Analysis and Prediction of a UV Laser Micro-machining Process

UV laser micro-machining of metallic materials has been used in microelectronic and other industries. Knowledge and-data about the process vary with feature size, material, laser wavelength and pulse duration. This paper carries out experimental and numerical investigation of micromachining of copper using a frequency tripled Nd: YAG laser with 50 nanosecond pulse duration. An axisymmetric model is developed and allows consideration oflaser beam distribution and its coupling with the target material. This is important for the process where the removal extent is in the same order of the removal depth. The model uses enthalpy method to track the solid/liquid interfuce, Stefan and kinetic boundary conditions are applied at the liquid-vapor interface, and property discontinuity across the Knudsen layer is considered. Relevant experimental results are also presented and compared with the model predicted results. The range of thermal vaporization dominated machining of copper using nanosecond time scale lasers was studied, and optimum laser intensity for micro-machining of copper was suggested.