Thermal laser micro-adjustment using picosecond pulse durations

Thermal laser micro forming (LμF) is a non-contact process for the precise adjustment of micro-scale metallic components. Micro-electronic systems often comprise functional components which require highly accurate micro-scale adjustment after fabrication. Such functional components are typically difficult to access and highly sensitive to mechanical force. The application of lasers offers the potential for controlled and repeatable micro-adjustment of these components in a contact free process. The use of a picosecond pulsed laser source reduces the heat diffusion depth when compared to longer pulse durations, resulting in less thermal loading of the bulk substrate. When combined with high repetition rates, localized heat accumulation in micro-scale components can be achieved and utilized in a thermal forming process. In this work, the micro-adjustment of 1000 μm × 300 μm stainless steel actuator arms using a mode locked fibre laser with a maximum pulse energy and duration of 3 μJ and 20 ps respectively was conducted. The effect of pulse overlap, laser power, irradiation strategy and number of irradiations on the net bend angle is presented.