Study On The Effect And Mechanism Of Sulfur And Nitrogen Additives On The Roughness Of Acid Copper Electroplating

Copper has good electrical conductivity,thermal conductivity,corrosion resistance and other characteristics.Copper plating process is widely used in PCB,IC packaging,integrated circuit chips and other technologies.With the development of electronic products towards miniaturization,higher requirements are put forward for coating roughness.The effect of thiourea and nitrogen additives on the surface roughness of electroplated copper coating was studied in this paper.The mechanism of thiourea additives and nitrogen additives in electroplating process was proposed by studying the surface roughness,micro-morphology and electrochemical properties of copper plating bath.The results are as follows:(1)When the concentration of ethylene thiourea,allyl thiourea,thiourea and N-phenyl thiourea were 150 ppm,10 ppm,50 ppm and 2 ppm respectively,the roughness was the lowest,and the roughness values were 0.12,0.29,0.1 and 0.24,respectively.The results of SEM combined with copper coating show that the copper coating obtained by 10 ppm allyl thiourea is the tightest and smoothest.The electrochemical performance study shows that the addition of thiourea additives makes the open-circuit potential and chronopotentiometric potential shift negatively.The cathodic polarization curve and AC impedance test show that the cathodic polarization is obvious.The cyclic voltammetry curve and Tafel curve test show that the addition of thiourea additives makes the cathodic electrode surface more stable and inhibits the reduction reaction of the electrode surface obviously.The results show that thiourea additives can inhibit copper deposition,and the inhibition will increase with the increase of the concentration of thiourea additives.However,excessive concentration of additives will adversely affect the surface smoothness of copper plating.It may be that the addition of excessive additives inhibits the copper electrodeposition too strongly,which makes it difficult for copper to adsorb and stabilize on the surface of Hastelloy sheet and form copper plating with small particles,tight bonding and good lattice morphology.This makes the surface morphology of copper plating confused and has higher roughness.Based on the research results,a theoretical model of thiourea additives adsorbed on the cathode surface to inhibit copper deposition and achieve surface smoothness was proposed.(2)When the concentration of benzotriazole,benzimidazole,indole and indazole are 40 ppm,50 ppm,120 ppm and 50 ppm respectively,the roughness is the lowest,and the roughness values are 0.13,0.15,0.18 and 0.16,respectively.The results of SEM combined with copper coating show that the copper coating obtained by 40 ppm benzotriazole is the tightest and smoothest.The electrochemical performance study shows that the addition of nitrogen additives makes the open-circuit potential and chronopotentiometric potential shift negatively.The cathodic polarization curve and AC impedance test show that the cathodic polarization is obvious.The cyclic voltammetry curve and Tafel curve test show that the addition of nitrogen additives makes the cathodic electrode surface more stable and inhibits the reduction reaction of the electrode surface obviously.The results show that the addition of nitrogen additives can inhibit copper electrodeposition,and the inhibition will increase with the increase of additive concentration.However,excessive concentration of additives will adversely affect the surface smoothness of copper plating.It may be that the addition of excessive additives can restrain the copper deposition too strongly,which makes it difficult for copper to adsorb and stabilize on the surface of Hastelloy sheet and form copper plating with small particles,tight bonding and good lattice morphology.This makes the surface morphology of copper plating confused and has higher roughness.Based on the research results,a theoretical model of nitrogen-containing additives adsorbed on the cathode surface to inhibit copper deposition and smooth the coating surface was proposed.