Copper ceramic interface

Figure 8-9 A SEM photograph of the copper/ceramic interface of a substrate fired for 1...

Figure 9-2 The copper/ceramic interface after applying thermal shock of AT 250°C to an LTCC with copper conductor (a) and the copper/ceramic interface after conducting a bending strength test on a sample that has undergone thermal shock (b).

Figure 8-11 SEM photograph of a copper and ceramic interface (example in which the glass is segregated at the surface of the copper) [Bar = 10 pm].

Scientists from Politecnico di Milano and Ineos Vinyls UK developed a tubular fixed-bed reactor comprising a metallic monolith [30]. The walls were coated with catalytically active material and the monolith pieces were loaded lengthwise. Corning, the world leader in ceramic structured supports, developed metallic supports with straight channels, zig-zag channels, and wall-flow channels. They were produced by extrusion of metal powders, for example, copper, fin, zinc, aluminum, iron, silver, nickel, and mixtures and alloys [31]. An alternative method is extrusion of softened bulk metal feed, for example, aluminum, copper, and their alloys. The metal surface can be covered with carbon, carbides, and alumina, using a CVD technique [32]. For metal monoliths, it is to be expected that the main resistance lies at the interface between reactor wall and monolith. Corning... 

In the case of so-called active soldering an active solder is used a metallic solder containing interface active additives which make certain that the molten solder wets the ceramics. An example of such a solder is a silver / copper alloy with a titanium or titanium / indium additive which can be used when soldering zirconium (IV) oxide to certain steels, aluminium oxide to nickel / cobalt or iron / nickel alloys and aluminium oxide to a iron / nickel / cobalt alloy. 

Les] Lesnik, N.D., Minakova, R.V., Khomenko, E.V., Chromium-Copper System Adhesion Characteristics, Doping, the Structure of Phase Boundary and Composites , Powder Metall. Met. Ceram., 40(7-8), 432-440 (2001) (Experimental, Morphology, Phys. Prop., Interface Phenomena, 12)... 

A system in which the interdiffusion was much more extensive was studied by Kriven and Risbud, who studied the reaction between copper and cordier-ite glass ceramics. They used cathodoluminescence to observe the intensity of the fluorescence from the Cu ions that diffused into the glass. Quantitatively, electron microprobe data indicated that the copper concentration 100 p,m from the interface was 7 atom %, although the backscattered electron image in the SEM did not indicate the presence of Cu particles, thus confirming the presence of Cu. ... 

The experimental techniques described above to analyze ceramic—metal interfaces will now be illustrated using an example of brazing AIN. Comparatively little work has been reported on brazing aluminum nitride ceramics. Since a primary application for aluminum nitride is as a substrate for electronic applications, the focus has been on low-temperature brazing, using a variety of commercially available alloys based on the copper—silver—titanium system. 

Other physical properties behave similarly to Young s modulus. If, for example, copper is used to dissipate heat from a ceramic structure, the coefficients of thermal expansion of the copper alloy and the ceramic should not differ too much to reduce thermal stresses at the interface. Adding tungsten particles to copper reduces its coefficient of thermal expansion so that it becomes closer to that of the ceramic. 

As one example, consider the interfacial phenomenon between ceramic and copper wiring. If the material or process conditions of the ceramic and copper are inappropriate, various macro and micro flaws occur. For example, in the firing process, minute pores are formed at the interface. Possible causes of the formation of the pores are (1) mismatch of the firing and shrinkage behaviors of the conductor and ceramic, (2) insufficient adherence between the conductor and ceramic in the laminating process, (3)... 

As can be seen from the figure, carbon is concentrated in the area of the interface between the copper and ceramic. This is probably due to the fact that since copper begins sintering faster and reaches its end temperature earlier than ceramic, the sintered copper on top of the unsintered ceramic... 

The majority of defects found in reliability and quality testing arise at the interface between the copper and ceramic. Since more than 95% of the circuit board overall is ceramic, there is a tendency to evaluate only the reliability of the ceramic part. However, LTCCs are ceramics formed with... 

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