CHARACTERIZATION AND RELIABILITY STUDY OF ANISOTROPIC CONDUCTIVE ADHESIVES FOR FINE-PITCH PACKAGE ASSEMBLY

The application of Anisotropic Conductive Adhesive (ACA) for the inter connection of fine pitch Surface Mount Devices (SMDs) to electroless n ickel/gold plated copper clad FR4 board was investigated. One ACA tape , one ACA paste, and one isotropic conductive adhesive paste were used in a Taguchi (L9) experimental design(1). The experiment was carried out with three different gull-wing leaded, Ceramic Quad Flat Pack (CQF P) packages. The packages were mounted onto FR4 boards using a hot bar (thermode) system with adjustable temperature and pressure setting. Q uality and reliability assessment was carried out by visual inspection , mechanical strength testing and electrical resistance measurements o f individual leads before and after humidity testing and temperature c ycling. The processing issues of conductive paste and tape adhesive as sembly compared to solder assembly were examined and valuable informat ion was also obtained from reliability testing. Although mechanical st rengths and electrical resistances were obtained similar to those expe cted for solder assembly; reliability, humidity testing in particular, needs to be addressed in greater detail in order to make the applicat ion of ACAs a viable alternative to solder.