The Study On Electroless Copper Plating Technology Of High Plating Rate On ABS Plastic

In this paper, because of the problem of slow deposition rate of the electroless copper plating, electroless copper deposition of high deposition rate on ABS plastic was studied. The basic formulation was determined, by using single factor test, the stability and deposition rate of the bath and quality of the coating as evaluation index, based formulation was optimized, the electroless copper deposition of high deposition rate was determined; the consumption of formaldehyde and copper ions in the bath were analyzed and the bath was adjusted; the role and mechanism of additives were studied with using electrochemical methods and Kelvin probe, results showed that.The formulation was copper chloride8g·L-1, EDTA30g·L-1, NaOH15g·L-1, triethanolamine4mL·L-1,2,2’-bipyridine2.5mg·L-1,1.10-phenanthroline1.5mg·L-additives J2mg·L-1, formaldehyde16mL·L-1, the pH value of12.4to12.6, temperature58℃. The deposition rate of the electroless copper plating solution was11.7μm·h-1and the bath was stability, the coating had good adhesion with substrate. The additives which mainly impact on the deposition rate of the bath in the formulation were triethanolamine,1.10-phenanthroline and additives J, and2,2’-dipyridyl is a stabilizing agent and a brightener, the deposition rate was reduced with adding2,2’-dipyridyl in bath. ABS plastic beginned plating about20min.Through the components of bath were analyzed when the bath was plating, the quality ratio of formaldehyde and copper chloride was0.96:1, the formaldehyde and copper chloride added in bath using the ratio. Substrate which surface area was0.75dm2deposited in the1L bath,0.248g of copper chloride and0.78mL of formaldehyde was added in the bath within an hour, the plating solution of copper ions and the concentration of formaldehyde were not changed, the deposition rate of the bath was still10μm·h-1～11.7μm·h-1, so the amount of load was0.75dm2·L-Through the molar amount of caoting and consumption of formaldehyde were analyzed, the11%of electronics which formaldehyde provided was used for the hydrogen evolution, so the formaldehyde utilization rate was39%; by collecting the hydrogen, the formaldehyde utilization rate is39%too,and this result was similar to the result of formaldehyde in titration.By using Tafel curve, AC impedance and kelvin probe, the role and mechanism of1.10-phenanthroline was studied, this results showed that1.10-phenanthroline accelerated oxidation of formaldehyde and reduction of the copper ions, the utilization of formaldehyde increased from29%to39%, the deposition rate increased100%by adding1.5mg·L-11.10-phenanthroline. When the bath containing1.10-phenanthroline, the current density of corresponding mixed potential was improved and the impedance of the bath was reduced. Copper ions was easier to obtain electronic, the utilization of formaldehyde was improved by adding1.10-phenanthroline.1.10-phenanthroline can promote the oxidation of formaldehyde and accelerate the oxidation reaction of formaldehyde, but1.10-phenanthroline can accelerate the deposition rate of the bath, because of mainly promoting the reduction reaction of copper ions, so the deposition rate was increased. When the concentrations of1.10-phenanthroline was greater than2.5mg·L-1, due to the mixed potential moved to the anode, the reduction reaction of copper ions was more difficult, while the cathodic reduction peak current of copper ion was decreased in reduction process, the deposition rate was decreased.The morphology and structure of copper coating were analyzed by using SEM and XRD, The results show that1.10-phenanthroline affected the grain growth of the electroless copper plating layer.1.10-phenanthroline make the coating grains smaller and the deposits more bright and more dense,(111) lattice plane of preferred orientation increased.