Area bonding conductive epoxy adhesive preforms for grid array and MCM substrate attach

A new type of z-axis epoxy tape adhesive, called an area bond conductive (ABC) adhesive, has been developed under ARPA contract to replace tin-lead solder for surface mounting grid array components. The ABC adhesive tapes contain discrete regions, or “dots”, on pitch down to 0.2 mm, of an electrically conductive epoxy within a high strength, high T_g, epoxy dielectric phase. The adhesives are supplied as die cut preforms, which match the size and bond pad pattern of the component to be attached. The preforms cure at 160-175°C and require no pressure during cure, to yield a shock resistant, void-free area bond to any FR4 or other board surface. This paper presents bond strength, conductivity, dielectric strength, humidity and thermal shock results for daisy chain test circuits and other components attached to FR4 boards