High-Quality Surface Micromachining on Polymer Using Visible-LIBWE

This work describes optically smooth high quality surface machining on poly methyl methacrylate (PMMA) using simple visible-LIBWE (laser induced back-side wet etching using visible laser, v-LIBWE). Micromachining of polymer such as PMMA usually utilizes CO2 lasers. However, minimal feature smaller than 100 mu m is difficult to achieve and that the surface quality is not good. Using ultra-violet (UV) laser direct ablation reduces the minimal feature to be below 20 mu m but the surface roughness is also not satisfactory (several mu m). Here we demonstrated that high surface quality etching on PMMA was achievable by v-LIBWE using low power nanosecond 532 nm laser. The etching threshold is similar to 50 J/cm(2), which corresponded to similar to 2 mW at 1 kHz repetition rate. Using pulse repetition rate of 1 kHz, trench depth saturated at about 2 mu m. Deeper trench (similar to 5 mu m) is achievable using 30 kHz repetition rate but the process is not consistent and that discontinued trench was often observed. A perspective on the future development of v-LIEBWE on polymer substrate was given.