Effect of bonding force on the reliability of the flip chip packages employing anisotropic conductive film with reflow process

Thermo-mechanical reliability of flip chip packages employing anisotropic conductive film (ACF) was investigated in terms of the effect of bonding forces on the failure mode of the packages. Conventional reflow process was conducted to evaluate the reliability of the package. Two kinds of failure modes were detected in this study. The first one is formation of a conduction gap between conductive particle and Ni/Au plated Cu pad, while the second one is delamination of the adhesive matrix from the plated Cu pad on flexible substrate. The determination of the failure mode was mainly affected by the variation of the bonding force. In case of the ACF joints with lower bonding forces, a conduction gap was the main failure mode of the reflowed joints, while the delamination of the adhesive matrix was frequently observed in case of the joints with higher bonding forces. The difference in failure mode was discussed in the main text.