Method for producing a connection between two ceramic parts - in particular, of parts of a pressure sensor

Abstract

A method according to the invention for producing a connection between two surfaces or surface sections of two ceramic parts comprises: provision of a first ceramic part and of a second ceramic part; provision of an active brazing solder material on at least one surface section of at least one of the ceramic parts; and heating the active brazing solder in a vacuum brazing process. The whole active brazing solder material is provided for connecting the first and the second ceramic part by a sputtering method, wherein at least one surface section of at least one of the ceramic parts, preferably of the two ceramic parts, is layered with a layer sequence of individual components of the active brazing solder material, wherein the average strength of the layers of an individual component of the active brazing solder is no more than 0.5%, in particular not more than 0.2%, preferably not more than 0.1% and especially preferably not more than 0.05% of the strength of the joining region.

Claims

1-18. (canceled)

19. A method for producing a connection between two surfaces or surface segments of two ceramic parts, including: provision of a first ceramic part and a second ceramic part; provision of an active brazing solder material on at least one surface segment of at least one of the ceramic parts; and heating the active brazing solder in a vacuum brazing process, wherein, according to the invention, the entirety of the active brazing solder material for connecting the first and second ceramic parts is provided via a sputtering method, wherein: at least one surface segment of at least one of the ceramic parts, and preferably both ceramic parts, is layered with a layer sequence of the individual components of the active brazing solder material; and the mean thickness of the layers of an individual component of the active brazing solder is no more than 0.5%—especially not more than 0.2%, preferably not more than 0.1%, and especially preferably not more than 0.05%—of the thickness of the joining region.

20. The method according to claim 19, wherein: the active brazing solder in the joining region has a thickness of no more than 20 μm—especially no more than 15 μm, preferably no more than 12 μm, and particularly preferably no more than 10 μm.

21. The method according to claim 19, wherein: the individual layers of the component have a thickness of no more than 10 nm—especially no more than 5 nm, preferably no more than 2 nm, and particularly preferably no more than 1 nm.

22. The method according to claim 19, wherein: the mean layer thickness of the layers of a component, and/or their frequency, is a function of the proportion of the component in the alloy.

23. The method according to claim 19, wherein: the mean layer thickness of the layers of a component is proportional to the proportion of the component in the alloy.

24. The method according to claim 19, wherein: the components are respectively sputtered from pure sputter targets that respectively comprise exclusively the material of the component.

25. The method according to claim 19, wherein: the thickness of the individual layers is controlled over the respective layering time as a function of the deposition rate of the individual components.

26. The method according to claim 19, wherein: a deposition rate of the individual components is respectively monitored by means of a quartz crystal microbalance.

27. The method according to claim 19, wherein: a first layer sequence of a first composition of the components of the active brazing solder is first deposited on the at least one surface; a second layer sequence of a second composition of the components of the active brazing solder follows the first layer sequence; and the first composition especially has a melting point that is not less than 100 K° lower than the melting point of the second composition.

28. The method according to claim 27, wherein: the second composition has a coefficient of thermal expansion that has a smaller difference from the coefficient of thermal expansion of the ceramic material than the coefficient of thermal expansion of the first composition.

29. The method according to claim 27, wherein: the first layer sequence has a thickness that is no more than 10%—especially, no more than 5%—of the thickness of the joining region.

30. The method according to claim 19, wherein: a first layer, with which at least one of the joining partners is layered, has an active component of the active brazing solder.

31. The method according to claim 19, wherein: the active brazing solder has a Zr—Ni—Ti alloy, wherein the at least one active component especially comprises titanium or zirconium.

32. The method according to claim 19, wherein: the first and/or second ceramic part comprise corundum.

33. The method according to claim 19, wherein: the first ceramic part and the second ceramic part are connected so as to be pressure-sealed along an annular joining region which encloses a cavity between the first ceramic part and the second ceramic part; the active brazing solder is deposited on at least one annular surface segment of a ceramic part; and a region enclosed by the annular surface segment is masked during the deposition of the active brazing solder.

34. The method according to claim 19, wherein: the brazing process includes a vacuum brazing process or a brazing process under inert gas.

35. The method according to claim 19, wherein: the first ceramic part comprises a base body of the pressure sensor; the second ceramic part comprises the measurement membrane of the pressure sensor; and the measurement membrane is connected with the base body so as to be pressure-sealed along an annular joining region which has the active brazing solder.

36. The method according to claim 33, wherein: the pressure sensor is a differential pressure sensor which has a measurement membrane between two base bodies or one base body between two measurement membranes, which two base bodies or two measurement membranes are to be joined with one another; and the active brazing solder material is respectively provided in the same manner for the two joining regions between the measurement membrane and the counter-bodies or the measurement membranes and the counter-body.

Description

[0032] The invention will now be explained on the basis of the exemplary embodiment shown in the drawings.

[0033] Illustrated in the drawings:

[0034] FIG. 1: components of a ceramic pressure sensor which are joined by means of the method according to the invention;

[0035] FIG. 2a: a flow diagram of an exemplary embodiment of the method according to the invention; and

[0036] FIG. 2b: a more detailed flow diagram for implementing a method step of the exemplary embodiment from FIG. 2a

[0037] The components of a ceramic pressure sensor 1 that are depicted in FIG. 1 comprise a circular, disc-shaped measurement membrane 2 of a circular, disc-shaped base body 3 which comprise corundum. The measurement membrane may especially comprise highly pure corundum with a purity of better than 99.98%. Depending upon the embodiment, the measurement membrane 1 and the base body 2 have a diameter of approximately 15 to 25 mm, for example. For example, the material thickness of the measurement membrane 2 is 100 μm to 2 mm, whereas the base body has a material thickness of a few mm. However, the cited dimensions are not a value significant to the invention, and may be chosen according to the requirements of the measurement technology or other boundary conditions, for example. The measurement membrane 1 and the base body 2 are to be connected so as to be pressure-sealed by means of a Zr—Ni—Ti active brazing solder in a high-vacuum brazing process.

[0038] For this, the faces to be joined of the measurement membrane 2 and of the base body 3 are respectively first masked, except for an annular border region, in order to then prepare the active brazing solder for the joining region in the annular border region by means of chemical vapor deposition.

[0039] After the complete deposition of the active brazing solder to form the joining region, the measurement membrane 2 and the base body 3 with the active brazing solder layers are placed one atop the other and, in a vacuum brazing process, connected with one another so as to be pressure-sealed.

[0040] Electrodes for a capacitive transducer of the pressure sensor are preferably prepared before the deposition of the active brazing solder (not shown here). This may likewise take place by means of chemical vapor deposition in a sputtering process. For example, Ta, which is deposited in a thickness of, for example, 0.1 to 0.2 μm, is suitable as an electrode material. For example, a preferred electrode arrangement may enable a formation of a differential capacitor, for which a central measurement electrode in the shape of a circular area and an annular reference electrode of the same capacitance, surrounding said measurement electrode, are deposited on the facing side of the base body in the region to be surrounded by the annular joining region. The measurement electrode, the reference electrode, and the joining region are preferably electrically isolated from one another in the finished pressure sensor. A counter-electrode is preferably prepared over the entire surface of the membrane, which counter-electrode is preferably in galvanic contact with the joining region in the finished sensor.

[0041] An exemplary embodiment of a method for producing a connection between ceramic bodies, e.g., the above components of a pressure sensor, is now explained using FIGS. 2a through 2b. FIG. 2a, in this connection, initially shows, in general, a method 100 known per se, with a sequence of steps which includes the provision 110 of ceramic bodies, masking 120 of regions that are not to be layered, layering 130 of the ceramic bodies with active brazing solder, positioning 140 of the ceramic bodies relative to one another, and joining 150 the ceramic bodies in a vacuum brazing process. The characteristic feature of the present invention relates to the layering 130, which is presented in detail in FIG. 2b. According to this, the layering 130 is achieved via a repeated sequence of sputtering steps 131, 132, 133 until a desired layer sequence thickness of, for example, 5 μm is achieved, wherein the maximum individual layer thickness is approximately 5 nm. The layers of a first component may thus have a layer thickness of 1 nm, for example, the layers of a second component may have a thickness of 2 nm, and the layers of a third component may have a thickness of 5 nm, for example.

[0042] In sputtering, the thickness of the individual layers is controlled via the component-specific electrical power and the sputtering time, wherein the atomic mass and the density of the component at a given power are involved in the deposition rate.

[0043] However, given the same frequency of the layers of the individual components, there are necessarily alloys that can no longer be reasonably represented, due to a variation of the layer thickness. Therefore, for the components c.sub.Zr, c.sub.Ni, C.sub.Ti of a preferred Zr—Ni—Ti alloy, it applies that (in atomic %): 61<c.sub.Zr<63.5; 21.5<c.sub.Ni<24 and 14.5<C.sub.Ti<15.5.

[0044] Taking into account the respective atomic masses and solid densities of the pure materials, the following layer thickness ratios therefore result for a composition (in atomic %) with c.sub.Zr=62; c.sub.Ni=23 and d.sub.Ti=15:

d.sub.Zr=5 nm; d.sub.Ni=1.0 nm and d.sub.Ti=0.4 nm

[0045] In order to achieve a greater thickness of the titanium layer, the frequency of the zirconium layer may be doubled. The layer sequence is then Ti, Zr, Ni, Zr, Ti, Zr, Ni, Zr, . . . with the following layer thickness ratios:

d.sub.Zr=5 nm; d.sub.Ni=2.0 nm and d.sub.Ti=0.8 nm

[0046] A corresponding sub-process for the layering step 230 is depicted in FIG. 2c, wherein Zr corresponds to the first component, while Ni and Ti form the second or third component.

[0047] In order to achieve an efficient deposition rate with sufficiently good control of the rate, a sputtering system with a high-power magnetron is preferably used. With this, deposition rates between approximately 0.2 nm/s and approximately 2 nm/s can be set in a controlled manner. For the deposition of 5 μm, 2500 s (thus, nearly 42 minutes) are required, given a deposition rate of 2 nm/s.