A potential silver catalyst system for new generation of electroless Cu process as a palladium substitution

Abstract

Electroless plating of copper onto insulating substrates is a process broadly applied in the electronics industry for manufacture of printed circuit boards and decorative plating of plastic parts for automotive or consumer appliance. The key step involves surface activation of the dielectric surface for deposition in electroless copper bath. Palladium catalyst, either in its ionic form or metallic form, is most widely used for this purpose. However, the high and volatile unit metal price causes the catalyst solution to be the most expensive part among the electroless process. The economic pressure imposed on manufacturers and consumers would be the major driving force for developing an alternative catalyst system with lower cost. Previously we have introduced the innovative nano-silver catalyst system such as the physical properties, catalytic performance on conventional electroless copper deposition, and reliability performance in copper-copper interconnects area. [1] In this paper, comparison of silver catalyst with traditional palladium catalyst for MHC process will be described. Further study on deposition profile, microvia coverage and morphology, and reliability performance with liquid-to-liquid thermal shock will be illustrated. In the last section, the concerns on silver migration with silver catalyst applications on printed circuit board will be discussed.