TY - GEN
T1 - Moisture ingression effect on stress distributions in NCF-bonded COG packages
AU - Tsai, M. Y.
AU - Wu, C. Y.
AU - Huang, C. Y.
AU - Yang, S. S.
PY - 2007
Y1 - 2007
N2 - The NCF (Non-Conductive Film) adhesives have potentials to replace the ACF (Anisotropic Conductive Film) adhesive in the COG or other packages in LCDs (Liquid Crystal Displays) due to their feasible features of finer bump pitch and cost reduction. Prior to applying the NCF to the COG packages, reliability issues, such as interfacial delamination and increase of bump contact resistance under thermal and moisture loads, have to be overcome. The objective of this paper is to investigate the effect of moisture ingression on stress field of the COG packages with NCF bending. The coefficients of moisture diffusion and the hygro-strains of the NCF adhesive have been determined by an innovative approach of measuring the out-of-plane deformation of the bi-material specimens during moisture absorption at the condition of 30°C /85%RH using Twyman-Green interferometry, associated with a finite element analysis and bi-material theory. The results show that the average of the coefficients of moisture diffusion and saturated hygro-strains of the NCF under 30°C /85%RH are 1.09 × 10-6 mm2/s and 1.51 × 10-3, respectively. After being validated by the diffusion theory, the moisture-transient finite element analysis reveals that the moisture absorption of the COG package under 30deg;C/ 85%RH is nearly saturated after 1000 hrs. It is also found that there is a large tensile stress at pad corner and the tensile stresses gradually increase with moisture absorption and up to the maximum at the state of moisture saturation. Through the parametric study by the validated finite element model, the results show that the tensile bump-joint and interfacial stresses increase nonlinearly with the NCF elastic modulus and linearly with the saturated moisture-induced strain (SMIS) of the NCFs. Furthermore, the COG package with polyimide bumps is found to have lower moisture-induced tensile stresses than that with gold bumps. It is further shown that the tensile stresses from the longitudinal-section and transverse-section models are similar only with a few percent difference in values. It can be concluded that the stress states of the NCF-bonded COG packages induced by transient moisture ingression have been fully addressed through experimental, theoretical and numerical approaches in this study.
AB - The NCF (Non-Conductive Film) adhesives have potentials to replace the ACF (Anisotropic Conductive Film) adhesive in the COG or other packages in LCDs (Liquid Crystal Displays) due to their feasible features of finer bump pitch and cost reduction. Prior to applying the NCF to the COG packages, reliability issues, such as interfacial delamination and increase of bump contact resistance under thermal and moisture loads, have to be overcome. The objective of this paper is to investigate the effect of moisture ingression on stress field of the COG packages with NCF bending. The coefficients of moisture diffusion and the hygro-strains of the NCF adhesive have been determined by an innovative approach of measuring the out-of-plane deformation of the bi-material specimens during moisture absorption at the condition of 30°C /85%RH using Twyman-Green interferometry, associated with a finite element analysis and bi-material theory. The results show that the average of the coefficients of moisture diffusion and saturated hygro-strains of the NCF under 30°C /85%RH are 1.09 × 10-6 mm2/s and 1.51 × 10-3, respectively. After being validated by the diffusion theory, the moisture-transient finite element analysis reveals that the moisture absorption of the COG package under 30deg;C/ 85%RH is nearly saturated after 1000 hrs. It is also found that there is a large tensile stress at pad corner and the tensile stresses gradually increase with moisture absorption and up to the maximum at the state of moisture saturation. Through the parametric study by the validated finite element model, the results show that the tensile bump-joint and interfacial stresses increase nonlinearly with the NCF elastic modulus and linearly with the saturated moisture-induced strain (SMIS) of the NCFs. Furthermore, the COG package with polyimide bumps is found to have lower moisture-induced tensile stresses than that with gold bumps. It is further shown that the tensile stresses from the longitudinal-section and transverse-section models are similar only with a few percent difference in values. It can be concluded that the stress states of the NCF-bonded COG packages induced by transient moisture ingression have been fully addressed through experimental, theoretical and numerical approaches in this study.
UR - http://www.scopus.com/inward/record.url?scp=35348871913&partnerID=8YFLogxK
U2 - 10.1109/ECTC.2007.373839
DO - 10.1109/ECTC.2007.373839
M3 - 会议稿件
AN - SCOPUS:35348871913
SN - 1424409853
SN - 9781424409853
T3 - Proceedings - Electronic Components and Technology Conference
SP - 467
EP - 474
BT - Proceedings - 57th Electronic Components and Technology Conference 2007, ECTC '07
T2 - 57th Electronic Components and Technology Conference 2007, ECTC '07
Y2 - 29 May 2007 through 1 June 2007
ER -