Using novel materials to enhance the efficiency of conductive polymer

Abstract

Conductive polymers have a vast market in integrated circuits (IC) and microsystems packaging to enhance mechanical, thermal, electrical performance, and cost effectiveness[1]. Isotropically conductive adhesives (ICAs) have been explored for attaching encapsulated surface mount components on rigid and flexible printed circuits [2]. However, the practical use of conductive adhesives in surface mount applications is limited because of the weak electric conductivity. Jiang et al [3] used nano-sized silver particles as a candidate for conducting filers in order to reduce the sintering temperature, but the contact resistance is still high. Some groups [4, 5] studied a series of methods such as using carboxylic acid group containing chemicals as surfactants to enhance the conductivity of ICAs in a variety of conditions, but because the micron-sized silver fillers have a high sintering temperature, the enhancement in conductivity is still limited. In order to further improve the conductivity of ICAs and minimize the cost, we experimented on a series of materials for silver surface pretreatment. We noticed an about 20 times improvement in conductivity of the modified ICA than the control sample (75% silver content in all samples). The volume resistivity of the optimum formulation reached the level of 10-6 Omegaldrcm. We also analyzed the adhesion strength and thermal property of the modified ICA material. The study indicated that both the electrical properties and the mechanical property were improved without negatively affecting the other physical properties, and they are both remain stable after subjecting to the 85degC and 85% relative humidity conditioning test.