When electroplating electric heating tubes, according to the theory of electrodeposition

When electroplating electric heating tubes, according to the theory of electrodeposition

And the flow of electroplating solution caused by temperature difference. The closer the surface of the solid electrode is, the convection of the plating solution occurs through external or internal mechanical stirring and pump stirring, as well as the oscillation or rotation of the electrode itself. Due to its frictional resistance, the flow of the electroplating solution becomes increasingly slow, and the convective rate on the surface of the solid electrode is zero at this time. The rate gradient layer formed between the electrode surface and the convective plating solution is called the flow interface layer. The thickness of the flow interface layer is about ten times that of the diffusion layer, so the transport of ions within the diffusion layer is almost unaffected by convection.

The ion transport caused by electrostatic force in electroplating solution is called ion migration. The migration rate is expressed as follows: u=zeoE/6 π r η Yes. Where u is the ion migration rate, z is the charge number of the ion, and eo is the charge amount of one electron (i.e. 1.61019CE is the potential, r is the radius of the hydrated ion η Is the viscosity of the electroplating solution. According to the calculation of the equation, it can be seen that under the action of the electric field. The greater the decrease in potential E, the smaller the viscosity of the electroplating solution, and the faster the rate of ion migration.

When electroplating, according to the theory of electrodeposition. The PCB located on the cathode is a non ideal polarized electrode. Copper ions adsorbed on the surface of the cathode obtain electrons and are reduced to copper atoms, resulting in a decrease in the concentration of copper ions near the cathode. Therefore, a copper ion concentration gradient will form near the cathode. The diffusion layer of the plating solution is the layer where the concentration of copper ions is lower than that of the main plating solution. The copper ion concentration in the main plating solution is relatively high, and it will diffuse towards the lower copper ion concentration near the cathode, occasionally supplementing the cathode area. A PCB is similar to a planar cathode, and the relationship between its current and the thickness of the diffusion layer is the COTTRELL equation.

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