The electroplating process consists of using electricity to coat a material (e.g., copper (Cu)) with a thin layer of another material (e.g., nickel (Ni), zinc (Zn)), usually for protective reasons.

Zinc and its alloys (e.g., Zn/Ni) are some of the main materials used for protection against steel corrosion. However, Zn-Ni alloys are primarily used because they are five to six times stronger than pure Zn to counter corrosion [1].

Organic additives or complexing agents are added to the electrolyte solution in the bath to improve the deposition process, and hence the corrosion resistance [2].

During the electroplating process, complexing agents are used to form complexes with metal ions in the electrolyte-plating solution. These complexes help to keep the metal ions in solution, preventing their premature precipitation or unwanted side reactions. Amines, for instance, can act as complexing agents in alkaline Zn/Ni baths. They form stable complexes with metal ions (e.g., Zn²⁺ and Ni²⁺), preventing them from reacting with other ions. This helps to control the deposition potential, improve conductivity, and suppress dendrite formation [3].

Traditionally, monitoring the concentration of complexing agents in electroplating baths is done manually. This is a cumbersome process, involving the extraction of bath samples which must be transported to a laboratory for analysis.

These actions not only fail to capture the real-time composition of the baths but also entail safety risks. The delay between sample collection and analysis can lead to prejudiced results, as changes in the electroplating process may occur before the analysis is complete.

The utilization of inline Raman spectroscopy addresses these challenges by enabling the continuous analysis of inorganic and organic components, including complexing agents, in real-time. Unlike traditional wet chemical methods, spectroscopy requires no sample preparation and can be seamlessly integrated into the electroplating process. This allows minute-by-minute insights into the bath's condition and facilitates more precise control over the deposition potential, conductivity, and dendrite formation. Not only does this enhance efficiency, but it also contributes to the safety and reliability of electroplating operations.

An inline process analyzer can be connected to the galvanic bath via fiber optics and a flow cell (Figure 1). To take advantage of the multiplexing capability (i.e., several baths in alternation), valves can be activated which ensure filling of the sample line and subsequent cleaning. The entire workflow including liquid handling is carried out completely automatically.

Metrohm Process Analytics provides an analytical solution for electroplating bath monitoring – Raman process analyzers. The 2060 Raman Analyzer (Figure 2) offers fast, reagent-free, nondestructive analysis of complexing agents (amines) in alkaline Zn/Ni baths.

For automated analysis during routine operation, the application is developed in advance by Metrohm Process Analytics. For this purpose, spectra are recorded with the 2060 Raman Analyzer (Figure 2). The spectra are correlated with data from a reference analysis method and a robust calibration model is created.

The calibration model is used automatically in the process. The user receives the results of the concentration measurement both in tabular form and as a process trend chart (Figure 3). The values can be transferred to a process control system via a process communication interface.

Raman spectroscopy is an easy-to-use analytical technique that identifies liquids and solids within seconds. The 2060 Raman Analyzer from Metrohm Process Analytics is a high-performance Raman system designed for monitoring different processes like electroplating.

Together with Metrohm’s Vision and IMPACT software, the 2060 Raman Analyzer can be used to acquire real-time results, increase productivity, and lower production costs.

• «Real-time» feedback to the process to guarantee a high level of control for coatings.
• Early detection of bath failures.
• Multiple parameters from a single measurement.
• Unique Raman spectra that serve as specific fingerprints for material identification.