and a moveable mass secured thereto, wherein at least a portion of the moveable mass and / or the suspension member are adapted to vibrate when the vibration sensor is exposed to external vibrations; and c) a readout mechanism for detecting vibrations of at least a portion of the moving mass and / or the suspension member; d) a signal processor for processing at least the electrical signals from the readout mechanism; This is met by providing a vibration sensor in which the movable mass forms a first projected area in a plane defined by the carrier substrate and the signal processor forms a second projected area in the plane defined by the carrier substrate, and the first and second projected areas at least partially spatially overlap in the plane defined by the carrier substrate.

[0008] The vibration sensor of the present invention is advantageous due to the relative arrangement of the movable mass and the signal processor having first and second projected areas that at least partially spatially overlap in a plane defined by the carrier substrate. As will be described in more detail below, the at least partial spatial overlap of the first and second projected areas reduces the overall size of the vibration sensor.

[0009] The term projected area in this context should be understood as the geometric projection of the outer contour of the mobile mass and the signal processor onto a plane defined by the carrier substrate. In other words, the projected area should be understood as the shadow cast by the mobile mass and the signal processor onto the plane defined by the carrier substrate. The plane onto which the mobile mass and the signal processor are projected may coincide with the first or second surface of the carrier substrate, or it may be an imaginary plane associated with the carrier substrate, such as an imaginary plane that is parallel to the first or second surface of the carrier substrate.

[0010] The mobile mass and the signal processor are preferably arranged on opposite sides of a carrier substrate. In this context, the term opposite means that the mobile mass is arranged on one side of the carrier substrate, while the signal processor is arranged on another side of the carrier substrate. This arrangement results in the carrier substrate being arranged between the mobile mass and the signal processor. Arranging the mobile mass and the signal processor on opposite sides of the carrier substrate, i.e. in a superimposed arrangement, is advantageous in that a dimension, such as one or more surface areas, of the mobile mass can then be maximized.

[0011] The vibration sensor of the present invention is preferably suitable for integration into hearing devices, such as hearing aids, hearables, headsets, earbuds or similar devices. The overall dimensions of the vibration sensor should therefore be kept as small as possible without compromising the performance of the vibration sensor. The role of the vibration sensor can be many, such as detecting sound-induced vibrations via bone conduction in the skull. Detection of such sound-induced vibrations in the skull is preferably used in the context of voice recognition, where the user's own voice is separated or recognized in an otherwise acoustically noisy environment.

[0012] Preferably, the carrier substrate comprises a first printed circuit board (PCB) with opposing first and second surfaces. The first surface of the first PCB is preferably on the same side as the mobile mass of the first PCB, while the second surface of the first PCB is preferably on the same side as the signal processor of the first PCB. The first and second surfaces comprise conductive patterns that are preferably electrically connected by one or more vias provided through the first PCB. Preferably, the signal processor is fixed to the second surface of the first PCB via flip chip bonds. Moreover, the signal processor is preferably electrically connected to the conductive patterns on the second surface of the first PCB.

[0013] Preferably, the vibration sensor further comprises a spacer fixed to the second surface of the first PCB, the spacer comprising one or more vias electrically connected to the second surface of the first PCB. The one or more vias in the spacer provide one or more electrical connections across the spacer. Moreover, the spacer preferably further comprises a recess, in which the signal processor is at least partially disposed. Thus, according to the invention, the signal processor is at least partially disposed in a recess or cavity formed in the spacer. This disposition of the signal processor is advantageous in that it provides a space-saving arrangement, making the implementation of the vibration sensor more compact. The recess or cavity in the spacer may be implemented as a through opening or passage in the spacer.

[0014] A recess in the spacer may be at least partially filled with a fill material with the signal processor disposed therein, and a conductive shielding layer may be provided covering the filled recess in the spacer to provide electrical shielding for the signal processor. Preferably, the conductive shielding layer is electrically connected to ground. The presence of the fill material around the signal processor is advantageous in that it structurally supports the signal processor which becomes embedded in the fill material, thus improving the robustness of the sensor.

[0015] The vibration sensor preferably further comprises a second PCB with opposing first and second surfaces, the one or more vias of the spacer being electrically connected to the first surface of the second PCB, and one or more contact pads being provided on the second surface of the second PCB for connecting the vibration sensor to an external electronic device, which in this context may include a power supply and additional signal processors such as amplifiers, filters, etc.

[0016] In one embodiment of the vibration sensor, the readout mechanism comprises a capacitor formed by a first capacitor electrode and a second capacitor electrode, preferably separated by an air gap. The vibration sensor of this embodiment is advantageous in that it provides a low noise level and high sensitivity. The low noise level and high sensitivity are provided due to the incorporation of a relatively large moving mass (>1 mg) and a thin air gap (5-15 μm) between the first and second capacitor electrodes. Moreover, the vibration sensor of the present invention is advantageous because it is reflowable.

[0017] To save space, at least a part of the suspension member is preferably conductive. Moreover, at least the conductive part of the suspension member preferably forms a first capacitor electrode. The second capacitor electrode is preferably provided on a first surface of the carrier substrate. Thus, an air gap is formed between the conductive suspension member forming the first capacitor electrode and the second capacitor electrode, which is preferably provided on a first surface of the first PCB.

[0018] In order to guide air to and / or from the air gap, one or more air passages are preferably provided in the first and / or second capacitor electrodes. The one or more air passages should therefore preferably prevent air from being pressurized in the air gap when the air gap is reduced, and ensure that air can be guided to the air gap when the air gap is increased. This is advantageous in that the squeeze film damping effect between the first and second capacitor electrodes is then significantly reduced. In the present context, the term squeeze film damping should be understood as the viscous damping caused by air trapped in the air gap between the first and second capacitor electrodes. The air gap in the vibration sensor of the present invention is typically in the range of 5 to 15 μm.

[0019] Preferably, the first capacitor electrode is electrically connected to ground and the second capacitor electrode is electrically biased by a signal processor, which is adapted to provide a substantially constant charge to the second capacitor electrode in addition to processing the electrical signal from the readout mechanism. The fact that both the electrode biasing and the signal processing are combined in a single integrated circuit is advantageous in that it saves space.

[0020] In another embodiment, the readout mechanism preferably comprises one or more piezoelectric layers and one or more electrodes disposed on each piezoelectric layer. In this embodiment, the suspension member preferably forms a cantilever beam with a stationary end and a movable end. To respond to external vibrations, the movable mass is preferably fixed to the cantilever beam at or near its movable end, while the one or more piezoelectric layers are preferably fixed to the cantilever beam in a manner such that the one or more piezoelectric layers cross a virtual hinge line.

[0021] In the present context, the term virtual hinge line defines a line between the resting and moving ends of the cantilever about which the cantilever effectively bends when the moving mass is displaced due to external vibration.

[0022] Preferably, the vibration sensor further comprises a shielding mechanism for suppressing electromagnetic interference, the shielding mechanism comprising one or more signal electrodes and a ground electrode separated by a dielectric layer, and the one or more signal electrodes, the ground electrode and the dielectric layer are embedded in the first PCB. This shielding mechanism is advantageous in that it shields signals to / from the signal processor from incident electromagnetic radiation. The shielding mechanism is further advantageous in that it is embedded in the first PCB, so that it does not increase the overall size of the vibration sensor.

[0023] In a second aspect, the present invention relates to a hearing device comprising a vibration sensor according to the first aspect, the hearing device comprising a hearing aid, a hearable, a headset, an earbud or a similar device.

[0024] In a third aspect, the present invention relates to a use of a vibration sensor according to the first aspect, wherein the vibration sensor is used to detect sound-induced vibrations within the skull of a user of a hearing device, and the detected sound-induced vibrations are used for voice recognition of the user's own voice.

[0025] Generally, the various aspects of the invention may be combined and combined in any manner possible within the scope of the invention. These and other aspects, features and / or advantages of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter.

[0026] The present invention will now be described with reference to the accompanying drawings. [Brief description of the drawings]

[0027] [Figure 1] FIG. 1 shows a cross-sectional view of one embodiment of a vibration sensor having a capacitive readout mechanism. [Diagram 2] 1 illustrates spatially overlapping projections of a movable mass and a signal processor on a plane defined by a carrier substrate. [Diagram 3]1 shows a cross-sectional view of another embodiment of a vibration sensor having a piezoelectric readout mechanism. [Figure 4] FIG. 2 shows an enlarged cross-sectional view of a signal processor of the vibration sensor. [Diagram 5] FIG. 2 shows an enlarged cross-sectional view of a shielding mechanism for a signal processor of a vibration sensor. [Figure 6] FIG. 1 shows an enlarged cross-sectional view of the second PCB (bottom PCB) of the vibration sensor. [Figure 7] 1 shows a bottom view of a spacer with additional vias disposed therein to provide electromagnetic shielding. [Figure 8] 1 shows an enlarged cross-sectional view of an embedded shielding mechanism for suppressing electromagnetic interference. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0028] In general, the present invention relates to a miniature vibration sensor, and in particular to a vibration sensor in which a moving mass and a signal processor are arranged in a stacked arrangement in which their respective projections (of the moving mass and the signal processor) in a plane defined by a carrier substrate of the vibration sensor at least partially spatially overlap.

[0029] As already mentioned, the vibration sensor is adapted to be integrated into a hearing device, such as a hearing aid, hearable, headset, earbud or similar device. Due to the limited space available in the hearing device, the overall dimensions of the vibration sensor should therefore be kept as small as possible without compromising the performance of the vibration sensor. As previously mentioned, the role of the vibration sensor can be multiple, such as detecting sound-induced vibrations via bone conduction in the skull. The detection of such sound-induced vibrations in the skull is preferably used in the context of voice recognition, where the user's own voice is separated or recognized in an otherwise acoustically noisy environment.

[0030] To detect sound-induced vibration signals via bone conduction, the bandwidth of the vibration sensor is typically greater than 6 kHz. In addition, the resonant frequency of the vibration sensor is typically close to the upper bandwidth limit, e.g., greater than 4 kHz, and the resonant peak is typically less than 10 dB compared to the sensitivity at 1 kHz. With this approach, the Q will typically be less than 3. Moreover, the noise floor of the vibration sensor should be low, i.e., <-98 dB re. 1g in the 1 / 3 octave band at the resonant frequency. To meet these requirements, the mass of the moving mass needs to be relatively high, e.g., higher than 1 mg. Since the moving mass typically has a thickness in the range of 100-200 μm, the large and opposed, and therefore projected surface area of ​​the moving mass is at most 2.5 mm. 2 From a manufacturing standpoint, the movable mass may be made from a variety of materials including steel, tantalum or tungsten.

[0031] Referring now to FIG. 1, a cross-sectional view of one embodiment of a vibration sensor is depicted. As seen in FIG. 1, the mobile mass 17 and the signal processor 7 are arranged in a superimposed arrangement in that their respective shadows, i.e. their projected areas, at least partially, spatially overlap on the first PCB 1. The spatial overlap of the mobile mass 17 and the signal processor 7 is illustrated in FIG. 2, where FIG. 2a shows a cross-sectional view of a vibration sensor comprising, among other elements, the mobile mass 17 and the signal processor 7. The horizontal line 1' in FIG. 2a illustrates an imaginary plane defined by the carrier substrate 1, see FIG. 1. As already mentioned, the imaginary plane may coincide with the first or second surface of the carrier substrate, or it may be an imaginary plane that is parallel to the first or second surface of the carrier substrate. As seen in FIG. 2b, the mobile mass 17 forms a projected area 17' in this imaginary plane 1', and the signal processor 7 forms a projected area 7' in the same imaginary plane 1'. It is clear from Fig. 2b that the projected areas 7', 17' spatially overlap as indicated by the hatched area. In general, the embodiment illustrated in Fig. 1 relies on a capacitive detection scheme in which the distance, and therefore the capacitance, between the first capacitor electrode 11 and the second capacitor electrode 10 is adapted to change when the vibration sensor is exposed to external vibrations. In the embodiment illustrated in Fig. 1, the first capacitor electrode 11 is electrically connected to ground, while the second capacitor electrode 10 is electrically biased by the signal processor 7. Moreover, the signal processor 7 is adapted to process the voltage change caused by the capacitance change between the first capacitor electrode 11 and the second capacitor electrode 10. The signal processor 7 is electrically connected to the second capacitor electrode 10 through a flip chip bond 8 and a via 5 in the first PCB 1. The first PCB 1 comprises an additional via 4.

[0032] As can be seen in figure 1, the first capacitor electrode 11 and the second capacitor electrode 10 are separated by an air gap 16 defined by a spacer 12'. As already mentioned, the size of this air gap 16, i.e. the distance between the first capacitor electrode 11 and the second capacitor electrode 10, is adapted to change when the vibration sensor is exposed to external vibrations, since the first capacitor electrode 11 also acts as a suspension member for the mobile mass 17 to which it is fixed. The air gap is typically in the range of 5 to 15 µm.

[0033] Around or outside the second capacitor electrode 10 is provided a rim 12 forming a perimeter. Preferably, the rim 12 forms part of the same layer as the second capacitor electrode 10 so that the second capacitor electrode 10 and the rim 12 have exactly the same thickness. On top of the rim 12 a spacer 12' is arranged. Preferably, both the rim 12 and the spacer 12' are electrically conductive. Moreover, the rim 12 and the spacer 12' are electrically connected to ground, preferably through vias 4 in the first PCB 1 and through vias 3 in a spacer 2 fixed to the first PCB 1.

[0034] Resilience of the suspension member / first capacitor electrode 11 is provided by a resilient member 13 which is secured to or forms part of the suspension member / first capacitor electrode 11. A housing 19 defining a cavity 18 is provided over the moveable mass 17 and the suspension member / first capacitor electrode 11.

[0035] 1, the vibration sensor further comprises a spacer 2 comprising a recess or cavity 6 in which a signal processor 7 is disposed. The spacer 2 comprises one or more vias 3, 9 for electrically connecting the first PCB 1 to one or more contact pads disposed on the underside of the spacer 2. The one or more contact pads facilitate easy connection of the vibration sensor to an external electronic device.

[0036] As depicted in FIG. 6, a second PCB 27 may be fixed to the spacer 2. The second PCB 27 comprises one or more contact pads 28, 29 that facilitate easy connection of the vibration sensor to an external electronic device. The cavity 6 formed by the first PCB 1, the spacer 2 and the second PCB 27 may be filled with a filling material such that the signal processor 7 is embedded in this filling material. The signal processor 7 may be operating in the analog or digital domain applying any digital coding scheme. In terms of signal conditioning, the signal processor 7 may be configured for amplification, buffering, filtering, digitization, etc.

[0037] Returning now to Figure 1 and the capacitive sensing scheme, the electrically active portion of the first capacitor electrode 11 is a central electrode portion 11' that is fixed to the movable mass 17. The second capacitor electrode 10 is separated from the outer rim 12 by air passages 14, 15 to reduce the squeeze film damping effect between the first capacitor electrode portion 11' and the second capacitor electrode 10. Thus, as the distance between the electrically active portion of the first capacitor electrode 11 and the second capacitor electrode 10 is reduced, air is allowed to escape via the air passages 14, 15, thereby reducing the squeeze film damping effect.

[0038] Turning now to Figure 3, a cross-sectional view of another embodiment of a vibration sensor is depicted. As can be seen in Figure 3, the movable mass 17 and the signal processor 7 are also arranged in a stacked arrangement in that their respective projected areas at least partially spatially overlap on the first PCB 1.

[0039] As can be seen in Figure 3, the mobile mass 17 is fixed to a suspension member 20. The suspension member 20 has the shape of a cantilever beam having a stationary end at the remainder 12' and a mobile end to which the mobile mass 17 is fixed. At least the mobile end of the mobile mass 17 and the cantilever beam 20 are adapted to be displaced when the vibration sensor is exposed to external vibrations. A housing 19 protects the cantilever beam 20 and the mobile mass 17 fixed thereto.

[0040] Generally, the embodiment illustrated in Fig. 3 relies on a piezoelectric detection scheme to detect the displacement of the mobile mass 17 when the vibration sensor is exposed to external vibrations. In the embodiment illustrated in Fig. 3, a piezoelectric layer 22, on which an electrode 21 is disposed, is arranged on the cantilever beam 20 such that the piezoelectric layer crosses a virtual hinge line (not shown). It should be noted that instead of a single piezoelectric layer, multiple piezoelectric layers, on which respective electrodes are disposed, may optionally be applied.

[0041] The displacement (up or down) of the mobile mass 17 bends the cantilever beam 20 at the virtual hinge line, which causes the piezoelectric layer 22 to expand or contract laterally. The change in the lateral strain of the piezoelectric layer 22 induces a change in the electric field intensity across the piezoelectric layer 22, i.e. across the thickness of the piezoelectric layer 22. The change in the electric field intensity across the piezoelectric layer 22 provides a change in the voltage generated between two electrodes arranged on opposite sides of the piezoelectric layer 22. In the embodiment illustrated in FIG. 3, the lower electrode (grounded) of the piezoelectric layer 22 is formed by the cantilever beam 20, while an electrode 21 is formed on the piezoelectric layer 22. This separate electrode 21 is electrically connected to the signal processor 7 via wire bonding, an electrode 23 on the first PCB 1, vias 4 through the first PCB 1 and flip chip bonding 8 to the signal processor 7. The detected voltage change across the piezoelectric layer 22 is then processed by the signal processor 7, which may be operating in the analog or digital domain applying any digital coding scheme. Again, in terms of signal conditioning, the signal processor 7 may be configured for amplification, buffering, filtering, digitization, and the like.

[0042] 3, the vibration sensor further comprises a spacer 2 comprising a recess or cavity 6 in which a signal processor 7 is disposed. The spacer 2 comprises one or more vias 4, 5 for electrically connecting the first PCB 1 to one or more contact pads disposed on the underside of the spacer 2. The one or more contact pads facilitate easy connection of the vibration sensor to an external electronic device.

[0043] Referring now to Figure 4, an enlarged cross-sectional view of an embodiment is depicted that includes a thinner spacer 2 with integrated vias 3, 3'. The embodiment illustrated in Figure 4 may include a capacitive or piezoelectric readout mechanism as described above. A signal processor 7 is secured to the first PCB 1 via flip chip bonding 8. A pair of solder balls 24, 24' are provided to facilitate reflow soldering of the vibration sensor. It should be noted that the number of solder balls may differ from the two depicted in Figure 4.

[0044] Turning now to Figure 5, an enlarged cross-sectional view of an embodiment with an embedded signal processor 7 is depicted. In Figure 5, a recess or cavity 6 in the spacer 2 is filled with a filling material such that the signal processor 7 is embedded in the recess or cavity 6. A conductive shielding layer 25 is provided over the filled recess or cavity 6 in the spacer 2 to provide electrical shielding for the embedded signal processor 7. The conductive shielding layer 25 is electrically connected to a via 3 in the spacer 2 which is electrically connected to ground. The via 3' and contact pad 26 may be connected to a power supply, additional signal processor, amplifier, etc. The embodiment illustrated in Figure 5 may include a capacitive or piezoelectric readout mechanism as described above. The signal processor 7 is secured to the first PCB 1 via flip chip bonding 8.

[0045] As depicted in FIG. 6, the vibration sensor may comprise a second PCB 27 with opposing first and second surfaces. One or more contact pads 28, 29 are provided on the second surface of the second PCB 27 to facilitate easy connection of the vibration sensor to an external electronic device. The second PCB 27 is fixed to the spacer 2. The cavity 6 formed by the first PCB 1, the spacer 2 and the second PCB 27 may be filled with a filling material such that the signal processor 7 is embedded in this filling material, as described above. The vibration sensor according to the embodiment depicted in FIG. 6 may comprise a capacitive or piezoelectric readout mechanism, and the signal processor 7 is fixed to the first PCB 1 via flip chip bonding 8.

[0046] 7, a bottom view of a vibration sensor comprising a spacer 2 having a number of electrically grounded vias 30 to provide electromagnetic shielding of a signal processor 7 disposed in a recess or cavity 6 of the spacer 2. Larger vias 3 may be adapted to pass sensor signals, power signals, etc. across the spacer 2. The vibration sensor according to the embodiment illustrated in FIG. 7 may comprise a capacitive or piezoelectric readout mechanism, and the signal processor 7 may be secured to a first PCB (not shown) via flip chip bonding.

[0047] Turning now to FIG. 8, an enlarged cross-sectional view of the capacitive vibration sensor is depicted. The implementation of the movable mass 17, the first capacitor electrode portion 11', the second capacitor electrode 10, the air gap 16, the spacer 12', the air passage 15, the elastic member 13 and the housing 19 has already been described with respect to the embodiment illustrated in FIG. 1. With respect to the implementation of the signal processor 7, including the spacer 2 with its vias 3, the recess or cavity 6 and its flip-chip attachment 8 to the first PCB 1, reference is also made to the disclosure of the previous embodiment. With respect to the first PCB 1, a filter mechanism for suppressing high frequency interference was embedded therein. As depicted in FIG. 8, the mechanism comprises one or more conductive layers 31, each electrically connected to ground through vias 3 and 4. The rim 12, the spacer 12' and the housing 19 are also electrically connected to ground. The first capacitor electrode 11 (including the first capacitor electrode portion 11'), the rim 12 and the spacer 12' are also electrically connected to ground. One or more signal electrodes 33 are connected to the external contact pads of the vibration sensor and each form a capacitor with one or more conductive layers 31. The capacitance of these capacitors is determined by the dielectric constant of the dielectric layer 32, the thickness of the dielectric layer 32 and the area of ​​the respective electrodes 33. The capacitance is designed and selected such that high frequency currents arriving at the external contact pads of the vibration sensor are diverted to ground.

[0048] According to the above-mentioned embodiment, the displacement of the mobile mass and at least part of the suspension member is detected using a capacitor or a piezoelectric layer. It should be noted that for example pneumatic or optical means may be applied. With pneumatic means, the air pressure change due to the displacement of the mobile mass and at least part of the suspension member can be measured. With optical means, the diffraction of a laser beam on a grating attached to the mobile mass can be measured.

[0049] Although the present invention has been described above with reference to exemplary embodiments thereof, the present invention is not limited to these specific embodiments, which can be modified in many ways without departing from the present invention. The described exemplary embodiments should therefore not be used to interpret the appended claims in their exact terms. On the contrary, the embodiments are merely intended to explain the wording of the appended claims, and are not intended to limit the claims to these exemplary embodiments. The scope of protection of the present invention should therefore be interpreted only according to the appended claims, and possible ambiguities in the wording of the claims should be resolved using these exemplary embodiments. [Explanation of symbols]

[0050] 1. First PCB 1' horizontal line 2 Spacers 3, 3', 9 via 4, 5 vias 6. Hollows or Cavities 7 Signal Processor 7' projected area 8. Flip Chip Bonding 10 Second capacitor electrode 11 First capacitor electrode 11' Center electrode part 12 Rims 12' spacer 13 Elastic member 14, 15 Air passage 16 Air gap 17 Movable mass 17' projected area 18 Cavity 19 Housing 20 cantilever beam 21 electrodes 22 Piezoelectric layer 23 electrodes 24, 24' solder balls 25 Conductive Shielding Layer 26 Contact Pad 27 Second PCB 28, 29 Contact pads 30 Via 31 Conductive layer 32 Dielectric layer 33 Signal electrode

Claims

1. A vibration sensor, comprising: a) a carrier substrate (1) having a first surface and a second surface; b) a suspension member (11, 11', 20) and a movable mass (17) fixed thereto, wherein at least a part of the movable mass (17) and the suspension member (11, 11', 20) is adapted to vibrate when the vibration sensor is exposed to external vibrations, the suspension member (11, 11', 20) and the movable mass (17); c) a readout mechanism for detecting vibrations of at least a part of the movable mass (17) and the suspension member (11, 11', 20); d) a signal processor (7) for processing at least electrical signals from the readout mechanism, wherein the movable mass (17) forms a first projected area (17') in a plane defined by the carrier substrate (1), and the signal processor (7) forms a second projected area (7') in the plane defined by the carrier substrate (1), in the vibration sensor, wherein the first and second projected areas (7', 17') at least partially spatially overlap in the plane defined by the carrier substrate (1). A vibration sensor, characterized in that.

2. The vibration sensor according to claim 1, characterized in that the movable mass (17) and the signal processor (7) are arranged on opposite sides of the carrier substrate (1).

3. The vibration sensor according to claim 1, characterized in that the carrier substrate (1) comprises a first PCB (1) having opposing first and second surfaces.

4. The vibration sensor according to claim 3, characterized in that the signal processor (7) is fixed to the second surface of the first PCB (1) via flip chip bonding (8).

5. The vibration sensor according to claim 4, further comprising a spacer (2) fixed to the second surface of the first PCB (1), and the spacer (2) comprising one or more vias (3, 9) electrically connected to the second surface of the first PCB (1).

6. The vibration sensor according to claim 5, characterized in that the spacer (2) further comprises a recess (6), and the signal processor (7) is at least partially arranged in the recess.

7. The recess (6) within the spacer (2) is at least partially filled with a filling material with the signal processor (7) at least partially disposed therein, and a conductive shielding layer (25) is provided to cover the filled recess within the spacer (2) to provide electrical shielding with respect to the signal processor (7), the vibration sensor according to claim 6, characterized in that.

8. The vibration sensor according to claim 7, characterized in that the conductive shielding layer (25) is electrically connected to ground.

9. The vibration sensor according to claim 5, further comprising a second PCB (27) having opposing first and second surfaces, and the one or more vias (3) of the spacer (2) are electrically connected to the first surface of the second PCB (27), and one or more contact pads (28, 29) are provided on the second surface of the second PCB (27) for connecting the vibration sensor to an external electronic device.

10. The vibration sensor according to claim 3, characterized in that the readout mechanism comprises a capacitor formed by a first capacitor electrode (11') and a second capacitor electrode (10) separated by an air gap (16).

11. The vibration sensor according to claim 10, characterized in that at least a part of the suspension members (11, 11') is conductive.

12. The vibration sensor according to claim 11, characterized in that at least the conductive portion of the suspension member forms the first capacitor electrode (11').

13. The vibration sensor according to claim 11, characterized in that the second capacitor electrode (10) is provided on the first surface of the first PCB (1).

14. The vibration sensor according to claim 13, characterized in that the first and / or second capacitor electrodes (11', 10) are provided with one or more air passages (14, 15) to reduce the squeeze film damping effect between the first and second capacitor electrodes (11', 10).

15. The vibration sensor according to claim 10, characterized in that the first capacitor electrode (11') is electrically connected to ground and the second capacitor electrode (10) is electrically biased by the signal processor (7).

16. The vibration sensor according to claim 3, wherein the reading mechanism includes one or more piezoelectric layers (22) and one or more electrodes (21) disposed on each of the piezoelectric layers (22).

17. The vibration sensor according to claim 16, wherein the suspension member forms a cantilever beam (20) having a stationary end and a movable end.

18. The vibration sensor according to claim 17, wherein the movable mass (17) is fixed to the cantilever beam (20) at or near its movable end, and the one or more piezoelectric layers (22) are fixed to the cantilever beam (20) in such a manner that the one or more piezoelectric layers (22) intersect a virtual hinge line.

19. The vibration sensor according to claim 1, further comprising a filter mechanism for suppressing high-frequency interference, and the filter mechanism includes one or more signal electrodes (33) and one or more ground electrodes (31) separated by a dielectric layer (32).

20. The vibration sensor according to claim 19, wherein the one or more signal electrodes (33), the one or more ground electrodes (31), and the dielectric layer (32) are embedded in the first PCB (1).

21. An auditory device comprising the vibration sensor according to any one of claims 1 to 20, wherein the auditory device includes a hearing aid, a wearable device, a headset, earbuds, or a similar device.

22. In a method of using the vibration sensor according to any one of claims 1 to 20 in an auditory device, the vibration sensor is used to detect voice-induced vibrations within the skull of a user of the auditory device, and the detected voice-induced vibrations are used for voice recognition of the user's own voice.

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