Phase formation and reaction kinetics in M–In systems (M = Pt, Pd, Mn)

Abstract

A systematic search for metal ‐ indium systems which show a potentially high remelting temperature in diffusion-soldered bonds was done by investigation of phase formation and reaction kinetics in M ‐ In systems (M = Pt, Pd, Mn). Phase equilibration experiments M ‐ In (M = Pd, Mn) were done with powder samples prepared from pure elements, heated in evacuated silica capsules between 200 and 700 ∞C for 15 min to 570 h, and studied by X-ray diffraction analysis. Diffusion couples M/In (M = Pt, Pd, Mn) were prepared from the foils or wires of pure elements and heated in a bonding furnace or in evacuated silica tubes at 250 ‐ 700 ∞C for 30 min to 96 h. The couples were cross-sectioned and studied by scanning electron microscopy with energy-dispersive X-ray analysis. The rates of M ‐ In reactions can be semiquantitatively ordered in the sequence Pt > Pd4 Mn ( ‐ In). The activation energy of the well-defined reaction of Mn ‐ In powder samples was calculated to be 56 ‐ 10 kJ/mol. The activation energies calculated from the layer growth in diffusion couples show a large uncertainty, they are 39 kJ/mol (Pt/In), 23 kJ/mol (Pd/In) and 41 kJ/mol (Mn/In). Pt ‐ In and Pd ‐ In are very promising candidates for diffusion soldering of high-temperature stable bonds.