Effects of anisotropic conductive adhesive (ACA) material properties on package reliability performance [flip-chip interconnects]

Solder alternative technologies for flip-chip interconnections are fast emerging due to the drive for environmental friendly processes. The anisotropic conductive adhesive (ACA) is one promising solder alternative candidate that shows potential for further pitch reduction. The main concern with ACA interconnection is their long-term reliability performance especially in humid environments. Although much work has been published on ACA joint behaviour, studies on correlation of material properties with reliability performance is still lacking. The main objective in this study was to identify the impact of material properties on reliability, so as to engineer highly reliable microelectronics assemblies. Four representative ACA materials (both film and paste types) with diverse properties were selected and reliability tests were carried out. Correlation analysis identified key material properties that contribute to good reliability performance. Findings indicate that the best properties for high reliability assemblies are: high adhesion strength after subjecting to reliability test conditions, low coefficient of moisture expansion and low storage modulus.