Micrometric scale topography of a watch dial - PO3D

The manufacture of the first watch mechanisms using springs was established in the 16th century. With it, precision, automatism, and meticulous metalworking developed, which would then influence other strategic activities, in particular the navy, and all mechanized industries. Watchmaking requires precision and a keen eye for detail.

The watchmaking industry continues to innovate, in perpetual search for improvement on increasingly miniaturized mechanisms.

In the 1970s, an optimal oscillation frequency (32,768 Hertz) for a quartz movement was established; it still represents a universal standard today. The “Constant Escapement” can also be cited, launched in 2008, it is based on a silicon blade as thin as a hair which improves the precision of the movement over time. For all these cutting-edge developments, ultra-precise characterization techniques are popular.

PO3D analyzes provide access to a 3D representation at the micrometric scale of the surface of a sample, as well as its roughness parameters.

Optical profilometry (confocal/interferometric microscopy) is a non-contact imaging method for observing and characterizing the topography of

surfaces over measurement ranges from a few tens of µm² to a few mm², with a lateral resolution of order of 200 nm and a vertical resolution ranging from nanometers to several tens of µm.

Optical profilometry in confocal mode, based on the reflection of a light signal on a surface, makes it possible to observe the topography on any type of sample (flat or very rough with slopes of up to 70%).

Optical profilometry in confocal mode makes it possible to produce images with very shallow depth of field or “optical sections”. By positioning the focal plane of the objective at different depth levels below the surface of the sample and eliminating light from out-of-focus points, it is possible to produce series of images from which a three-dimensional representation of the The object is reconstructed.

TESCAN ANALYTICS has recognized expertise in the use of PO3D profilometry on all types of materials. Our team of experts works with all industrial sectors to find solutions to their problems linked to the development of their innovations.

Figure 1: (a) PO3D image of a watch face made with the 5X objective (2.5 x 1.9 mm2 area) (b) Roughness profile

Figure 1 shows the overall morphology of the area of ​​interest with the 5X objective. Two main observations can be made:
- wide millimeter ranges giving a “sawtooth” profile
- paths distributed evenly over the different beaches

Figure 2: (a) PO3D image of a watch dial made with the 20X objective (surface 450 x 600 µm²) (b) Roughness profile

Figure 2 shows an image taken with the 20X objective and the associated profile, perpendicular to the furrows. The furrow patterns repeat with a frequency of 6 to 7 streaks.

Figure 3: (a) PO3D image of a watch dial taken with the 50X objective (200 x 250 µm2) (b) Roughness profile

Figure 3 shows an image taken with the 50X objective and an associated profile. The furrows are observed more finely. The profile which is perpendicular to the furrows confirms that the latter are made up of 3 low-height striations, followed by 3 higher-height striations.

It is possible to go up to a 100X objective, for each of these magnifications the PO3D provides the associated roughness parameters.

In this example, it was demonstrated that PO3D profilometry is an optimal non-contact microscopy tool for observing topography, roughness profiles and obtaining Ra and Rq parameters (Sa and Sq).

PO3D allows the observation and characterization of surface topography over areas of a few tens of µm² to a few mm², with a lateral resolution of 200 nm and height resolutions of up to 1 nm.

For more analysis applications using PO3D or our other analytical techniques and microscopy, click here.

Other complementary techniques can be used to study topography such as AFM. The ‘nano-triology’ phenomena encountered in mechanical watchmaking may require analyzes by ToF-SIMS or TEM.