Electroless copper plating is a process in circuit board manufacturing, commonly known as copper deposition or pore forming (PTH), which is a self catalytic oxidation-reduction reaction. Firstly, an activator is used to adsorb a layer of active particles on the surface of the insulating substrate. Typically, palladium metal particles are used (palladium is a very expensive metal that is expensive
Author: Marisa
Electroless copper plating is a process in circuit board manufacturing, commonly known as copper deposition or pore forming (PTH), which is a self catalytic oxidation-reduction reaction. Firstly, an activator is used to adsorb a layer of active particles on the surface of the insulating substrate. Typically, palladium metal particles are used (palladium is a very expensive metal that is expensive and constantly rising, and practical colloidal copper processes are currently operating abroad to reduce costs). Copper ions are first reduced on these active metal palladium particles, and these reduced metal copper nuclei themselves become the catalytic layer of copper ions, allowing the reduction reaction of copper to continue on the surface of these new copper nuclei.
Traditional electroless copper plating is mostly done on vertical lines, and the process is similar to each other. The general process is:
Expansion → removal of drilling dirt → neutralization → oil removal → micro etching → pre impregnation → activation → acceleration → chemical copper plating
The main components are the cathode and anode.
Cathode: A pair of stainless steel rods at the starting end of the plating section have copper electrical contact rings, and copper brushes are pressed onto the copper rings to obtain good contact and connected to the negative electrode of the rectifier. The cathode is isolated and in contact with the medicine through a water blocking roller.
Anode: Two titanium plates installed in the tank, which are directly connected to the positive electrode of the rectifier through two cables. The anode is immersed in a solution of medicine.
Electroless copper plating is the process of reducing and precipitating copper ions on a surface with catalytic activity through the action of a reducing agent:
Reduction (cathodic) reaction: CuL2++2e - → Cu+L
Oxidation (anodic) reaction: R → O+2e-
Therefore, the main reaction formula for using sodium hypophosphite as a reducing agent for electroless copper plating is: 2H2PO2-+Cu2++2OH - → Cu+2H2PO3+H2 ↑
In addition to being thermodynamically valid, chemical reactions must also satisfy kinetic conditions. Chemical copper plating, like other catalytic reactions, requires thermal energy to allow the reaction to proceed, which is why the plating rate only occurs when the chemical plating solution reaches a certain temperature. In theory, the rate of electroless copper plating can be expressed by the rate at which the concentration of reaction products increases and the concentration of reactants decreases. Due to the presence of certain additives in the actual chemical copper plating solution, its influence factors become too numerous and the situation becomes too complex. Therefore, most studies on the kinetics of chemical copper plating reactions start with the most basic components in the plating solution.