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Nucleation and growth of bubbles in the ACF packaging process

서울대학교 대학원
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  • 이방성전도필름
  • Aniosotropic Conductive Film
  • 기포기핵화
  • Acf
  • 기포성장
  • Decompression Rate
  • 감압율
  • Chip On Glass Packaging
  • 패키징
  • Bubble Nucleation
  • 유한요소해석
  • Bubble Growth
  • 칩 온 글래스 공정


ACF(anisotropic conductive film)s are widely used in display packaging area for the interconnection of driver IC chip bonding such as a chip-on-glass(COG) and a chip-on-film(COF), out lead bonding (OLB), and flex to printed circuit board bonding(PCB). ACF interconnection is well-established technology but the quality of ACF interconnection is very dependent on bonding process variables. Especially, formation of process bubbles, which are generated inside ACF layer during thermo-compression bonding process, is strongly influenced by bonding process variables. These bubbles can reduce mechanical and electrical property, such as adhesion strength and contact resistance. Therefore, bubbles can reduce the reliability of ACF interconnection. An experimental and numerical study was carried out to analyze the behavior of the bubble and to decrease the bubble formation. For the experimental study, a real bonding apparatus was constructed. The number of bubble and the volume fractions were obtained in each bonded specimens. The average size of bubbles¡¯ was measured by image analysis and compression force was detected by a load cell. For the numerical study, a finite element analysis was performed using commercial software (COMSOL Multiphysics) to evaluate the effect of the variation of temperature on pressure distribution. The process variables considered were the temperature, time and pressure as well as the decompression rate. In results, as the decompression rate was decreased, the number of nucleated bubble was decreased while the average bubble size was not changed due to curing reaction. As the bonding temperature and time increased, Bubble formation was found to be changed. Because bonding temperature and time affects the degree of cure, the degree of cure is the cause of bubble formation change. To analyze the experimental result, structural analysis was performed by using FEM simulation. The simulation result shows the normal stress distribution at the different temper

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