PULSED 532-NM LASER WIRESTRIPPING - REMOVAL OF DYE-DOPED POLYURETHANEINSULATION

Removal of rhodamine 6G doped polyurethane insulation coated onto 50 m um diameter wire is shown to proceed efficiently and cleanly by irradi ation 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 includin g fluence, pulse duration, dye concentration, and the number of incide nt pulses. Acceptable stripping conditions were obtained for a 3-5 s e xposure at 10 Hz, using a dye concentration of 10% by weight, and 12 n pulses at 650 mJ/cm2. Nearly 0.5 mum/pulse is removed at this fluence , which exceeds the threshold fluence of almost-equal-to 600 mJ/cm2 by only 50 mJ/cm2. The measured 532 nm absorption coefficient of the 10% dye-doped polyurethane was almost-equal-to 4 x 10(4) cm-1. Lower flue nces and/or dye concentrations produced inadequate stripping, while sh orter duration pulses caused unacceptable melting of the thin gold lay er which covered the copper core of the wire. Pulse-by-pulse photograp hs of the stripping action clearly show melting of the dye/polymer ins ulation, and thermal ''rollback'' of the insulation near the stripped end. Regardless, excellent edge definition is obtained by this method.