It is now recognized that voiding failures in Al–Cu interconnects in integrated circuits are due to the high residual stresses developed as a result of thermal expansion mismatch between Al and Si or SiO2. In this paper, we review some of the current theoretical developments in calculating times to failure for these interconnects. Thermal cycling experiments were performed to determine times to failure under different testing conditions. These results were then compared with the recent theory developed here at Northwestern. It is based on consideration of grain-boundary and surface diffusion and fracture mechanics. The theory appears to give predictions that agree very well with experiments.

Temperature cycling

10.1116/1.577266

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Further progress toward enabling a deployable shape memory alloy normal incidence space telescope for the extreme ultraviolet

M. P. Ulmer Daniel Quispe Lenward Seals Giovanni De Vita Stephen Stagon

In a previous paper, we presented the concept of using shape memory alloy sheets as the substrate for normal incidence multi-layer coated mirrors. A shape set sheet has been shown to deploy a figure good to 1 micron. This shape is good enough for a "light bucket." However, if imaging is desired, then post-deployment corrections can be applied. We provide an update on the improvements we have made to our study. These improvements include ray tracing, polishing, adhesion, and fine (nm) surface adjustments.

Ultraviolet

Extreme ultraviolet

Spitzer Space Telescope

10.1117/12.2677459

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Transformative research issues and opportunities in alternative energy generation and storage

Current Opinion in Solid State and Materials Science (2010)

Angus Rockett Yip-Wah Chung Hans P. Blaschek S. Butterfield R. R. Chance

Transformative Learning

Energy source

10.1016/j.cossms.2010.09.001

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Role of Surfaces and Interfaces in Controlling the Mechanical Properties of Metallic Alloys

Langmuir (2010)

Won-Jong Lee W. J. Chia Jinliu Wang Yanfeng Chen Semyon Vaynman

This article explores the subtle effects of surfaces and interfaces on the mechanical properties of bulk metallic alloys using three examples: environmental effects on fatigue life, hydrogen embrittlement effects on the ductility of intermetallics, and the role of coherent precipitates in the toughness of steels. It is demonstrated that the marked degradation of the fatigue life of metals is due to the strong chemisorption of adsorbates on exposed slip steps that are formed during fatigue deformation. These adsorbates reduce the reversibility of slip, thus accelerating fatigue damage in a chemically active gas environment. For certain intermetallic alloys such as Ni(3)Al and Ni(3)Fe, the ductility depends on the ambient gas composition and the atomic ordering in these alloys, both of which govern the complex surface chemical reactions taking place in the vicinity of crack tips. Finally, it is shown that local stresses at a coherent precipitate-matrix interface can activate dislocation motion at low temperatures, thus improving the fracture toughness of bulk alloys such as steels at cryogenic temperatures. These examples illustrate the complex interplay between surface chemistry and mechanics, often yielding unexpected results.

Embrittlement

Ductility (Earth science)

Chemisorption

10.1021/la101361n

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Citations (6)