Pressure sensor for determining and / or monitoring a pressure of a medium

Abstract

The invention relates to a pressure sensor (1) having a pressure measuring cell (3), an electronic unit (4) and at least one connecting element (5), which electrically and mechanically connects the pressure measuring cell (3) and the electronic unit (4) to one another, the pressure measuring cell (3) having a carrier body (6) and a ceramic measuring membrane (8) connected to the carrier body (6) by means of a joint (7), wherein the measuring membrane (8) can be acted on by the pressure of the medium (2), wherein the carrier body (6) has at least one metallised region (9) on a surface (6a) facing away from the measuring membrane (8), wherein the at least one connecting element (5) has a cylindrical base body (10) with a first end region (11) and a second end region (12), the second end region (12) being connected to the metallised region (9), and the first end region (11) having a first end face (13) in which at least a first recess (14) is arranged, the first end face (13) being connected to the electronic unit (4) by means of a solder point (15).

Description

[0001] Pressure sensor for determining and / or monitoring the pressure of a medium

[0002] The invention relates to a pressure sensor for determining and / or monitoring the pressure of a medium.

[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, where the prevailing atmospheric pressure in the vicinity of the gauge serves as the reference pressure.

[0004] Pressure sensors have a pressure-sensitive measuring element, the so-called pressure sensor, on whose first and second surfaces pressure is applied. In the case of relative or absolute pressure sensors, the pressure of the process medium to be measured 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 sensors, a first and a second pressure of the process medium are applied to each surface. The measuring element bends depending on the relative pressure, which is formed by 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, among other things, between capacitive and piezoresistive pressure sensors.A large number of such pressure sensors are manufactured and distributed by companies of the Endress+Hauser Group.

[0005] A ceramic pressure sensor, for example, includes a ceramic

[0006] A pressure sensor consists of a carrier body and a ceramic measuring diaphragm, which is pressure-tightly bonded to the carrier body using an active brazing alloy to form a measuring chamber. The pressure sensor also typically includes a transducer for converting pressure-dependent deformation of the measuring diaphragm into a primary electrical signal, as well as a primary signal path extending through the carrier body. The transducer can be, for example, a capacitive or a resistive transducer. The primary signal path usually includes at least one electrical feedthrough through the carrier body. Silicon chips, typically bonded to a silicon substrate, are also known as pressure sensors instead of ceramic ones.

[0007] An electronic unit is also mounted on the substrate, which receives the electrical signals from the converter and, if necessary, transmits them to an evaluation unit. The electronic unit is usually attached to the substrate by means of a solder joint. However, the standard soft solder joints between the electronic unit and the substrate cannot withstand sustained temperatures above 130°C or a high number of rapid temperature changes.

[0008] It is therefore an object of the present invention to provide a pressure sensor which can be used permanently at temperatures above 130°C.

[0009] The problem is solved according to the invention by claim 1.

[0010] According to the invention, the problem is solved by a pressure sensor for determining and / or monitoring the pressure of a medium, comprising a pressure measuring cell, an electronic unit, and at least one connecting element which electrically and mechanically connects the pressure measuring cell and the electronic unit, wherein the pressure measuring cell has a carrier body and a ceramic measuring membrane connected to the carrier body by means of an joining point, wherein the measuring membrane can be subjected to the pressure of the medium, wherein the carrier body has at least one metallized area on a surface facing away from the measuring membrane, wherein the at least one connecting element has a cylindrical base body with a first end region and a second end region, wherein the second end region is connected to the metallized area, and wherein the first end region has a first end face in which at least one first recess is arranged.the first end face is connected to the electronic unit by means of a solder joint.

[0011] The at least one initial recess creates a more stable solder joint between the at least one connecting element and the electronic unit. This is particularly advantageous compared to previous connecting elements that were soldered using a flat, unstructured end face. By modifying the geometry of the first end face, a solder joint is achieved that exhibits minimal cracking even at elevated temperatures and thus offers increased strength, especially at temperatures above 130°C. The at least one recess can be a cutout.

[0012] In one embodiment, at least one first recess is designed as a blind hole.

[0013] In one embodiment, at least one first recess is designed as a groove.

[0014] In one embodiment, at least one first recess is designed as two intersecting grooves.

[0015] In one embodiment, the basic body is a hollow cylinder with an interior space, and the at least one first recess is formed by this interior space. The at least one connecting element is therefore designed as a hollow cylinder with an interior space.

[0016] In one embodiment, the second end area is connected to the metallized area by means of a solder joint or an adhesive bond.

[0017] In one embodiment, the second end region has a second, in particular flat, end face which has at least one second recess. The at least one second recess can be configured analogously to the at least one first recess or deviate from it. In particular, the second recess can be configured as a blind hole, a groove, or as two intersecting grooves.

[0018] In one embodiment, the electronic unit comprises a printed circuit board with several contact surfaces, wherein the first end area is connected to one of the several contact surfaces.

[0019] Furthermore, the problem can be solved by a pressure sensor for determining and / or monitoring the pressure of a medium, comprising a pressure measuring cell, an electronic unit, and at least one connecting element that electrically and mechanically connects the pressure measuring cell and the electronic unit, wherein the pressure measuring cell has a carrier body and a ceramic measuring diaphragm connected to the carrier body by means of an joining point, wherein the measuring diaphragm is subjected to the pressure of the medium, wherein the carrier body has at least one metallized area on a surface facing away from the measuring diaphragm, wherein the electronic unit has a printed circuit board with at least one through-hole, wherein the at least one connecting element has a cylindrical base body with a first end region and a second end region, wherein the second end region is connected to the metallized area.wherein the first end region has a first end face with a first pin projecting from the first end face, which projects into the at least one through-hole and is connected to it by means of a solder joint.

[0020] The first pins create a more stable solder joint between the at least one connecting element and the electronic unit. This is particularly true compared to previous connecting elements, which were soldered using a flat, unstructured end face. Through the

[0021] Changing the geometry of the first end face will result in a solder joint which shows little cracking even at elevated temperatures and thus has increased strength, especially at temperatures above 130°C.

[0022] In one embodiment, the first pin is rod-shaped.

[0023] In one embodiment, the first pin projects into the at least one through-hole up to the end region opposite the first pin. Preferably, the first pin does not project beyond the at least one through-hole. The length of the first pin can be adapted to the depth of the at least one through-hole.

[0024] In one embodiment, the second end region has a second end face with a second pin protruding from the second end face.

[0025] In one embodiment, the second pin is connected to the metallized area by means of a solder joint or an adhesive bond.

[0026] In one embodiment, a connection element is arranged on the circuit board.

[0027] In one embodiment, the connecting element is a plug.

[0028] In one embodiment, the first end face is flat.

[0029] The present invention will now be explained in more detail with reference to the following figures, Figs. 1-6. They show:

[0030] Fig. 1: an embodiment of a pressure sensor.

[0031] Fig. 2: a first embodiment of the connecting element.

[0032] Fig. 3: The first embodiment of the connecting element, which is soldered. Fig. 4a-c: Three embodiments of the at least one first recess.

[0033] Fig. 5: a second embodiment of the connecting element.

[0034] Fig. 6: an alternative embodiment of the connecting element.

[0035] Fig. 1 shows a pressure sensor 1 according to the invention, comprising a pressure measuring cell 3, an electronic unit 4, and at least one connecting element 5. The pressure measuring cell 3 has a carrier body 6 and a measuring diaphragm 8, which are connected to each other by means of a joint 7, in particular such that a pressure chamber 25 is enclosed. An electrical transducer can be arranged in the pressure chamber 25, which may have a measuring electrode 20 and a counter electrode 21. The counter electrode 21 can be electrically connected to the electronic unit 4 by means of a lead 22. A pressure p1 of a medium 2 can act on the measuring diaphragm 8. The carrier body 6 has at least one metallized area 9 on a surface 6a facing away from the measuring diaphragm 8.

[0036] The at least one connecting element 5 electrically and mechanically connects the pressure measuring cell 3 and the electronic unit 4. The electronic unit 4 can have at least one contact surface 19 for this purpose. The electronic unit 4 can be designed as a printed circuit board 18. The electronic unit 4 can also be electrically and, if necessary, mechanically connected to a connection element 24, in particular by means of at least one solder joint 23. The connection element 24 can, for example, be a plug.

[0037] A first embodiment of the at least one connecting element 5 is shown in Fig. 2. The at least one connecting element 5 has a base body 10 with a first end region 10 and a second end region 11. The first end region 10 is preferably located opposite the second end region 11. The first end region 11 has a first end face 13, which is preferably flat. At least one first recess 14 is arranged in the first end face 13. The first end face 13 is connected to the electronic unit 15 by means of a solder joint 15 (see Fig. 3). The second end region 12 is connected to the at least one metallized area 9, preferably electrically, for example by means of a solder joint 15. For example, a pin 28 can protrude from the second end region 12, which is soldered to the at least one metallized area 9, as shown in Fig. 3.Alternatively, the second end region 12 can have a second end face 26 in which at least one second recess 27 is arranged. Such a configuration is shown in Fig. 2.

[0038] Figures 4a-c show three possible configurations of the at least one first recess 14. The at least one first recess 14 can be configured as a groove (see Fig. 4a), as two intersecting grooves, particularly intersecting at right angles (see Fig. 4b), or as a blind hole (see Fig. 4c). The at least one second recess 27 can also be configured as shown in Figures 4a-c.

[0039] Figure 5 shows a second embodiment of the at least one connecting element 5. In this case, the connecting element 5 is designed as a hollow cylinder 16 with an interior space 17. The interior space 17 is the at least one first recess 14. The connections of this embodiment of the connecting element 5 can be designed in the same way as those of the first embodiment.

[0040] Figure 6 shows a further embodiment of the at least one connecting element 5. In this case, the at least one connecting element 5 has a cylindrical base body 10 with a first end region 11 and a second end region 12. The first end region 11 has a first end face 13 with a first pin 28 projecting from the first end face 13. In connection with this embodiment of the connecting element 5, the electronic unit is a printed circuit board 18 with at least one through-hole 30 (shown with dashed lines). The first pin 28 projects into the at least one through-hole 30 and is connected to the printed circuit board 18 by means of a solder joint 15. In particular, the first pin 28 projects into the at least one through-hole 30 up to an end region 31 opposite the first pin 28. The solder joint is in contact with the through-hole 30.The first pin 28 is soldered into the at least one through-hole 30.

[0041] The second end region 12 is connected to the at least one metallized region 9, in particular electrically, for example by a solder joint 15. For example, a second pin 29 can protrude from the second end region 12, which is soldered to the at least one metallized region 9. The remaining structure of the pressure sensor 1, in particular the pressure measuring cell 3, from Fig. 1 also applies to this embodiment of the at least one connecting element 5.

[0042] Reference symbol list

[0043] 1 pressure sensor

[0044] 2 Medium

[0045] 3 pressure measuring cells

[0046] 4 Electronic unit

[0047] 5 Connecting element

[0048] 6 carrier bodies

[0049] 6a Surface

[0050] 7 Joint

[0051] 8 measuring membrane

[0052] 9 metallized areas

[0053] 10 basic shapes

[0054] 11 first end area

[0055] 12 second end area

[0056] 13 first front face

[0057] 14 first exception

[0058] 15 solder joints

[0059] 16 hollow cylinders

[0060] 17 Interior

[0061] 18 circuit boards

[0062] 19 Contact area

[0063] 20 Measuring electrode

[0064] 21 Counter electrode

[0065] 22 Feed

[0066] 23 solder joints

[0067] 24 connection element

[0068] 25 pressure chamber

[0069] 26 second front face

[0070] 27 second exception

[0071] 28 first pin

[0072] 29 second pin

[0073] 30 through holes

[0074] 31 End area of ​​the through hole

Claims

Patent claims 1. Pressure sensor (1) for determining and / or monitoring the pressure of a medium (2), comprising a pressure measuring cell (3), an electronic unit (4), and at least one connecting element (5) which electrically and mechanically connects the pressure measuring cell (3) and the electronic unit (4), wherein the pressure measuring cell (3) has a carrier body (6) and a ceramic measuring diaphragm (8) connected to the carrier body (6) by means of a joining point (7), wherein the measuring diaphragm (8) is subject to the pressure of the medium (2), wherein the carrier body (6) has at least one metallized area (9) on a surface (6a) facing away from the measuring diaphragm (8), wherein the at least one connecting element (5) has a cylindrical base body (10) with a first end region (11) and a second end region (12), wherein the second end region (12) is connected to the metallized area (9), and wherein the first end region (11) has a first end face (13).in which at least one first recess (14) is arranged, wherein the first end face (13) is connected to the electronic unit (4) by means of a solder joint (15).

2. Pressure sensor (1) according to claim 1, wherein the at least one first recess (14) is designed as a blind hole.

3. Pressure sensor (1) according to claim 1, wherein the at least one first recess (14) is designed as a groove.

4. Pressure sensor (1) according to claim 1, wherein the at least one first recess (14) is configured as two intersecting grooves.

5. Pressure sensor (1) according to claim 1 , wherein the base body (10) is a hollow cylinder (16) with an interior space (17) and the at least one first recess (14) is formed by the interior space (17).

6. Pressure sensor (1) according to one of the preceding claims, wherein the second end region (12) is connected to the metallized region (9) by means of a solder joint or an adhesive joint.

7. Pressure sensor (1) according to one of the preceding claims, wherein the second end region (12) has a second end face (26) which has at least a second recess (27).

8. Pressure sensor (1 ) according to one of the preceding claims, wherein the electronic unit (4) comprises a printed circuit board (18) with multiple contact surfaces (19), wherein the first end region (11 ) is connected to one of the multiple contact surfaces (19).

9. Pressure sensor (1 ) according to one of the preceding claims, wherein the first end face (13) is flat.

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