Study On Pyrophosphate-based Alkaline Copper Plating Technology For Steel Substrates

Cyanide compound is toxic and the effluent of cyanide copper plating becomes environmentally disfavored because of ecological considerations. So non-cyanide copper plating technology becomes one of the main research hotspots.The dissertation investigated the effects of HEDP(1-Hydroxyethylidene-1,1-diphosphonic acid) and outfield(ultrasonic, magnetic field, pulse) on the miscrostructure, morphology, electrochemical curve and nucleation mechanism during electrodeposition process in pyrophosphate copper plating system. The paper is divided into four parts:Ⅰ. Pulse electrodeposition of Cu coatings in pyrophosphate copper plating systemCopper pulse electroplating without cyanide possesses many advantages. Puls e plating process has the effect of Ton and T off. In the duration of T on, metal ions diffu se to cathode surface. Metal ions start to react in the solution during Toff times. Henc e, higer current density could be used during pluse plating process. Copper films were covered with typical nodular structures and increasing pause duration from 0.1 s to 5 s was favorable to the refinement in grain structures and the improvement of microstructures. With the increase of pause duration, the size of crystal particle decreased and the surface looked compact covered. When the pause duration of 1 s and the deposition pulses of 5s, the surface looked compact covered and the holes decrease.Ⅱ. Effect of HEDP on Copper Electroplating in pyrophosphate copper plating systemWhen the concentration of HEDP increases, the surface of Cu thin films becomes coarse and the thickness of Cu thin films decreases. When the concentration of HEDP is 40g/L, the Surface looks compact covered and very smooth. Moreover, the thickness of Cu thin film is 7.5μm and the current efficiency of the solutions is93.76%. It also can be found that with the solution without HEDP the nucleation approaches to the instantaneous nucleation mechanism and with the plating solution with HEDP the nucleation is progressive.Ⅲ. Effect of ultrasonic on Copper Electroplating in pyrophosphate copper plating systemThe ultrasonic vibration effects can accelerate mass transport, increase number of nucleation, and inhibit excessive growth of grain. Consequently, with the impacts of ultrasonic, it is possible to obtain coatings with uniform and dense surface. The surface looks looser with quite a lot of holes without ultrasonic during deposition process. By comparison, the surface looks compact covered and very smooth and the grains are fine and uniform when the Cu thin films were deposited under 40 W, 60 W and 80 W power of ultrasonic. When the power of ultrasonic is 100 W, cavitation will not continue to strengthen. This is because the intensity of ultrasonic increases, the cavitation produced a large number of useless cavitation bubbles. The current efficiency of electrolyte under 0W, 40 W, 60 W, 80 W and 100 W is 91.95%, 98.48%,92.14%, 89.25% and 96.11%, respectively.Ⅳ. Effects of magnetic fields on Copper Electroplating in pyrophosphate copper plating systemMagnetic fields parallel to the electric field were introduced during the electrodeposition process. It was found out that when the magnetic intensities increases, the surface looks compact covered and very smooth and the thickness of Cu thin films decreases. The surface looks looser with quite a lot of holes without magnetic fields during deposition process and the roughness of the surface is 520 nm.The surface looks compact covered and very smooth and the roughness of the surface decreases when the Cu thin films were deposited under 0.3T, 0.5T and 0.8T of Magnetic fields. The roughness of the surface is 226 nm under 0.3T of Magnetic fields.