Petra Kluge-Weiss

Directly Bonded Copper Metallization of AℓN Substrates for Power Hybrids

Aluminum nitride (AlN) ceramic is emerging as an attractive substrate material for high performance heat sinking in hybrid circuits be -cause of its high thermal conductivity. We report on the application of the direct bonding technique for Cu on AlN substrates. For successful bonds, the surface of the AlN has to be oxidized. Oxidation rates are reported and the oxide morphology is analyzed. The peel strength of the Cu sheet depends on oxide thickness, growth method and Cu-type used. Under optimum conditions the peel strength exceeds 50 N/cm. A detailed analysis using optical microscopy as well as SEM, STEM, EDX, and electron diffraction techniques of the AlN/Al 2 O 3 /Cu interface is carried out.

Varistor Ceramic: Residual Strain and Texture Analysis by Neutron Time-of-Flight Diffraction

Strain/stress experiments for characterization of micro- and macro-strain distribution and texture experiments were carried out on a varistor ceramic using neutron-TOF-diffraction. By a radial strain scan, residual strain has been determined on the (1010 ), (0002), (1012), and (1120 ) Bragg reflections of the hexagonal ZnO as well as on the (400) reflections of the cubic spinel Zn7Sb2O12. Residual strain values in the range of -1.5x10-4 (contraction) and 4x10-4 (dilatation) were observed for ZnO, with indications of macro-strains across the cylindrical sample and substantial micro-strains between the different phases. The texture on both phases (ZnO, Zn7Sb2O12) is characterized by a weak, non-ideal fibre texture around the cylinder axis. The results indicate that the texture pattern might coincide with the strain. To our knowledge, these are the first texture and residual strain investigations in metal oxide varistor elements and they will be discussed in detail.