High-resolution scanning electromicroscopy (SEM) is a powerful technique to elucidate surface information. Because Upilex S® film, a polyimide film (PI film), possesses excellent properties such as chemical and heat resistance, it has been used in many flexible printed board fabrications. When surfaces of the PI film with high permittivity are observed using SEM, the thin film coating of a noble metal by evaporation methods is necessary to avoid charging problems. Such a thin film coating creates artifacts on SEM images. Consequently, high-resolution observation often becomes difficult, especially if we attempt to observe the adsorption of nanoparticles such as Pd-Sn catalysts on the PI film. Surface scientists know empirically that Ar ion beam treatment inhibits charging phenomena of the observed samples. To prevent charging problems during SEM observations, we examined Ar ion implantation for the PI film sample with low acceleration voltage (200—300 V) applied to Ar ion gun. Regarding acceleration voltage at 300 V, high-resolution SEM images of the PI film surface were obtained without any thin film coating of noble metal. Furthermore, elemental analyses of the PI film were enabled by energy dispersive X-ray spectrometry (EDS) performed with high current.
For evaluation of the microstructure between Pb-free solder alloy and a Ni-P coating layer, the spatial resolution of a field emission electron probe microanalyzer (FE-EPMA) was measured using interfacial morphologies of GaP/InAlP of light emitting diode (LED). The Ni was alloyed with Sn, producing an approximately 300-nm-thick P-rich layer.