Observation of water droplets of approximately 1 μL using an optical camera（OC）is generally performed using a contact angle meter to evaluate the material surface and to design an optimal surface structure for controlling water repellency. In this study, scanning electron microscopy（SEM）was used for detailed evaluation of water droplet evaporation processes. Under atmospheric pressure, we observed droplets of approximately 1 μL positioned at a specific location on a substrate. The evaporation revealed that changes of the contact angle, the contact baseline diameter, and the decrease in height versus the water droplet volume exhibited similar tendencies for the OC method under atmospheric pressure and the SEM method under 650 Pa, irrespective of the substrate temperature. Furthermore, using SEM observation of a water droplet on a substrate with a structure to facilitate water repellency, it was possible to observe fine changes accompanying the pinning effect in the droplet, in addition to fine changes of the contact interface of water droplets influenced by the substrate surface structure. Observing these features using the OC method is difficult. In summary, results show that the SEM method is effective, along with evaluation using the OC method, for evaluating water droplet evaporation.
This study was conducted to investigate changes in hydrogen amounts in metal films obtained using electroless nickel/immersion gold（Ni-P/Au）and electroless nickel/electroless palladium/immersion gold（Ni-P/Pd/Au and Ni-P/Pd-P/Au）surface finishes used for microelectronic solder joints. Thermal desorption spectroscopy revealed that the Ni-P films contained large amounts of diffusible hydrogen that desorbs at room temperature. During electroless deposition of Pd and Pd-P on Ni-P films, the greater part of the hydrogen in the Ni-P films desorbed. Although no hydrogen evolution accompanied immersion gold deposition, the hydrogen amounts in Ni-P/Au, Ni-P/Pd/Au, and Ni-P/Pd-P/Au films were much greater than in films without a Au layer. Moreover, at room temperature, they remained almost unchanged for one month after deposition, indicating that the thin Au layer（＜0.1 μm）prevents hydrogen desorption from the metal films. The high hydrogen concentration in Ni-P/Au films improved solder wettability.
Carbon nitride films are anticipated for application as hard films in various fields. The authors synthesized a carbon nitride film using unbalanced magnetron sputtering（UBM）while changing the pulse period of sputtering and negative bias voltage. Both the pulse period and the substrate bias voltage affect the synthesized carbon nitride films' surface morphology.
At all negative bias voltages, the film thickness decreases in the pulse period of 40-65 μs, but it increases at pulse periods of 65 μs or more. The sputtering rate is considered to decrease because carbon nitride is generated on the carbon target surface in pulse periods of 40-65 μs.
The film hardness is influenced strongly by the substrate negative bias voltage. It becomes higher as the substrate negative bias voltage is lower. The substrate bias voltage and the pulse period also influence the N/C concentration ratio, the chemical bonding state, and the film structure of the carbon nitride films. These results are thought to be attributable to changes in the deposition process caused by application of negative bias voltage and sputtering of carbon nitride formed on the carbon target.