Sensor Element, Sensor Arrangement, and Method for Manufacturing a Sensor Element and a Sensor Arrangment

Abstract

A sensor element, a sensor arrangement, and a method for manufacturing a sensor element and a sensor arrangement are disclosed. In an embodiment, a sensor element includes a ceramic main body having at least one electrode arranged at the main body and having at least one contact piece for the electrical contacting of the electrode, wherein the contact piece is fastened to the electrode by welding or bonding.

Claims

1-15. (canceled)

16. A sensor element comprising: a ceramic main body having at least one electrode arranged at the main body and having at least one contact piece for the electrical contacting of the electrode, wherein the contact piece is fastened to the electrode by welding or bonding.

17. The sensor element according to claim 16, wherein the contact piece is fastened by gap welding, thermode welding or laser welding.

18. The sensor element according to claim 16, wherein the contact piece is fastened to the electrode by thick-wire bonding or thin-wire bonding.

19. The sensor element according to claim 16, wherein the contact piece comprises a metal from the group consisting of Cu, Fe and Ni.

20. The sensor element according to claim 16, wherein the electrode has at least one layer which is formed by a burnt-in paste.

21. The sensor element according to claim 16, wherein the electrode has at least one sputtered layer.

22. The sensor element according to claim 21, wherein the sputtered layer comprises nickel.

23. The sensor element according to claim 16, wherein the electrode has multiple layers which are arranged directly one above the other.

24. The sensor element according to claim 23, wherein the electrode has a layer comprising nickel and has a surface layer arranged thereabove.

25. The sensor element according to claim 24, wherein the contact piece is fastened directly to the surface layer.

26. The sensor element according to claim 24, wherein the contact piece is fastened to a layer which is partially covered by the surface layer.

27. A sensor arrangement comprising: a sensor element according to claim 16; and a support for supporting the main body.

28. The sensor arrangement according to claim 27, wherein the support has a rod-shaped form.

29. The sensor arrangement according to claim 27, wherein the contact piece is a separate wire connecting the sensor element with the support.

30. The sensor arrangement according to claim 27, wherein the contact piece forms an integral constituent part of the support.

31. The sensor arrangement according to claim 27, wherein the support is a circuit board, has at least one thick wire or is a ceramic support.

32. The sensor arrangement according to claim 27, wherein the support comprises a ceramic, and wherein metallizations are located on two sides of the support.

33. The sensor arrangement according to claim 27, wherein the support comprises two support elements, wherein the sensor element comprises two electrodes and two contact elements, and wherein each of the contact elements connects one of the electrodes with one of the support elements.

34. The sensor arrangement according to claim 33, wherein the contact elements are thick wires or bars.

35. A method for producing a sensor element, the method comprising: fastening at least one electrical contact piece to at least one electrode by welding or bonding, wherein the at least one electrode is arranged at a ceramic main body.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Below, the subjects described here will be discussed in more detail on the basis of schematic exemplary embodiments, which are not true to scale:

[0051] In the figures:

[0052] FIG. 1 shows a perspective view of a sensor element,

[0053] FIG. 2 shows a first embodiment of a sensor arrangement,

[0054] FIG. 3A shows a second embodiment of a sensor arrangement,

[0055] FIG. 3B shows an enlarged detail from FIG. 3A,

[0056] FIG. 4A shows a third embodiment of a sensor arrangement,

[0057] FIG. 4B shows an enlarged detail from FIG. 4 A,

[0058] FIG. 5A shows a fourth embodiment of a sensor arrangement,

[0059] FIG. 5B shows an enlarged detail from FIG. 5A.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

[0060] It is preferably the case that, in the following figures, the same reference signs refer to functionally or structurally corresponding parts of the various embodiments.

[0061] FIG. 1 shows a sensor element 1, in particular a sensor chip. The sensor element 1 is preferably designed for measuring a temperature. The sensor element has a ceramic main body 2. In particular, the ceramic is an NTC (negative temperature coefficient) ceramic. For example, the ceramic has a perovskite structure. In particular, the ceramic may be based on the system Y—Ca—Cr—Al—(Sn)—O, wherein elements placed between parentheses are optionally provided. A sensor element 1 of said type is suitable in particular for high-temperature applications. Alternatively, the sensor element 1 may, in particular in the case of relatively low usage temperatures, have a ceramic with a spinel structure. For example, the ceramic may be based on the system Ni—Co—Mn—(Al)—(Fe)—(Cu)—(Zn)—(Ca)—(Zr)—(Ti)—(Mg)—O.

[0062] The sensor element 1 has an electrode 4 which is arranged on a side face 3 of the main body 2. A further electrode 8 is arranged on a further, oppositely situated side face 7. Below, the construction of one electrode 4 will be described, wherein the description may apply analogously to the further electrode 8.

[0063] The electrode 4 is a layered electrode with multiple layers 5, 6. The layers 5, 6 are, for example, sputtered. The electrode 4 is designed such that reliable electrical contacting of the electrode 4 is possible by bonding or by welding.

[0064] The electrode 4 has a layer 5 which is also referred to as an electrode base. The layer 5 is applied directly to the ceramic of the main body 2. The layer 5 comprises, for example, nickel with a fraction of vanadium, or is composed of said metals.

[0065] A surface layer 6 is applied to the layer 5. For example, the surface layer 6 serves as a corrosion preventer for the electrode base, in particular for preventing oxidation. The surface layer 6 comprises, for example, silver, gold, copper or aluminum, or is composed of one of said materials.

[0066] In one embodiment, the electrode base may be of multi-layer form. A lower layer of the electrode base is, for example, in direct contact with the ceramic. The lower layer comprises, for example, chromium, or is composed of chromium. The electrode base may furthermore have an upper layer which is applied to the lower layer. The upper layer comprises, for example, nickel with a fraction of vanadium, or is composed of said metals.

[0067] For example, all layers 5, 6 of the electrode 4 are applied by sputtering. Alternatively, the electrode base may be formed by burning-in of a metal paste, for example, a gold or silver paste.

[0068] Contact pieces 19, 20 are fastened to the electrodes 4, 8 by welding or bonding. The contact pieces 19, 20 are formed as contact elements in the form of short wires. For example, the wires are fastened to the electrodes 4, 8 by bonding.

[0069] Those ends of the contact pieces 19, 20 which are still free in this case may be connected to connector elements. For example, the connector elements produce the electrical connection of the sensor element and may at the same time also form a support for the sensor element. The fastening of the contact pieces 10, 20 to the connector elements may likewise be realized by way of welding or bonding. Alternatively, the contact pieces may also be soldered to the connector elements.

[0070] In one embodiment, the contact pieces form an integral constituent part of a support. In this case, the contact pieces have sufficient inherent stability to support the main body. For example, the contact pieces are in the form of thick wires.

[0071] The contact pieces 19, 20 preferably have temperature-stable metals with a low corrosion tendency. It is, for example, possible for precious metals such as, for example, Pt, Au, Ag or semi-precious metals such as, for example, Cu, and also non-precious metals such as, for example, Fe, Ni, or alloys, to be used. Furthermore, the contact pieces 19, 20 may also be constructed with different regions having different materials. For example, the contact pieces 19, 20 have subregions of different materials. The contact pieces 19, 20 may have a metallic wire core and be encased with one or more other metals. The surface of the contact pieces 19, 20 may additionally also have a coating such as, for example, a tin coating, a nickel coating etc.

[0072] FIG. 2 shows a sensor arrangement 24 having a sensor element 1 which is fastened to a circuit board 9. Said construction may be used in particular in the field of power electronics. The main body 2 and the electrodes 4, 8 of the sensor element 1 are designed as in FIG. 1.

[0073] The circuit board 9 functions as a support 25 for the main body 2 of the sensor element 1 and for the electrical connection of the electrodes 4, 8. The sensor element 1 has a top side 10 and a bottom side 11. The sensor element 1 is fastened by way of its bottom side 11 to the circuit board 9. The electrode 4 arranged on the top side 10 is electrically connected to a first conductor track 12, and the further electrode 8 arranged on the bottom side 11 is electrically connected to a further conductor track 13 of the circuit board 9.

[0074] The sensor element 1 is, for example, soldered by way of its bottom side 11 to the further conductor track 13. For a migration-resistant connection, which is free from silver and free from lead, by way of soldering, a surface layer 6 comprising gold or composed of gold is advantageous. Alternatively, the further electrode 8 is sintered with the further conductor track 13. For this purpose, it is, for example, the case that a fine-particle silver paste is applied to the conductor track 13 and/or to the further electrode 8. Sintering is performed, for example, under pressure at low temperatures. In this case, the surface layer of the further electrode 8 preferably has silver or is composed of silver.

[0075] The electrode 4 on the top side 10 is connected by way of a contact piece 14 to the conductor track 12. The contact piece 14 is fastened to the electrode 4 and/or to the circuit board 9, for example, by bonding. In particular, the contact piece 14 is formed by a wire bridge. The wire is flattened at its ends. In particular, the contact piece involves a thin wire, which may be fastened by thin-wire bonding. It is, for example, the case that a gold wire, an aluminum wire or a copper wire is used. The surface layer 6 of the electrode 4 has, for example, gold. The contact piece 14 may, in terms of material and construction, be formed similarly to the contact pieces 19, 20 described in FIG. 1.

[0076] FIG. 3A shows a further embodiment of a sensor arrangement 24. FIG. 3B shows an enlarged detail from FIG. 3A. In particular, the sensor arrangement involves a probe 15 having a sensor element 1. The probe 15 is, for example, in the form of a temperature probe. The sensor element 1 is, for example, designed as in FIG. 1.

[0077] The probe 15 is of rod-shaped form. The probe 15 is, for example, used for measuring a temperature of a flowing medium. For example, the probe 15 can be inserted through an opening into the wall of a pipe.

[0078] The probe 15 has a support 25 comprising two support elements 17, 18. The support elements 17, 18 are, for example, in the form of thick wires which can support the main body 2 of the sensor element 1 and which exhibit adequate dimensional stability. The support elements 17, 18 are in each case of rod-shaped form.

[0079] The sensor element 1 is surrounded by an encasement 16. The encasement 16 can ensure adequate mechanical stability of the probe 15. Furthermore, by way of the encasement 16, protection against external influences is possible, and it is, for example, possible for corrosion of the sensor element 1 by aggressive media to be prevented. For example, the encasement 16 has a polymer or glass. The support elements 17, 18 project into the encasement 16. In particular, the contact pieces 19, 20 and thus the contact points between the support elements 17, 18 and the sensor element 1 are surrounded by the encasement 16.

[0080] The support elements 17, 18 also serve for the electrical connection of the sensor element 1. In particular, the support elements 17, 18 are electrically conductive. The ends of the support elements 17, 18 are in the form of contact pieces 19, 20 for the direct electrical contacting with the electrodes 4, 8. The contact pieces 19, 20 form an integral part of the support elements 17, 18. The contact pieces 19, 20 of the support elements 17, 18 are, for example welded, or fastened by thick-wire bonding, to the electrodes 4, 8.

[0081] It is preferably the case that no solder is used for the connection between the support elements 17, 18 and the electrodes 4, 8. In the case of a welding or bonding process, a migration can be prevented, and the reliability of the sensor element 1 can be increased.

[0082] The support elements 17, 18 and in particular the contact pieces 19, 20 may, in terms of material and structure, be designed similarly to the contact pieces 19, 20 described in FIG. 1. However, the contact pieces 19, 20 together with the remaining part of the support elements 17,18 exhibit sufficient inherent stability to support the sensor element 1.

[0083] FIG. 4A shows a further embodiment of a sensor arrangement 24 in the form of a probe 15. FIG. 4B shows an enlarged detail from FIG. 4A. The sensor arrangement 24 is of similar form to the sensor arrangement 24 from FIG. 3A. However, in the embodiment shown here, the sensor element 1 is not directly fastened to the support elements 17, 18, in particular is not directly electrically connected to the support elements 17, 18. In the present case, the encasement 16 provides the mechanical fastening of the sensor element 1 to the support 25.

[0084] Instead, the sensor element 1 is fastened by way of separate contact pieces 19, 20 to the support elements 17, 18. The contact pieces 19, 20 are in the form of wires, in particular bonding wires. The sensor element 1 with the contact pieces 19, 20 may in particular be designed as described in FIG. 1.

[0085] FIG. 5A shows a further embodiment of a sensor arrangement 24 in the form of a probe 15 in a semitransparent illustration. FIG. 5B shows an enlarged detail from FIG. 5A. The sensor element 1 is designed as in FIG. 1.

[0086] The probe 15 has a support 25 which is provided, on two sides, with metallizations 22, 23. The support 25 has a ceramic. The electrodes 4, 8 of the sensor element 1 are electrically connected to the metallizations 22, 23 by way of in each case one contact piece 19, 20. The contact pieces 19, 20 are fastened to the electrodes 4, 8 of the sensor element 1 by welding or bonding. The contact pieces 19, 20 are fastened to the support 25 likewise by welding or bonding.