Polypyrrole as an interlayer for bonding conductive adhesives to activated aluminum bond pads

Polymeric electronic packaging using conductive adhesives has been identified as a key technology for future assembly and manufacturing. This paper presents a study on process development for conductive adhesives as solder replacement. The main objective investigated is the use of intrinsic conductive polymers directly bonded to bond pads as a low cost effective procedure. The process consists of a technology for the chemical deposition of polypyrrole as an interlayer on aluminum bond pads including the activation of the aluminum surface and the deposition of an isotropic conductive adhesive. Results regarding the chemical characterization of the conductive interlayer by energy disperse analysis of X-ray Spectroscopy and the physical properties of the bumps consisting of a commercially used isotropic conductive adhesive are presented. The paper emphasizes electrical measurements, i.e., contact resistance and the shear strength of the bumps to the bond pads. The approach and analyses described, as well as the practical conclusions for the optimal fabrication of the conductive interlayer for the deposition of adhesives, are an important step forward in low cost procedures in the field of micro packaging.