(1)Measurement principle

This is a method of measuring plating thickness using a fluorescence X-ray thickness meter. A test piece is exposed to X-rays emitted from the meter, which detects fluorescence X-rays generated from the plating surface and substrate. This method allows you to measure the thickness of single-layer and multi-layer plating in a short period without destroying the plating film on the metallic or nonmetallic substrate.

(2)Measurement device

Wavelength-dispersive- and energy-dispersive- type fluorescence X-ray thickness meters are available. The energy-dispersive type is more common within the industry because it is easier to operate.
The principle shown in [Fig.] applies to the energy-dispersive type. A proportional counter or a semiconductor detector is used as the detector. The semiconductor detectors are capable of measuring a broader range. However, they have to be cooled with liquid nitrogen at all times.
A collimator is used to narrow the X-ray beam directed into a certain area. This allows the measurement of micro parts of 100 µm or 50 µm in diameter.

(3)Precautions for measurement

When you measure plating thickness using this method, it is necessary to comply with the operating instructions for the equipment. In addition, you need to be careful with the following factors, which could affect the measuring accuracy:
1.Plating thickness; 2. Material and plating thickness of the substrate; 3. Surface roughness of a sample; 4. Degree of curvature, etc.

(4)Restrictions on measurement

A certain combination of substrate and plating or that of substrate and multilayer plating is not compatible with this method:
if the combination of substrate and plating, including alloy substrate and plating, contains any overlapping element in each layer, the thickness cannot be measured by this method. The following are examples of incompatible combinations: copper or zinc plating on brass substrate, nickel or chrome plating on stainless-steel substrate, nickel, zinc, or copper plating on nickel silver, and brass plating on copper substrate.