Review paper: Flip chip bonding with anisotropic conductive film (ACF) and nonconductive adhesive (NCA)

Recently, the flip-chip bonding technology using adhesives has been widely used in the packaging industry because of environmental friendliness (elimination of lead material and flux cleaning), low temperature process (no soldering process), fewer processing steps (no underfill process), and the fine pitch capability. In flip-chip assembly using adhesives, the electrical interconnection is established by mechanical contact between the bumps on the chip and the corresponding pads on the substrate after the adhesive is cured. The adhesive can be categorized into two types with respect to the presence of the conductive particles: anisotropic conductive film (ACF) and nonconductive adhesive (NCA). ACF is the adhesive polymer film with dispersed conductive particles, and NCA is just adhesive which contains no conductive particles. In this review, the bonding technologies with ACF and NCA are introduced, and the principle and characteristics of each bonding method are discussed.