DE102020214796A1 - Process for manufacturing a sensor and sensor - Google Patents

Abstract

The invention relates to a method for producing a sensor, the sensor having a sensing element and a housing, the housing having an interior which is accessible through a housing opening, and the sensing element being arranged in the interior and for detecting a property and/or or a composition of a medium surrounding the sensor, comprising:• Filling a protective medium into the interior, the protective medium being designed to transmit the property and/or the composition of the surrounding medium to the sensing element,• Fixing a membrane on or in the housing opening for Closing the housing opening, the membrane being at least partially permeable to a gas, whereby a gas present in the interior can escape from the interior through molecular interstices of the membrane, and• closing the molecular interstices of the membrane to form a gas-tight membrane.The invention relates also a sensor that has been manufactured using a corresponding method.

Description

technical field

The invention relates to a method for producing a sensor, the sensor having a sensing element and a housing, the housing having an interior which is accessible through a housing opening, and the sensing element being arranged in the interior and for detecting a property and/or or a composition of a medium surrounding the sensor.

The invention also relates to a sensor.

State of the art

Although the present invention is generally applicable to any sensor capable of sensing a property and/or composition of a surrounding medium, the present disclosure will be discussed in relation to pressure sensors.

Pressure sensors have found widespread adoption in consumer electronic devices such as smartphones and smartwatches. Driven by new applications, such as indoor navigation or tracking fitness exercises, the demands on the measurement accuracy of pressure sensors are constantly increasing. At the same time, new device generations are designed to be media-tight and dirt-repellent, so that high-precision and media-tight pressure sensors are required. It is also necessary for the pressure sensors to get as little dirt as possible over the course of their service life in order to ensure trouble-free functionality. The surfaces of the sensor that are required for the sensor system and are exposed to a surrounding medium should therefore have the lowest possible tendency to become soiled. Very similar requirements also exist outside of the consumer electronics sector.

In order to achieve high-precision sensors that can nevertheless be easily miniaturized, it is known to design the sensing element of the sensor as a MEMS—micro-electro-mechanical system. In order to achieve a medium-tight sensor, the sensing element can be embedded in a protective medium and thereby protected against direct contact with a surrounding medium. Known protective media are formed by gels or oils. The protective medium also has the task of conducting a property and/or a composition of the surrounding medium to the sensing element and enabling the property and/or the composition to be detected by the sensing element. It is known to use a membrane to protect the surface of the protective medium that is in contact with the surrounding medium. In the case of a fluid as the protective medium, this membrane also prevents the protective medium from leaking out.

When using a membrane - especially when using a fluid as the protective medium - it should be ensured that no air pockets remain between the protective medium and the membrane. According to a known solution, the sensor housing has a filling opening and a suction opening. The protective medium is filled into the interior through the filling opening and excess air is sucked out through the suction opening. After the protective medium has been filled into the interior, the filling opening and the suction opening are closed, for example with a plug. The disadvantage of this is that the manufacture of the sensor housing becomes complex due to the additional openings.

Disclosure of Invention

• • Einfüllen eines Schutzmediums in den Innenraum, wobei das Schutzmedium zum Übertragen der Eigenschaft und/oder der Zusammensetzung des Umgebungsmediums an das Sensierelement ausgebildet ist,
• • Festlegen einer Membran an oder in der Gehäuseöffnung zum Verschließen der Gehäuseöffnung, wobei die Membran zumindest teilweise für ein Gas permeabel ist, wodurch ein in dem Innenraum vorhandenes Gas durch molekulare Zwischenräume der Membran aus dem Innenraum entweichen kann, und
• • Verschließen der molekularen Zwischenräume der Membran zum Bilden einer gasdichten Membran.

In one embodiment, the present invention provides a method for manufacturing a sensor, the sensor having a sensing element and a housing, the housing having an interior space that is accessible through a housing opening, and the sensing element being arranged in the interior space and for detecting a property and/or a composition of an environmental medium of the sensor, comprising:

• • filling a protective medium into the interior, the protective medium being designed to transfer the property and/or the composition of the surrounding medium to the sensing element,
• • fixing a membrane on or in the housing opening to close the housing opening, the membrane being at least partially permeable to a gas, whereby a gas present in the interior space can escape from the interior space through molecular interstices of the membrane, and
• • Closing the molecular interstices of the membrane to form a gas-tight membrane.

In a further embodiment, the present invention provides a sensor, preferably a pressure sensor, produced with a method according to the aforementioned embodiment.

A sensor is prepared as a kind of “sensor blank” before a protective medium is filled in, a membrane is fixed and the molecular interstices of the membrane are sealed placed. This sensor includes a housing that has an interior space and a housing opening. A sensing element is arranged in the interior. The housing opening allows access to the interior. On the one hand, this means that a property and/or a composition of an environmental medium can reach the sensing element from outside the sensor through the housing opening—directly or indirectly. On the other hand, access allows the protective medium to be filled into the interior.

The membrane can be formed of various materials as long as this membrane is permeable to a gas. In this case, only one area or individual areas of the membrane can be permeable to gas, while other areas of the membrane are impermeable. In the case of a pressure sensor in particular, it is advisable if the membrane is as flexible as possible. The membrane can have a low modulus of elasticity, be thin--for example one to a few tens of micrometers thick--and/or be structured--for example with a wavy profile.

Due to the permeability of the membrane, it is not necessary for the membrane to be fixed under special environmental conditions. In particular, it is not necessary to fix the membrane under negative pressure.

For "a gas permeable" means in general that a gas can pass through the membrane. The permeability of the membrane may arise from molecular interstices of the membrane through which gas can pass from one side of the membrane to another side by diffusion. How specifically these molecular spaces are formed is not critical to the present disclosure. The gas can be formed by various gases or gas mixtures, in particular air. The permeability can be so pronounced that the gas can leave the membrane without an external trigger, for example a pronounced pressure difference. Since removing the gas from the interior of the sensor can be part of a manufacturing process of the sensor, the permeability can also allow sufficiently rapid outgassing. In principle, the membrane can also be permeable to liquids. In particular when using a fluid as the protective medium, however, permeability for liquids can also be unfavorable, since this means that the protective medium can pass through the membrane unintentionally. Therefore, in one embodiment, the membrane is impermeable to liquids or other non-gaseous substances and mixtures of substances. Overall, the dimensioning of the permeability of the membrane can be the result of an optimization with regard to the respective conditions of use.

A “fixing of a membrane on or in the housing opening” can take place in various ways. A fixing area can be formed on or in the housing opening, to which the membrane can be fixed. How the fixing area is designed will depend in particular on the type of fixing and the positioning of the fixing area relative to the housing opening. The membrane can be welded to the fixing area or connected in some other way with a material fit and/or can be clamped to the fixing area or held in some other mechanical way. It can be useful if a medium-tight connection between the membrane and the housing opening is created after the fixing.

The "sensing element" can be implemented in various ways, as long as it is able to detect a property and/or a composition of a surrounding medium. Such properties and/or compositions can be, for example, a pressure, a temperature, a content of a gas, for example carbon dioxide or carbon monoxide, and/or a humidity level, to name just a few conceivable embodiments. The sensing element can be correspondingly diverse, with the sensor also being able to have a plurality of sensing elements, including different ones. The sensing element can be designed as an MEMS—micro-electro-mechanical system—so that a particularly compact sensor can be implemented.

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

In one embodiment, before the molecular interstices of the membrane are closed, the protective medium is degassed, the protective medium preferably being degassed by applying a negative pressure to the membrane and/or by heating the protective medium. An additional degassing step can accelerate the removal of a gas from the interior. In addition, gas contained in the protective medium can be effectively removed. The degassing step can be carried out in various ways. Applying negative pressure to the membrane offers the advantage that existing techniques can be used anyway. It is also possible to use negative pressure environments for degassing, which would be necessary anyway when closing the molecular interstices of the membrane. A heating of the protective medium can be used advantageously in particular when the membrane is welded or glued to or in the housing opening.

In one embodiment, a chemical reaction is initiated in the membrane by means of a trigger in order to close the molecular interstices of the membrane, the trigger preferably being formed by electromagnetic radiation, particularly preferably by ultraviolet light. In this embodiment, a material property of the membrane can be changed. In principle, the material of the membrane is designed to be reactive, with a trigger being required to start a reaction. Such a material can be, for example, an ionomer whose ion channels form molecular interstices within the meaning of the present disclosure. A trigger can generally be formed by sufficiently high-energy electromagnetic radiation, preferably by ultraviolet light. This type of sealing of the molecular interstices offers the advantage that the membrane, which is still permeable, can be handled with conventional techniques, for example welded or deformed, and that the molecular interstices can be reliably sealed after the chemical reaction has been triggered.

In one embodiment, a chemical reaction is triggered in the membrane to close the molecular interstices of the membrane while supplying an additional reactant, the reactant preferably being introduced in a liquid or gaseous phase. Such a reactant can be formed, for example, by higher valent cations, e.g. Fe3+, which seal ion channels in the membrane, thereby changing the macroscopic material properties from a permeable state to a non-permeable state. In this way, the point in time of the chemical reaction can be controlled particularly reliably.

In one embodiment, a coating is applied to the membrane to seal the molecular interstices of the membrane, preferably using PVD—Physical Vapor Deposition. In this embodiment, the membrane and its material properties are retained in principle. The coating nevertheless reliably closes the molecular interstices. The use of PVD allows the creation of particularly thin coatings of one micron and thinner. The resilience of the membrane can be largely retained.

In one embodiment, the coating is formed by a metal film. Metal films can be produced well with PVD. In addition, a metal film offers the advantage that the membrane also offers a certain shielding of the sensing element against electromagnetic interference from outside the sensor. The membrane can thus represent a good supplement to an at least partially metallic housing of the sensor.

In one embodiment, the membrane is fixed to a fixing area on the housing by means of a material connection process, preferably by means of welding or gluing. Cohesive connections offer the advantage that particularly stable and media-tight connections can be created between the membrane and the housing.

In one embodiment, the membrane is fixed to an intermediate support and, when the membrane is fixed to or in the housing opening, the intermediate support is fixed to or in the housing opening. Such an intermediate carrier—also called an interposer—can simplify the production of the sensor or the fixing of the membrane on or in the housing opening. For this purpose, the membrane is connected to the intermediate carrier in an upstream production step. The intermediate carrier together with the membrane can then be inserted into the housing opening or fixed to the housing opening. This means that manufacturing steps can be parallelized.

In one embodiment, the housing and intermediate carrier and/or intermediate carrier and membrane are fixed to one another by means of a clip connection and/or by means of being pressed into one another. As a result, a stable and/or media-tight fixing of the membrane in or on the housing opening can be implemented in a simple manner.

In one embodiment, the membrane is formed by a plastic, preferably a polymer or an ionomer. A membrane made of plastic offers the advantage that some plastics are inherently permeable if they are sufficiently thin and that permeability does not have to be produced using complex process steps. Polymers are plastics that can be used particularly cheaply in this context. Ionomers can be advantageously used in particular when the molecular interstices of the membrane are closed by a triggered chemical reaction.

In one embodiment, the protective medium is formed by an incompressible fluid, preferably an oil. As a result, a protective medium can be provided in a simple manner.

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 ver It is clear 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 eine Schrägansicht einer Ausführungsform eines Sensors gemäß der vorliegenden Offenbarung,
• 2 eine Draufsicht des Sensors gemäß 1,
• 3 einen Schnitt durch den Sensor gemäß den 1 und 2 entlang der Linie A - A,
• 4 eine schematische Ansicht einer Membran, die in einem Sensor gemäß 1 zum Einsatz kommen kann,
• 5 einen Schnitt durch eine weitere Ausführungsform eines Sensors gemäß der vorliegenden Offenbarung und
• 6 ein Ablaufdiagramm einer Ausführungsform eines Verfahren gemäß der vorliegenden Offenbarung.

It shows:

• 1 an oblique view of an embodiment of a sensor according to the present disclosure,
• 2 a plan view of the sensor according to FIG 1 ,
• 3 a section through the sensor according to the 1 and 2 along line A - A,
• 4 a schematic view of a membrane in a sensor according to 1 can be used
• 5 a section through another embodiment of a sensor according to the present disclosure and
• 6 10 is a flow diagram of an embodiment of a method according to the present disclosure.

Embodiments of the invention

Various views of a first embodiment of a sensor according to the present disclosure are shown in FIGS 1 until 3 shown. 1 shows an oblique view, 2 a top view and 3 a section through the sensor along a line A - A 2 .

The sensor 1 comprises a housing 2 which is surrounded by a rewiring substrate 3 and a sleeve 4 . The sleeve 4 is essentially a hollow cylinder, which is closed off at the bottom by the rewiring substrate 3 and provides a housing opening 5 at the top. In the housing opening 5, a membrane 6 is fixed, which - after completion of a manufacturing process disclosed here - seals an interior space 7 formed in the housing 2 in a media-tight manner.

The interior 7 is in 3 to recognize. A protective medium 8 is filled into the interior 7, which in this example is formed by an oil. An ASIC—Application Specific Integrated Circuit—9 and a sensing element 10 are arranged in the interior. In this case, the ASIC 9 is arranged on the rewiring substrate 3 and the sensing element 10 on the ASIC 9. The membrane 6 is curved into the interior 7, as a result of which wetting of the surface of the membrane 6 by the protective means 8 can be promoted. The membrane 6 is fixed to a fixing area 11 on the sleeve 4, for example by means of a material connection process. A coating 12 in the form of a metal film is applied to the membrane 6 in order to close molecular interstices in the membrane 6 .

During the operation of the sensor 1, a property and/or a composition of a surrounding medium 13, in the present example a pressure, is detected by the sensing element 10. A pressure in the surrounding medium 13 is transmitted via the membrane 6 and the protective medium 8 to the sensing element 10, which can then detect the pressure.

4 FIG. 12 shows a highly simplified view of the membrane 6, which has a large number of molecular interstices 14. FIG. In particular, it should be noted that the width of the molecular spaces 14 is not drawn to scale with the thickness of the membrane 6 and that the molecular spaces 14 will typically not be rectangular in shape. The molecular interstices 14 lead to a permeability of the membrane 6 for a gas 14 that is in 4 is symbolized by small circles. The molecular interstices 14 allow the gas 14 to be able to get from the interior space 7 into the surrounding medium 13 . Diffusion can act as a transport mechanism, which is 4 is symbolized by arrows. The components of the protective medium 8 are represented by larger circles that cannot pass through the molecular interstices 14 .

5 12 shows a section through another embodiment of a sensor according to the present disclosure. The sensor 1 in turn comprises a housing 2 which is formed by a rewiring substrate 3 and a sleeve 4 . The housing includes a housing opening 5 and an interior space 7. An ASIC 9 and a sensing element 10 are arranged in the interior space. A protective medium 8 is filled in the interior 7 . In the housing opening 5 is an intermediate carrier 16 - also known as an interposer - arranged, on which a membrane 6 is fixed. A chemical reaction can be triggered to close the molecular interstices of the membrane, by means of which the material property of the membrane 6 has changed from “permeable to gas” to “non-permeable”.

6 10 shows a flow chart of an embodiment of a method according to the present disclosure. In step S1, a sensor 1 is provided, which has a sensing element 10 and a housing 2, wherein an interior space 7 is formed in the housing 2, which is accessible through a housing opening 5 and in which the sensing element 10 is arranged. In step S2, a protective medium 11 is filled into the interior space 7 and then, in step S3, a membrane 6 is fixed on or in the housing opening 5, the membrane 6 being permeable to a gas. The interior 7 can be filled with protective medium 8 under atmospheric pressure. The setting of the membrane can in accordance with the embodiment 1 until 3 be done by gluing or welding the membrane to the fixing area. In the embodiment according to 5 the membrane can be fixed by pressing the intermediate carrier 16 into the sleeve 4 (with optional material connection) or by inserting the intermediate carrier 16 and subsequent material connection. The integral connection can be made by a welding process.

In an optional step S4, the protective medium 8 can be degassed, for example by heating the protective medium 8 or by applying a negative pressure to the membrane 6.

Then, in step S5, the molecular interstices 14 of the membrane 6 are sealed in order to produce a media-tight membrane. This sealing can be carried out by creating a coating, for example by means of PVD, or by triggering a chemical reaction.

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)

A method for producing a sensor, the sensor (1) having a sensing element (10) and a housing (2), the housing (2) having an interior space (7) which is accessible through a housing opening (5), and wherein the sensing element (10) is arranged in the interior (7) and is designed to detect a property and/or a composition of a medium (13) surrounding the sensor (1), comprising: • Filling (S2) of a protective medium (8) into the interior (7), the protective medium (8) being designed to transmit the property and/or the composition of the surrounding medium (13) to the sensing element (10), • Fixing (S3) a membrane (6) on or in the housing opening (5) to close the housing opening (5), wherein the membrane (6) is at least partially permeable to a gas (15), whereby in the interior (7 ) Existing gas (15) can escape from the interior (7) through molecular interstices (14) of the membrane (6), and • Closing (S5) the molecular interstices (14) of the membrane (6) to form a gas-tight membrane. procedure after claim 1 , characterized in that before the molecular interstices (14) of the membrane (6) are closed, the protective medium (8) is degassed (S4), the protective medium (8) being degassed preferably by subjecting the membrane (6) to a Negative pressure and / or by heating the protective medium (8). procedure after claim 1 or 2 , characterized in that a chemical reaction is triggered in the membrane (6) to close the molecular interstices (14) of the membrane (6) by means of a trigger, the trigger preferably being formed by electromagnetic radiation, particularly preferably by ultraviolet light . Procedure according to one of Claims 1 until 3 , characterized in that a chemical reaction is triggered in the membrane (6) to close the molecular interstices (14) of the membrane (6) by supplying an additional reactant, the reactant preferably being provided in a liquid or gaseous phase. procedure after claim 1 or 2 , characterized in that to close the molecular interstices (14) of the membrane (6), preferably using PVD - Physical Vapor Deposition -, a coating (12) is applied to the membrane (6). procedure after claim 5 , characterized in that the coating (12) is formed by a metal film. Procedure according to one of Claims 1 until 6 , characterized in that the membrane (6) is fixed to a fixing area (11) on the housing (2) by means of a cohesive connection process, preferably by means of welding or gluing. Procedure according to one of Claims 1 until 6 , characterized in that the membrane (6) is fixed to an intermediate carrier (16) and that when the membrane (6) is fixed on or in the housing opening (5), the intermediate carrier (16) is fixed on or in the housing opening (5). procedure after claim 8 , characterized in that housing (2) and intermediate carrier (16) and/or intermediate carrier (16) and membrane (6) are fixed to one another by means of a clip connection and/or by means of being pressed into one another. Sensor, preferably pressure sensor, produced with a method according to one of Claims 1 until 9 . sensor after claim 10 , characterized in that the membrane (6) is formed by a plastic, preferably a polymer or an ionomer. sensor after claim 10 or 11 , characterized in that the protective medium (8) is formed by an incompressible fluid, preferably an oil.

Images