Method for joining ceramic bodies by means of an active hard solder, or braze, assembly having at least two ceramic bodies joined with one another, especially a pressure measuring cell

• US 9,631,994 B2
• Filed: 06/07/2013
• Issued: 04/25/2017
• Est. Priority Date: 07/11/2012
• Status: Active Grant

• Current Assignee: Endress + Hauser GmbH + Company KG (Endress+Hauser AG)
• Original Assignee: Endress + Hauser GmbH + Company KG (Endress+Hauser AG)
• Inventors: Ponath, Nils, Rossberg, Andreas, Schmidt, Elke
• Primary Examiner(s): BOLDUC, DAVID J
• Application Number:
  US14/413,470
• Publication Number:
  US 20150160086A1
• Time in Patent Office: 1,418 Days
• CPC Class Codes: B23K 1/0008 specially adapted for particular articles or work
• CPC Class Codes: B23K 1/0016 Brazing of electronic components
• CPC Class Codes: B23K 1/19 taking account of the properties of the materials to be soldered
• CPC Class Codes: C04B 2237/12 Metallic interlayers
• CPC Class Codes: C04B 2237/122 based on refractory metals
• CPC Class Codes: C04B 2237/126 wherein the active component for bonding is not the largest fraction of the interlayer
• CPC Class Codes: C04B 2237/343 Alumina or aluminates
• CPC Class Codes: C04B 2237/55 Pre-treatments of a coated or not coated substrate other than oxidation treatment in order to form an active joining layer
• CPC Class Codes: C04B 2237/597 whereby the interlayer is continuous but porous, e.g. containing hollow or porous particles, macro- or micropores or cracks
• CPC Class Codes: C04B 2237/708 of one or more of the interlayers
• CPC Class Codes: C04B 2237/72 Forming laminates or joined articles comprising at least two interlayers directly next to each other
• CPC Class Codes: C04B 37/006 consisting of metals or metal salts
• CPC Class Codes: G01L 9/0044 Constructional details of non-semiconductive diaphragms
• CPC Class Codes: G01L 9/0072 using variations in capacitance
• CPC Class Codes: G01L 9/0075 using a ceramic diaphragm, e.g. alumina, fused quartz, glass

Abstract

An assembly, comprising: a first ceramic body and a second ceramic body connected by means of a joint of an active hard solder, or braze, wherein the active hard solder, or braze, averaged over a continuous main volume, which includes at least 50% of the volume of the joint, has an average composition C_M with a liquidus temperature T_l(C_M). An edge region of the joint, which contacts at least one of the ceramic bodies, has an average composition C_E with a liquidus temperature T_l(C_E), which lies not less than 20 K, preferably not less than 50 K, and especially preferably not less than 100 K above the liquidus temperature T_l(C_M) of the average composition C_M of the main volume.

Claims

1. An assembly, comprising:

a first ceramic body; and

a second ceramic body, wherein;

said first ceramic body and said second ceramic body are connected by means of a joint, said joint contains an active hard solder, or braze;

said active hard solder, or braze, averaged over a continuous main volume, which includes at least 50% of the volume of the joint, has an average composition C_M with a liquidus temperature T_l(C_M), wherein C_M;

=(c_M1, . . . , c_MN), wherein |C_M|=1, and wherein the c_Mi are the stoichiometric fractions of the components K_i i=1, . . . , N of the average composition of the active hard solder, or braze, in the main volume; and

an edge region of said joint, which contacts at least one of said ceramic bodies and which overlaps no more than 8% of the main volume, has an average composition C_E with a liquidus temperature T_l(C_E), which lies not less than 20 K, above the liquidus temperature T_l(C_M) of the average composition C_M of the main volume, wherein C_E;

=(c_E1, . . . , c_EN), wherein |C_E|=1, and wherein the c_Ei are the stoichiometric fractions of the components K_i i=1, . . . , N of the average composition of the active hard solder, or braze, in the edge region.

2. The assembly as claimed in claim 1, wherein:

the edge region with the average composition C_E has a volume, which amounts to not less than 0.1% of the volume of the joint.

3. The assembly as a claimed in claim 1, wherein:

said joint is ring-shaped; and

the main volume is defined by a body of revolution, which is formed by rotation of a convex polygon, especially a rectangle, about the principal axis of rotation of said ring-shaped joint.

4. The assembly as claimed in claim 3, wherein:

the edge region with composition C_E extends along the inner edge of said ring-shaped joint.

5. The assembly as claimed in claim 1, wherein:

the liquidus temperature of T_l(C_M) rises monotonically to the liquidus temperature T_l(C_E) with change of composition from C_M to C_E.

6. The assembly as claimed in claim 1, wherein:

the composition C_M has a liquidus temperature T_l(C_M), which lies no more than 300 K, above the liquidus temperature T_l(C_e) of a eutectic point, respectively of a nearest intersection with a eutectic valley with a composition C_e in the composition space,

wherein C_e;

=(c_e1, . . . , c_eN), wherein |C_e|=1, and wherein the c_ei are the stoichiometric fractions of the components K_i with i=1, . . . , N at the eutectic point, respectively a nearest intersection with a eutectic valley.

7. The assembly as claimed in claim 1, wherein:

an alloy of said joint has at an eutectic point, respectively at the nearest intersection with a eutectic valley in the composition space a composition C_e, wherein C_e ;

=(c_e1, . . . , c_eN), wherein |C_e|=1, wherein the c_ei are the stoichiometric fractions of the components K_i with i=1, N at the eutectic point, respectively at the nearest intersection with a eutectic valley;

the difference between the composition C_e and the composition C_M is describable with a normalized vector difference D_eM, wherein;

C_e=C_M+a_eM*D_eM, with |D_eM|=1; and

wherein the difference between the composition C_E and the composition C_M is describable with a normalized vector difference D_EM, wherein;

C_E=C_M+a_EM*D_EM, with |D_EM|=1, wherein a_eM and a_EM are positive scalars, wherein for the scalar product S_eE;

=D_eM·

D_EM;

S_eE<

0.

8. The assembly as claimed in claim 1, wherein:

the composition C_E of the edge region contains the same metals as the composition C_M of the main volume or other metals.

9. The assembly as claimed in claim 1, wherein:

said first ceramic body and/or said second ceramic body comprises Al₂O₃.

10. The assembly as claimed in claim 1, wherein

said active hard solder, or braze, contains Zr, Ni and Ti.

11. The assembly as claimed in claim 10, wherein:

the composition C_M comprises 20 atom-% to 24 atom-% Ni, 13 atom-% to 17 atom-% Ti and remainder Zr, and aluminum, which diffuses in the soldering process from the ceramic into said joint;

the composition C_M comprises 63 atom-% Zr, 22 atom-% Ni and 15 atom-% Ti;

in cases when Al is present, the titanium fraction is reduced; and

the composition C_E has compared with the composition C_M an increased Ni fraction.

18. The assembly as claimed in claim 1, wherein:

the main volume includes at least 70% of the volume of the joint.

19. The assembly as claimed in claim 1, wherein:

the main volume includes at least 80% of the volume of the joint.

20. The assembly as claimed in claim 1, wherein:

the edge region overlaps no more than 4% of the main volume.

21. The assembly as claimed in claim 1, wherein:

the edge region overlaps no more than 2% of the main volume.

22. The assembly as claimed in claim 1, wherein:

the edge region lies outside of the main volume.

23. The assembly as claimed in claim 1, wherein:

the composition C_E of the edge region has a liquidus temperature T_l(C_E), which lies not less than 50 K above the liquidus temperature T_l(C_M) of the average composition C_M of the main volume.

24. The assembly as claimed in claim 1, wherein:

the composition C_E of the edge region has a liquidus temperature T_l(C_E), which lies not less than 100 K above the liquidus temperature T_l(C_M) of the average composition C_M of the main volume.

25. The assembly as claimed in claim 1, wherein:

the edge region with the average composition C_E has a volume, which amounts to not less than 0.5% of the volume of the joint.

26. The assembly as claimed in claim 1, wherein:

the edge region with the average composition C_E has a volume, which amounts to not less than 1% of the volume of the joint.

29. The assembly as claimed in claim 18, wherein:

s_eE<

−

0.5.

30. The assembly as claimed in claim 18, wherein:

s_eE<

−

0.8.

31. The assembly as claimed in claim 24, wherein:

the composition C_M comprises 63 atom-% Zr, 22 atom-% Ni and 15 atom-% Ti.

32. The assembly as claimed in claim 23, wherein:

the composition C_M comprises 20 atom-% to 24 atom-% Ni, 13 atom-% to 17 atom-% Ti and remainder Zr, as well as, aluminum, which diffuses in the soldering process from the ceramic into said joint.

33. The assembly as claimed in claim 26, wherein:

the composition C_M comprises 63 atom-% Zr, 22 atom-% Ni and 15 atom-% Ti;

the titanium fraction is reduced; and

the composition C_E has compared with the composition C_M an increased Ni fraction.

12. A pressure sensor, comprising:

an assembly having a first ceramic body; and

a second ceramic body, wherein;

said first ceramic body and said second ceramic body are connected by means of a joint, said joint contains an active hard solder, or braze;

said active hard solder, or braze, averaged over a continuous main volume, which includes at least 50%, of the volume of the joint, has an average composition C_M with a liquidus temperature T_l(C_M), wherein C_M;

=(c_M1, . . . ,c_MN), wherein |C_M|=1, and wherein the c_Mi are the stoichiometric fractions of the components K_i i=1, . . ., N of the average composition of the active hard solder, or braze, in the main volume; and

an edge region of said joint, which contacts at least one of said ceramic bodies and which overlaps no more than 8% of the main volume, has an average composition C_E with a liquidus temperature T_l(C_E), which lies not less than 20 K, above the liquidus temperature T_l(C_M) of the average composition C_M of the main volume, wherein C_E ;

=(c_E1, . . . , c_EN), wherein |C_E|=1, and wherein the c_Ei are the stoichiometric fractions of the components K_i i=1, . . . , N of the average composition of the active hard solder, or braze, in the edge region;

wherein;

said first ceramic body is a membrane body of a measuring membrane of the pressure sensor;

said second ceramic body is a platform of the pressure sensor; and

said platform and said measuring membrane are joined pressure-tightly with one another by means of said joint, which is ring-shaped.

13. The pressure sensor as claimed in claim 12;

further having;

a capacitive transducer, wherein;

a surface of said platform facing said measuring membrane and/or the surface of said measuring membrane facing said platform, have, respectively, a metal electrode; and

said metal electrode comprises a metal, which is enriched in the composition C_E in comparison to the composition C_M.

14. The pressure sensor as claimed in claim 13,

wherein:

said metal, which the electrode comprises, comprises nickel.

15. A method for manufacturing an assembly, especially an assembly which comprises a first ceramic body and a second ceramic body, wherein the first ceramic body and the second ceramic body are to be joined by means of an active hard solder, or braze, the method comprises the steps of:

providing the active hard solder, or braze, and a solder stop between the ceramic bodies, wherein the active hard solder, or braze, has, averaged over a continuous main volume, which includes at least 50%, 90% of the volume of the active hard solder, or braze, an average composition C_M0 with a liquidus temperature T_l(C_M0), wherein C_M0;

=(c_M01, . . . , c_M0N), wherein |C_M0|=1, and wherein the c_Mi are the stoichiometric fractions of the components K_i i=1, N of the average composition of the active hard solder, or braze, in the main volume, the solder stop has at least one material, whose liquidus temperature lies above the liquidus temperature of the composition C_M of the main volume, and a mixing of the material of the solder stop with the composition C_M leads, at least in the edge region of a joint to be formed by the method, to an average composition C_E, wherein the composition C_E has a liquidus temperature T_l(C_E), which lies not less than 20 K above the liquidus temperature T_l(C_M0) of the average composition C_M0 of the main volume, wherein C_E;

=(c_E1, . . . , c_EN), wherein |C_E|=1, and wherein the c_Ei are the stoichiometric fractions of the components K_i i=1, . . ., N of the average composition of the active hard solder, or braze, in the edge region; and

heating the ceramic bodies, the active hard solder, or braze, and the solder stop in a vacuum soldering, brazing process, at least up to melting of the composition C_M, wherein the melt in the edge region of the active hard solder, or braze, mixes with the material of the solder stop, whereby the melt in the edge region isothermally solidifies or becomes more viscous, and stops.

16. The method as claimed in claim 15, wherein:

the solder stop is provided by depositing a metal or a mixture of various metals on at least one surface section of at least one ceramic body; and

an enrichment of the metal or the mixture of metals in the active hard solder, or braze, leads to an increased liquidus temperature compared with the liquidus temperature of the composition of the main volume of the active hard solder, or braze.

17. The method as claimed in claim 16, wherein:

the surface section of the ceramic body, in which the solder stop is provided, overlaps the contact surface between the joint and the ceramic body no more than 25%, of the contact surface between the joint and the ceramic body.

27. The assembly as claimed in claim 15, wherein:

the composition C_M has a liquidus temperature T_l(C_M), which lies no more than 150 K above the liquidus temperature T_l(C_e) of said eutectic point, respectively of said nearest intersection with said eutectic valley.

28. The assembly as claimed in claim 15, wherein:

the composition C_M has a liquidus temperature T_l(C_M), which lies no more than 50 K above the liquidus temperature T_l(C_e) of said eutectic point, respectively of said nearest intersection with said eutectic valley.

34. The pressure sensor as claimed in claim 28, wherein:

said average composition C_M of said active hard solder, or braze is averaged over a continuous main volume, which includes at least 70% of the volume of the joint.

35. The pressure sensor as claimed in claim 28, wherein:

said average composition C_M of said active hard solder, or braze is averaged over a continuous main volume, which includes at least 80% of the volume of the joint.

36. The pressure sensor as claimed in claim 28, wherein:

said edge region of said joint overlaps no more than 4% of the main volume.

37. The pressure sensor as claimed in claim 28, wherein:

said edge region of said joint overlaps no more than 2% of the main volume.

38. The pressure sensor as claimed in claim 28, wherein:

said edge region of said joint lies outside of the main volume.

39. The pressure sensor as claimed in claim 28, wherein:

said edge region of said joint has an average composition C_E with a liquidus temperature Tl(C_E), which lies not less than 50 K above the liquidus temperature T_l(C_M) of the average composition C_M of the main volume.

40. The pressure sensor as claimed in claim 28, wherein:

said edge region of said joint has an average composition C_E with a liquidus temperature Tl(C_E), which lies not less than 100 K above the liquidus temperature Tl(C_M) of the average composition C_M of the main volume.

41. The method as claimed in claim 38, wherein:

the active hard solder, or braze, has, averaged over a continuous main volume, which includes at least 70% and preferably of the volume of the active hard solder, or braze, said average composition C_M0.

42. The method as claimed in claim 38, wherein:

the active hard solder, or braze, has, averaged over a continuous main volume, which includes at least 90% and preferably of the volume of the active hard solder, or braze, said average composition C_M0.

43. The method as claimed in claim 38, wherein:

the composition C_E has a liquidus temperature T_l(C_E), which lies not less than 50 K above the liquidus temperature T_l(C_M0) of the average composition C_M0 of the main volume.

44. The method as claimed in claim 38, wherein:

the composition C_E has a liquidus temperature T_l(C_E), which lies not less than 100 K above the liquidus temperature Tl(C_M0) of the average composition C_M0 of the main volume.

45. The method as claimed in claim 44, wherein:

the surface section of the ceramic body, in which the solder stop is provided, overlaps the contact surface between the joint and the ceramic body no more than 10% of the contact surface between the joint and the ceramic body.