Vibration reduction of electronic components using vibroacoustic metamaterials

Abstract

A device for reducing mechanical vibrations on an electronic component (1), comprising an array (2) of local resonators (3) adjusted such that each resonator has at least one natural frequency in a relevant frequency range, wherein the array (2) of local resonators (3) is configured to generate at least one stop band for the propagation of mechanical waves in the electronic component (1) in the relevant frequency range.

Description

Technical Field

[0001] The present invention relates to a device for reducing vibrations in electronic components based on vibroacoustic metamaterials.

Background Art

[0002] Mechanical vibrations are a relevant form of stress on electrical components, which can thereby reduce the service life and significantly increase the probability of failure. For example, vibrations can cause fatigue failure at the contact points and, in the worst case, lead to system failure. Large mechanical loads can also temporarily impair the function of electronic components. These problems affect, in particular, capacitors, diodes, and transistors, but also more complex components such as sensors and integrated circuits. Thus, in addition to reducing the reliability of the affected electronic systems and increasing maintenance costs, mechanical vibrations can also pose safety-related problems in fields such as automotive or aircraft technology.

[0003] To reduce the loads on these electronic components due to mechanical vibrations, a connecting element made of silicone or elastomer is used, for example, to separate the printed circuit board from the component transmitting the vibration. However, such a "soft" connection is not practical or desirable under all conditions and is ineffective, for example, when connecting a printed circuit board to a cable. Also, by enclosing the affected components in a potting compound, they can be protected from the effects of vibration, but such enclosure can also have a negative impact on the functions of some components and generally increase the required installation space. However, when vibrations cannot be avoided or components cannot be effectively protected, special components are often used. These have a stronger form and are sometimes too large and have additional contacts, for example, to ensure a secure connection between the component and the printed circuit board. However, such components have drawbacks with regard to mass and space requirements in many fields of application, needless to say.

[0004] Vibration acoustic metamaterials can be used to overcome the drawbacks of conventional methods of vibration attenuation for electronic components. A metamaterial is an artificial and usually periodic structure configured to achieve special conductive, insulating, damping, or strengthening properties. Thus, for example, a structure can be provided that forms a stop band. A stop band is a frequency range in which wave propagation is significantly attenuated. In vibration acoustic metamaterials, this concept is used to control and manipulate the propagation of mechanical waves. The properties of solids such as density, compressibility modulus, and elastic modulus are relevant in this context. A periodic arrangement of resonant structures, so-called local resonators, is one way to generate a stop band using vibration acoustic metamaterials. Due to the interaction of the local resonators with the environment, the resulting structure behaves as if it has a negative effective mass in a specific frequency range, and as a result, wave propagation is strongly impeded for this range. In order to generate a strong stop band, all individual resonators need to be tuned to the same frequency. Deviations in the periodicity and frequency tuning of the resonators result in a wider but less distinct stop band. By successfully designing vibration acoustic metamaterials, a desired frequency range in which the propagation of mechanical vibrations is attenuated can be set.

[0005] Therefore, the object of the present application for protection is to propose a device for attenuating the propagation of mechanical vibrations in a frequency range. At the same time, this device should have advantages over conventional methods of vibration attenuation in electronic components from the perspectives of installation space requirements, weight, heat dissipation, and handling.

[0006] This object is achieved by a device for reducing mechanical vibrations on an electronic component according to independent claim 1.

[0007] Such a device for reducing mechanical vibrations on an electronic component comprises an array of local resonators adjusted such that each resonator has at least one natural frequency in the relevant frequency range, where the array of local resonators is configured to generate at least one stop band for the propagation of mechanical waves in the electronic component in the relevant frequency range.

[0008] The electronic component is, for example, an electrical component such as a capacitor, resistor, coil, diode and transistor, but also a more complex component such as a sensor and an integrated circuit. However, in the context of the present application, the term "electronic component" is also intended to include elements such as connectors, cables, switches and relays, as well as other electrical, electromechanical or mechanical components used in electronic devices and systems.

[0009] The electronic component is provided with an array of local resonators for reducing vibration. This array of local resonators forms a vibroacoustic metamaterial. The array can be two-dimensional, i.e., planar, or three-dimensional in space. Each individual resonator consists of at least one vibrating mass and one spring element. The vibrating mass can have any shape and dimensions and can be made of different materials. The mass of the vibrating mass is an important factor in adjusting the vibration frequency of the resonator. The spring element has elastic properties. The spring element can be formed integrally with the vibrating mass. It can also be a single elastic element such as a leaf spring. The spring element can have any shape and dimensions. In particular, the shape and dimensions of the spring element are important factors in adjusting the vibration frequency of the resonator. The spring element can be made of the same material as the vibrating mass or, for example, an elastomer. It should be noted that the vibrating mass and the spring element are not necessarily clearly distinguishable from each other. The vibrating mass and the spring element can be formed integrally, and the vibrating mass can also deform during vibration. The vibrating mass, the spring element, and a specific region around the resonator form a unit cell of the resonator. The array of local resonators consists of a spatial repetition of these unit cells.

[0010] Each individual resonator has at least one first associated resonance vibration frequency. When stimulated at the resonance vibration frequency, the magnitude of the vibration of the resonator is maximized. The resonance vibration frequency of the resonator is determined by the characteristics of the entire unit cell. In addition to the masses of the vibrating mass and the spring element and the elastic properties of the spring element, the shape, mass, and elasticity of the surrounding structure also play a role. Therefore, the vibration frequency of the resonator can be adjusted by varying these characteristics. The unit cell needs to be on the order of or smaller than half the wavelength of the first associated vibration frequency.

[0011] All local resonators of the metamaterial are tuned to the same or at least approximately the same resonant frequency. This forms a stop band around this frequency, significantly attenuating wave propagation in the metamaterial and the electronic components provided therewith. By adjusting the resonant frequency of the local resonator, a stop band can be formed that limits the propagation of mechanical waves in the electronic component. If the resonator has multiple resonant frequencies in the relevant frequency range, multiple stop bands can occur around them. These multiple stop bands can separately reduce vibrations in different frequency ranges or can form a large stop band by overlapping.

[0012] The arrangement of local resonators can be periodic. The periodic structure results from the spatial repetition of the unit cell of the local resonator.

[0013] To ensure the preferred behavior of the array, the distance between local resonators in the array of local resonators can be less than half the wavelength of the first relevant frequency. Together with the unit cell of the local resonator that is on the order of half the wavelength of the first frequency, the dispersion behavior of the array can also be independent of direction.

[0014] A periodic array of local resonators with a distance equal to or less than half the wavelength can also ensure that at least one additional stop band formed by Bragg scattering in the array is formed in the tool. Thus, the additional stop band can be utilized by additional frequencies.

[0015] The additional stop band can also be generated by forming the local resonator in such a way that it has multiple resonant frequencies. Further, the array of local resonators can be selected in such a way that it provides additional resonant frequencies for the array by using resonators with different relevant frequencies in the array or by using additional stop bands due to the shape of the array.

[0016] When individual local resonators are adjusted to be slightly different, the stop band can be broadened by the first resonance frequency. However, also, its sharpness is lost and the reduction of vibrations in this frequency range becomes less pronounced. However, these effects may be desirable. In addition, for example, if additional forces are expected to act on specific regions of the array, slightly different frequency adjustments of the resonators may be useful to adapt the resonators to their positions in the array of local resonators.

[0017] At least some of the local resonators can be embodied as bending beam resonators. This is a beam that is clamped, i.e., fixed, at one end and the other end can vibrate freely, i.e., a general rectangular parallelepiped body. This embodiment has advantages from the viewpoints of simplicity of construction and adjustability of the resonance frequency, which can be controlled by the dimensions of the beam and the support points. Here, it should be noted that the beam does not necessarily have to be a classical long beam and generally can be a prism attached on one side or at one point in such a way that it can vibrate. In particular, the resonator can also be formed by machining from the surrounding material as a plate connected at one corner. Another form of resonator that should be explicitly mentioned is the cross-shaped arrangement, which is coupled to a body that is damped at the center of the cross and has four vibrating masses at the ends of the arms of the cross. By selecting the shape of the resonator, the normal vibration modes of the resonator, and their natural frequencies, and thus the frequency range of the stop band generated in the array can also be determined. The shape of the individual resonators does not have to be limited to those described here and can be selected according to each requirement. In particular, not all resonators in the array of local resonators have to have the same shape and can be adapted to the conditions of each position as long as they have approximately matching frequency adjustments.

[0018] To attach the local resonators to electronic components or support structures, they can be provided with soldering pins or soldering surfaces. By using standardized connections, the application of the resonators can be easily integrated into conventional industrial manufacturing processes.

[0019] The local resonator can be directly applied to the electronic component to be attenuated. In this way, while saving installation space, effective reduction of vibration can be achieved.

[0020] In particular, the local resonator can be integrally formed with the electronic component. Thereby, although the labor of construction increases, additional installation space can be saved. Such an example of constructing the local resonator integrally with the electronic component can be a bent connection pin that also functions as a flexural beam resonator. The array of local resonators can also be cut out from a wafer of chips.

[0021] Alternatively, the array of local resonators can also be arranged on the support structure of the electronic component. This can have the advantage that the electronic component can be installed without change and is not exposed to any additional influence. In addition, the array of local resonators can be embodied to form a stop band for vibrations in a plurality of electronic components arranged on the support structure. The array of local resonators on the support structure of the electronic component can directly surround it in order to attenuate the mechanical vibration in the component or to prevent vibration from occurring therein. The array can also be formed at or around the point where the support structure is coupled to the environment, specifically to attenuate the introduction of mechanical vibration to the support structure and the electronic component.

[0022] The simplest example of such a support structure can be a printed circuit board. In particular, by using a vibroacoustic metamaterial in the form of an array of local resonators, the flexural waves generated at the connection points of the printed circuit board due to the contact force in a strong connection can be removed. By applying the array of local resonators to a conventional printed circuit board, a device for reducing mechanical vibration can also be easily integrated into an existing manufacturing process.

[0023] The array of local resonators can also be formed integrally with the printed circuit board, i.e., can be cut out from the material of the printed circuit board. The resonator types already described are particularly suitable for this purpose, with individual plates being cut out from the material of the printed circuit board that are connected to the rest of the printed circuit board structure in the corner regions and thus being mounted so as to vibrate. A special form in which the array of local resonators is part of the printed circuit board can be a sandwich-structured printed circuit board where the local resonator is cut out from one of the inner layers of the printed circuit board. This embodiment can save additional installation space as the surface of the PCB for placing electronic components is ensured.

[0024] In a further form, the array of local resonators can be attached to the housing of a device comprising electronic components. In this way, mechanical vibrations can be reduced across the entire structure. In particular, it can be useful to surround the point where the support structure of the electronic components is coupled to the housing having the array of local resonators so as to prevent the introduction of mechanical vibrations.

[0025] The electronic component can be a cable. In this case, the array of local resonators can be applied directly to the outer periphery of the cable. In this way, the conduction of mechanical vibrations in the cable can be attenuated.

[0026] The local resonator can also be integrated into the heat sink. Thus, the space requirements can be further reduced by combining the attenuation of mechanical vibrations with the additional effect of heat dissipation that is already provided in the heat sink. To achieve this effect, the heat sink or fins need to be shaped such that they can act as local resonators.

[0027] Another possibility is to embody at least part of the local resonator as an active element, for example, as a miniaturized piezoelectric speaker. In this way, the natural frequency of the local resonator can be actively controlled, and thus, the characteristics of the generated stop band or stop bands can be adapted to specific conditions even if they are temporary.

[0028] The described embodiments of the subject matter of the present application can be used individually or in combination to achieve additional effects and provide a device provided with an array of local resonators for reducing mechanical vibrations of electronic components.

[0029] The above and other aspects of the invention will become apparent from the detailed description of exemplary embodiments with reference to the following drawings.

Brief Description of the Drawings

[0030]

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DETAILED DESCRIPTION OF THE INVENTION

[0031] In the following, the claimed subject matter will be described in more detail based on the accompanying drawings. Like reference numerals refer to like elements.

[0032] Figure 1 shows a simplified schematic representation of a device for reducing mechanical vibrations on an electronic component 1. The electronic component can be, for example, a capacitor, diode, transistor, sensor or integrated circuit. The electronic component 1 is arranged on a printed circuit board 4. The printed circuit board 4 is only shown schematically. It can also include other components, connections, and conductor tracks. The printed circuit board 4 can be made of an electrically insulating material, for example, a fiber composite plastic. The electronic component 1 is mechanically and electrically connected to the printed circuit board 4 via a plug-in or soldered connection. This connection can be one of the weaknesses in the function of the electronic component 1 when exposed to mechanical vibrations. For example, fatigue failure can occur in the soldered connection. To reduce the load on the electronic component 1 caused by mechanical vibrations, the component is provided with an array 2 of local resonators 3. The array 2 of local resonators 3 is applied directly to the electronic component 1. The local resonator is an L-shaped bending beam resonator, where the short beam of the L connects the longer beam to the surface of the electronic component 1. The array 2 includes a plurality of local resonators 3 in a periodic pattern.

[0033] A similar structure is also shown in Figure 2. In this figure, a larger array 2 of local resonators 3 embodied as bending beam resonators is shown, which is not mounted on the electronic component 1 but is mounted on a support plate 5 and arranged directly on the printed circuit board 4 via this. For example, this can be the back side of the printed circuit board 4, on the front side of which electronic components protected from mechanical vibrations are arranged. The presence of the array 2 of local resonators 3 on the back side of the printed circuit board 4 means that the entire installation space on the front side of the printed circuit board 4 can be used for the electronic component 1, and as a result, no special layout is required here. It should also be noted that all the figures in this application show the printed circuit board 4. However, it can also be a different support structure for the electronic component 1 depending on the application, and here the described concept can be easily transferred.

[0034] The arrays of local resonators shown in FIGS. 1 and 2 function similarly. All local resonators 3 have approximately the same frequency tuning. Therefore, the array 2 of local resonators 3 forms a vibroacoustic metamaterial having a negative effective mass characteristic in the frequency range around the resonant frequency of the local resonators 3. When the electronic component 1 or the printed circuit board 4 is externally stimulated or by the function of the electronic component 1 vibrating at this resonant frequency, it is strongly attenuated and the vibration energy is absorbed in the local resonator 3. This forms a stop band, i.e., a frequency range in which wave propagation in the electronic component 1 and the printed circuit board 4 is suppressed. Thereby, the mechanical vibrations acting on the electronic component 1 are significantly reduced. Since the local resonators can have multiple resonant frequencies depending on their embodiments, multiple stop bands can also be formed around other frequencies. These stop bands can include different frequency ranges or overlap to form an extended stop band. The individual local resonators can also be embodied with slightly different frequency tunings. This actually weakens the vibration reduction in the stop band range, but the stop band range widens.

[0035] Figures 3a and 3b show the local resonator 3 in a cross-shaped embodiment having four arms and a main beam at each end. This embodiment has additional normal modes and can be used to attenuate additional frequency ranges. However, the operating modes of this embodiment of the local resonator 3 otherwise correspond to the flexural beam resonators of FIGS. 1 and 2. FIGS. 3a and 3b also show how the local resonator 3 can be arranged on the printed circuit board 4. In FIG. 3a, the local resonator 3 has soldering pins 6 for this purpose. In FIG. 3b, the local resonator has soldering pads 7. The local resonator 3 can be attached to the printed circuit board 4 via the soldering pins 6 or the soldering pads 7, just like any other component. The local resonator 3 can be arranged by soldering, which is mainly a mechanical connection. This is because the resonator 3 shown does not require an electrical connection. This situation can be different if active elements such as piezoelectric speakers are used as the local resonator 3. To control them and thus adjust their natural frequencies, the soldering pins 6 / soldering pads 7 can also be configured for electrical connection. By using conventional fixing methods such as the soldering pins 6 or the soldering pads 7, the local resonator can be integrated into the standard printed circuit board manufacturing process with little effort. For example, conventional placement machines can be used to place the resonators 3 and then automatically solder them.

[0036] To ensure the formation of the stop band, the arrangement 2 of the local resonators 3 needs to be approximately periodic, and the distance between the local resonators 3 needs to be less than half of the wavelength of the relevant frequency. However, the position of the arrangement 2 of the local resonators 3 is also relevant. This is shown in FIGS. 4a - 4f. FIG. 4a provides an overview and shows the printed circuit board 4 with the electronic component 1 attached. This corresponds to the figure of FIG. 1 without the arrangement 2 of the local resonators 3. FIGS. 4b - 4f show plan views of the same printed circuit board and show other ways in which the arrangement 2 of the local resonators 3 can be distributed to reduce mechanical vibrations on the electronic component 1. The arrangement 2 of the local resonators 3 is shown here as the hatched area.

[0037] In FIG. 4b, the array 2 of local resonators 3 is applied directly to the electronic component 1. This corresponds to the embodiment shown in FIG. 1. This embodiment directly attenuates the relevant mechanical vibrations in the electronic component 1 and no additional installation space is required on the printed circuit board 4.

[0038] In FIG. 4c, the array 2 surrounds the electronic component 1 on the printed circuit board 4, and as a result, a stop band is formed therein in the relevant frequency range. This enables a wider array 2.

[0039] FIG. 4d shows an embodiment in which the array 2 is limited to the region around the connection point of the printed circuit board 4, and thus has a direct damping effect in that most of the mechanical vibrations are introduced into the printed circuit board 4.

[0040] FIGS. 4e and 4f additionally show the plug connection 8 on the printed circuit board 4. Since mechanical vibrations can also be introduced into the system consisting of the printed circuit board 4 and the electronic component 1 via such a plug connection 8, it may be advantageous to dampen these separately. In FIG. 4e, this is achieved by the array 2 of local resonators 3 arranged between the plug connection 8 and the electronic component 1, thus suppressing the propagation of mechanical vibrations to the latter.

[0041] In FIG. 4f, the array 2 of local resonators 3 is provided directly on the plug connection 8, thereby damping the vibrations introduced here.

[0042] Naturally, the application patterns shown in FIGS. 4b to 4f can also be combined with each other to protect the electronic component 1 against mechanical vibrations from different sources of origin.

[0043] Figures 5a and 5b show a printed circuit board 4 integrated with local resonators 3. In this figure, the local resonators 3 are formed integrally with the printed circuit board 4 and are then cut out directly, for example, by conventional drilling or milling. Thus, the individual resonators 3 are connected to the surrounding printed circuit board 4 via corners and thus consist of a square plate mounted to vibrate. The recess between the vibrating mass and the rest of the printed circuit board 4 can also be filled with an elastic damping compound. By exciting the local resonators 3 at their natural frequencies, a stop band can be formed in the printed circuit board 4. It should be noted that this embodiment is shown in a very simplified form in Figures 5a and 5b, as the arrangement 2 of the local resonators 3 extends across the entire printed circuit board. However, this also needs to accommodate at least one electronic component 1. For this purpose, the mounting pattern shown in Figures 4c - 4d can be used for an actual embodiment with integrated local resonators.

[0044] A further embodiment with integrated local resonators 3 is shown in Figure 6. This is a printed circuit board 4 with a sandwich structure consisting of at least three layers. The central layer 9 is provided with an arrangement 2 of local resonators 3, which in its function corresponds to the printed circuit board 4 shown in Figures 5a and 5b. However, in this embodiment, the arrangement 2 of the local resonators does not need to be limited to the area of the printed circuit board. Two cover layers 10 are used to accommodate electronic components.

[0045] Figures 7a and 7b show a further embodiment in which the array 2 of local resonators 3 is mounted not directly on the electronic component 1 or the printed circuit board 4, but on the housing 11. In this figure, the housing 11 surrounds the printed circuit board 4 and the electronic component 1. However, the housing can also cover other elements. It is also conceivable that the housing 11 directly covers the electronic component 1 without being disposed on the printed circuit board 4. The plan view in Fig. 7b shows that the array 2 of local resonators 3 is provided in a region surrounding the connection points where the printed circuit board 4 is coupled to the housing 11. The connection between the housing 11 and the printed circuit board 4 is usually made via a strong connection, so that mechanical vibrations are transmitted to the electronic component 1 through these points, which is particularly advantageous. However, for example, if other components that generate vibrations are disposed within the housing, it may also be useful to provide the array 2 of local resonators in other regions of the housing 11.

[0046] Figures 8a - 8c show how the array 2 of local resonators 3 can also be attached to the cable 12 in order to attenuate the propagation of mechanical vibrations therein. In Fig. 8a, the local resonator is in the shape of a disk, where the edge of the disk forms the vibrating mass of the resonator. Fig. 8b shows a cross-section of this cable. In Fig. 8c, an array 2 of flexural beam resonators is provided on the outer periphery of the cable. These arrays 2 of local resonators 3 can also be used to generate a stop band for the propagation of mechanical vibrations in the cable 12.

[0047] Figures 9a and 9b show the heat sink 13, whose cooling fins 14 also act as local resonators 3. For this purpose, a part of the cooling fins 14 is in the form of flexural beam resonators. Since the heat sink 13 includes a plurality of these fins, the array 2 of local resonators 3 can be realized in a simple manner. Since corresponding heat sinks are already provided in many electronic systems, no additional installation space is required and no additional effort is involved in construction and assembly.

[0048] Figure 10 shows a miniaturized embodiment of the concept. A MEMS sensor 15 is shown surrounded by an array 2 of local resonators 3 cut directly from a wafer of sensor chips. Thus, the array 2 of local resonators 3 is formed integrally with the electronic component 1, and the size of the local resonators 3 can be selected to form a stop band for mechanical wave propagation in the frequency range associated with the MEMS sensor.

[0049] The exemplary embodiments described herein clearly provide a space-saving option with less construction effort by using a vibroacoustic metamaterial formed by an array 2 of local resonators 3 to reduce mechanical vibrations on the electronic component 1. It can also be appreciated that there are multiple ways to attach such a vibroacoustic metamaterial to the electronic component 1, the printed circuit board 4, and the housing 11 so as to form an advantageous effect.

[0050] Therefore, the exemplary embodiments shown here are not limiting. In particular, these exemplary embodiments can be combined with each other to achieve additional effects. It is clear to those skilled in the art that modifications can be made to these exemplary embodiments without departing from the basic principles of the subject matter of this patent application as defined in the claims.

Claims

1. A device for reducing mechanical vibrations on an electronic component, an array of local resonators adjusted such that each resonator has at least one natural frequency in a relevant frequency range wherein the array of local resonators is configured to generate at least one stop band for the propagation of mechanical waves in the electronic component in the relevant frequency range. Device.

2. The device according to claim 1, wherein the array of local resonators is periodic.

3. The device according to claim 1, wherein the distance between the local resonators relative to each other is less than half a wavelength in the relevant frequency range.

4. The device according to claim 1, wherein the individual local resonators have slightly different frequency adjustments, such that the at least one stop band is broadened.

5. The device according to claim 1, wherein at least some of the local resonators are embodied as bending beam resonators.

6. The device according to any one of claims 1 to 5, wherein the local resonators are provided with soldering pins or soldering surfaces.

7. The device according to any one of claims 1 to 5, wherein the array of local resonators is directly attached to the electronic component.

8. The device according to any one of claims 1 to 5, wherein the array of local resonators is formed integrally with the electronic component.

9. The device according to any one of claims 1 to 5, wherein the array of local resonators is arranged on a support structure for the electronic component.

10. The device according to claim 9, wherein the support structure is a printed circuit board.

11. The device according to claim 10, wherein the arrangement of the local resonators is formed integrally with the printed circuit board.

12. The device according to any one of claims 1 to 5, wherein the array of local resonators is mounted within the housing of the electronic component.

13. The device according to any one of claims 1 to 5, wherein the array of local resonators is mounted on a cable.

14. The device according to any one of claims 1 to 5, wherein the local resonators are integrated into a heat sink.

15. The device according to any one of claims 1 to 5, wherein at least a part of the local resonator is embodied as an active element.

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