Abstract: Colloidal suspensions of nanoparticles are increasingly employed in the fabrication process of electronic devices using inkjet-printing technology and a consecutive thermal treatment. The evolution of internal stresses during the conversion of silver nanoparticle-based ink into a metallic thin-film by a thermal sintering process has been investigated by in-situ XRD using the sin2ψ method. Despite the CTE mismatch at the film/substrate interface, the residual stress in silver films (below 70 MPa) remains lower than in conventional PVD thin-films, as a result of the remaining porosity. A Warren-Averbach analysis further showed that the crystallite growth is associated with a minimization of the twin fault density and the elastic microstrain energy above 150°C. A stabilization of the microstructure and internal stress is observed above 300°C. Inkjet-printing technology thus appears as a good alternative to conventional metallization techniques and offers significant opportunities asset for interconnect and electronic packaging.
Abstract: Composite materials present interesting mechanical properties. The metal provides the toughness and the particles are adding elastic stiffness, strength, hardness and wear resistance. High energy X-ray diffraction has been used to characterize the microstructure evolution of two types of MMCs (titanium and steel matrix) reinforced with TiC particles.Evolutions of mass fraction and mean cell parameters shows the effect of reinforcement on the kinetics and mechanical state of the final composites.
Abstract: For metal matrix composites, internal stresses are a key factor for understanding the interactions between matrix and reinforcements and the mechanical properties of the composite. From in situ high energy X-ray diffraction on a steel matrix composite reinforced with TiC, the evolutions of the phase fractions and mean cell parameters of each phase during thermal treatment have been determined. In addition, a methodology is developed in order to get more information on the stress state evolutions in each phase during the treatment.
Abstract: The X-ray diffraction method is used to evaluate the residual stress in injection-molded plates of short-fiber reinforced plastics (SFRP) made of crystalline thermoplastics, polyphenylene sulphide (PPS), reinforced by carbon fibers with 30 mass%. The stress in the matrix in the skin layer was determined using Cr-Kα radiation with the sin2 ψ method. The X-ray evaluation of stress in carbon fibers was not possible because of high texture. A new method was proposed to evaluate the macrostress in SFRP from the measurement of the matrix stress. According to micromechanics analysis of SFRP, the matrix stresses in the fiber direction and perpendicular to the fiber direction, and shear stress can be expressed as linear functions of the applied (macro-) stresses in the fiber direction and perpendicular to the fiber direction, and shear stress. The proportional constants are named stress-partitioning coefficients. Using skin-layer strips cut parallel, perpendicular and 45° to the molding direction, the stress in the matrix was evaluated under the uniaxial applied stress and the stress-partitioning coefficients of the above equations were determined. Once the relations between the macrostress and matrix stress are established, the macrostress in SFRP can be evaluated from the measurements of the matrix stresses using X-rays.
Abstract: In this work, the residual stresses for composite laminates [02/θ2]S determined by means of the incremental hole-drilling method with a formula to express the relationship between the residual stresses and the relaxed strains around the drilled hole. Then the ageing tests related to hydrothermal condition are carried out to analyze the influence on the residual stress redistributions and also on the mechanical behaviors of the carbon/epoxy laminates.
Abstract: In this paper the residual stress states induced by conventional shot peening (SP) and surface mechanical attrition treatment (SMAT) are compared. The treated part correspond to plates made of a titanium alloy. Different intensities of these two mechanical treatments are first considered: their influence on the surface characteristics (roughness, hardness...) is studied. These experimental data are then used to develop a model for the residual stress profiles with dimensional analysis, Experimental and analytical approaches are then discussed.
Abstract: Three natural polycrystalline diamond samples have been investigated non-destructively in their raw as-discovered forms. The samples originate from different locations in the world and possibly have different mechanisms of formation. The study reveals that the stones are primarily composed of cubic diamond with varying amounts of impurities that emanate from their excessive porosities and entrapped environmental contamination from the areas they were formed and subsequently discovered. Residual stress analyses with X-ray and neutron diffraction techniques of the diamond phase in the interior regions of the diamonds revealed low stress values.
Abstract: This work deals with a methodology to evaluate residual stresses within microelectronic devices by using MOS (Metal Oxide Semiconductor) rosette stress sensors. The stress tensor was evaluated by carrying out electrical measurements on test vehicle: the bridge from electrical to stress values was ensured by the piezoresistive relations and, prior to further in-house calibration, coefficients from literature were employed. For correlation purpose, numerical simulations were performed in order to evaluate stresses induced by TSV (Through Silicon Via). In this paper, the whole framework is described, and stress fields evaluated from in-situ electrical measurements on CMOS65 rosette sensor are compared to simulated ones. Some of the ultimate targets of this work are to develop a validated framework to deeply understand TSV induced thermo-mechanical stresses and to allow design rules definitions for products reliability and transistor performances.