A Study on the Optimization of IR Laser Flip-chip Bonding Process Using Taguchi Methods

다구찌법을 이용한 IR 레이저 Flip-chip 접합공정 최적화 연구

  • Published : 2008.06.30


A flip-chip bonding system using IR laser with a wavelength of 1064 nm was developed and associated process parameters were analyzed using Taguchi methods. An infrared laser beam is designed to transmit through a silicon chip and used for transferring laser energy directly to micro-bumps. This process has several advantages: minimized heat affect zone, fast bonding and good reliability in the microchip bonding interface. Approximately 50 % of the irradiated energy can be directly used for bonding the solder bumps with a few seconds of bonding time. A flip-chip with 120 solder bumps was used for this experiment and the composition of the solder bump was Sn3.0Ag0.5Cu. The main processing parameters for IR laser flip-chip bonding were laser power, scanning speed, a spot size and UBM thickness. Taguchi methods were applied for optimizing these four main processing parameters. The optimized bump shape and its shear force were modeled and the experimental results were compared with them. The analysis results indicate that the bump shape and its shear force are dominantly influenced by laser power and scanning speed over a laser spot size. In addition, various effects of processing parameters for IR laser flip-chip bonding are presented and discussed.




  1. K. N. Chiang and C.A. Yuan : An overview of solder bump shape prediction algorithms with validations, IEEE transactions on advanced packaging, 24-2 (2001), 158-162
  2. JSA : JIS Z 3198 Test methods for lead free solders, 2003
  3. J. W. Kim, D.G. Kim and S.B. Jung : Investigation of the test parameters and bump structures in the shear test of flip chip solder bump, Thin solid films, 504-1-2 (2006), 405-409
  4. T. Teutsch, E. Zakel and G. Azdasht: advanced packaging, PennWell, 2006, 420-450
  5. J. F. Ready, D. F. Farson and T. Feeley: Handbook of Laser Materials Processing, Laser Institute of America, 2001, 138
  6. Y. E. Shin, Y.W. Koh and J.M. Kim : Trend of electronic packaging and charateristics evaluation by shape of solder joints, Journal of KWS, 20-3 (2002), 24-30
  7. M. Y. Li, C. Q. Wang, H. S. Bang and Y. P. Kim: Development of a Flux-less Soldering Method by Ultrasonic Modulated Laser, Journal of Materials Processing Technology, 168-2 (2005), 303-307
  8. R. K. Ulrich, and W. D. Brown: Advanced Electronic Packaging, Wiley-Interscience, 2006, 417-418
  9. H. Schafer, P. Yuan and Z. P. Wang: Investigation of Ultrasonic Filp Chip Bonding on Flex Substartes, Electronic Packaging Technology Proceeding, (2003), 117-120
  10. S. Theppakuttai, D. B. Shao and S. C. Chen: Localized Laser Transmission Bonding for Microsystem Fabrication and Packaging, Journal of Manufacturing Process, 6-1 (2004), 1-8
  11. R. R. Tummala: Fundamentals of Microsystems Packaging, McGraw Hill, 2001, 281-284
  12. J. W. Kim, D. G. Kim, S. S. Ha, W. C. Moon, C. S. Yoo, J. H. Moon and S. B. Jung: Evaluation of Thermo-mechanical Reliability of Flip Chip Solder Joints(I):I Pb-bearing Solder, The Korean Institute of Metals and Materials, 44-8 (2006), 581-586
  13. S. W. Kim, S. H. Kim and B. H. Youn: Bonding Properties of BGA Solder Ball with Laser Process, KWS, 45-Autumn (2005)