With the rising popularity of ceramic and precious metal coatings on watches and jewellery, ASMAC has received requests from overseas buyers to develop an affordable testing solution for regularly checking the composition and thickness of these coatings.
Challenges in Coating Analysis
Unlike traditional electroplating layers, which typically have a thickness of several microns, ceramic layers such as titanium nitride or carbide coatings used for decorative purposes are much thinner, with a thickness of about 1 micron. Similarly, Physical Vapor Deposition (PVD) gold layers in Ion Plating Gold/Ion Plating Rose Gold (IPG/IPRG) structures are even thinner, measuring approximately 0.1–0.2 microns. For this reason, routine X-ray Fluorescence (XRF) techniques and optical microscopy are no longer suitable for obtaining accurate composition and thickness information for these coatings.
Surface-Sensitive Analysis Techniques
To address these challenges, a surface-sensitive analysis technique capable of capturing composition information from such thin layers is required. Energy Dispersive X-ray Spectroscopy (EDX) is not suitable due to its analytical depth of several microns. Instead, we recommend X-ray Photoelectron Spectroscopy (XPS), as it offers surface sensitivity as thin as 10 nanometers.
Using XPS, we can determine the composition of the PVD gold layer after removing the outermost 10–20 nanometers of coating material, which often contains adventitious carbon. Once the PVD gold layer composition is determined, the underlying ceramic coating—typically titanium-based nitride or carbonitride—can be analyzed by "stripping" off the top PVD gold layer using an ion sputter gun.
Measuring Multi-Layer Thickness
Conventionally, measuring the thickness of multi-layers involves cross-section sample preparation. However, optical microscopy is unsuitable for this purpose due to its limited resolution. Instead, we recommend using an electron microscope, which can magnify the cross-section to tens of thousands of times, allowing us to distinguish the extremely thin PVD gold layer from the underlying ceramic coating and accurately measure their respective thicknesses.
Importance of Reliable Coating Quality Control
Reliable and efficient coating quality control is critical for buyers, as unqualified coatings reaching end-users can lead to costly recalls and rework procedures. More importantly, such issues can severely damage a brand's reputation.
With our long-standing reputation for integrity and professionalism, ASMAC has collaborated closely with both buyers and suppliers to develop functional testing procedures tailored to their specific needs, ensuring the quality and reliability of their products.
