Influence Mechanism of Synergistic Additives on the Nucleation and Coating Morphology and Structure of Copper Electronic Plating
In this work,based on the acidic copper sulfate electronic plating formula and process for through-hole uniform thickening of printed circuit board(PCB)with 1-(2-pyridylazo)-2-naphthol(PAN)as a synergistic additive,the influence mechanism of the additives on the copper electro-crystallization process was clarified by using the elec-trochemical chronoamperometry.Polyethylene glycol(PEG)destroys the copper nucleation process,bis-(3-sulfopro-pyl)disulfide(SPS)and PAN do not affect the occurrence of copper nucleation behavior,and the synergic effects of PEG,SPS and PAN can further promote the formation of copper nuclei.Both PEG and SPS promote the adsorption of PAN on the copper surface confirmed through electrochemical in situ Raman spectroscopy.The effects of additives on the morphology of copper coating are analyzed by scanning electron microscopy.Only SPS can refine the copper coating particles,and the synergistic effects of PEG,SPS and PAN is beneficial to obtain copper coating with finer and more uniform particles.The crystal face orientation of copper coating and the crystal face sites adsorbed by additives are revealed by X-ray diffraction.Both PEG and PAN are easy to adsorb on the(111)crystal face and inhibit the(220)crystal face.SPS is easy to adsorb on the(220)crystal face and promotes the(220)crystal face to be preferred.The combined action of PEG and SPS can make copper grow along the(111),(200)and(220)crystal faces,and(200)is a relatively preferred crystal face.The complex synergistic effects among the three additives promote the preferential growth of copper along the(111)and(200)crystal faces.
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