3D replication using PDMS mold for microcoil Feng-Fu Chuang Institute of Mechanical Engineering Date ﹕ 2011/05/23 Paper Survey a Core Research for Evolutional Science and Technology (CREST), Japan Science and Technology Agency (JST), Japan b Advanced Manufacturing Research Institute (AMRI), National Institute of Advanced Industrial Science and Technology (AIST), 1-2-1, Namiki, Tsukuba, Ibaraki , Japan Microelectronic Engineering 86 (2009) 920–924

2 Outlin e  Pre-process  Post-process: microcoil fabrication results  Conclusion

Pre-process Fig. 1. Schematic illustration of the pre-process procedure for the fabrication of UV resin replica pattern of a spiral structure by the 3D replication method.

Fig. 2. SEM microphotographs of the master pattern and UV resin replica pattern: (a) is the image of the master pattern; (b)–(d) are the partial magnified images of UV resin replica pattern corresponding to the outer diameters (uouter) of 0.8–1.00 mm, respectively. Pitch: 250  m Thread height:155  m Inner diameter:850  m Outer diameter:1.159 mm Table 1 Dimensions of the master and replica patterns measured by a non- contact depthmeasuring microscope.

Post-process: microcoil fabrication results Fig. 3. SEM microphotographs of the master pattern (a) and UV resin replica pattern (b); UV resin replica pattern was fully photopolymerized along the surface of the sputterdeposited Ti layer.

Fig. 4. Schematic diagram for the dimensions and shape change of threads by the compressive force resulting from the inserted Al wire with the lager diameter than that of mold cavity.

Fig. 5. SEM microphotographs of Ni electroplating result between threads of UV resin replica pattern, (a) is the partial magnified image of UV resin replica pattern, (b)–(d) are the partial magnified images of Ni electroplating results after 3 min, 6 min, and 9 min 30 s, respectively.

8 Fig. 6. SEM microphotographs of the deformed Ni microcoil structure before Au wet etching (a), after Au wet etching (c), and Ni microcoil structure (e). (b) and (d) are the partial magnified images of the deformed Ni microcoil structure of (a) and (c), respectively.

Conclusions 1.The development of a 3D replication method using PDMS mold for the fabrication of microcoil structures was successfully conducted by combining with Ni electroplating. 2.An easier separation method of the UV resin replica pattern (coil width 10 lm) from the PDMS mold cavity is imperative for simpler and low-cost fabrication.

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