Abstract
Pd nanoparticles stabilized by poly(vinylpyrrolidone) (PVP) have been synthesized in ethylene glycol (Pd/PVP/EG) and in water (Pd/PVP). The PVP-stabilized Pd nanoparticles (Pd-based activators) were found to hold strong potential to replace conventional activator Pd/Sn colloid for electroless copper deposition.However, Pd-based activators led to poor back-light performance with SPS process. Adding phosphoric acid to adjust pH of the activator would improve back-light performance with SPS process for both Pd/PVP and Pd/PVP/EG. We measured the copper deposition rate and palladium adsorption amount by inductively coupled plasma (ICP-MS). The back-light performance of FR-4 substrates with through holes was measured with optical microscope (OM). Zeta potential and X-ray photoelectron spectroscopy (XPS) results confirmed the adsorptive mechanism of Pd-based activators. We found that Pd/PVP added with acid was more easily prepared than Pd/PVP/EG. Furthermore, Pd/PVP added with acid led to higher specific activity and stability than Pd/PVP/EG even though both of them led to qualified back-light performance and similar copper deposition rate. The Pd consumption of Pd/PVP/EG was much more than that of Pd/PVP. We considered that Pd/PVP was more likely to be a candidate than Pd/PVP/EG to compete with Pd/Sn colloid. We also found aeration caused serious oxidation of Pd for acid added Pd/PVP.