For polymeric materials, microscopy provides useful information for the additive distribution (glass-fiber reinforcement, flame retardants, mineral additives, and etc) in a polymeric matrix.
For metallic materials, microscopy provides information about grain structure, physical continuity, surface topography, and measurements for applied surface finishes.
For composite materials such as printed circuit board (PCB) components and complex components, microscopy provides visualization of important connections, interfaces, and structures.
Scanning Electron Microscope (SEM):
The scanning electron microscope (SEM) images were performed on a JEOL 6460LV microscope. The SEM has two detectors to provide images based on the raster scanning of the electron beam. The secondary electron detector (SEI) measures scattered electrons from the surface of the conductive sample. The backscatter electron detector provided images using three modes: BES, BEC, and BET. The BEC mode provides images with contrast dependent on the chemical composition of the imaged material with the lighter contrast directly proportional to a higher atomic number. The BET mode provides images with contrast dependent on the topography (z-axis) of the imaged material. The BES (shadow) mode provides images with a combination of BEC and BET with the strength of the topography component increasing shadow value (1-10). Unless otherwise indicated SEM images are provided using BEC. The magnification for an SEM is a general reference based on the factor where X100 provides a pixel size of 1µm/pixel for the software's highest available scanning resolution which provides images of 1280 pixels x 960 pixels. The resolution of an SEM is more complicated than an optical microscope and is well presented in this reference.
SEM Resolution Limitation
The plating thickness (~100 nm) for the silver flash specified is below the appropriately discernable resolution for a coating that requires mounting and preparation. In optimal conditions, the SEM can discern metal colloid substrates with dimensions of 5-10 nm. The metal colloid substrate is perfectly conductive and formed as distinctive spherical structures. In this circumstance of a silver flash coating, there is difficulty discerning it distinctively from the mounting medium (which is partially insulating) and the body of the metal part with additional preparation issue of the last available polishing step has the limitation of using Nap with a 1 µm diamond polishing media.
The stereomicroscope (SMZ) images were provided by a Nikon SMZ-10 stereoscope and Olympus SC100 digital microscope camera. The SMZ technique provides images with minimal magnification which imitates the viewing of a surface by the human eye using reflected visible light. The Olympus SC100 digital microscope camera is a CMOS color camera with an effective area of 6.12 mm x 4.59 mm, a pixel size of 1.67 µm x 1.67 µm, and a maximum resolution of 3840 pixels x 2748 pixels.
Inverted Light Microscopy (ILM)
The inverted light microscopy images were provided using an Olympus GX71F5 microscope (metallograph) and Olympus UC30 digital camera.