Method for producing a pressure sensor for determining and / or monitoring a pressure of a medium, and pressure sensor

Abstract

The invention relates to a method for producing a pressure sensor (1) for determining and / or monitoring a pressure (p) of a medium (2), wherein the pressure sensor (1) has a pressure measuring cell (3) and in-situ electronics (4), wherein the pressure measuring cell (3) has a carrier body (5) and a ceramic measuring membrane (7) connected to the carrier body (5) by means of a joint (6), wherein the pressure (p) of the medium (2) can be applied to the measuring membrane (7), wherein the carrier body (5) has, on a surface (8) facing away from the measuring membrane (7), at least one metallised region (9) having a defined layer thickness (n), wherein the pressure measuring cell (3) and the in-situ electronics (4) are electrically connected to one another by means of at least one connecting element (10), wherein the method comprises at least the following steps: - connecting the first end region (12) to the at least one metallised region (9) by means of ultrasonic welding, - connecting the second end region (13) to the in-situ electronics (4).

Description

[0001] Method for producing a pressure sensor for determining and / or monitoring a pressure of a medium and pressure sensor

[0002] The invention relates to a method for producing a pressure sensor for determining and / or monitoring a medium, wherein the pressure sensor comprises a pressure measuring cell and on-site electronics. The pressure measuring cell comprises a carrier body and a ceramic measuring diaphragm connected to the carrier body by means of a joint, wherein the measuring diaphragm can be subjected to the pressure of the medium. The invention further relates to a pressure sensor.

[0003] In pressure measurement technology, absolute pressure, differential pressure, and gauge pressure sensors are known. Absolute pressure sensors determine the prevailing pressure of a process medium absolutely, i.e., relative to a vacuum, while differential pressure sensors determine the difference between two different pressures of the process medium or media. With gauge pressure sensors, the pressure of the process medium to be measured is determined relative to a reference pressure, with the atmospheric pressure prevailing in the vicinity of the gauge pressure sensor serving as the reference pressure.

[0004] Pressure transducers have a pressure-sensitive measuring element, the so-called pressure sensor, with a pressure applied to its first and second surfaces. In the case of relative or absolute pressure transducers, the pressure of the process medium to be determined acts on the first surface of the pressure sensor, while an absolute or reference pressure acts on the second surface. In the case of differential pressure transducers, a first pressure and a second pressure of a process medium are applied to both surfaces. The measuring element bends depending on the existing relative pressure, which is calculated from the difference between the pressures applied to the two surfaces. This bending is converted by an electronic unit into an electrical signal dependent on the relative pressure, which is then available for further processing or evaluation. A distinction is made between capacitive and piezoresistive pressure sensors, among others.A large number of such pressure sensors are manufactured and distributed by companies in the Endress+Hauser Group.

[0005] A ceramic pressure sensor, for example, comprises a pressure measuring cell with a ceramic base body and a ceramic measuring diaphragm, which is pressure-tightly connected to the base body by means of an active brazing alloy, forming a measuring chamber. Furthermore, the pressure sensor typically includes a transducer for converting a pressure-dependent deformation of the measuring diaphragm into an electrical primary signal, as well as a primary signal path extending through the base body. The transducer can be a capacitive or resistive transducer, for example. The primary signal path usually includes at least one electrical feedthrough through the base body. Instead of ceramic pressure sensors, silicon chips, which are usually bonded to a silicon substrate, are also known as pressure sensors.

[0006] For processing and / or converting the electrical primary signal of the transducer, on-site electronics are provided, which are electrically connected to the pressure measuring cell. The on-site electronics are typically connected via a connector or circuit board to an electronic unit, which is used to evaluate the processed and / or converted primary signal and determine the pressure of the medium.

[0007] Due to its direct contact with the medium, the pressure sensor is exposed to the process temperatures of the medium. High temperatures place particular strain on the mechanical and / or electrical connections between the pressure measuring cell and the on-site electronics. As a rule, the pressure measuring cell and the on-site electronics are electrically and often also mechanically connected to one another using one or more connecting elements. In particular, the connection between the pressure measuring cell and the connecting elements is exposed to high temperatures due to the short distance to the medium. Common soft solder connections between the pressure measuring cell and the connecting elements can only withstand temperatures up to approximately 130°C. The object of the present invention is therefore to provide a method and a pressure sensor which enables the use of the pressure sensor at high temperatures, in particular at temperatures up to 150°C.

[0008] According to the invention, the object is achieved by a method according to claim 1 and a pressure sensor according to claim 14.

[0009] With regard to the method, the object is achieved according to the invention by a method for producing a pressure sensor for determining and / or monitoring a pressure of a medium, wherein the pressure sensor has a pressure measuring cell and on-site electronics, wherein the pressure measuring cell has a carrier body and a ceramic measuring membrane connected to the carrier body by means of a joint, wherein the measuring membrane can be subjected to the pressure of the medium, wherein the carrier body has at least one metallized area with a defined layer thickness on a surface facing away from the measuring membrane, wherein the pressure measuring cell and the on-site electronics are electrically connected to one another by means of at least one connecting element, wherein the method comprises at least the following steps:

[0010] - Providing the pressure measuring cell, the on-site electronics and the at least one connecting element, wherein the connecting element has a base body with a first end region and a second end region opposite the first end region,

[0011] - connecting the first end region to the at least one metallized region by means of ultrasonic welding,

[0012] - Connecting the second end section to the on-site electronics.

[0013] The ultrasonic weld between the first end region and the at least one metallized region has a high temperature resistance, so that the pressure sensor can be used at temperatures up to 150°C. The at least one metallized region is obtained by applying a metallic coating to the surface of the pressure measuring cell. The layer thickness of the at least one metallized region is designed such that an ultrasonic weld between the first end region and the at least one metallized region is enabled. The at least one metallized region can comprise copper, aluminum, nickel, a nickel-vanadium alloy and / or a copper-nickel alloy or consist of one or more of the aforementioned metals or alloys. The carrier body is in particular ceramic. If necessary.Multiple metallized areas may be present, each connecting a metallized area to the on-site electronics by means of a connecting element. Alternatively, a metallized area may be present, which is connected to the on-site electronics by means of one or more connecting elements. The at least one connecting element is designed to provide an electrical connection between the pressure measuring cell and the on-site electronics. The at least one connecting element is preferably made of metal.

[0014] Ultrasonic welding is a friction welding process in which ultrasonic waves are used to generate surface friction and resulting local heating in the area of ​​the surfaces to be joined, resulting in a material bond between the two surfaces. If necessary, the ultrasonic welding process can be facilitated by applying a weight or force to one of the components to be joined. Preferably, the first end region is first connected to the at least one metallized area, followed by the second end region to the on-site electronics.

[0015] In a further development, the second end region is connected to the on-site electronics by soldering, gluing, or ultrasonic welding. Since the connection between the second end region and the on-site electronics is generally exposed to somewhat lower temperatures than the connection between the first end region and the pressure measuring cell, a soft solder connection can be used for this connection. Alternatively, it is also possible to use an adhesive, in particular an electrically conductive adhesive. The use of an ultrasonic welding connection results in a particularly temperature-resistant pressure sensor. In one embodiment, a metallic bolt- or wire-shaped base body is used as the base body.

[0016] In a further embodiment, a metal wire, a bolt, or a spring contact pin is used as the at least one connecting element. The bolt and the spring contact pin are preferably arranged substantially perpendicular to the pressure measuring cell and connected to it in this position. The bolt and the spring contact pin can be connected to the pressure measuring cell or the on-site electronics with their end surfaces or regions. In the case of a metal wire, this can be bent in its end regions in order to create a larger contact surface between the metal wire and the pressure measuring cell or the on-site electronics. A connecting element which has a diameter of less than 0.5 mm is referred to as a metal wire, in particular. The spring contact pin can have resilient properties, whereby a particularly mechanically stable connection between the pressure measuring cell and the on-site electronics is obtained.

[0017] In particular, a spring contact pin is used as a spring contact pin, which has a two-part sleeve in which a spring is arranged. In particular, the two-part sleeve can have a piston and a casing, between which the spring is arranged, so that when a force acts on the piston or the casing, the distance between the piston and the casing can be adjusted by means of the spring. The spring contact pin is, in particular, a Pogo-Pin®.

[0018] A further embodiment provides that a bolt or a spring contact pin is used as the at least one connecting element, which is designed to establish a mechanical connection between the pressure measuring cell and the on-site electronics.

[0019] In a further development, a diameter in the range of 0.5 mm to 3 mm is used as a predetermined diameter of the at least one connecting element. The at least one connecting element can be designed as a bolt. In this way, a mechanical connection between the pressure measuring cell and the on-site electronics is achieved by means of the at least one connecting element.

[0020] In an alternative development, a diameter in the range of 0.6 mm to 1.5 mm is used as a predetermined diameter of the at least one connecting element. The at least one connecting element can be designed as a bolt. In this way, a mechanical connection between the pressure measuring cell and the on-site electronics is achieved by means of the at least one connecting element.

[0021] In an alternative embodiment, a printed circuit board is used as the connecting element. The printed circuit board can include metallic components that provide an electrical connection between the pressure measuring cell and the on-site electronics. In the case of a rigid printed circuit board, the printed circuit board can also serve as a mechanical connection between the pressure measuring cell and the on-site electronics.

[0022] In particular, a flexible circuit board is used as the printed circuit board. Using a flexible circuit board allows the on-site electronics to be arranged in a space-saving manner.

[0023] In a further development, the circuit board is connected to the on-site electronics by soldering, ultrasonic welding or gluing.

[0024] In one embodiment, a layer thickness of 2 μm to 50 μm is used as the defined layer thickness. With this defined layer thickness, a stable ultrasonic weld is obtained between the first end region and the at least one metallized region.

[0025] In a further embodiment, a layer thickness of 3 μm to 20 μm is used as the defined layer thickness. With this defined layer thickness, a stable ultrasonic weld is obtained between the first end region and the at least one metallized region. With regard to the pressure sensor, the object underlying the present invention is achieved by a pressure sensor for determining and / or monitoring the pressure of a medium, wherein the pressure sensor has a pressure measuring cell and on-site electronics, wherein the pressure measuring cell has a carrier body and a ceramic measuring diaphragm connected to the carrier body by means of a joint, wherein the measuring diaphragm can be subjected to the pressure of the medium, wherein the carrier body has at least one metallized region with a defined layer thickness on a surface facing away from the measuring diaphragm,wherein the pressure measuring cell and the on-site electronics are electrically connected to one another by means of at least one connecting element, wherein the at least one connecting element has a base body with a first end region and a second end region opposite the first end region, wherein the first end region is connected to the at least one metallized region by means of ultrasonic welding and the second end region is connected to the on-site electronics.

[0026] The ultrasonic welding connection between the pressure measuring cell and at least one connecting element results in a pressure sensor that can also be used at high temperatures.

[0027] The embodiments of the method according to the invention also apply mutatis mutandis to the pressure sensor according to the invention. The pressure sensor is manufactured, in particular, according to the method according to the invention.

[0028] The invention will be explained further with reference to the following figures 1 - 5. They show:

[0029] Fig. 1 : a first embodiment of the pressure sensor according to the invention.

[0030] Fig. 2: a design of the connecting element.

[0031] Fig. 3: another embodiment of the connecting element. Fig. 4: a second embodiment of the pressure sensor according to the invention.

[0032] Fig. 5: a third embodiment of the pressure sensor according to the invention.

[0033] Fig. 1 shows a first embodiment of the pressure sensor 1 according to the invention. The pressure sensor 1 comprises a pressure measuring cell 3 with a, in particular ceramic, carrier body 5 and a ceramic measuring diaphragm 7. The measuring diaphragm 7 can be subjected to the pressure p of the medium 2 and is connected to the carrier body 5 by means of a joint 6, enclosing a pressure chamber 19. In the pressure chamber 19, a measuring electrode 20a and a counter electrode 20b can be arranged on the measuring diaphragm 7 and the carrier body 5, which form an electrical transducer, in particular a capacitive transducer. The electrical transducer serves to provide measured variable-dependent electrical primary signals. A pressure p of the medium 2 acts on the measuring diaphragm 7, wherein, optionally, in the case of a reference or differential pressure measuring device, a further pressure can be fed into the pressure chamber 19 through the pressure supply 21.A pressure-dependent deflection of the measuring membrane 7 influences the capacitance between the two electrodes 20a, 20b.

[0034] At least the second electrode 20b can be connected to the at least one metallized region 9 of the carrier body 5 via a feedthrough or a contact pin 22 and to the on-site electronics 4 by means of the at least one connecting element 10. The carrier body 5 has at least one metallized region 9 with a defined layer thickness n on a surface 8 facing away from the measuring membrane 7. The metallized region 9 can be designed as a coating that covers a portion of the surface 8.

[0035] The at least one connecting element 10 is designed to establish an electrical connection between the metallized region 9 and the on-site electronics. The at least one connecting element 10 is in particular made of metal and has a base body 11 with a first end region 12 and a second end region 13, which lie opposite one another. The first end region 12 is connected to the at least one metallized region 9 by means of an ultrasonic weld 14, and the second end region 13 is connected to the on-site electronics 4, for example by means of an adhesive, a soldered connection, or an ultrasonic weld. In the method, the ultrasonic weld 14 is preferably first created between the first end region 12 and the pressure measuring cell 3, before the second end region 13 is connected to the on-site electronics 4.To produce the ultrasonic weld 14, the at least one metallized region 9 can have a defined layer thickness in the range of 2 pm to 50 pm, in particular in the range of 3 pm to 20 pm. In the example shown, three connecting elements are used; this does not preclude a different number of connecting elements.

[0036] In the embodiment shown in Fig. 1, the at least one connecting element 10 is designed as a metallic bolt 23. A predetermined diameter D of the at least one connecting element 10 can, for example, be in the range from 0.5 mm to 3 mm or, in particular, in the range from 0.6 mm to 1.5 mm. If the at least one connecting element 10 has such a predetermined diameter D, a mechanical connection is created between the pressure measuring cell 3 and the on-site electronics 4 in addition to the electrical connection.

[0037] Instead of a bolt 23, the at least one connecting element 10 can also be designed as a spring contact pin 15, in particular as a Pogo-Pin®, as shown in Fig. 2. The spring contact pin 15 can, for example, have a two-part sleeve 16 in which a spring 17 is arranged. The spring contact pin 15 or the Pogo-Pin® is preferably connected to the pressure measuring cell 3 and the on-site electronics 4 in such a way that a spring connection is created between the pressure measuring cell 3 and the on-site electronics 4. For example, the spring contact pin 15 is arranged essentially perpendicular to the surface 8. In Fig. 2, for example, a base of the spring contact pin 15 is assigned to the first end region 12. Alternatively, it is also possible to assign the tip of the spring contact pin 15 to the first end region 12. By means of the spring contact pin 15, a mechanical connection can be established between the pressure measuring cell 3 and the on-site electronics 4.

[0038] For predetermined diameters of the at least one connecting element of less than 0.5 mm, the at least one connecting element 10 is considered a metal wire 24 in the context of the present application. An example with a connecting element 10 designed as a metal wire 24 is shown in Fig. 3. In order to connect the metal wire 24 to the pressure measuring cell 3 by ultrasonic welding, a respective end region of the metal wire 24 is bent once or several times to create a larger contact area between the metal wire 24 and the at least one metallized region 9. If necessary, an end section of the metal wire 24 can protrude from the ultrasonic weld 14, as shown on the left in Fig. 3.

[0039] The at least one connecting element 10 can alternatively be designed as a printed circuit board 18. Two examples of this are shown in Figures 4-5. The printed circuit board 18 can be designed as a rigid printed circuit board, but is preferably designed as a flexible printed circuit board. The printed circuit board 18 is connected in a first end region 12 to the at least one metallized region 9 by means of one or more ultrasonic welds 14. One metallized region 9 (as in Figure 4) or several metallized regions (as in Figure 5) can be used; the configuration shown in the respective figure can be replaced by the alternative configuration. The second end region 13 of the printed circuit board 18 is connected to the on-site electronics 4. The printed circuit board 18 can serve as a carrier for the circuitry of the on-site electronics, as shown in Figure 5.Alternatively, the on-site electronics 4 can be enclosed by a housing 25, and the housing 25 can be connected to the circuit board 18 (see Fig. 4). For the respective connection to the pressure measuring cell 3 and / or the on-site electronics 4, the circuit board 18 can have metallic contact surfaces. The circuit board 18 can further have metallic components designed to establish an electrical connection between the pressure measuring cell 3 and the on-site electronics. List of reference symbols.

[0040] 1 pressure sensor

[0041] 2 Medium

[0042] 3 pressure measuring cell

[0043] 4 On-site electronics

[0044] 5 carrier bodies

[0045] 6 joint

[0046] 7 measuring membrane

[0047] 8 Surface

[0048] 9 metallized area

[0049] 10 Connecting element

[0050] 11 Basic body

[0051] 12 first end area

[0052] 13 second end area

[0053] 14 Ultrasonic welding connection

[0054] 15 spring contact pin

[0055] 16 sleeve

[0056] 17 spring

[0057] 18 circuit board

[0058] 19 Pressure chamber

[0059] 20a measuring electrode

[0060] 20b Counter electrode

[0061] 21 Pressure feed

[0062] 22 contact pin

[0063] 23 bolts

[0064] 24 metal wire

[0065] 25 housings

[0066] P pressure

[0067] D Diameter n Layer thickness

Claims

Patent claims 1. A method for producing a pressure sensor (1) for determining and / or monitoring a pressure (p) of a medium (2), wherein the pressure sensor (1) comprises a pressure measuring cell (3) and on-site electronics (4), wherein the pressure measuring cell (3) comprises a carrier body (5) and a ceramic measuring membrane (7) connected to the carrier body (5) by means of a joint (6), wherein the measuring membrane (7) can be subjected to the pressure (p) of the medium (2), wherein the carrier body (5) has at least one metallized region (9) with a defined layer thickness (n) on a surface (8) facing away from the measuring membrane (7), wherein the pressure measuring cell (3) and the on-site electronics (4) are electrically connected to one another by means of at least one connecting element (10), wherein the method comprises at least the following steps: - Providing the pressure measuring cell (3), the on-site electronics (4) and the at least one connecting element (10), wherein the connecting element (10) has a base body (11) with a first end region (12) and a second end region (13) opposite the first end region (12), - connecting the first end region (12) to the at least one metallized region (9) by means of ultrasonic welding, - Connecting the second end section (13) to the on-site electronics (4).

2. The method according to claim 1, wherein the second end region (13) is connected to the on-site electronics (4) by means of soldering or gluing or ultrasonic welding.

3. Method according to one of the preceding claims, wherein a metallic bolt-shaped or wire-shaped base body is used as the base body (11).

4. Method according to one of the preceding claims, wherein the at least one connecting element (10) is a metal wire, a bolt or a spring contact pin (15) is used.

5. Method according to claim 4, wherein a spring contact pin is used as the spring contact pin (15) which has a two-part sleeve (16) in which a spring (17) is arranged.

6. Method according to one of the preceding claims, wherein a bolt or a spring contact pin (15) is used as the at least one connecting element (10), which is designed to establish a mechanical connection between the pressure measuring cell (3) and the on-site electronics (4).

7. Method according to one of claims 4-6, wherein a diameter in the range of 0.5 mm to 3 mm is used as a predetermined diameter (D) of the at least one connecting element (10).

8. Method according to one of claims 4-6, wherein a diameter in the range of 0.6 mm to 1.5 mm is used as a predetermined diameter (D) of the at least one connecting element (10).

9. Method according to one of claims 1-2, wherein a printed circuit board (18) is used as the connecting element (10).

10. The method according to claim 9, wherein a flexible circuit board is used as the circuit board (18).

11. Method according to one of claims 9-10, wherein the circuit board (18) is connected to the on-site electronics (4) by soldering or gluing.

12. Method according to one of the preceding claims, wherein a layer thickness of 2 pm to 50 pm is used as the defined layer thickness (n).

13. Method according to one of claims 1-12, wherein a layer thickness of 3 pm to 20 pm is used as the defined layer thickness (n).

14. Pressure sensor (1) for determining and / or monitoring a pressure (p) of a medium (2), wherein the pressure sensor (1) has a pressure measuring cell (3) and on-site electronics (4), wherein the pressure measuring cell (3) has a carrier body (5) and a ceramic measuring membrane (7) connected to the carrier body (5) by means of a joint (6), wherein the measuring membrane (7) can be subjected to the pressure (p) of the medium (2), wherein the carrier body (5) has at least one metallized area (9) with a defined layer thickness (n) on a surface (8) facing away from the measuring membrane (7), wherein the pressure measuring cell (3) and the on-site electronics (4) are electrically connected to one another by means of at least one connecting element (10), wherein the at least one connecting element (10) has a base body (11) with a first end region (12) and a first end region (12) opposite second end region (13),wherein the first end region (12) is connected to the at least one metallized region (9) by ultrasonic welding and the second end region (13) is connected to the on-site electronics (4).

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