We report an experimental investigation of the absorption and ablation
characteristics of the high-temperature polymer Upilex polyimide, usi
ng a line-tunable TEA CO2 laser. It is demonstrated that excellent qua
lity through-holes (vias) can be produced in thin films of Upilex when
the CO2 laser is tuned to a strongly absorbed wavelength as a result
of thermal decomposition produced by laser heating of the bulk polymer
. For weakly absorbed wavelengths, transmission and probe beam deflect
ion measurements reveal an incubation effect in the ablation which is
thought to be related to particulate contamination in the film.