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

Patent metadata

Field	Value
Publication number	US-9631994-B2
Application number	US-201314413470-A
Country	US
Kind code	B2
Filing date	Jun 7, 2013
Priority date	Jul 11, 2012
Publication date	Apr 25, 2017
Grant date	Apr 25, 2017

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.

First claim

The invention claimed is:

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 Al 2 O 3 .

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.

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 composit

Assignees

• Endress Hauser Gmbh Co Kg

Inventors

• Ponath Nils
• Rossberg Andreas
• Schmidt Elke

Classifications

• C04B2237/55

  Pre-treatments of a coated or not coated substrate other than oxidation treatment in order to form an active joining layer · CPC title

• C04B2237/126

  wherein the active component for bonding is not the largest fraction of the interlayer · CPC title

• B23K1/19

  taking account of the properties of the materials to be soldered · CPC title

• C04B2237/708

  of one or more of the interlayers · CPC title

• B23K1/0008 Primary

  specially adapted for particular articles or work · CPC title