The right composition of the electroplating bath is the key to the quality of metallic coatings. Do you actually know how easy it is to analyze electroplating baths? The solution is XRF analysis! Read more in our fascinating, informative article in the current issue of the German trade magazine JOT – Journal für Oberflächentechnik.
The quality of metallic coatings depends significantly on the composition of the electroplating bath. Usually, chemical electrolyte analysis methods are used for bath monitoring. However, these methods are time-consuming and costly. A simple alternative is the X-ray fluorescence analysis method.
In order to apply electroplated coatings with a defined deposition rate and homogeneous composition, electroplating companies have to monitor the composition of their coating baths very closely. That´s not only the case regarding decorative metallic coatings such as the AuCuCd, AuCuIn or RhRu coatings frequently used in the jewelry industry. Whether to meet specifications or for their decorative aspects, it must be ensured that the coating is evenly applied over the entire surface. Like this, the required functionality and uniform coloration can be achieved.
For bath analysis, various chemical methods are available: for example ICP-OES, AAS or titration. However, disadvantage of these methods is that they are time-consuming, cost-intensive as well as complex to carry out. A simple, fast and cost-effective alternative that delivers equally precise results is the X-ray fluorescence analysis method (XRF analysis). With just a few simple steps the measurement is prepared and no consumables other than a plastic foil is used. Neither analysis gases such as argon nor purified water are required.
Fischer, the global expert on measuring technologies, offers a wide range of different measuring instruments for XRF analysis. The high-precision X-ray fluorescence measuring systems are predestined for the analysis of the metal content of electroplating baths and can be used for solution analysis of almost all electrolytes commonly used in industry. The accessories required for this are included in a solution analysis kit so the corresponding XRF measuring instrument does not need special upgrades to perform the analysis. The preparations and measurements can be conducted without any great prior knowledge, though support is available through the Fischer global support system.
Precise measurement results in shortest time
First, a cell is filled with the solution to be analyzed. After, the cell is covered with a thin but robust Mylar film and tightly sealed with a black plastic ring. Cells prepared in this way can also be measured with XRF instruments whose measurement direction is from the upwards.
Subsequently, the solution analysis cell is positioned on the table of the XRF instrument and focused using the software also developed by Fischer. The appropriate solution analysis measuring program is stored in the software and can be selected via the corresponding button or a previously determined shortcut key. The measurement conditions such as measuring time and number of measurements can be set flexibly and stored directly in the measuring program.
With only one keystroke, the measurement is started and delivers precise results within a few moments. Thereby, it is possible to implement any changes in the bath composition more quickly. In addition to the SPC display, many other options are available for visualizing the measurement results. The solution analysis cells are resistant to chemicals and can therefore be reused which additionally minimizes running costs, provided they are cleaned appropriately.
Determine metal content from 0.1 g/l
Three types of detectors are available: the proportional counter tube, the silicon PIN diode and the silicon drift detector (SDD). Measuring instruments equipped with a proportional counter tube can be used for solutions with metal contents from 1 g/l. Instruments with a silicon PIN or silicon drift detector are much more sensitive, due to their better energy resolution, and can be used for concentrations from 0.1 g/l.
An initial calibration of the X-ray fluorescence instrument is not absolutely necessary. For plant control, a standardless measurement is often enough. If necessary, at any time, a calibration can be performed with a solution of known concentration. Important in practice, the calibration is always conducted with the electroplating bath to be measured.
Three different measuring cells
However, the matrix of an electroplating bath is not only defined by the metal ions. Often, organic components or other light elements such as chlorine, sulfates or copernicium are contained. These do not provide a visible fluorescence signal but have an absorbing effect on the elements to be analyzed. For this reason, the solution analysis kit includes three different measuring cells that vary in the material of the cell base: molybdenum, nickel or zirconium. The cell base generates a fluorescence signal which is used to respond predictably to such matrix effects. The use of the right measuring cell ensures that the fluorescence signal of the cell base does not overlap and interfere with the fluorescence lines of the elements to be analyzed.
Equipped with the appropriate solution analysis cell, the high-precision X-ray fluorescence measurement systems lead to significant time savings compared to other analysis methods and can be applied directly in the production process without the need for specially qualified personnel.