Copper Interconnects for Ceramic Substrates and Packages

Copper metallization on ceramic substrates and packages is used because of two key physical parameters and one economic parameter: low electrical resistivity, high thermal conductivity, and low cost. Direct Bond Copper (DBC) is a patented process that was developed at the General Electric Company. In this process, copper is eutectically attached to oxygen-bearing ceramics such as alumina and beryllium oxide without any adhesive or bonding material. Multilayer structures of DBC substrates can be made using the same copper-oxygen eutectic principle. Thick-film copper metallization is typically selected for the low cost of the conductor inks in comparison to gold inks. Copper can be plated on the surface conductors of both high-temperature cofired ceramic and low-temperature cofired ceramic packages and substrates. The electroless copper plating of ceramics was originally developed at PCK Technology Division of Kollmorgen Corporation. Copper can be either electrolytically plated to an entire surface, and then photographically defined using etching, or selectively plated.