Influence of interconnection surface finishes on quality of adhesive joints

Electrically conductive adhesives electrically connect and mechanically bond circuits to a variety of substrates. Four different silver-filled isotropically conductive adhesives have been used for attaching of 1206 chip components (resistors with "zero" values -jumpers) on printed-circuit boards with six different interconnection surface finishes: Cu (standard cleaning), oxidized Cu, Cu after degradation vapors of H₂SO₃, Ni, Au over Ni, Sn (HAL). The resistances, nonlinearity, and noise of joints have been investigated before and after application of the dynamic mechanical load, which has been realized by periodical deflection of the printed circuit boards with assembled resistive chips. The load of the individual joints has been calculated. It has been found that degradation of Cu surface does not cause significant changes of electrical properties of the joints. The worst electrical parameters as well as the lowest resistance against the dynamic mechanical load have been found for the joints realized on Ni and Sn surface finishes