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- Fenstermacher, M.E., et al.
(författare)
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DIII-D research advancing the physics basis for optimizing the tokamak approach to fusion energy
- 2022
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Ingår i: Nuclear Fusion. - : IOP Publishing. - 0029-5515 .- 1741-4326. ; 62:4
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Tidskriftsartikel (refereegranskat)abstract
- DIII-D physics research addresses critical challenges for the operation of ITER and the next generation of fusion energy devices. This is done through a focus on innovations to provide solutions for high performance long pulse operation, coupled with fundamental plasma physics understanding and model validation, to drive scenario development by integrating high performance core and boundary plasmas. Substantial increases in off-axis current drive efficiency from an innovative top launch system for EC power, and in pressure broadening for Alfven eigenmode control from a co-/counter-I p steerable off-axis neutral beam, all improve the prospects for optimization of future long pulse/steady state high performance tokamak operation. Fundamental studies into the modes that drive the evolution of the pedestal pressure profile and electron vs ion heat flux validate predictive models of pedestal recovery after ELMs. Understanding the physics mechanisms of ELM control and density pumpout by 3D magnetic perturbation fields leads to confident predictions for ITER and future devices. Validated modeling of high-Z shattered pellet injection for disruption mitigation, runaway electron dissipation, and techniques for disruption prediction and avoidance including machine learning, give confidence in handling disruptivity for future devices. For the non-nuclear phase of ITER, two actuators are identified to lower the L-H threshold power in hydrogen plasmas. With this physics understanding and suite of capabilities, a high poloidal beta optimized-core scenario with an internal transport barrier that projects nearly to Q = 10 in ITER at ∼8 MA was coupled to a detached divertor, and a near super H-mode optimized-pedestal scenario with co-I p beam injection was coupled to a radiative divertor. The hybrid core scenario was achieved directly, without the need for anomalous current diffusion, using off-axis current drive actuators. Also, a controller to assess proximity to stability limits and regulate β N in the ITER baseline scenario, based on plasma response to probing 3D fields, was demonstrated. Finally, innovative tokamak operation using a negative triangularity shape showed many attractive features for future pilot plant operation.
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- Chen, Liu, 1973, et al.
(författare)
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Reliability Investigation for Encapsulated Isotropic Conductive Adhesives Flip Chip Interconnection
- 2006
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Ingår i: Journal of Electronic Packaging, Transactions of the ASME. - : ASME International. - 1528-9044 .- 1043-7398. ; 128:3, s. 177-183
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Tidskriftsartikel (refereegranskat)abstract
- Isotropic conductive adhesives (ICA) are gaining more and more application interests in electronic manufacturing, however, their failure mechanism is not been fully understood. In this paper we present reliability investigations on an encapsulated ICA flip chip interconnection. Experimental work included product lifetime measurement, cross section observation, and whole module warpage scanning. Results revealed that the chip-size effect on the ICA lifetime was obvious. A theoretical analysis was conducted with Finite Element Method (FEM) simulation. Viscoelastic models for adhesives and underfill materials were employed, and the comparison with an elastic model was made. Calculated equivalent stresses S eqv and shear stress σ xy fitted well with the experimental lifetime measurement, thus a lifetime relationship similar to the Coffin-Manson formula was established to predict the thermal fatigue life of an encapsulated ICA flip chip. Furthermore, the influences of underfill properties on the ICA reliability were discussed. Copyright © 2006 by ASME.
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- Chen, Liu, 1973
(författare)
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Process development and Reliability Study for System-in-a-Package by using a Liquid Crystal Polymer Substrate
- 2005
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- System-in-a-package (SiP) aims to integrate all of the system functions within a system-level package, containing multiple ICs and other components interconnected through a high-density substrate. SiP is characterized by dividing chip functions among several smaller chips, by connecting chips in the first stage of board manufacture, and by integrating passive components in the substrate. The aim of this work is to develop enabling technologies for SiP concept. These technologies consist of exploring new substrate material (known as Liquid Crystal Polymer (LCP)), process development for electroless Cu deposition, embedding active and passive components, and reliability test and modeling. The advantage of using LCP as the substrate is specifically addressed.A structure based on the SiP concept is proposed in the present work, in which both active and passive components are embedded in a flexible substrate. To evaluate substrate material for this application, their mechanical reliability, electrical performance and environmental impact were first investigated. The LCP gave the best reliability both in bending and cooling situation, better microwave performance and less dissipation factor. It is also an environmental acceptable material.A new process enabling metallization of the LCP substrate has been demonstrated. The best adhesion between deposited copper and LCP is achieved under the process condition as H2SO4 etch acid, 30 second etching time, and using heat treatment after plating. Humidity test doesnt influence the adhesion so much. This adhesion is believed to have both mechanical and chemical origin. The results obtained can be used for further development of a cheap flex laminate technology. Embedding process is demonstrated and developed by experiments. The failure was observed to be located on the copper lines, and the separation of chip and adhesives. 3D finite element method (FEM) gives stress distributions and warpage of the whole package, which has good agreements to the failure observed. The SiP structure optimization was done by the design of experiments method. Steady state and transient thermal modeling were employed, in which heat dissipation in SiP was revealed. Epoxy around the chip plays an important role to remove the heat when the thermal conductivity of the substrate is high. Thermal resistance was quantified for different copper thicknesses. Parameter studies on structure dimensions and materials properties were also made. For high power density application, channel cooling can increase the heat dissipation dramatically.Key words: System-in-a-Package, Embedded Active and Passives Technology, Liquid Crystal Polymer, Finite Element Simulation, Electroless Copper Plating, and Adhesion
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