Abstract

Precise coating removal from ultra-thin wires is critical in industries such as aerospace, automotive, and biomedical, where maintaining substrate integrity and meeting high-performance standards are essential.
Common insulating materials like polyimides and enamels must be removed without damaging the underlying conductor, often requiring advanced methods such as laser ablation, chemical etching, or
ultrasonic stripping. Among these, laser ablation offers significant advantages in precision, repeatability, and compatibility with automation, while also minimizing environmental and safety concerns. This work investigates the use of UV laser ablation for stripping polyamide insulation from 50 µm platinum wires used in the production of high-sensitivity Resistance Temperature Detector (RTD) sensors. The UV
laser system operates at a wavelength of 355 nm with a 20 µm spot size, a repetition rate ranging from 20 to 200 kHz, and an average power of 3 watts. The UV enables removal of the polyamide coating, without affecting the platinum substrate. Initial experiments were conducted in air ambient, where various laser parameters such as Number of loops, Line distance, and scanning speed were systematically varied. However, thermal effects from localized heating posed challenges, risking damage to the substrate and
reducing surface quality. To overcome these issues, experiments were conducted in water ambient, which provided effective thermal management through a controlled ablation process. Scanning speed of
1200 mm/s; line spacing of 1 µm; and single loop was identified as optimal parameter settings to produce a clean surface comparable to that achieved by chemical stripping.
Further analysis of these parameters using ANOVA in Python highlighted the key influence and their interactions on output parameters such as the Tensile strength and Surface Roughness. Increasing the line distance to 2 µm and introducing an additional loop significantly improved the tensile strength [104 gr.f], and the surface roughness [0.129 µm], as close to that can be achieved by chemical stripping.
These findings contribute to the development of reliable, repeatable laser de-coating protocols for ultra-thin wires. By identifying optimal processing parameters, this work supports the broader implementation of a laser-based process toward automation particularly in SMEs.