Research On The Uniformity Of Micro-electroforming Devices

Micro-fabrication technology is the crucial procedure in MEMS due to its transformation of various designs into productions. It is the basis of MEMS technology, so much attention has been paid on micro-fabrication technology. In various micro-fabrication technologies, LIGA/LIGA-Like technology has been playing an important leading role because of its applicability of different materials and its convenience for bulk production. Micro-electroforming is indispensable to LIGA/LIGA-Like technology. However, micro devices fabricated by micro electroforming technique often have disadvantage of nonuniformity, which lowers quality and worsens working performances. Therefore, theoretical and experimental research was carried out to improve uniformity of metal micro-mold insert used in microfluidic chips.Because of the great influence of current waveform on micro-device quality, the effect of negative current on surface finishing was studied theoretically. Because the height of micro tips on cathode surface can be eroded by the negative current, surface finishing is better in the micro-electroforming by periodic reverse pulse current than pulse current.Based on the theoretical ananlysis, micro-electroforming experiments of two periodic reverse pulse currents were done. They were periodic reverse pulse current with pulse both in positive and negative direction and that with pulse only in positive direction, respectively. No backing process was employed, and the processing parameters were summarized from lots of pulse-current micro-electroforming experiments. Through comparison between the results of pulse current and periodic reverse pulse currents, it was showed that better uniformity of micro-electroforming mold was obtained when periodic reverse pulse current was used. Experimental results were consistent with the theoretical prediction.Nonuniform concentration of metal ions and mass transportation in the micro-channels of photoresist mold leads to nonuniformiy of micro-electroforming layer. Therefore, diffusion current density distribution on the cathode surface was theoretically investigated, and rotating cathode was favorable to obtain the uniform distribution of diffusion current density and improve the uniformity of micro-electroforming. Fluid velocity in micro electroforming channels under the circumstance of different cathodes was studied by simulation. Experimental investigation of rotating cathode was put up, and the result showed that thickness uniformity of micro-electroforming mold using rotating cathode was greatly better than that by moving cathode.There was no rotating cathode mechanism in the precise electroforming equipment so a mechanism of rotating cathode was designed and manufactured. These problems of supporting, electricity leading and fixing of the base substrate were well solved, and the...