Influence of Laser Parameters on the Activation of Cr2O3-Doped ZTA Ceramics for Selective Electroless Copper Plating in the Manufacture of 3D Ceramic Circuit Carriers

Due to the superior thermal, mechanical and chemical properties of ceramics, metallized ceramics are widely used as circuit carriers and interconnect devices, wherever standard polymer-based circuit boards come to their limits. 2D metallization represents the current state of the art. The metallization of 3D-shaped ceramics cannot be achieved with standard metallization techniques, such as screen printing, but, for example, with the so-called laser-induced direct metallization (LDM). For LDM, a pulsed laser is used to locally activate the ceramic surface, followed by a selective electroless copper plating on the laser-irradiated areas. Although it has already been shown that LDM on Al2O3-based ceramics is possible with different laser systems, a comprehensive study on the effect of different laser parameters on ablation and activation, which includes the influences of structuring on inclined surfaces, has not been done yet. In this study, laser power, pulse repetition frequency, pulse overlap and the number of passes were varied systematically to determine the parametric sensitivity of the ablation and metallization behavior for pulsed infrared laser activation of Cr2O3-doped ZTA. It was found that ablation is necessary for the metallization and that the peak fluence is the governing factor for the ablation and metallization process. It was further shown that ablation can be well predicted with an accumulated fluence, which includes pulse overlap. Structuring under an inclination angle up to 60° does not result in a reduced activation or adhesion strength of the deposited copper. Injection-molded 3D ceramic substrates were successfully metallized and functionalized by applying an optimized set of laser parameters, showing that LDM enables the functionalization of complex 3D ceramic substrates and therefore opens up new possibilities for integrated ceramic circuit carriers.