DE102020210076A1 - Sensor and method of making a sensor - Google Patents

Abstract

The invention relates to a sensor, in particular a pressure sensor, comprising a sensing element for detecting a property and/or composition of a medium surrounding the sensor, a transmission medium for transmitting a property and/or composition of the surrounding medium to the sensing element, the transmission medium being arranged in such a way that the Sensing element is acted upon by the transmission medium, the transmission medium being designed in such a way that it at least partially diffusely scatters and/or at least partially absorbs waves impinging on the transmission medium in at least one frequency range, in particular sound waves.

Description

technical field

The invention relates to a sensor, in particular a pressure sensor, comprising a sensing element for detecting a property and/or composition of a medium surrounding the sensor.

The invention further relates to a method for producing a sensor, in particular a pressure sensor.

State of the art

Although the present invention is generally applicable to any sensor, the present invention will be discussed in relation to barometric pressure sensors.

Barometric pressure sensors are used today in a variety of consumer electronics devices, such as smartphones and smart watches. The measurement signal from the pressure sensors is used, among other things, to determine the height, which makes it possible, for example, to determine the floor for indoor navigation. Since pressure sensors use the ambient pressure to detect an ambient property, the sensing element of the pressure sensor must have pressure-transmitting access to the environment. This requirement conflicts with the aim of making the consumer electronics device watertight: the known methods for watertight sealing do not permit sufficiently sensitive transmission of the ambient pressure signal to the sensing element of the pressure sensor.

To solve the problem, it has become known to use a gel for pressure transmission. In these pressure sensors, the sensing element is inside a housing. Once the chip has been mounted and wired, the inside of the housing is encapsulated with the gel. Because the gel tightly wets the inner sidewall of the sleeve, and because gel itself is waterproof, the sensing element is protected from an environmental medium such as water. The pressure signal is transmitted from the environment to the sensing element by the gel itself, as this is sufficiently flexible to function as a transmission medium.

During system integration, for example when installed in the smartphone housing, these pressure sensors are usually arranged in the immediate vicinity of the loudspeaker and/or microphone, since similar requirements regarding access to the environment apply to all these components. These components are usually arranged in a tubular duct that opens into the outer surface of the smartphone housing and thus ensures access to the ambient air for the microphone, loudspeaker and pressure sensor, but at the same time isolates the rest of the smartphone interior from the environment.

However, the close proximity of the gel-filled, waterproof pressure sensor to the speaker and/or microphone in a tubular duct creates a potential problem for the acoustic performance of the device. Due to their nature, the acoustic properties of the exposed gel of the pressure sensor can cause unwanted interactions with the loudspeaker and/or microphone, for example echoes or a reduction in signal strength due to interference. In particular, the concave shape of the gel surface, as is usually formed during the usual hardening/crosslinking of the gel, can act as a focusing reflector.

Disclosure of Invention

In one embodiment, the present invention provides a sensor, in particular a pressure sensor, comprising
a sensing element for detecting a property and/or composition of a medium surrounding the sensor,
a transmission medium for the transmission of a property and/or composition of the surrounding medium to the sensing element, wherein the transmission medium is arranged in such a way that the sensing element is acted upon by the transmission medium, wherein
the transmission medium is designed in such a way that it at least partially diffusely scatters and/or at least partially absorbs waves impinging on the transmission medium in at least one frequency range, in particular sound waves.

• - Bereitstellen eines Sensierelements,
• - Bereitstellen eines aushärtbaren Übertragungsmediums, sodass das Sensierelement von dem Übertragungsmedium beaufschlagt wird,
• - Aushärten des Übertragungsmediums, und
• - Ausbilden des Übertragungsmediums, sodass dieses in zumindest einem Frequenzbereich auf das Übertragungsmedium auftreffende Wellen, insbesondere Schallwellen, zumindest teilweise diffus streut und/oder zumindest teilweise absorbiert.

In a further embodiment, the present invention provides a method for producing a sensor, in particular a pressure sensor, comprising the steps

• - providing a sensing element,
• - Providing a curable transmission medium, so that the sensing element is acted upon by the transmission medium,
• - curing of the transmission medium, and
• Forming the transmission medium so that these waves, in particular sound waves, impinging on the transmission medium in at least one frequency range, at least partially diffusely scatters and/or at least partially absorbs.

The term "sound wave" is to be understood in the broadest sense and refers in particular in the claims, preferably in the description, to any progressive mechanical deformation in a surrounding medium.

One of the advantages achieved in this way is that if the sensor is unfavorably integrated into the system, unwanted interactions, for example with the loudspeaker and/or microphone in a terminal device, are avoided. A further advantage is that cost-intensive and time-consuming corrections to the arrangement of the sensor and microphone, loudspeaker or the like are avoided, in particular given that the undesired interactions are usually only discovered by testing functional near-series models.

Other features, advantages, and other embodiments of the invention are described below or will become apparent thereby.

According to a development, the transmission medium has a surface facing the transmission medium, on which scattering elements for diffuse scattering and/or for at least partial absorption are arranged and/or formed. In this way, a simple and efficient, at least partially diffuse, scattering and/or absorption is made possible.

According to a further development, the scattering elements are produced from the transmission medium. One of the possible advantages is that scattering elements can be provided in a cost-effective manner. A further possible advantage is that material stresses, for example in the event of temperature changes, do not occur if the scattering elements are made from the transmission medium.

According to a further development, the scattering elements are produced by indentations and elevations in the surface of the transmission medium. In this way, scattering elements can be provided in a particularly simple manner.

According to a further development, the scattering elements are distributed symmetrically on the surface of the transmission medium and/or arranged concentrically to at least one point on the surface. A possible advantage of this is that they can be manufactured in a simple and inexpensive manner.

According to a further development, the transmission medium is provided in the form of a hardened gel. A cost-effective and flexibly manageable transmission medium is thus provided.

According to a further development, the sensing element is arranged in a housing which is open on at least one side and the transmission medium fills the housing at least partially. A possible advantage of this is that the transmission medium can be arranged particularly easily in the uncured state and can be cured later since this is restricted by the housing.

According to a development of the method, the step of forming the transmission medium includes arranging and/or forming scattering elements on the surface. In this way, a simple and efficient, at least partially diffuse, scattering and/or absorption is made possible.

According to a further development of the method, the scattering elements are formed during the curing of the transmission medium. This improves the overall efficiency of the method, since the transmission medium and the arrangement or formation of the scattering elements are cured at the same time.

According to a further development of the method, the scattering elements are formed by means of a stamp which acts on the surface of the transmission medium and has a negative form of scattering elements. The advantage of a stamp is its ease of use. In addition, a large number of sensors can be provided with scattering elements by means of a stamp.

According to a further development of the method, before the step of forming the transfer medium, an intermediate layer is arranged between the stamp and the surface of the transfer medium, in particular in the form of a foil and/or a film, so that the stamp and the surface of the transfer medium are spaced apart during the formation of the transfer medium. This efficiently prevents possible contamination of the stamp: after each use of the stamp on a surface of a transmission medium, a new intermediate layer is arranged, with which a further embossing process can then be carried out to produce scattering elements on the surface of the transmission medium of another sensor. Material transfer through the stamping process between two sensors can thus be avoided.

Further important features and advantages of the invention result from the dependent claims, from the drawings and from the associated description of the figures based on the drawings.

It goes without saying that the features mentioned above and those still to be explained below can be used not only in the combination specified in each case, but also in other combinations or on their own, without departing from the scope of the present invention.

Preferred designs and embodiments of the invention are shown in the drawings and are explained in more detail in the following description, with the same reference symbols referring to identical or similar or functionally identical components or elements.

character list

• 1 einen Sensor gemäß einer Ausführungsform der vorliegenden Erfindung im Querschnitt während der Herstellung;
• 2 den hergestellten Sensor gemäß 1 in perspektivischer Ansicht;
• 3 den Sensor gemäß 2 im Querschnitt; und
• 4 Schritte eines Verfahrens gemäß einer Ausführungsform der vorliegenden Erfindung.

It shows in schematic form

• 1 a sensor according to an embodiment of the present invention in cross section during manufacture;
• 2 according to the manufactured sensor 1 in perspective view;
• 3 according to the sensor 2 in cross section; and
• 4 Steps of a method according to an embodiment of the present invention.

Embodiments of the invention

1 Figure 12 shows a sensor according to an embodiment of the present invention in cross-section during manufacture.

shows in detail 1 a sensor 1. The sensor 1 has a substrate 2 with a rewiring level (not shown). A housing in the form of a sleeve 6 is also arranged on the substrate 2 . A chipset 4 with at least one sensing element 4a is arranged in the sleeve 6 on the substrate 2 . The chipset 4 includes, for example, evaluation electronics for the sensing element. The sensing element 4a can be embodied as an MEMS. The sleeve 6 is thus closed by the substrate 2 on one side.

A gel 5 is now filled into the remaining opening 12 of the sleeve 6 until the sleeve 5 is essentially full. In 1 A stamp 7 is now pressed from above onto the surface of the gel 5 in the opening 12 . On its side facing the gel 5, the stamp 7 has a topography or structure 10 that includes elevations and depressions. Before the stamp 7 now comes into contact with the surface of the gel 5, a thin foil or an interposer film 8 is arranged between the gel surface and the stamp 7. This film 8 clings to the topography of the stamp surface and transfers the topography 10 of the stamp 7 to the gel surface. This then has a topography 9 corresponding to the stamp topography 10 when the stamp 7 is pressed onto or into the gel surface. The film 8 is optional and can also be omitted.

The gel 5 is then thermally cured and then the stamp 7 is removed again. The thermal curing can take place in an oven process at more than 100 degrees Celsius.

In other words, during the curing of the gel 5, a structure 9 is specifically embossed into the gel surface by applying a stamp 7 to the gel 5, which is still liquid at the beginning of the curing process. The structure of the contact surface of the stamp 7 with the gel 5 is the negative mold the topography 9 desired in the hardened state of the gel surface. The contact of the stamp 7 with the gel 5 can - as explained above - take place directly or, in order to avoid soiling and contamination of the stamp, indirectly through a film-like interposer 8 between stamp 7 and gel 5 , analogous to the procedure that is customary for "film-assisted molding". The stamp 7 can also be used to prevent the gel 5 from forming a concave surface due to capillary forces during hardening and thus acting as a focusing reflector.

To optimize the hardening process, the stamp 7 can be temperature-controlled in a targeted manner. A position-controlled or force-controlled positioning of the stamp relative to the sensor 1 during the curing process is also conceivable. For example, corresponding temperature, force or position sensors can be arranged which, together with a control and/or regulating device, can control or regulate a relative positioning of the stamp 7 to the surface of the gel 5, a corresponding application of force or temperature control of the stamp 7.

The gel surface is structured by stamp 7 in such a way that the gel surface acts as an acoustic diffuser and/or acoustic absorber in the frequency range relevant to the intended use of the terminal device, particularly when used. It is also conceivable here to arrange or form a plurality of larger scattering elements, on which a plurality of smaller scattering elements are then arranged or formed. For example, one porous structure that allows partial absorption of sound waves. The larger scattering elements can be produced, for example, by machining or eroding, and then the smaller scattering elements can be produced, for example, by roughening sandblasting.

In particular, the in 1 sensor shown is a waterproof sensor, in particular a waterproof pressure sensor.

2 shows the manufactured sensor according to FIG 1 in perspective view.

In 2 is a sensor 1 according to 1 shown. The sleeve 6 is round and the surface of the gel 5 has a concentric undulation 9 for diffusely scattering an incoming acoustic signal. In addition to the concentric undulation, other topographies are also conceivable, for example indentations arranged in the manner of a chessboard or linear slopes or the like.

3 shows the sensor according to 2 in cross section.

In 3 the paths of acoustic waves 20 impinging on the surface are shown. These are diffusely scattered due to the topography 9 of the gel surface (reference number 21).

4 shows steps of a method according to an embodiment of the present invention.

In 4 steps of a method for producing a sensor, in particular a pressure sensor, are shown.

• - Bereitstellen S1 eines Sensorelements,
• - Bereitstellen S2 eines aushärtbaren Übertragungsmediums, sodass das Sensierelement von dem Übertragungsmedium beaufschlagt wird,
• - Aushärten S3 des Übertragungsmediums, und
• - Ausbilden S4 des Übertragungsmediums, sodass dieses in zumindest einem Frequenzbereich auf das Übertragungsmedium auftreffende Wellen, insbesondere Schallwellen zumindest teilweise diffus streut und/oder zumindest teilweise absorbiert.

The procedure includes the following steps

• - Providing S1 a sensor element,
• - Providing S2 a curable transmission medium, so that the sensing element is acted upon by the transmission medium,
• - curing S3 of the transmission medium, and
• Forming S4 of the transmission medium such that it at least partially diffusely scatters and/or at least partially absorbs waves impinging on the transmission medium in at least one frequency range, in particular sound waves.

• - Einfache, kostengünstige Herstellung, insbesondere einer Vielzahl von Sensoren
• - ungewollte Wechselwirkungen beispielsweise mit Lautsprecher und/oder Mikrofon in einem Endgerät werden vermieden
• - kostenintensive und zeitaufwändige Korrekturen der Anordnung von Sensor und Mikrofon, Lautsprecher oder dergleichen werden vermieden
• - zuverlässige, kostengünstige und flexible Anordnung von Streuelementen

In summary, at least one of the embodiments of the invention can provide at least one of the following features and/or one of the following advantages:

• - Simple, inexpensive production, in particular a large number of sensors
• - Unwanted interactions, for example with speakers and / or microphone in a terminal are avoided
• - Costly and time-consuming corrections of the arrangement of sensor and microphone, loudspeaker or the like are avoided
• - Reliable, inexpensive and flexible arrangement of scattering elements

Although the present invention has been described on the basis of preferred exemplary embodiments, it is not limited thereto but can be modified in many different ways.

Claims (12)

Sensor (1), in particular a pressure sensor, comprising a sensing element (4a) for detecting a property and/or composition of a medium surrounding the sensor (1), a transmission medium (5) for transmitting a property and/or composition of the surrounding medium to the sensing element (4a), the transmission medium (5) being arranged in such a way that the sensing element (4a) is acted upon by the transmission medium (5), the Transmission medium (5) is designed in such a way that it at least partially diffusely scatters and/or at least partially absorbs (21) waves (20) impinging on the transmission medium (5) in at least one frequency range, in particular sound waves. Sensor (1) according to claim 1 , wherein the transmission medium (5) has a surface facing the transmission medium (5), on which scattering elements (9) are arranged and/or formed for diffuse scattering and/or for at least partial absorption. Sensor (1) according to claim 2 , wherein the scattering elements (9) are made of the transmission medium (5). Sensor (1) according to one of claims 2 - 3 , wherein the scattering elements (9) are produced by depressions and elevations in the surface of the transmission medium (5). Sensor (1) according to one of Claims 1 - 4 , wherein the scattering elements (9) distributed symmetrically on the surface of the transmission medium (5). and/or are arranged concentrically to at least one point of the surface. Sensor (1) according to one of Claims 1 - 5 , wherein the transmission medium (5) is provided in the form of a hardened gel. Sensor (1) according to one of Claims 1 - 6 , wherein the sensing element (4a) is arranged in a housing (6) which is open on at least one side and the transmission medium (5) at least partially fills the housing (6). Method for producing a sensor (1), in particular a pressure sensor, comprising the steps - Providing (S1) a sensing element, - Providing (S2) a curable transmission medium, so that the sensing element is acted upon by the transmission medium, - curing (S3) of the transmission medium, Forming (S4) the transmission medium so that it at least partially diffusely scatters and/or at least partially absorbs waves impinging on the transmission medium in at least one frequency range, in particular sound waves. procedure according to claim 8 , wherein the step of forming (S4) the transmission medium comprises arranging and/or forming scattering elements (9) on the surface. Method according to one of Claims 8 - 9 , wherein the formation of the scattering elements (9) takes place during the curing of the transmission medium (5). procedure according to claim 9 or 10 , wherein the formation of the scattering elements (9) by means of a stamp (7) acting on the surface of the transmission medium (5) and having a negative form (10) of scattering elements takes place. procedure according to claim 11 , wherein before the step of forming the transfer medium (5), an intermediate layer (8) is arranged between the stamp (7) and the surface of the transfer medium, in particular in the form of a foil and/or a film, so that this stamp (7 ) and surface of the transmission medium (5) spaced apart.

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