Planar square-spiral inductor generated from the ITO film removal by using UV laser ablation

Full text: Inductive efficiency is the major parameter to induce current for wireless charging module and it would be affected by the electric properties and shape of inductances. In general, the inductances can be made of the Cu coils or the copper (Cu) ring coated on the glass substrate. The quality of the copper (Cu) ring such as the oxidation degree could affect the inductive efficiency. Therein, the planar square-spiral inductances (PSSIs) were designed on a copper-coated glass substrate and employed in the wireless charging module, and the results in one of studies showed the PSSIs with the Cu thickness of 200 nm and the ratio of 0.75 between line width and pitch has higher efficiency than other PSSIs and the highest induction capacity was 11.34 %. In the study, the indium-tin oxide (ITO) with a thickness of 30 nm was coated on glass for the fabrication of PSSIs, and the patterns were ablated using the UV laser system with the laser of 355 nm. The processing parameters including the pulsed frequencies (80, 100 and 120 kHz) and the scanning speed (500, 1000 and 1500 mm/s) were adjusted to develop the oxidation degree at the edge of patterns, and the patterns with different dimensions and shapes were designed to investigate the variation of the inductive efficiency. The dimension of PSSIs on ITO glass was reduced from 3 × 3 cm² to 0.5 × 0.5 cm² in the experiments, and the oxidation and contour at the ablated edge were discussed. The efficiency of the inductance from Cu-coated substrate and ITO glass were compared and the ratio between the line width and pitch of patterns was varied to enhance the inductive efficiency up to 5 - 10 %. In addition, the inductances of matrix pattern were designed to discuss the enhanced efficiency compared to the single pattern. The results can provide the information of the relationship between the inductive efficiency and ratio of the patterns, and the designed inductances can be applied in micro wireless charging module in future. (author)