Relationship between microstructure homogeneity and bonding stability of ultrafine gold wire

Abstract

Inhomogeneous microtexture evolution during the cold drawing process usually results in lean, sway, or sweep failure. The <111> longitudinal fiber texture has higher stiffness than the <100> texture and its proportion and distribution in the cross-section are critical for the bonding stability of fine gold wire. We investigated the inhomogeneous microtexture evolution of gold wire that was cold drawn through an asymmetric diamond die. In this study, the distributions of the <111> and <100> textures in a 20 μm diameter fine gold wire are the variables and their effects on the bonding stability of the wire were estimated by electron backscattered diffraction (EBSD) and finite element method (FEM) simulations. The use of a focused ion beam apparatus enabled a high quality of band contrast of the EBSD to be achieved in the exact half cross-sectional area of the fine gold wire. The detailed three-dimensional FEM results show that the asymmetric distribution of the textures plays a crucial role in increasing the spatial displacement of the gold bonding wire.

Stiffening of nanoporous gold: experiment, simulation and theory

“…Now, if we consider the specific case of a porous material with a volume fraction equal to 0.5, we obtain that the effective Young's modulus is approximately divided by 5 with respect to its bulk value, and this is true for a rather large class of microstructures [51,52]. For bulk gold, the measured Young modulus is around 80 GPa [53][54][55], and therefore the NP Au sample with a volume fraction equal to 0.5 should have a Young's modulus of about 16 GPa (without scale effects or defects). Thus, higher and lower values than this reference should be explained by intrinsic scale effects or by the presence of local or surface defects induced by the length scale itself.…”

Functionalized Gold Nanoparticles with a Cohesion Enhancer for Robust Flexible Electrodes

“…The bending strain (ε) in the convex surface was calculated using the following equation 38 where subscripts f and s denote the film and substrate, respectively; η = d f / d s , where d f and d s denote the thickness of the film and substrate, respectively; χ = E f / E s , where E f and E s denote Young’s modulus of the film and substrate, respectively. For calculation of the bending strain, Young’s modulus ( E f ) values of 77.2, 54, and 7 GPa were used for bulk gold, 39 thin gold film, 40 and PEN, 41 respectively.…”

Application of Statistical Representation of Microstructure during Simulation of Ferritic-Pearlitic Steel Wire Drawing

“…In this case, the final products are different axes, shafts and rod constructions, which are usually used under the static and cyclic loads during all life period of products. For this reason, the inhomogeneity of mechanical properties due to non-uniform deformation is crucial in prediction of the potential reliability of the finished product [1][2][3][4][5][6]. This problem plays particularly important role in the case of rod drawing process of ferritic-pearlitic steels [7], because inhomogeneity of deformation can lead to large differences in mechanical properties in the workpiece layers.…”