고출력 Nd:YAG UV레이저를 이용한 polyimide층과 Cu-metal층의 가공상태에 대한 실험적 고찰

Experimental Investigation for Ablation Characteristics of Polyimide Layer and Cu-metal Layer using High Power Nd:YAG UV Laser

  • 최경진 (강남대학교 공과대학 전자공학과) ;
  • 이용현 (강남대학교 공과대학 전자공학과)
  • 발행 : 2009.12.31

초록

In this paper, the laser cutting characteristics of the flexible PCB using high power Nd:YAG UV laser were investigated. A specific FPCB model was selected for the experiment. Test sheets were made, which had equal materials and layer structure to those of the outline (OL) region and the contact pad (CP) region in the FPCB. The experiment is made up of two stages. In the first stage of the experiment, the laser cutting fluence was found, which is the threshold fluence to cut the test sheets completely. The laser cutting fluence of the OL sheet is $1781.26{\sim}1970.16\;J/cm^2$ and that of the CP sheet is $2109.34{\sim}2134.34\;J/cm^2$. In the second stage, cutting performance and its qualities were analyzed by the experiment. The laser cutting performance remained almost unchanged for all laser and process parameter sets. The average cutting width (top side/bottom side) of the OL sheet was $40.45\;{\mu}m/11.52\;{\mu}m$ and that of the CP sheet was $22.14\;{\mu}m/10.93\;{\mu}m$. However, the laser cutting qualities were different according to the parameters. The adjacent region of the cutting line on the OL sheet was carbonized as the beam speed was low and the overlap coefficient was high. The surface quality around the cutting line of the CP sheet was about the same. Carbonization and debris occurred on the surface of the cutting line. As a result of the experiment, the cutting qualities were better as the overlap coefficient was made low and beam speed high. Therefore, the overlap coefficient 2 or 3 is proper for the FPCB laser cutting.

키워드

참고문헌

  1. Marc Huske, “Burr and Stree-Free Cutting of Flexible Printed Circuits”, OnBoard Technology, pp.18-21, June 2006.
  2. Oh, J. Y. and Shin, B. S., “A Study on Laser Ablation of Copper Thin Foil by 355nm UV laser Processing”, Journal of the Korean Society for Precision Engineering, Vol.24, No. 2, pp.134-139, February 2007.
  3. Shin, D. S., Lee, J. H., Suh, J. and Kim, T. H., “Excimer laser induced ablation of PMMA and PET”, Journal of Korean Society of Laser Processing, Vol.6, No.1, pp.33-40, 2003.
  4. Yoon, K. K. and Bang, S. Y., “Modeling of polymer ablation with excimer lasers”, Journal of the Korean Society for Precision Engineering, Vol.22, No.9, pp.60-68, 2005.
  5. Shin, B. S., Oh, J. Y. and Sohn, H., “Theoretical and experimental investigations into laser ablation of polyimide and copper films with 355-nm Nd:YVO4 laser”, Journal of Material Processing Technology, 187-188(2007) 260-263. https://doi.org/10.1016/j.jmatprotec.2006.11.106
  6. Shin, D. S., Lee, J. H., Suh, J. and Sohn, H. K., “Laser Cutting process for FPCB using ps and ns UV laser”, Proceedings of the Korean Society of Precision Engineering Conference, pp.329-330, June 2008.
  7. Bae, H. S., Ryu, K. H. and Nam, G. J., “Study of Laser Machining Properties about Raw Material FPCB”, Proceedings of the Korean Society of Precision Engineering Conference, pp.379-380, June 2008.