Triethanolamine And Edta 2na With The System Fast Electroless Copper Plating

First electroless copper plating system and secondary electroless copper plating system of triethanolamine(TEA) and EDTA·2Na were investigated in this paper and the coating of fine performance with rapid plating speed was gained by optimizing the conditions in each system. In addition, the electrochemical polarization characteristics of that system were investigated by linear sweep and the relationship between the polarization behavior of anode and cathode and the experimental technology results were described as well.The optimum conditions of once electroless copper plating system with primary chelating agent of EDTA·2Na and secondary chelating agent of TEA are that the concentration of CuSO₄·5H₂O,HCHO, EDTA·2Na, TEA, potassium ferrocyanide,α,α'-bipyridine, PEG-1000 , 2-MBT, NiCl₂ and ethylene diamine is 16g/L, 16ml/L, 29g/L, 7g/L, 20mg/L, 6.7mg/L, 0.5g/L, 0.5mg/L, 2g/L and 0.3ml/L respectively, the pH value of solution is 13.2 and reaction temperature is 50℃. The appearance of coating is red and even, the crystal grain is thin, the plating solution is stable and the plating rate is 3.4μm/h, the grade of backlight test is 9th of 10 grades, the adhesion force of coating accords with Chinese standard of GB5270-85 under optimum conditions above. Therefore the once electroless copper plating system of triethanolamine(TEA) and EDTA·2Na can be used in electroless copper plating of additive method PCB technologies.The optimum conditions of secondary electroless copper plating system of EDTA·2Na and TEA are that the concentration of CuSO₄·5H₂O,HCHO, EDTA·2Na, TEA, potassium ferrocyanide,α,α'-bipyridine,PEG-1000 and 2-MBT is 16g/L, 16ml/L, 6g/L, 28.6g/L, 100mg/L, 20mg/L, 1g/L and 0.5mg/L, the pH value of solution is 12.75 and reaction temperature is 50℃. The appearance of coating is shining and even, the crystal grain is thin by SEM experiments, the plating solution is stable and the plating rate is 10.57μm/h and the adhesion force of coating accords with Chinese standard of GB5270-85 under optimum conditions above. Therefore the secondary electroless copper plating system of triethanolamine(TEA) and EDTA·2Na can be used in electroless copper plating of entire method PCB technologies.On the basis of the electrochemical polarization characteristics of elctroless copper plating solution containing TEA and EDTA·2Na it can be concluded that the main reaction of anode oxidation occurs at potential of -062V, which is the oxidation reaction of adsorbed HCHO with hydrogen evolution. The secondary reaction occurs at potential of -0.45V, which is the oxidation reaction of adsorbed HCHO without hydrogen evolution. The oxidation dissolution reaction of anode copper occurs at potential of -0.17V, the reduction reaction of Cu²⁺-TEA occurs at potential of -0.64V and the reduction reaction of Cu²⁺ -EDTA occurs at potential of -1.0V. The relationship between the polarization behavior of anode and cathode and the experimental technology results were found fine by experiments, which shows that the appropriate additive concentration of electroless plating solution can and should be ascertained by experiments in order to realize the aim of improving the performance of coating and stability of solution as well as improving the plating rate.