Pulsed 532 nm laser wirestripping: Removal of dye-doped polyurethane insulation

Abstract

Removal of rhodamine 6G doped polyurethane insulation coated onto 50 μm diameter wire is shown to proceed efficiently and cleanly by irradiation with 532 nm Q-switched pulses from a Nd:YAG laser. The stripping action produced by this method is similar in quality to excimer laser wirestripping. Several experimental parameters were explored including fluence, pulse duration, dye concentration, and the number of incident pulses. Acceptable stripping conditions were obtained for a 3–5 s exposure at 10 Hz, using a dye concentration of 10% by weight, and 12 n pulses at 650 mJ/cm². Nearly 0.5 μm/pulse is removed at this fluence, which exceeds the threshold fluence of ≈600 mJ/cm² by only 50 mJ/cm². The measured 532 nm absorption coefficient of the 10% dye-doped polyurethane was ≈4×10⁴ cm⁻¹. Lower fluences and/or dye concentrations produced inadequate stripping, while shorter duration pulses caused unacceptable melting of the thin gold layer which covered the copper core of the wire. Pulse-by-pulse photographs of the stripping action clearly show melting of the dye/polymer insulation, and thermal “rollback” of the insulation near the stripped end. Regardless, excellent edge definition is obtained by this method.