ABSTRACT
Flip chip interconnects formed using adhesives have been recognized as a promising substitute for solder interconnects because of their fine-pitch, lead-free and low-temperature processing capabilities. The two leading candidates for adhesive flip chip technology include anisotropic conductive adhesives (ACAs) and non-
conductive adhesives (NCAs) [1, 2]. Both ACAs and NCAs are comprised of a fast-cure thermosetting epoxy matrix, with ACAs also containing a small amount of electrically conductive particles. Unlike a solder flip chip joint, an adhesive interconnect is a non-metallurgical joint and its reliability performance depends largely on the adhesion strength and resultant compressive force arising from the applied load during flip chip bonding, adhesive cure shrinkage and thermal shrinkage during the cool-down process. The compressive force is essential to establish stable and low resistance electrical connections [3, 4]. Of the three factors mentioned, cure shrinkage is the most complex to determine, and has attracted considerable interest in recent years [5-9]. For adhesion strength measurement, the most commonly used techniques are die shear test and lap shear test [10, 11]. It has been highlighted in several studies that adhesion strength is largely influenced by degree of cure of the adhesive [12-18]. Therefore, an optimized cure process is critical to achieve the ultimate performance and reliability of these adhesive joints.
