Properties Investigation on Chip-on-Film (COF) Thermosonic Bonding Using Anisotropic Conductive Films (ACFs)

초록

Chip-on-film (COF) technology has been developed for liquid crystal displays (LCD) due to its high yield capability in fine pitch products. In this study, a new COF thermosonic (TS) bonding process using anisotropic conductive adhesive and ultrasonic vibrations will be introduced. Si chips with 16 cylindrical Cu bumps (phi 100 mu m) and polyimide (PI) film substrate with a thickness of 70 mu m were prepared. For the bonding condition, the bonding temperature and ultrasonic time were varied from 413 to 453K and from 0.5 to 1 s, respectively. Also, thermocompression (TC) bonding was conducted with a bonding temperature of 453K and bonding time of 8 s to compare it to the bonding characteristics of TS bonding. The shear strength and electrical resistance of COF assemblies were measured to verify the feasibility of COF TS bonding using ACFs. The cross-sectional inspection and fracture surface analysis of COF joints were also conducted using field-emission scanning electron microscopy (FE-SEM). As a result, the mechanical and electrical properties of the COF assembly were improved by increasing the bonding temperature and ultrasonic dwell time. It was also determined that ultrasonic energy has a significant influence in improving the mechanical and electrical properties of the TS COF assembly.

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