Abstract

In free abrasive wafer slicing process (FAM) using wiresaw, hydrodynamic pressure exerted by the thin slurry film is crucial to the process of cutting and material removal from substrate surface. It affects the process quality by introducing viscous damping effect to the transverse motion of the wire. The pressure distribution in the slurry film is subjected to the interaction of multi-physical phenomena induced in the wire-saw cutting process, including the axially moving wire transverse vibration under high tension (20N to 35N), as well as the hydrodynamic lubrication behavior of the thin slurry film. In this paper, the interaction between thin-film hydrodynamics and wire vibration is modeled using the coupling of basic Reynold’s equation for fluid lubrication and the dynamic equation describing the transverse vibration of the translating wire. The time-variant hydrodynamic pressure field is used to obtain the dynamic damping force exerted on the wire by the thin slurry film. A computational model is constructed and typical parametric studies are conducted based on the simulation results. Numerical scheme of semi-discretization is carried out to simulate the dynamic multi-disciplinary model. Galerkin method of weighted residual is used to carry out the spatial finite element discretization of the governing non-linear partial differential equations of the system with certain boundary conditions. In addition, Newmark method is applied to perform the time integration of the semi-discretized computational model from initial conditions. The direct numerical simulation dynamically yields the profile of the slurry hydrodynamic pressure distribution and the wire vibration response as functions of process parameters, such as the static film thickness of the slurry flow, wire translating speed and wire tension. From the simulation results, it is shown that the presence of the slurry film in the wiresaw process is important in eliminating the undesirable vibration modes and reducing the amplitude of wire vibration.

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