Effect of Cu based complexes on EFTECH 64 and C194 Cu alloy

Abstract

Cupric chloride etchant was used to removing the unwanted copper alloy carrier of molded units' strips and to expose the Ni bump interconnects. However, an uncontrolled etching process of the carrier led to rough Ni bumps' surface, contributing to cosmetic defect and poor electroless Ni plating's shear strength. The current paper investigates the effect of pH, Cu specific gravity and etching speed using cupric chloride-based etchant on the surface roughness of Ni bumps after the etching of respective EFTECH-64-or C194-grade Cu alloy carriers. The DOE input factors on Cu alloy were established with the help of CEDA software. The alkaline etching of C194 resulted in a higher Ni bump's surface roughness as compared to the EFTECH-64 etching. However, under low pH and high specific Cu density parameters, C914 etching produced low surface roughness which comparable to the EFTECH-64 sample due to the consistency of resulted bump's surface roughness at upper and lower levels of etching parameters.