The design and development of a novel micro-structured stencil for high precision printings

• Main Authors: Pi-Shun Chen, 陳必軒
• Other Authors: Che-Hsin Lin
• Format: Others
• Language: zh-TW
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/56718170217661473845

碩士 === 國立中山大學 === 機械與機電工程學系研究所 === 102 === This work developed a novel micro-structured stencil for high precision printings. Printing technology are the major techniques for producing printing circuit board in electronic industry. Because, printing process are usually in low-cost and mass production for producing products. However, it is difficult to produce small patterns using conventional printing technique due to the limitation of the woven mesh or stencil’s thickness. Therefore, the critical dimension for typical printing process is limited between 50 µm to 100 µm. The electronic products are tending to smaller, thinner and light for the consumer market. In other words, the printing methods are tending to smaller line width, thinner printing layer and higher printing resolution. This study developed a double layer structure stencil for printing ultra-fine line and thin film on three kind substrate. Each substrate has different surface energies. The printing test result compare the printed paste width and thickness from different printing condition. To understand the influence of surface energy for printed paste. This work successfully developed a novel process for fabricating ultra-thin stencil with a buffer reservoir utilizing the combination of AZ4620 positive photoresist (PR) and SU-8 negative PR as the electroplating molds. The fabrication process include multi- photolithography and electroplating process. A low-cost microscope glass slide was used as the substrate for producing the stencil. In order to meet the requirement for metal electroplating and structure releasing, the Ti/Au layers of 50 nm in thickness were coated on the substrate by sputtering. The injection hole is defined by the AZ4620 PR since AZ4620 can well sustain the nickel plating bath in a short electroplating time. On the contrary, the SU-8 PR can sustain long electroplating time of the nickel plating bath then prevented the first metal layer damage in second electroplating process. The high transparency of SU-8 PR also makes it easy to align the two PR plating molds. Prior to the nickel plating process, the patterned substrate was activated with CCP to enhance the surface wettability. The plasma treatment in order to further enhance the adhesion and the roughness for nickel layer. The metal structure was then released from the glass substrate using a diluted HF solution. The buffer reservoir was used to provide the necessary strength and uniform paste extrusion. Moreover, the buffer reservoir also reduced printing pressure from the injection hole. And the bridge structure to avoid the microstructure in stiction. Improved the stencil printing lifetime. Results showed that the developed stencil successfully printed silver paste with the pattern of around 15 μm in width and 1 μm in thickness. And the printing pitch also down to 20 μm. The complete right angle patterns confirmed that the developed stencil was capable for printing patterns with desired orientations. The blocking issued was excluded for the stencil and the printed pattern. The method develop in the present study will give substantial impact on the modern printing technology.