Adhesion and Reliability of Anisotropic Conductive Films (ACFs) Joints on Organic Solderability Preservatives (OSPs) Metal Surface Finish

• Published in: Journal of electronic materials Vol. 37; no. 7; pp. 1003 - 1011
• Main Authors: Kim, Hyoung-Joon, Paik, Kyung-Wook
• Format: Journal Article
• Language: English
• Published: Boston Springer US 01-07-2008; Institute of Electrical and Electronics Engineers; Springer Nature B.V
• Subjects: Adhesion; Applied sciences; Characterization and Evaluation of Materials; Chemistry and Materials Science; Condensed matter: structure, mechanical and thermal properties; Electronics; Electronics and Microelectronics; Exact sciences and technology; Flexibility; Instrumentation; Joint strength; Materials; Materials Science; Mechanical and acoustical properties; Microelectronic fabrication (materials and surfaces technology); Optical and Electronic Materials; Physical properties of thin films, nonelectronic; Physics; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Soldering; Solid State Physics; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); Anisotropic conductive film (ACF); flex-on-board (FOB); adhesion; organic solderability preservative (OSP); surface finish; flexible substrate; Carbon non metal bond; Fourier transform spectroscopy; Organometallic compounds; Epoxy resin; Surface treatments; High temperature; Coatings; Thin films; Microelectronic fabrication; Adhesive strength; Copper; Bonding; Gold; Ruptures; Mechanical properties; Adhesion; Interfaces; Transmission electron microscopy; Anisotropy; Curing; Nickel; Reliability; X-ray photoelectron spectra; Tribology
• ISSN: 0361-5235; 1543-186X
• DOI: 10.1007/s11664-008-0397-4

The effect of final metal finishes of Cu electrodes on the adhesion and reliability of anisotropic conductive film (ACF) joints was investigated. Two different metal surface finishes, electroless Ni/immersion Au (ENIG) and organic solderability preservatives (OSPs) coated on Cu, were selected in this study for ACF bonding. The adhesion strength of ACF/OSP joints was higher than that of ACF/bare Cu and ACF/ENIG joints. The fracture sites of the ACF/bare Cu and ACF/ENIG joints were ACF/metal interfaces, while those of ACF/OSP joints were inside the ACF. Transmission electron microscope (TEM) and Fourier-transform infrared (FT-IR) analyses showed that the OSP coating layer on the Cu electrodes reacted with the epoxy resin of the ACFs but still remained at the bonding interface. According to the in-depth X-ray photoelectron spectroscopy (XPS) analysis, additional C-N bonds formed after the OSP-epoxy reaction and the outermost nitrogen of the OSP layer participated in curing of the epoxy resin of the ACF. Therefore, the OSP layer acted as an adhesion promoter to ACFs. Furthermore, this role of the OSP layer enhanced the reliability of the ACF/OSP joints under high temperature and humid environments, as compared to the ACF/ENIG joints.