Research on the interfacial reaction between anisotropically conductive film and bumpless die

This paper systematically discusses the influence of bonding pressure, bonding temperature and humidity on the adhesion strength of bumpless die (aluminum surface) with two kinds of Anisotropically Conductive Films (ACFs). Evaluated by die shear test, the adhesion. strength between the ACFs and aluminum is not affected seriously by bonding pressure but it increases when bonding temperature increases. Adhesion strength at the ACF/aluminum interface increases while the adhesion at the ACF/glass surface decreases after aging in the same high temperature and high humidity environment. For the ACF/aluminum layer, the adhesion enhancement mechanism after humidity aging is studied by SAM, SEM & EDX, and XPS. Moisture mainly diffused into aluminum and resulted in an oxidation reaction, instead of diffusing into adhesive to make it swell. Less swelling of adhesive and less delamination occurred at the ACF/aluminum surface. Thus, the adhesion strength of shear samples increased after temperature/humidity exposure. In addition, the oxidation reaction can provide a fresh rougher surface that may enhance adhesion strength.