GB/T 38783-2020Method of coating thickness determination for precious metal composites by scanning electron microscope (English PDF)

3.1 Focused ion beam; FIB

The metal ions (Ga ions) produced by the liquid metal ion source are accelerated and focused by an ion gun to form an ion beam.

6.1 Inlay method

6.1.1 Sampling

Cut the portion of precious metal composite profile or device to be tested which has coating. The coating at the sampling position shall be complete and representative.

6.1.2 Preparation before inlay

The removed composite material sample is cleaned by an ultrasonic cleaning machine and dried for use. If the coating thickness is less than 10 µm, the sample surface shall be plated with a 10 µm thick nickel or other metal protective layer. The nickel-plating formula shall be implemented in accordance with the provisions of Appendix A in GB/T 17722-1999.

6.1.3 Inlay

Inlay the composite material samples in accordance with 6.1.3.1 of GB/T 17722-1999.

6.1.4 Grinding and polishing of the sample section

According to Chapter 3 of GB/T 13298-2015, take out the inlaid specimen; grind and polish to meet the requirements of metallographic samples.

6.2 FIB method

6.2.1 Sampling

Perform in accordance with 6.1.1.

6.2.2 Installation of samples

6.2.2.1 Horizontal installation method

Install the sample horizontally on the surface of the flat sample stage, with the coated side of the sample facing up. according to GB/T 17359. For multi-layer coatings, it is necessary to confirm whether there is a case where the coating is not visible. If the coating is found to be not visible, metallographic etching (inlaid method) or FIB irradiation etching (FIB) can be used to make the coating appear.

6.4 Getting photos

6.4.1 Inlay method

Move the coating to be tested to the center of the field of view. Select a suitable magnification to obtain the secondary electron image or backscattered electron image. The captured image shall have a good contrast effect; the composite interface is obvious; the coating can be measured. Ensure that the thickness of the measured coating is enlarged to more than 5 mm.

6.4.2 FIB method

The horizontal installation method is to shoot when the sample stage is tilted 52°. For the sample of the pre-tilt installation method, the sample stage is first tilted back to 0°; the cross-sectional position is rotated 180° and then tilted 54°, as shown in Figure 7. Move the coating to be tested to the center of the field of view; select the appropriate magnification; obtain the secondary electron image (SE) or backscattered electron image (BSE). The captured image shall have a good contrast effect; the composite interface is obvious; the coating is measurable. Ensure that the thickness of the measured coating is enlarged to more than 5 mm.

a) Horizontal installation method b) Pre-tilt installation method

6.5 Measurement of local coating thickness

Coating stag e for […]