Micro-electromechanical transducers with sprung mass

Abstract

To provide a micro-electromechanical transducer with high sensitivity and low noise.SOLUTION: The present invention relates to a micro-electromechanical transducer including a pressure detection arrangement and a sub-assembly adapted to cooperate with the pressure detection arrangement via a coupling volume. The sub-assembly includes one or more movable masses, and a suspension member supporting a number of movable masses. The coupling volume is at least partly defined by the suspension member and acoustically connected to an interior volume of the pressure detection arrangement. The suspension member includes a viscoelastic material with a predetermined viscous and sealant behavior in order to dampen one or more resonance peaks of the micro-electromechanical transducer and acoustically seal the coupling volume. The present invention further relates to a hearing device including such a micro-electromechanical transducer.SELECTED DRAWING: Figure 1a

Description

[Technical Field]

[0001] The present invention relates to a micro-electromechanical transducer comprising a pressure sensing configuration such as a MEMS microphone and a sub-assembly adapted to cooperate with the pressure sensing configuration via a coupling volume, wherein the sub-assembly comprises one or more movable masses and suspension members supporting several movable masses. According to the present invention, the coupling volume is at least partially defined by the suspension members. Furthermore, the coupling volume is acoustically coupled to the internal volume of the pressure sensing configuration. [Background technology]

[0002] For bone conduction-related voice pickup, a vibration sensor with high sensitivity and low noise in the speech frequency band is required. To obtain high sensitivity S, S∝1 / f pk Therefore, the resonant frequency f of the vibration sensor pk It must be low. To obtain low noise,

[0003]

number

[0004] Therefore, the movable mass m of the vibration sensor must be large.

[0005] However, large moving masses are not well-suited to compact vibration sensors that utilize MEMS technology.

[0006] Several performance-related issues need to be addressed when designing vibration sensors that utilize a movable mass. First, the movable mass must be held in place, i.e., the suspension element supporting the movable mass must have a certain mechanical stiffness. Second, the displacement of the movable mass should generate a pressure change, thereby requiring one or more seals between the air volumes on either side of the movable mass. Third, the movement of the movable mass should be damped using the viscoelastic and / or sealing material of the suspension element, as proposed, for example, in European Patent Application Publication No. 3279621, European Patent Application Publication No. 3467457, and European Patent Application Publication No. 3342749.

[0007] However, all the solutions proposed in European Patent Application Publication Nos. 3279621, 3467457, and 3342749 have several drawbacks, including 1) plastic deformation of the suspension elements under excessive mechanical impact, and 2) the overall mechanical stiffness of the pressure generating configuration being dominated by the suspension elements. Regarding plastic deformation, this results in a permanent displacement of the movable mass, which affects the acoustically coupled volume. Furthermore, the plastic deformation affects the acoustic coupling between the pressure generating configuration (supported movable mass) and the pressure sensing configuration (MEMS microphone). Regarding overall mechanical stiffness, the contribution to mechanical stiffness from sealing and damping materials must be small, which undesirably limits the selection of materials for sealing and damping.

[0008] Therefore, it seems necessary to solve the aforementioned problems, particularly with regard to compact vibration sensors for use in applications such as bone conduction. [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] European Patent Application Publication No. 3279621

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0010] Therefore, it can be understood that an object of embodiments of the present invention is to provide a microelectromechanical transducer with high sensitivity and low noise, particularly in the speech frequency band.

[0011] It can be understood that a further object of embodiments of the present invention is to provide a microelectromechanical transducer that requires a minimum number of process steps during manufacturing.

[0012] It can be understood that a still further object of embodiments of the present invention is to provide a microelectromechanical transducer having a simple integrated configuration with predetermined support, sealing, and damping characteristics.

Means for Solving the Problems

[0013] In a first aspect, the aforementioned object is a microelectromechanical transducer comprising a pressure detection configuration and a sub-assembly adapted to cooperate with the pressure detection configuration via a coupling volume, wherein the sub-assembly - one or more movable masses, - a suspension member for supporting some of the movable masses and the coupling volume is at least partially defined by the suspension member, and the coupling volume is acoustically connected to the internal volume of the pressure detection configuration, The suspension member is provided by providing a microelectromechanical transducer that includes a viscoelastic material with predetermined viscous and sealing properties in order to attenuate one or more resonance peaks of the microelectromechanical transducer and in order to acoustically seal the coupling volume.

[0014] Preferably, the pressure detection configuration is a MEMS microphone. The present invention is advantageous in that the sub-assembly forms part of a pressure generation configuration for generating a pressure change, and the MEMS microphone preferably forms part of a pressure detection configuration for detecting the pressure change, which is the pressure change generated by the pressure generation configuration, i.e., the sub-assembly.

[0015] It is further advantageous that the movable mass that generates the pressure change is separate from the pressure sensing configuration / MEMS microphone. Instead, the movable mass forms part of the pressure generating configuration, i.e., a subassembly, and is acoustically coupled to the pressure sensing configuration / MEMS microphone via a coupling volume, preferably via an opening on the outer surface of the pressure sensing configuration / MEMS microphone. Thus, the coupling volume is acoustically coupled to the internal volume of the pressure sensing configuration, preferably via an opening on the outer surface of the pressure sensing configuration / MEMS microphone. Preferably, the pressure sensing configuration / MEMS microphone comprises a housing / casing that encloses the components of the pressure sensing configuration / MEMS microphone. In this context, the term “outer surface” should be understood as the outer surface of this housing / casing of the pressure sensing configuration / MEMS microphone.

[0016] Therefore, the term “adapted to cooperate with ~” should be understood in this context as “acoustically coupled / connected with ~.” The subassembly may be adapted to cooperate with the pressure sensing configuration by means other than coupling volumes, such means may involve ventilation openings between the respective rear volumes disclosed later.

[0017] As will be discussed in more detail later, the internal volume of the MEMS microphone, to which the coupled volume is acoustically coupled, preferably includes the front volume of the MEMS cartridge of the MEMS microphone. The MEMS microphone further comprises a signal processing device for processing the electrical signals generated by the MEMS cartridge. Preferably, the outer surface of the MEMS microphone is formed by the outer surface of a printed circuit board (PCB). The same PCB also comprises an inner surface to which the MEMS cartridge and signal processing device are preferably fixed.

[0018] Preferably, the micro-electromechanical transducer of the present invention is a vibration sensor, such as a vibration sensor, suitable for use in bone conduction-related applications.

[0019] From a functional standpoint, it is advantageous for a suspension member to combine three functionalities—support, sealing, and damping—in a single element, in that the viscoelasticity of the suspension member determines the pressure generation configuration, i.e., the mechanical stiffness and damping of the suspension member and one or more movable masses.

[0020] The micro electromechanical transducer of the present invention has an advantage in that the suspension member is preferably manufactured from a viscoelastic material that does not inherently exhibit plastic deformation. Preferably, the viscoelastic material is a thermosetting elastomer with a small Young's modulus and a large viscosity, such as silicone rubber.

[0021] As will be discussed in more detail later, the suspension members can be molded using a molding process, or they can be implemented as membranes stretched across a spacer configuration. The membranes can be single-layer membranes, or alternatively, multi-layer membranes.

[0022] The suspension member of the micro-electromechanical transducer of the present invention offers a better ratio between damping and stiffness, as well as better tolerances during manufacturing, which is further advantageous as it enables the manufacture of smaller transducers. As discussed in relation to Figure 1, the molded suspension member is advantageous in that it facilitates the integration of additional elements such as one or more spacers that determine the dimensions of one or more volumes, such as the coupling volume and / or the rear volume of the sub-assembly. With respect to the suspension member implemented as a membrane covered with silicone rubber, for example, silicone rubber has low tackiness, which is advantageous as it facilitates low-tackiness micro-electromechanical transducers. Furthermore, the stiffness of the suspension member is not affected by tackiness bleed-out, and the dimensions are not affected by the thickness of the tackiness layer.

[0023] From an implementation standpoint, in one embodiment, the suspension member may form a surrounding portion that encloses a support structure to which it is fixed, and one or more movable masses are fixed to the support structure. In this context, the term “surrounding portion” is understood as a suspension member that encloses the support structure to which it is fixed in a continuous, sealed manner.

[0024] Preferably, the suspension member comprises, in its cross-sectional contour, an inner portion having an inner thickness and an outer portion having an outer thickness, the outer thickness being greater than the inner thickness. The fact that the outer portion of the suspension member is thicker is advantageous in that the outer portion can be considered to have an integrated spacer built into it. For this reason, the outer portion of the suspension member is preferably fixed to the outer surface of the MEMS microphone. Thus, the outer portion of the suspension member sets the volume of the coupling volume.

[0025] It is even more advantageous for the recess to be formed between the inner and outer portions of the suspension member. At the location of the recess, i.e., between the inner and outer portions, the suspension member preferably has its thinnest portion, i.e., its minimum thickness. Due to its thinness, the viscoelasticity of the suspension member is mainly determined by this thinnest portion.

[0026] In other embodiments, the suspension member comprises a viscoelastic film stretched between spacer portions, with one or more movable masses fixed to one or both sides of the stretched film. The spacer portions are fixed directly or indirectly to the outer surface of the MEMS microphone. Preferably, two essentially identical movable masses are fixed to both sides of the stretched film using appropriate means such as suitable adhesive.

[0027] In practice, the spacer portion may constitute at least a part of the peripheral edge further comprising a central recess surrounded by the peripheral edge of the spacer structure. Therefore, the spacer structure may be cup-shaped, with the central recess fixed to the outer surface of the MEMS microphone by appropriate means such as suitable adhesive. The height of the spacer structure sets the volume of the coupling volume. To acoustically connect the coupling volume to the internal volume of the MEMS microphone, the spacer structure preferably comprises a ventilation opening aligned with an opening on the outer surface of the MEMS microphone.

[0028] In other embodiments, the spacer portion may be fixed to the outer surface of the MEMS microphone or form a peripheral spacer that forms part of the outer surface of the MEMS microphone. Thus, the peripheral spacer may be a separate element fixed to the outer surface of the MEMS microphone by appropriate means, or it may form an integral part of the outer surface of the MEMS microphone. Here again, the height of the peripheral spacer sets the volume of the coupling volume.

[0029] Regardless of the implementation of the outer portion of the spacer or suspension member, the outer surface of the MEMS microphone may have further openings that acoustically connect the rear volume of the subassembly to the rear volume of the MEMS microphone. Furthermore, the suspension member may have ventilation openings for ventilating the coupling volume. Such ventilation openings in the suspension member can acoustically connect the coupling volume to the rear volume of the subassembly. Integrating the ventilation openings into the suspension member is advantageous in that it eliminates the need for an additional separate aluminum disc on which the ventilation openings are located.

[0030] Preferably, the sub-assembly further comprises a housing fixed to the outer surface of the MEMS microphone, the housing defining the outer boundary of the sub-assembly's rear volume. The sub-assembly housing is further advantageous in that, during undesirable impact events, the movement of one or more movable masses is restricted by the sub-assembly housing on one side and the outer surface of the MEMS microphone on the other side. Thus, the maximum travel distance of one or more movable masses is limited.

[0031] As already mentioned, a MEMS microphone preferably comprises a pressure-sensing element such as a MEMS cartridge and a signal processing device for processing electrical signals from the pressure-sensing element.

[0032] In relation to suspension members, the viscoelastic material forming the suspension member is preferably selected from the group of thermosetting elastomers having a small Young's modulus and a large viscosity, such as silicone rubber.

[0033] In a second embodiment, the present invention relates to an auditory device comprising a micro-electromechanical transducer according to the first embodiment. Preferably, the auditory device of the second embodiment is a hearing aid, an audible device, an earphone, or a similar device.

[0034] In general, various aspects of the present invention can be combined and combined in any way possible within the scope of the invention. These and other aspects, features, and / or advantages of the present invention will become apparent from the embodiments described hereafter and will be made apparent by reference to those embodiments.

[0035] The present invention will be described in further detail here with reference to the accompanying drawings. [Brief explanation of the drawing]

[0036] [Figure 1a] This is a cross-sectional view of a first embodiment of the present invention having a spacer in which a suspension member is integrated. [Figure 1b] This is a cross-sectional view of a first embodiment of the present invention having a spacer in which a suspension member is integrated. [Figure 2a] This is a cross-sectional view of a second embodiment of the present invention, in which the suspension member is a film of viscoelastic material stretched between spacer portions. [Figure 2b] This is a cross-sectional view of a second embodiment of the present invention, in which the suspension member is a film of viscoelastic material stretched between spacer portions. [Figure 3] This is a cross-sectional view of a third embodiment of the present invention, in which the suspension member is a membrane covered with a viscoelastic material, and the rear volume of the MEMS microphone and the sub-assembly are acoustically connected. [Modes for carrying out the invention]

[0037] In general, the present invention relates to a micro-electromechanical transducer, such as a vibration sensor, comprising a MEMS microphone and a sub-assembly fixed thereto. The role of the sub-assembly is to generate a pressure change in the coupling volume when the micro-electromechanical transducer is exposed to vibration, and the role of the MEMS microphone is to detect this pressure change and convert it into an electrical output signal. Therefore, according to the present invention, the sub-assembly forms part of a pressure generation configuration for generating a pressure change, and the MEMS microphone forms part of a pressure detection configuration for detecting the pressure change, which is in particular the pressure change generated by the sub-assembly.

[0038] Figure 1a shows a first embodiment of a vibration sensor 1 comprising a MEMS microphone and a subassembly positioned on top of the MEMS microphone. As will be discussed in more detail later, the MEMS microphone comprises a MEMS cartridge 5 (pressure sensing element) and a signal processing device 7 for processing the electrical signal generated by the MEMS cartridge 5 when exposed to vibration. The MEMS cartridge 5 of the MEMS microphone can be fitted with various detection schemes, including piezoelectric, charged plate capacitor, etc. The signal processing device 7 of the MEMS microphone can operate in the analog or digital domain, applying any digital coding scheme.

[0039] The MEMS microphone further comprises a housing having an upper PCB (printed circuit board) 2 and a lower PCB 3 on which electrodes (not shown) for electrically connecting to a vibration sensor 1 are provided. The electrodes may be in the form of solder pads. A wall portion 4 is provided between the upper PCB 2 and the lower PCB 3, and an acoustic opening 12 is provided in the upper PCB 2. As will be discussed in more detail later, the acoustic opening 12 acoustically connects the coupling volume 15 between the subassembly and the MEMS microphone to the front volume 6 of the MEMS cartridge 5.

[0040] The MEMS cartridge 5 of the MEMS microphone comprises a thin film 17 and a front volume 6. The MEMS microphone further comprises a rear volume 14, within which the signal processing device 7 is located. As previously specified, the subassembly is located on top of the MEMS microphone. As seen in Figure 1a, the subassembly is fixed to the outer surface of the upper PCB 2, and the MEMS cartridge 5 and the signal processing device 7 are fixed to the inner surface of the same PCB, i.e., the inner surface of the upper PCB 2.

[0041] The sub-assembly comprises a housing 8, a suspension member 11, a support 10, and a movable mass 9 fixed to the support 10. The suspension member 11 may have an acoustic opening (not shown) so as to connect the coupling volume 15 and the rear volume 13.

[0042] When the entire vibration sensor 1 is exposed to vibration, the movable mass 9 and support 10 move relative to the upper PCB 2, creating a pressure change in the coupling volume 15. This pressure change is detected by the MEMS microphone through the aperture 12, and the MEMS microphone converts the detected pressure change into an electrical output signal.

[0043] The suspension member 11 is preferably manufactured, i.e., molded, using a viscoelastic material such as silicone rubber that is essentially non-plastically deformable. It is advantageous that the suspension member 11 combines three functions—support, sealing, and damping—in a single element, in which the viscoelasticity of the suspension member 11 determines the mechanical stiffness and damping of the pressure generating configuration, i.e., the suspension member 11, the support 10, and the movable mass 9.

[0044] The housing 8 of the subassembly can be made from any suitable material, as long as it completely seals the inside of the subassembly. Preferably, a thin shielding material is applied. Small holes in the housing 8 with low-frequency roll-off of less than 10 Hz may be acceptable because such small holes do not introduce acoustic noise.

[0045] The mass of the movable mass 9 is preferably about 4 mg. The practical minimum mass is estimated to be about 0.004 mg in order to increase the noise level by 30 dB. Similarly, a mass of 0.04 mg increases the noise level by 20 dB, and a mass of 0.4 mg increases the noise level by 10 dB. Therefore, as the mass of the movable mass 9 increases, the influence of the thermal transfer noise of the vibration sensor becomes smaller. As can be seen in FIG. 1a, the movable mass 9 abuts against the suspension member 11 at the interface surface 16. Therefore, although it is fixed to the support 10, the suspension member 11 also supports the movable mass 9.

[0046] Still referring to FIG. 1a, a small coupling volume 15 exists between the suspension member 11, the support 10, and the upper side of the upper PCB 2. This coupling volume 15 should be made as small as possible. Preferably, the coupling volume 15 is smaller than 2 mm 3 such as smaller than 1 mm 3 such as smaller than 0.75 mm 3 such as smaller than 0.5 mm 3 such as smaller than 0.25 mm 3 such as smaller than 0.1 mm 3 such as smaller than 5 mm 3 is smaller.

[0047] Referring to Figure 1b, the details of the suspension member 11 are depicted. As seen in Figure 1b, the suspension member has three parts in cross-sectional view: an outer portion 11', an inner portion 11'', and a central portion 11'''', with a recess 18 separating the inner portion 11'' from the outer portion 11'. Also depicted in Figure 1b (and Figure 1a), the thickness of the outer portion 11' is greater than the thickness of the inner portion 11''. This allows the support 10 to be fixed to the inner portion 11'' of the suspension member and the coupling volume 15 to be formed beneath the support 10. The outer portion 11' of the suspension member is fixed to the outer surface of the upper PCB 2 of the MEMS microphone. Thus, the volume of the coupling volume 15 is determined by the thickness of the outer portion 11' of the suspension member. The viscoelasticity of the suspension member is mainly determined by the central portion 11''' due to the reduced thickness of the central portion 11''''. Preferably, the outer portion 11', inner portion 11'', and central portion 11''' of the suspension member form a molded, one-piece structure made of silicone or rubber.

[0048] Preferably, the viscoelastic material of the suspension member 11 should be able to withstand typical reflow temperatures, as reflow soldering is a critical issue in relation to modern manufacturing processes. To meet the requirements of modern reflow soldering, the viscoelastic material should be able to withstand temperatures of at least 80°C, such as at least 100°C, at least 120°C, at least 150°C, at least 200°C, at least 250°C, at least 300°C, at least 350°C, at least 400°C, etc.

[0049] The total area between the suspension member 11 and the support 10 should be as large as possible, up to 1 mm 2 Larger than, for example, 2mm 2 Larger than 4mm 2 Larger than 6mm 2 Larger than 8mm 2 Larger than 10mm 2 Larger than, preferably 0.5 mm2 It should be larger. A larger overall area is advantageous because it requires only a smaller amplitude of movement of the movable mass 9 to reach sensitivity by reaching a certain volume change.

[0050] Optionally, the rear volume 13 above the suspension member 11 and the movable mass 9 can be acoustically coupled to the rear volume 14 of the MEMS microphone. This acoustic coupling (not shown) can be provided by various means, such as further openings in the upper PCB 2, as discussed in detail in relation to Figure 3.

[0051] Figure 2a depicts a second embodiment of the vibration sensor 19. Similar to the embodiment shown in Figure 1a, the vibration sensor depicted in Figure 2a also comprises a subassembly mounted on a MEMS microphone, which includes a MEMS cartridge 23 (pressure sensing element), and a signal processing device 26 for processing the electrical signal generated by the MEMS cartridge 23 when the vibration sensor is exposed to vibration. The MEMS cartridge 23 of the MEMS microphone can again be fitted with various detection schemes, including piezoelectric, charged plate capacitor, etc., and the signal processing device 26 can operate in the analog or digital domain, applying any digital encoding scheme.

[0052] The MEMS microphone also comprises a housing having an upper PCB 20 and a lower PCB 21 on which electrodes (not shown) for electrically connecting to a vibration sensor 19 are provided. The electrodes may be in the form of solder pads. A wall portion 22 is provided between the upper PCB 20 and the lower PCB 21, and an acoustic opening 33 is provided in the upper PCB 20. The acoustic opening 33 acoustically connects the coupling volume 36 and the front volume 24 of the MEMS cartridge.

[0053] Similar to the study related to Figure 1a, the MEMS cartridge 23 of the MEMS microphone comprises a thin film 25 and a front volume 24. The MEMS microphone further comprises a rear volume 37, in which a signal processing device 26 is located.

[0054] As specified above, the subassembly is fixed to the upper PCB 20 of the MEMS microphone. As can be seen in Figure 2a, the subassembly is fixed to the outer surface of the upper PCB 20, and the MEMS cartridge 23 and the signal processing device 26 are fixed to the inner surface of the same PCB, i.e., the inner surface of the upper PCB 20.

[0055] The sub-assembly comprises a housing 27, a suspension member 30 in the form of a membrane, and movable masses 28 and 29 fixed to the surfaces on both sides of the suspension member 30. The suspension member 30 may be a single-layer membrane or a multi-layer membrane, and may have an acoustic opening (not shown) so that the coupling volume 36 and the rear volume 35 are acoustically connected.

[0056] When the entire vibration sensor 19 is exposed to vibration, the movable masses 28 and 29 move relative to the cup-shaped spacer structure 31, and the suspension member 30 acts as a thin film that creates a pressure change in the coupling volume 36 in response to the vibration. This pressure change is detected by MEMS microphones through apertures 33 and 34, and the MEMS microphones convert the detected pressure change into an electrical output signal.

[0057] The suspension member 30 is preferably manufactured from a viscoelastic material, and preferably takes the form of a silicone rubber membrane that is essentially non-plastically deformable. It is also advantageous that the suspension member 30 combines three functions, namely support, sealing, and damping, in a single element, in that the viscoelasticity of the suspension member 30 determines the mechanical stiffness and damping of the suspension member 30 in combination with the pressure generating configuration, i.e., the movable masses 28, 29. However, it should be noted that a single movable mass may replace the two movable masses 28, 29 depicted in Figure 2a. This single movable mass may be fixed to either the upper or lower surface of the suspension member 30.

[0058] As depicted in Figure 2a, the suspension member 30 is spanned across a cup-shaped spacer structure 31 having a peripheral edge to which the suspension member 30 is fixed. An additional edge 32 is positioned on top of the suspension member 30. The cup-shaped spacer structure 31 includes an opening 34 that is aligned with an opening 33 in the upper PCB 20 so that the coupling volume 36 is acoustically connected to the front volume 24 of the MEMS cartridge.

[0059] The housing 27 of the subassembly can be made from any suitable material, as long as it completely seals the inside of the subassembly. Preferably, a thin metal shield is applied. Small holes in the housing 27 with low-frequency roll-off below 10 Hz may be acceptable because such small holes do not introduce acoustic noise.

[0060] The total mass of the movable masses 28 and 29 is preferably about 4 mg. As mentioned above, the practical minimum mass is estimated to be about 0.004 mg, as this increases the noise level by 30 dB. Similarly, a mass of 0.04 mg increases the noise level by 20 dB, and a mass of 0.4 mg increases the noise level by 10 dB. Therefore, as the mass of the movable masses 28 and 29 increases, the effect of thermal transfer noise on the vibration sensor decreases.

[0061] Referring further to Figure 2a, a small coupling volume 36 exists between the suspension member 30, the movable mass 29, and the bottom portion of the cup-shaped spacer structure 31. Preferably, the coupling volume 36 should be as small as possible, 2 mm 3 Smaller, such as 1mm 3 Smaller, such as 0.75mm 3 Smaller, such as 0.5mm 3 Smaller, such as 0.25mm 3 Smaller, such as 0.1 mm 3 Smaller, preferably 5 mm 3 It should be smaller.

[0062] Referring here to Figure 2b, the details of the membrane-based suspension member 30 are depicted. As seen in Figure 2b, the movable masses 28 and 29 are fixed to the surfaces on both sides of the suspension member 30. As already specified, the opening 34 in the cup-shaped spacer structure 31 is aligned with the opening 33 in the upper PCB 20 of the MEMS microphone, thereby acoustically coupling the coupling volume 36 to the front volume 24 of the MEMS cartridge 23. The suspension member 30 can be composed of a single viscoelastic layer, as already mentioned, or alternatively, of multiple viscoelastic layers.

[0063] Preferably, the viscoelastic material of the suspension member 30 should be able to withstand typical reflow temperatures, as reflow soldering is a critical issue in relation to modern manufacturing processes. To meet the requirements of modern reflow soldering, the viscoelastic material should be able to withstand temperatures of at least 80°C, such as at least 100°C, at least 120°C, at least 150°C, at least 200°C, at least 250°C, at least 300°C, at least 350°C, at least 400°C, etc.

[0064] The overall area of ​​the suspension member 30 should be as large as possible, 1 mm 2 Larger than, for example, 2mm 2 Larger than 4mm 2 Larger than 6mm 2 Larger than 8mm 2 Larger than 10mm 2 Larger than, preferably 0.5 mm 2 It should be larger. A larger overall area is advantageous because it requires only a smaller amplitude of movement of the movable masses 28, 29 to reach sensitivity by reaching a certain volume change.

[0065] Similar to the embodiment depicted in Figure 1a, the rear volume 35 above the suspension member 30 and the movable masses 28, 29 can be acoustically coupled to the rear volume 37 of the MEMS microphone. This acoustic coupling (not shown) can be provided by various means, such as further openings in the upper PCB 20, as discussed in relation to Figure 3.

[0066] Figure 3 shows a third embodiment of the vibration sensor 38. Similar to the previous embodiment, the vibration sensor depicted in Figure 3 also comprises a subassembly placed on a MEMS microphone equipped with a MEMS cartridge 42 (pressure sensing element), and a signal processing device 45 for processing the electrical signal generated by the MEMS cartridge 42. The MEMS cartridge 42 of the MEMS microphone can again be fitted with various detection schemes, including piezoelectric, charged plate capacitor, etc., and the signal processing device 45 can operate in the analog or digital domain, applying any digital encoding scheme.

[0067] Here too, the MEMS microphone comprises a housing having an upper PCB 39 and a lower PCB 40 on which electrodes (not shown) for electrically connecting to a vibration sensor 38 are provided. The electrodes may be in the form of solder pads. A wall portion 41 is provided between the upper PCB 39 and the lower PCB 40, and acoustic openings 51 and 52 are provided in the upper PCB 39. The acoustic opening 51 acoustically connects the coupling volume 54 to the front volume 43 of the MEMS cartridge 42, and the opening 52 acoustically connects the rear volume 53 of the sub-assembly to the rear volume 55 of the MEMS microphone.

[0068] Similar to the previous study, the MEMS cartridge 42 of the MEMS microphone comprises a thin film 44 and a front volume 43. The signal processing device 45 is located in the rear volume 55 of the MEMS microphone. The subassembly is fixed to the outer surface of the upper PCB 39 of the MEMS microphone and comprises a housing 46, a suspension member 48 in the form of a draped film, and a movable mass 47 fixed to the suspension member 48. The suspension member 48 may be a single-layer film or a multi-layer film, and may have an acoustic opening (not shown) so that the coupling volume 54 and the rear volume 53 are acoustically connected. The MEMS cartridge 42 and the signal processing device 45 are fixed to the inner surface of the upper PCB 39.

[0069] When the vibration sensor 38 is exposed to vibration, the movable mass 47 moves relative to the spacer 49, and the suspension member 48 (the suspended membrane) acts as a thin film that creates a pressure change in the coupling volume 54. This pressure change is detected by the MEMS microphone through the aperture 51, and the MEMS microphone converts the detected pressure change into an electrical output signal.

[0070] The suspension member 48 is manufactured from a viscoelastic material, and preferably takes the form of a silicone rubber membrane that is essentially non-plastically deformable. It is also advantageous that the suspension member 48 combines three functions, namely support, sealing, and damping, in a single element, in that the viscoelasticity of the suspension member 48 determines the mechanical stiffness and damping of the suspension member 48 when combined with the pressure generating configuration, i.e., the movable mass 47.

[0071] An anti-sticking layer 50 is provided on the lower surface of the suspension member 48 to prevent the suspension member 48 from sticking to the outer surface of the upper PCB 39 during large deflections.

[0072] As already mentioned, the suspension member 48 may consist of a single viscoelastic layer, or alternatively, multiple viscoelastic layers. Preferably, the viscoelastic material of the suspension member 48 should be able to withstand typical reflow temperatures, i.e., the viscoelastic material should be able to withstand temperatures of at least 80°C, such as at least 100°C, at least 120°C, at least 150°C, at least 200°C, at least 250°C, at least 300°C, at least 350°C, at least 400°C, etc.

[0073] As depicted in Figure 3, the suspension member 48 is distanced from the upper PCB 39 using a spacer 49, which may be a separate spacer or a spacer that forms an integral part of the upper PCB 39. The housing 46 of the subassembly can be made from any suitable material, as long as it completely seals the inside of the subassembly. Preferably, a thin metal shield is applied. Small holes in the housing 46 with low-frequency roll-off of less than 10 Hz may be acceptable because such small holes do not introduce acoustic noise.

[0074] The mass of the movable mass 47 is preferably about 4 mg. As mentioned above, the practical minimum mass is estimated to be about 0.004 mg, as this increases the noise level by 30 dB. Similarly, a mass of 0.04 mg increases the noise level by 20 dB, and a mass of 0.4 mg increases the noise level by 10 dB. Therefore, as the mass of the movable mass 47 increases, the effect of thermal transfer noise on the vibration sensor decreases.

[0075] Referring further to Figure 3, a small coupling volume 54 exists between the suspension member 48 and the upper PCB 39. This coupling volume should be as small as possible, approximately 2 mm. 3 Smaller, such as 1mm 3 Smaller, such as 0.75mm 3 Smaller, such as 0.5mm 3 Smaller, such as 0.25mm 3 Smaller, such as 0.1 mm3 Smaller, preferably 5 mm 3 It should be smaller.

[0076] The total area of ​​the suspension member 48 should be as large as possible, 1 mm 2 Larger than, for example, 2mm 2 Larger than 4mm 2 Larger than 6mm 2 Larger than 8mm 2 Larger than 10mm 2 Larger than, preferably 0.5 mm 2 It should be larger. A larger overall area is advantageous because it requires only a smaller amplitude of movement of the movable mass 47 to reach sensitivity by reaching a certain volume change. Furthermore, the movable mass 47 can be maximized by molding, while simultaneously keeping the surface connection to the suspension member 48 as small as possible. A smaller film area relative to the mass provides a larger suspension member gap 56, which is advantageous in that it ensures greater compliance of the suspension member 48.

[0077] Although the present invention has been discussed above with reference to exemplary embodiments, the present invention is not limited to these specific embodiments and can be modified in many ways without departing from the invention. Therefore, the exemplary embodiments discussed are not to be used to interpret the appended claims strictly by any means. Rather, the embodiments are not intended to limit the claims to these exemplary embodiments, but merely to illustrate the expression of the appended claims. Thus, the scope of protection of the present invention shall be interpreted solely according to the appended claims, and any ambiguity in the expression of the claims shall be resolved by using these exemplary embodiments. [Explanation of Symbols]

[0078] 1. Vibration sensor 2 Upper PCB 3 Lower PCB 4 Wall section 5 MEMS cartridges 6 Front volume 7 Signal Processing Device 8 cabinets 9 Movable mass 10 Support 11 Suspension components 11' outer part 11'' inner part 11''' center part 12 aperture 13 After volume 14 After volume 15 Combined volume 16. Interface 17 Thin film 18. Indentation 19. Vibration Sensor 20 Upper PCB 21 Lower PCB 22 Wall section 23 MEMS cartridges 24 Front volume 25 Thin Films 26 Signal Processing Equipment 27 cabinets 28, 29 Movable mass 30 Suspension components 31 Spacer structure 32 En 33, 34 aperture 35 After volume 36 Combined volume 37 Back volume 38. Vibration Sensor 39 Upper PCB 40 Lower PCB 42 MEMS cartridges 43 Front volume 44 Thin film 45 Signal Processing Equipment 46 cabinets 47 Movable mass 48 Suspension components 49 Spacers 50 Anti-sticking layer 51, 52 aperture 53 Back volume 54 Combined volume 55 After volume 56 Suspension component gap

Claims

1. A micro electromechanical transducer (1, 19, 38) comprising a pressure sensing configuration and a sub-assembly adapted to cooperate with the pressure sensing configuration via coupling volumes (15, 36, 54), wherein the sub-assembly is One or more movable masses (9, 28, 29, 47) Suspension members (11, 30, 48) supporting several movable masses (9, 28, 29, 47) and Equipped with, The coupling volumes (15, 36, 54) are defined at least partially by the suspension members (11, 30, 48), and the coupling volumes (15, 36, 54) are acoustically connected to the internal volumes (6, 24, 43) of the pressure detection configuration. The suspension members (11, 30, 48) include a viscoelastic material having predetermined viscosity and sealing properties for attenuating one or more resonance peaks of the micro electromechanical transducers (1, 19, 38) and for acoustically sealing the coupling volume (15, 36, 54), wherein the micro electromechanical transducers (1, 19, 38) are micro electromechanical transducers (1, 19, 38).

2. The miniature electromechanical converter (1) according to claim 1, wherein the suspension member (11) surrounds a support structure (10) to which it is fixed, and one or more movable masses (9) are fixed to the support structure (10).

3. The suspension member (11) comprises, in the cross-sectional contour, an inner portion (11'') having an inner thickness and an outer portion (11') having an outer thickness, wherein the outer thickness is greater than the inner thickness, the micro electromechanical transducer (1) according to claim 2.

4. The micro electromechanical transducer (1) according to claim 3, wherein a recess (18) is formed between the inner portion (11'') and the outer portion (11') of the suspension member.

5. The micro electromechanical transducer (1) according to claim 3 or 4, wherein the outer portion (11') of the suspension member (11) is fixed to the outer surface of the pressure detection configuration.

6. The micro electromechanical transducer (19) according to claim 1, wherein the suspension member (30) comprises a membrane of viscoelastic material stretched between spacer portions, and one or more movable masses (28, 29) are fixed to one or both sides of the stretched membrane (30).

7. The micro electromechanical transducer (19) according to claim 6, wherein the spacer portion constitutes at least a part of the peripheral edge, further comprising a central recess surrounded by the peripheral edge of the spacer structure (31).

8. The micro electromechanical transducer (19) according to claim 7, wherein the spacer structure (31) comprises a ventilation opening (34) adjacent to the opening (33) on the outer surface of the pressure detection configuration.

9. The micro electromechanical transducer (38) according to claim 6, wherein the spacer portion is fixed to the outer surface of the pressure detection configuration or forms a peripheral spacer (49) that forms a part of the outer surface of the pressure detection configuration.

10. The micro electromechanical transducer (38) according to claim 9, wherein the outer surface of the pressure detection configuration is provided with a further opening (52), and the further opening (52) acoustically connects the rear volume (53) of the sub-assembly with the rear volume (55) of the pressure detection configuration.

11. The subassembly further comprises a housing (8, 27, 46) fixed to the outer surface of the pressure detection configuration, wherein the housing sets the outer boundary of the volume after the subassembly (13, 35, 53), according to any one of claims 1 to 10 (1, 19, 38).

12. The pressure detection configuration comprises a pressure sensing element (5, 23, 42) and a signal processing device (7, 26, 45) for processing electrical signals from the pressure sensing element (5, 23, 42), as described in any one of claims 1 to 11 (1, 19, 38).

13. The viscoelastic material forming the suspension members (11, 30, 48) is selected from the group of thermosetting elastomers having a small Young's modulus and a large viscosity, such as silicone rubber, as described in the micro electromechanical transducer (1, 19, 38) according to any one of claims 1 to 12.

14. The pressure detection configuration comprises a MEMS microphone, according to any one of claims 1 to 13 (1, 19, 38).

15. An auditory device comprising a micro-electromechanical transducer (1, 19, 38) according to any one of claims 1 to 14, which is a hearing aid, an audible device, an earphone, or a similar device.

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