The Experts below are selected from a list of 33648 Experts worldwide ranked by ideXlab platform
Robert F. Cook - One of the best experts on this subject based on the ideXlab platform.
-
stress hysteresis during Thermal Cycling of plasma enhanced chemical vapor deposited silicon oxide films
Journal of Applied Physics, 2002Co-Authors: Jeremy Thurn, Robert F. CookAbstract:The mechanical response of plasma-enhanced chemical vapor deposited SiO2 to Thermal Cycling is examined by substrate curvature measurement and depth-sensing indentation. Film properties of deposition stress and stress hysteresis that accompanied Thermal Cycling are elucidated, as well as modulus, hardness, and coefficient of Thermal expansion. Thermal Cycling is shown to result in major plastic deformation of the film and a switch from a compressive to a tensile state of stress; both aThermal and Thermal components of the net stress alter in different ways during Cycling. A mechanism of hydrogen incorporation and release from as-deposited silanol groups is proposed that accounts for the change in film properties and state of stress.
G Eggeler - One of the best experts on this subject based on the ideXlab platform.
-
effect of low temperature precipitation on the transformation characteristics of ni rich niti shape memory alloys during Thermal Cycling
Intermetallics, 2010Co-Authors: Martin F X Wagner, H Gugel, J Frenzel, Ch Somsen, G EggelerAbstract:Abstract Thermal Cycling of NiTi shape memory alloys is associated with functional fatigue: the characteristic phase transformation temperatures decrease with increasing number of cycles, and the transformation behavior changes from a single- to a two-stage martensitic transformation involving the intermediate R-phase. These effects are usually attributed to a gradual increase of dislocation density associated with micro-plasticity during repeated Cycling through the transformation range. Here, these changes are shown to increase at a higher maximum temperature (in the fully austenitic state) during differential scanning calorimetric Cycling of a Ni-rich alloy. Additional Thermal Cycling experiments without repeated phase transformations, and post-mortem microstructural observations by transmission electron microscopy, demonstrate that a relevant portion of functional fatigue is due to the formation of nano-scale Ni-rich precipitates of type Ni 4 Ti 3 even at temperatures relatively close to the austenite finish temperature. These results show that both dislocation generation during the diffusion-less phase transformation, and diffusion-controlled nucleation and growth of Ni 4 Ti 3 precipitates, can interact and contribute to the evolution of functional properties during Thermal Cycling of Ni-rich NiTi.
I. Dutta - One of the best experts on this subject based on the ideXlab platform.
-
texture development and strain hysteresis in a niti shape memory alloy during Thermal Cycling under load
Acta Materialia, 2009Co-Authors: B S Majumdar, I. DuttaAbstract:Thermal Cycling experiments were conducted on a NiTi shape-memory alloy at different constant applied stresses below the yield strength of the martensite. The mechanical strain response manifested as strain hysteresis loops, whose range was proportional to the applied stress. In situ neutron diffraction experiments show that the strain hysteresis occurs as a result of the establishment of a stress-dependent crystallographic texture of the martensite during the first cool-down from austenite, and thereafter repeated during Thermal Cycling under the same load. This texture is found to depend on the stress during the Thermal Cycling experiments. A strain-pole map is derived and shown to explain the observed texture during Thermal Cycling. The strain-pole methodology is shown to work with similar martensitic transformations in other material systems.
-
role of interfacial and matrix creep during Thermal Cycling of continuous fiber reinforced metal matrix composites
Acta Materialia, 2000Co-Authors: I. DuttaAbstract:Abstract A uni-dimensional micro-mechanical model for Thermal Cycling of continuous fiber reinforced metal–matrix composites is developed. The model treats the fiber and matrix as thermo-elastic and thermo-elasto-plastic-creeping solids, respectively, and allows the operation of multiple matrix creep mechanisms at various stages of deformation through the use of unified creep laws. It also incorporates the effect of interfacial sliding by an interface-diffusion-controlled diffusional creep mechanism proposed earlier (Funn and Dutta, Acta mater. , 1999, 47 , 149). The results of Thermal Cycling simulations based on a graphite fiber reinforced pure aluminum–matrix composite were compared with experimental data on a P100 graphite–6061 Al composite. The model successfully captured all the important features of the observed strain responses of the composite for different experimental conditions, such as the observed heating/cooling rate dependence, strain hysteresis, residual permanent strain at the end of a cycle, as well as both intrusion and protrusion of the fiber-ends relative to the matrix at the completion of Cycling. The analysis showed that the dominant deformation mechanism operative in the matrix changes continually during Thermal Cycling due to continuous stress and temperature revision. Based on these results, a framework for the construction of a transient deformation mechanism map for Thermal excursions of continuous fiber composites is proposed.
Tong Hong Wang - One of the best experts on this subject based on the ideXlab platform.
-
reliability evaluations for board level chip scale packages under coupled power and Thermal Cycling test conditions
Microelectronics Reliability, 2008Co-Authors: Tong Hong Wang, Yi-shao Lai, Yucheng LinAbstract:Abstract To evaluate conjointly the effects of ambient temperature fluctuation and operation bias on the reliability of board-level electronic packages, a coupled power and Thermal Cycling test has been proposed. In this study, the sequential Thermal–mechanical coupling analysis, which solves in turn the transient temperature field and subsequent thermomechanical deformations, is performed to investigate Thermal characteristics along with fatigue reliability of board-level thin-profile fine-pitch ball grid array chip-scale packages under coupled power and Thermal Cycling test conditions. Effects of different power Cycling durations are studied. A pure Thermal Cycling condition is also examined and compared. Numerical results indicate that, for the coupled power and Thermal Cycling test, a shorter power Cycling duration in general leads to a shorter fatigue life. However, the temperature compensation effect elongates the fatigue life under certain power Cycling durations.
-
transient Thermal analysis for board level chip scale packages subjected to coupled power and Thermal Cycling test conditions
Journal of Electronic Packaging, 2006Co-Authors: Tong Hong Wang, Changchi Lee, Yl Shao Lai, Yucheng LinAbstract:In this work, Thermal characteristics of a board-level chip-scale package, subjected to coupled power and Thermal Cycling test conditions defined by JEDEC, are investigated through the transient Thermal analysis. Tabular boundary conditions are utilized to deal with time-varying Thermal boundary conditions brought by Thermal Cycling. It is obvious from the analysis that the presence of power Cycling leads to a significant deviation of the junction temperature from the Thermal Cycling profile. However, for components away from the die, the deviation is insignificant. Moreover, for low-power applications, temperature histories from coupled power and Thermal Cycling are approximately linear combinations of temperature histories from pure power Cycling and the ones from pure Thermal Cycling.
-
effect of power Cycling duration on coupled power and Thermal Cycling reliability of board level chip scale packages
Electronic Packaging Technology Conference, 2005Co-Authors: Tong Hong Wang, Yi-shao Lai, Changchi LeeAbstract:To evaluate conjointly the effects of ambient temperature fluctuation and operation bias on the reliability of board-level electronic packages, a coupled power and Thermal Cycling test has been proposed. In this study, the sequential Thermal-mechanical coupling analysis, which solves in turn the transient temperature field and subsequent thermomechanical deformations, is performed to investigate Thermal characteristics along with fatigue reliability of board-level thin-profile fine-pitch ball grid array chip-scale packages under coupled power and Thermal Cycling test conditions. Effects of different power Cycling durations are studied. Pure Thermal Cycling and pure power Cycling test conditions are also examined and compared. Numerical results indicate that, for the coupled power and Thermal Cycling test, a shorter power Cycling duration in general leads to a shorter fatigue life. However, the temperature compensation effect elongates the fatigue life under certain power Cycling durations
-
board level power Cycling and Thermal Cycling fatigue reliability of chip scale packages
Journal of microelectronics and electronic packaging, 2005Co-Authors: Tong Hong Wang, Yi-shao Lai, Changchi LeeAbstract:In this paper, the sequential Thermal-mechanical coupling analysis, which solves in turn the transient temperature field and subsequent thermomechanical deformations, was carried out to investigate board-level fatigue reliability of a thin profile and fine pitch ball grid array (TFBGA) chip-scale package under accelerated power Cycling test conditions. Experiments for steady-state and transient Thermal dissipations were conducted to verify the Thermal analysis. Comparing between numerical results for power Cycling and Thermal Cycling, it is noticed that for the tests with similar low and high temperature extremes, power Cycling results in a much longer fatigue life than Thermal Cycling, which indicates that Thermal Cycling is a more conservative criterion than power Cycling is in evaluating the fatigue resistance of the electronic packages.
-
Thermal mechanical coupling analysis for coupled power and Thermal Cycling reliability of chip scale packages
International Conference on Thermal Mechanial and Multi-Physics Simulation and Experiments in Micro-Electronics and Micro-Systems, 2005Co-Authors: Yi-shao Lai, Tong Hong Wang, Changchi LeeAbstract:The sequential Thermal-mechanical coupling analysis, which solves in turn the transient temperature field and subsequent thermo-mechanical deformations, is carried out in this paper to investigate Thermal characteristics along with fatigue reliability of board-level thin-profile fine-pitch ball grid array chip-scale packages under coupled power and Thermal Cycling test conditions. Pure Thermal Cycling and pure power Cycling test conditions are also examined and compared.
Jeremy Thurn - One of the best experts on this subject based on the ideXlab platform.
-
stress hysteresis during Thermal Cycling of plasma enhanced chemical vapor deposited silicon oxide films
Journal of Applied Physics, 2002Co-Authors: Jeremy Thurn, Robert F. CookAbstract:The mechanical response of plasma-enhanced chemical vapor deposited SiO2 to Thermal Cycling is examined by substrate curvature measurement and depth-sensing indentation. Film properties of deposition stress and stress hysteresis that accompanied Thermal Cycling are elucidated, as well as modulus, hardness, and coefficient of Thermal expansion. Thermal Cycling is shown to result in major plastic deformation of the film and a switch from a compressive to a tensile state of stress; both aThermal and Thermal components of the net stress alter in different ways during Cycling. A mechanism of hydrogen incorporation and release from as-deposited silanol groups is proposed that accounts for the change in film properties and state of stress.
