Morphology and adhesion strength in electroless Cu metallized AlN substrate

The metallization of aluminum nitride substrates by electroless copper plating is investigated. The AlN substrate is etched by 4% NaOH to study the correlation between the adhesion strength and the surface roughness of etched AlN substrate. Both the as-received nonpolished and the polished AlN are studied. For the nonpolished substrate, the adhesion strength increases from 130 kg/cm² for the sample with an average surface roughness of 0.2 μm to 230 kgf/cm² for one with an average surface roughness of 0.82 μm. For the polished substrate, the adhesion strength reaches 271 kg/cm² with a surface roughness of 0.19 μm. Mechanical interlocking is the major cause for the adhesion strength between the Cu and AlN substrates. The polished substrate that was subsequently etched could form fine cavities on the AlN surface, and the microetching effect resulted in a stronger mechanical interlocking, which increases the adhesion strength