Quantitative Depth Profile (QDP) Analysis of Plated Samples

Significance of the Topic

Surface plating enhances corrosion resistance, wear performance and decorative qualities of base materials by depositing metallic layers of controlled composition and thickness.

Objectives and Study Overview

This study demonstrates quantitative depth profile (QDP) analysis of plated samples using glow discharge spectroscopy (GDS). It covers plating depth determination, coating weight measurement and compositional profiling for various plating techniques including electrodeposition and electroless methods.

Methodology

Layer-by-layer sputtering is performed in a low-pressure argon glow discharge, with Ar+ ions accelerated onto the sample surface to remove material uniformly. Emitted atomic and ionic species are excited in the plasma, and their characteristic optical emission is measured to quantify elemental composition as a function of depth.

Used Instrumentation

LECO GDS-Series glow discharge spectrometer equipped with a Grimm-type lamp. Operating conditions include argon pressure of 5–10 Torr, sample bias between –800 and –1200 V, and real-time optical emission detection for elements of interest.

Main Results and Discussion

Tinplate samples exhibited Sn layer thickness of approximately 0.52 µm with coating weights around 4 g/m² and high repeatability (RSD < 3%). Decorative chromium over nickel and copper under-layers showed Cr thickness < 1 µm and multilayer stacks extending over 100 µm in under 10 minutes of analysis. Electroless nickel coatings (Ni-P) on aluminum alloys reached depths up to 20 µm, with uniform phosphorus distribution in surface layers. Gold electrodesposits on circuit boards delivered Au thickness around 0.38 µm atop Ni (1.36 µm) and Cu substrates, measured in a single run.

Benefits and Practical Applications

• Rapid and quantitative depth profiling of thin and thick coatings
• Minimal matrix and self-absorption effects due to separate sputtering and excitation
• Wide dynamic range with linear calibration curves and few spectral interferences
• Suitable for QA/QC in plating industries, electronics, automotive components and packaging materials

Future Trends and Opportunities

Advances may include integration of GDS with in situ process control, coupling with complementary surface analysis techniques (e.g., SIMS, XPS), application of machine learning for spectral interpretation and miniaturization of glow discharge sources for field-deployable systems.

Conclusion

Glow discharge QDP analysis provides a robust, high-throughput solution for detailed characterization of plated materials. It delivers accurate thickness and composition profiles across diverse electroplated and electroless systems, meeting industrial and research needs.

References

No references were cited in the original document.