New Process for Selective Additive Metallization of Alumina Ceramic Substrates

A newly developed laser-assisted process is presented, by which a selective additive metallization of injection-molded alumina ceramic substrates without additional additives is enabled. Alumina substrates were manufactured by ceramic injection molding (CIM) with subsequent debinding and sintering. The substrate surfaces are activated by laser patterning for subsequent electroless plating of the activated areas with copper, nickel, and gold. Three-dimensionally shaped ceramic interconnect devices are enabled by CIM combined with 3-D laser patterning. The conducting paths fabricated in this way are characterized and compared to conducting paths made by a laser-direct-structure technology on thermoplastics developed by the company LPKF Laser & Electronics AG (LPKF-laser direct structuring process). The obtained metal layer thickness with about $10~\mu \text{m}$ is similar to metal layer thickness on thermoplastic substrates. Obtained metal surface roughness on ceramic substrates of below $10~\mu \text{m}$ is even lower than on thermoplastics. The high adhesion of approximately 30 N mm $^{-2}$ combined with the low thermal expansion coefficient of the alumina substrate promises good reliability even under thermal load.