Physical properties and thermocycling performance of electrically conductive adhesives (ECAs) modified by flexible molecules

Flexible polymer binders were introduced into electrically conductive adhesive (ECA) formulations in order to improve the reliability performance of ECA/component joints under thermal cycling/shock conditions while maintaining a comparable bulk conductivity. The curing behavior, modulus, coefficient of thermal expansion and moisture absorption were measured on the ECA formulations designed. Adhesion to Cu/OSP and tin surfaces was studied through substrate shear tests. Electrical bulk resistivity and contact resistances were monitored on specially prepared test coupons that were exposed to 85°C/85%RH atmosphere. Experimental results showed that the rubbery ECA samples could typically give very similar bulk conductivity to that of conventional ECA materials. Some of the formulations exhibited acceptable contact resistance stability under thermal cycling conditions, while the ECA/component joint interfaces kept intact through the thermal cycling tests.