Ceramic-metal joining
OwnerChou H. Liinventor
Life of this patent
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Abstract
A method for improving the reliability of a ceramic-metal joint by reducing the dynamic mismatch stresses and strains on the ceramic due to the mismatch in thermal expansions of the two materials. This is done by bonding with a metal layer the ceramic to metal to form a bonding interfacial region between the ceramic and metal; and radially grading the interface region the thermal conductivity, thermal expansion coefficient, or tensile strength of the metal layer. An article in the form of a laterally graded, metallic bonding disc for overcoming problems of dynamic mismatch stresses and strains is also disclosed and claimed.
Claims38
A method for improving the reliability of a joint between a first body of a first solid material and a second body of a second solid material, said first solid material being dissimilar from and relatively weaker than said second solid material, said method comprising reducing the dynamic mismatch stresses on the relatively weaker first solid material body due to dynamic mismatches in thermal expansions between the two solid materials during transient heating or cooling of the joint so that the relatively weaker first solid material is no longer subjected to high stresses, comprising:
- providing a metal layer on a selected surface of the body of the first solid material;
- bonding with the metal layer the second solid material body to the selected surface of the first solid material body thereby forming with the metal layer a joint or bonding interfacial region between the two bodies;
- and
- grading from a central portion toward a peripheral portion of the joint at least one thermomechanical property of the material of the metal layer in the interfacial region to ensure that the maximum residual mismatch stresses will not exceed the local material strength in the first solid material at any point and time, said one thermochemical property being selected from the group consisting of thermal conductivity, thermal expansion coefficient, and softness or shock-absorbing ability.
A method as in claim 23 wherein the grading step comprises providing at least the bonding metallic layer with the highest thermal conductivity material in the central portion relative to the remaining portions of the joint.
A solid metallic bonding layer for bonding a ceramic body to a second solid material body thereby forming a bonding interfacial region therebetween,
- said ceramic body and said second material body having different thermophysical properties thereby creating residual mismatch stresses in the bonding layer, comprising:
- a first solid metallic bonding material in one part of the bonding layer creating thereat a first actual or residual mismatch stress which is the theoretical local dynamic mismatch stress with a first portion thereof absorbed at least in the first bonding material;
- a second solid metallic bonding material in another part of the bonding layer creating thereat a second actual or residual dynamic mismatch stress which is the theoretical local mismatch stress with a second portion thereof absorbed at least in the second bonding material;
- said two solid bonding materials substantially differing in at least one physical properties thereby absorbing different portions of the actual mismatch stresses,
- said first theoretical local mismatch stress being higher than said second theoretical local mismatch stress but said first portion being larger than said second portion so that both actual or residual dynamic mismatch stresses after the absorptions are less than those than can damage the bond between the ceramic and the second solid material.
A method for reducing the dynamic mismatch stress failure of a joint between two solid material bodies joined together with a solid metallic bonding layer therebetween thereby forming a joint or bonding interfacial region between the bodies, comprising:
- providing a plurality of physically integrated joint elements in parallel at a plurality of locations on the bonding interfacial region;
- at least one physical property of the joint element at one location being substantially different from the same property of the joint element at another location, so that the maximum or critical transient or dynamic mismatch stresses never exceed the local material strength at any point inside the joint region, at any time during the heating or cooling of such joints in processing or service.
Dependencies are inferred from the claim text.