In Situ High Temperature Surface Morphology Using 3D Profilometry

The 3D dimensional shape of a material or device is vital to its service quality and functionality. Surface roughness and texture can change at elevated temperatures. For example, shape-memory alloys (also called smart metals) remember their original shape and return to the pre-deformed shape when heated. Most polymeric materials melt and degrade rapidly at high temperatures, leading to change of shape and structure. Therefore, it is crucial to investigate the mechanism of shape deformation and the limit of the materials exposed to high temperature environments so as to select the proper material for the target applications.

High temperature environments can change the surface texture, roughness and shapes of materials, resulting in device malfunction and mechanical failures. To ensure the quality of materials or devices used at elevated temperatures, accurate and reliable in situ monitoring of the shape evolution at high temperatures is needed to provide insight into the mechanism of material deformation. Moreover, real-time monitoring of surface morphologies at high temperatures is very useful in materials processing, such as laser machining.

The NANOVEA 3D Non-Contact Profilometers measure the surface morphology of materials without touching the sample, avoiding introducing additional scratches or shape alteration which may be caused by contact technologies such as a sliding stylus. Their capacity of non-contact measurement also makes it possible to measure the shape of melted samples.

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A Sn60Pb40 solder sample was heated up from room temperature to 400 °C. The evolution of its 3D topography was monitored in situ using the NANOVEA ST400 non-contact profilometer equipped with a line sensor. The optical line sensor generates a bright line of 192 points, as shown in Fig. 1. These 192 points scan the sample surface at the same time, leading to significantly increased scan speed. An 8×8 mm² area scan at each temperature in this study can be finished in 5 s.

The 3D view of the solder surface topography at representative temperatures is shown in Fig. 2, providing an ideal tool for users to observe the solder sample from different angles. The 2D cross section profiles are compared in Fig. 3. The solder maintains its shape as heated up from room temperature until ~180 °C, where its melting point is reached. The solder rapidly changes its shape and adheres to the copper substrate underneath it, forming a smooth spherical cap. As the temperature continues to rise to ~300 °C, rosin flux starts to burn at the edge of the solder, leading to roughening of the surface. When a temperature of ~400 °C is reached, the solder spreads to the surrounding area and lowers its height. Meanwhile, the rosin flux on and around the solder continues to burn, leaving behind traces of graphite. The evidence of such observations is displayed in Fig. 4.

In this application, we have showcased that the NANOVEA ST400 3D Non-Contact Profilometer monitors the evolution of the surface morphology on a solder sample heated from room temperature to 400 °C. The optical line sensor generates a line consisting of 192 light spots that scan the sample surface at the same time. It significantly increases the scan speed, enabling monitoring of the 3D shape evolution of the solder in situ. It is observed that the solder melts at ~180 °C. Its shape continues to change as the temperature progressively increases to 300 °C and 400 °C.

The data shown here represents only a portion of the calculations available in the analysis software. NANOVEA Profilometers measure virtually any surface in fields including Semiconductor, Microelectronics, Solar, Fiber Optics, Automotive, Aerospace, Metallurgy, Machining, Coatings, Pharmaceutical, Biomedical, Environmental and many others.