Etching Behaviors of Cu and Invar for Metal Core PCB Applications

Abstract

CIC (Cu-Invar-Cu) is made up of 3 piece clads of Cu and Invar and has high thermal conductivity and low coefficient of thermal expansion. It is one of the core candidate materials to compensate the disadvantages of conventional PCB. In order to use CIC as the metal core of PCB, etching process is required. In wet etching process, it is difficult to obtain uniform pattern due to different etching rates and etching characteristics of Cu and Invar. In this study, the etching rates and etching properties of Cu and Invar in FeCl3 and CuCl2 were compared. Results showed that FeCl3 had a faster etching rate and higher solubility than CuCl2. The etching characteristics with FeCl3 concentration were investigated and the effect of pattern on etching rate was also studied. In addition, CuCl2 was added to the FeCl3 etchant to change the etching rate and etching characteristics of Cu and invar. Finally, the optimum conditions for uniform patterning were obtained.