Development of Three Dimensional LIGA Process to Fabricate Spiral Microcoil

Abstract

The LIGA process has been developed as a 2.5-dimensional processing method on Si wafers to date. However, we have succeeded in extending the LIGA process to 3D for the first time. 3D-LIGA was achieved by the technical development of 3D X-ray lithography and worm injection molding replication technology with unscrewing. These technologies began from the development of equipment and have developed into quite original technologies. By combining this 3D-LIGA process with a metallization technique that consists of flat and smooth electroplating and isotropic chemical etching, a spiral copper microstructure with a linewidth of 10 µm, a pitch of 20 µm and a thickness of 2 µm was formed on a cylindrical surface made from LCP with a length of 1 mm and a diameter of 0.48 mm. Furthermore, we applied the process to fabricate a spiral microcoil and estimated the electrical properties of the microcoil. The numbers of turns were 15, the inductance was 91 nH and the quality factor was 5.8 for a frequency of 1 GHz. Direct-current resistance was measured as 99 Ω.