Simple microindentation techniques have been applied to investigate fracture and stress-corrosion cracking in singlecrystal silicon. The results obtained agree with the previously reported data obtained from conventional methods. Fracture toughness of silicon in {110}/{112} orientations was measured to be 1.00 +-0.08 MPa m '/2. No evidence of stresscorrosion cracking in silicon in both air and water environments was observed even at a temperature moderately above room temperature. An interpretation for this lack of stress-corrosion cracking has been proposed. These microindentation techniques, which have high spatial resolutions, are potentially useful for mechanical integrity assessment of siliconbased electronic components.

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This paper proposes a unified comprehension of the isothermal ceramic process kinetics stemming from mesoscopic irreversible thermodynamics. Accordingly, a unified process kinetic equation (UPKE) is derived, which predicts that the global isothermal process rate of any ceramic process is, in general, nonlinearly related both to its activation energy and its affinity. Nevertheless, for a low-affinity ceramic process conducted either in a field-free or resonant wave-field condition, its global isothermal rate, according to the proposed UPKE, is approximately linearly related to its affinity in the spirit of Fick's diffusion law. Therefore, the rate enhancement of a low-affinity process occurring in any resonant wave-field may be caused either by a reduction in activation energy, as in microwave-enhanced sintering, or by activation energy reduction along with an affinity augmentation, as in microwaveassisted glass-crystallization. Conversely, for a high-affinity ceramic process, e.g., a chemical reaction, the 'degenerate' UPKE predicts that its kinetics is exclusively dictated by the activation energy in the spirit of Arrhenius's rate law. Hence, isothermal rate enhancements of chemical reactions in ceramic processing under resonant wave-field conditions are believed to predominantly result from a field-induced reduction in activation energy.

Kinetic equations for the isothermal densification of a singlephase powder compact are formulated for the initial and intermediate stages of sintering; they are identified as continuous open-pore stages, with a decreasing number of voids and grains per unit volume accompanied by grain growth in the intermediate stage. Each stage can be represented by an equation based on mass transport along the forming grain boundary to the "neck" region as the rate-controlling step or by one on movement from the neck to the free surface regions as the rate-controlling step.

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A mechanistic model for eutectic Pb/Sn solder life predictions has been developed and applied to leadless surface mount solder joints. This model can quantitatively describe both crack initiation and crack propagation processes in the solder. There are four parts to this model: a crack initiation model, a crack propagation model [1], a microstructural coarsening model and an analysis of the deformation in the solder during thermal cycling. By merging these models together, it is possible to predict the time to crack initiation and the time to failure of these solder joints. Solder joint life predictions show good agreement with data obtained on thermally cycled surface mount leadless chip resistors.

Experimental sintering studies on undoped and CaO-doped MgO powder compacts in static air and flowing water vapor atmospheres were performed in the temperature range between 1230°C and 1600°C. Corresponding microstructural changes of specimens during sintering were examined by scanning electron microscopy. Kinetic and microstructural data were analyzed to determine sintering mechanisms during the initial and intermediate stages of sintering. 0 * Based on part of a thesis submitted by Boon Wong for the Ph.D. degree in materials science at the University of California, Berkeley. Now at GTE Laboratories (Sylvania) Waltham, Mass.

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