The use of chloride ions, sulfuric acid, copper sulfate plating solution can be made in the electric field force, the plating solution of copper ions to move to the negatively charged cathode, and in the cathode around the surface of the copper singlet reduction of electrons, and ultimately the formation of cathodic electrodeposition. The whole process relies on additives to promote or hinder the effect of copper deposition, by changing the rate of nucleation of copper atoms, to enhance the quality of the copper layer of deposited copper. At present, the more common copper plating additives on the market are accelerators, chloride ions, leveling agents, and inhibitor four.
Accelerators are mostly sulfur-containing organic matter and can accelerate the cathodic deposition rate of copper ions, but also allow the deposited copper surface to be more bright, and detailed, also known as a brightener. The relevant research shows that the accelerator only in the electroplating solution under the condition of chloride ions, to play its effective role in accelerating the deposition of copper ions, on the contrary, there are no chloride ions in the electroplating solution, then, adsorbed in the cathode surface around the accelerator has become an obstacle to prevent the flow of copper ions to the cathode surface of the obstruction layer, to play a role in inhibiting the reverse role of the copper ions deposited.
Chloride ions for inorganic additives, not only can prevent the motor passivation reflection, but also promote the effective dissolution and deposition of the electrode, so that adsorbed in the surface of the copper layer of chloride ions built into the chlorine bridge, to accelerate the rapid transfer of electrons, but also with the plating solution exists between the formation of synergistic effects between other additives to strengthen the chloride ions on the inhibitor to inhibit the strength of the circuit of the over-potential, thus increasing the density of the nucleation of the blind hole electroplating This will ultimately achieve the goal of improving the quality of copper plating.
Leveling agent with nitrogen-containing heterocyclic compounds or positively charged quaternary ammonium compounds, such as Kenna green, diazine black, blind hole plating, the leveling agent will first adsorb copper ions around the cathode surface in the area of the lower point, or the current density of the larger area of the copper ions, to achieve the effect of slowing down the rate of copper ion deposition in the region [2]. After many previous tests, it is known that the potential of the protruding tip part of the cathode surface is the most negative state, so the adsorption concentration of the leveling agent in this area is the highest, to play a full role in inhibiting the deposition rate of copper ions in this area, so that the cathode copper deposition rate becomes more uniform, and then improve the leveling of the coating of the blind hole plating. It can be seen that chloride ions still play a synergistic leveling function in the leveling agent plating process, playing the role of bridging the leveling agent and copper deposition rate.
Inhibitors are mostly fatty alcohol polyoxyethylene ether, polyethylene glycol, and other polyether-based organic substances, and chloride ions have a synergistic effect with the formation of a layer of high-density adsorption layer on the cathode surface, play a role in hindering the adsorption of copper ions to the cathode, the role of diffusion, thus enhancing the deposition of copper ions over-potential, to play a role in inhibiting the deposition rate of copper ions, to enhance the tightness of the interlayer copper plating.
