Title: A thermo temporal model of pulsed laser ablation of copper coated thin films on a polyimide substrate

Authors: Srinagalakshmi Nammi; Sooraj Shiby; Nilesh J. Vasa; G. Balaganesan; Anil C. Mathur

Addresses: Department of Engineering Design, Indian Institute of Technology Madras, Chennai 600036, India ' Department of Engineering Design, Indian Institute of Technology Madras, Chennai 600036, India ' Department of Engineering Design, Indian Institute of Technology Madras, Chennai 600036, India ' Department of Engineering Design, Indian Institute of Technology Madras, Chennai 600036, India ' Antenna Mechanical Design Division, Indian Space Research Organization, Ahmedabad 380015, India

Abstract: A heat transfer model of nanosecond laser irradiation on a copper thin film coated on a polyimide substrate is developed and studied to understand the thermal influence on thin films during the laser ablation. Temperature distribution inside the target is calculated using heat conduction equation considering hydrodynamic boundary conditions. Effect of plasma shielding on the ablation process due to inverse bremsstrahlung is considered in the model. The study clearly shows that the shielding effect of plasma decreases the laser energy reaching the target surface and therefore reduces the depth of micro crater formed by a single pulse. A comparative study has been made for depth achieved for micro-craters fabricated on copper thin films in air using a Q-switched Nd³⁺:YAG laser with 6 ns pulse duration for various laser intensities. The simulation results are compared with experimental data for the laser ablation depth which is measured using 3D optical non-contact profilometer.

Keywords: laser micro machining; plasma shielding; parabolic reflector; thin film scribing; recession rate; plasma temperature; plasma velocity; nanosecond laser ablation; laser material interaction; micro machining of copper thin films.

DOI: 10.1504/IJPTECH.2017.090767

International Journal of Precision Technology, 2017 Vol.7 No.2/3/4, pp.138 - 150

Received: 23 Feb 2017
Accepted: 31 Oct 2017
Published online: 27 Mar 2018 *

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