Effect of oxygen on segregation and chemical activity of titanium in silver-copper brazing alloys

Thermodn. of Ti-O interaction in the Ti-Al2O3 diffusion couples and in liq. Ag-Cu alloys were studied. In spite of strong Ti-O interaction in the Ti-Al2O3 diffusion couples Ti-oxides are not formed due to dissolved aluminum. Results indicate that there is a large liq. miscibility gap in the Ag-Cu-Ti system, which divides the liq. into high-Ti and low-Ti, high Ag solns. In Ag-rich Ag-Cu-Ti alloys a-Ti[O] or lower Ti-oxides may form due to high oxygen and Ti activities. Several other phase equil. and the isoactivities of dissolved Ti and O in both systems are presented. The present thermodn. description gives a good basis for further studies on chem. interactions in diffusion bonded or in brazed oxide-metals joints. [on SciFinder (R)

A diffusion-kinetic Model for predicting solder/conductor interactions in high density interconnections

A combined thermodynamic and diffusion-kinetic approach is very viable for developing microjoining and interconnection materials and processes, in particular, whenever thinner metallizations, coated overlayers, or smaller solder-joint volumes are encountered in very high density electronics. A diffusion-kinetic model based on the utilization of integrated diffusion coefficients and mobilities is introduced and discussed for calculating the layer growth of intermetallic compounds between metal conductors and tin-based solders and is exemplified with a relatively simple ternary Cu/SnBi system. The model has also been used for calculating the local nominal composition of the effective joint or contact region. Moreover, the mobilities of Sn and Cu in Cu6Sn5 and Cu3Sn intermetallic compounds are determined, and the role of both stable and metastable phase diagrams is discussed in predicting the appearance of possible reaction products as well as the driving forces for the dissolution, diffusion, and precipitation processes

Thermodynamic evaluation of solid-state reactions in which a volatile product is formed

Summary. The use of equilibrium thermodynamics in describing interfacial reactions between non-ionic inorganic solids is demonstrated using examples of high-temperature interactions in the Ti–Si–N and Mo–Si–N systems. In the case of a diffusion-controlled process, solid-state reactions can be interpreted with chemical potential (activity) diagrams. The role of volatile reaction products formed during interaction in developing the diffusion zone morphology is analysed. The interfacial phenomena in systems based on dense Si3N4 and non-nitride forming metals can be explained by assuming a nitrogen pressure build-up at the contact surface. This pressure determines the chemical potential of Si at the interface and, hence, the reaction products in the diffusion zone. Keywords. Ceramics; Phase diagrams; Thermodynamics; Transition metals compounds