What is Oxidation Reduction Potential (ORP)

Oxidation Reduction Potential (ORP) Oxidation also restores zeta potential. Many of the wet processes are oxidized and simultaneously reacted. For example, when the inner surface of the copper oxide bath is etched to the copper foil, the following ion equation occurs:

Cu+2 + Cu → 2Cu+1

That is, when the divalent copper ions (oxidants) in the bath liquid bite the copper metal, the copper metal will be oxidized from zero to one cuprous cuprous ion, but itself is also dipping from the second price to the first price. If you write it as a complete equation and add hydrochloric acid or chlorine gas, the changes are as follows:

CuCl2 + Cu → 2CuCl ... Oxidation/reduction

2CuCl + 2HCl + H2O2 → 2CuCl2 + 2H2O ... Oxidation/reduction (acid regeneration)

2CuCl + Cl2 → 2CuCl2 ... Oxidation / also helium (chlorine regeneration)

During the etching process, there is a readily soluble oxidant Cu+2 and a non-soluble antimony agent Cu+1 in the bath. The Nernst equation shows that the ORP potential (E) can be calculated as follows:

E = E0 + (2.3026RT/nF)*log10(Cu+2/Cu+1)

That is, the equilibrium potential (E) between Cu+2 and Cu+1 is proportional to the oxidant concentration [Cu+2], and when the concentration of the remaining antimony agent [Cu+1] is increased, the ORP decreases, when Cu As +2 increases, the ORP increases and the Etch rate also increases. When the ORP rises, the etching curve will also rise upward and accelerate.

However, the ORP cannot be set too high to speed up the etching so that Cl-1 is not oxidized to Cl2 and there is a danger of chlorine. It is best to control the ORP on a platform between 500 and 540mV and to obtain a maximum erosion rate of 27μm/min without the danger of chlorine generation.

If the production line needs to speed up the etching in order to mass-produce so as to have a higher output (Output), it may increase the length of the etching groove or elongate etching section, so that it will not have to take risks and take into account the production requirements, at this time ORP's Control will become an important role.

The current ORP controllers are all very sophisticated, and can direct automatic feeders and discharge pumps to perform effective work separately. All kinds of wet processes can be automatically monitored, which not only makes the process stable but also very convenient.