Research of High Aspect Ratio Electroforming Technology and Replication Process

• Main Authors: Tsung-Hsun Tsai, 蔡宗勳
• Other Authors: Reiyu Chein
• Format: Others
• Language: zh-TW
• Published: 2004
• Online Access: http://ndltd.ncl.edu.tw/handle/80336635010648849237

博士 === 國立中興大學 === 機械工程學系 === 92 === The major goal of this study is to investigate the high-aspect-ratio electroforming technique. Three fundamental difficulties are encountered in the microstructure electroforming: electrolyte filling, fast ion consumption rate, and poor structure strength. The strategies for solving these three problems are reported in this study. First, the influence of centrifugal force and surface tension on the fluid filling processes in high-aspect-ratio micromold is addressed. Under certain high rotation speed of the filling system, efficient filling can be attained regardless surface is hydrophilic or hydrophobic. Second, a theoretical model that predicts the metal ion concentration distribution during electroforming high aspect ratio microstructures (HARM) is built. The applied current density and microstructure aspect ratio were found as two important factors that affect the electroforming outcome. The analytical results are verified using electroforming microstructural posts experiments. Good agreement was obtained between the experimental and analytical solutions. Third, a new microelectroforming technique using air-pressure assistance in the electrolyte is developed. The related theories show that ion diffusivity can be increased and surface tension can be reduced by increasing the bulk electrolyte pressure. These two positive effects can help to obtain successful outcomes on high aspect ratio microstructure electroforming. The pressurized electrolyte reduces hydrogen bubble formation and defect on the substrate surface. The experimental results show that the metallurgical grains were finer when higher pressures were applied in the electrolyte based on SEM micrographs. Moreover, pressurized electroforming can increase the allowable current density which can shorten plating time in the LIGA process. The surface morphology of pressurized electroformed samples and hardness were improved compared with the conventional method. Based on these positive effects, Ni post arrays microstructures with HAR=12 in 85μm diameter is realized by using pressurized electroforming.