This paper is devoted to polystyrene thin film treatment under DC pulsed discharges in nitrogen, oxygen and oxygen-argon mixtures. XPS analysis is used in order to investigate the new chemical bonds generated by the reactive particles colliding the surface from the plasma. The experimental conditions are close to the best running conditions deduced from [16,75,86]. Correlations between microscopic analyses obtained by XPS through the knowledge of the surface chemical composition and macroscopic ones realized by studies of water drop deposited on the films (contact angle measurements) are presented. It is pointed out that the wettability is highly improved when the percentage of oxygen atoms incorporated in polystyrene surface reaches a high value. C − O, C = O and O − C = O are the main chemical bonds and it is found that the oxygen uptake happens during a very short time (about one second for the treatment duration time, i.e. about 10 ms on account of the duty factor value). A high oxygen rate is observed, correlated to the formation of a maximum $\Delta \theta/\theta_i$ plateau value (wettability). Reaction processes in the plasma bulk and on the polystyrene surface are proposed, taking into account the bond energies of polystyrene. As a consequence, the polystyrene treatment is interpreted assuming two steps for the reaction processes: in a first step, chemical bonds are broken by energy transfer from reactive particles to the surface and in a second step, new chemical bonds are generated. In this spirit, the main reactive plasma particles are described and surface reactions are proposed on the polystyrene surface.

This paper describes an optical investigation technique for visualizing the cross section of a vertical air stream flowing downward on a wet horizontal tube with moving liquid film. This method which associates the laser induced fluorescence and laser tomography techniques, uses Mie scattering tracers and fluorescent dye for marking the air and liquid flows, respectively. It allows us to visualize the air and liquid flows independently or simultaneously, and to measure the air flow separation angle. Results are compared with values obtained for a dry tube by the present and of other authors.

For thermal analysis, power module packages can often be considered as plane multilayered systems for which it has been demonstrated that appropriate Fourier transforms associated with the two-port network theory permit to develop very efficient solutions of the static or the time dependent 3D heat flow equation. However, in practice, the thermal resistances of soldered or pasted interfaces are most often not well known. Most of these parameters are theoretically unpredictable, therefore it is of highest interest to develop an experimental procedure intended for an adequate characterization of the 3D thermal behaviour of the cooling substrates. A two-port network theoretical basis for experimental characterization of the thermal behaviour of multilayered substrates (96% Alumina, AU4G, IMS), which are classically used for power module packaging, is presented. In spite of some difficulties in setting perfectly the boundary conditions for temperature and heat fluxes, the experimental results demonstrate the validity of the characterization method, and the soughted parameters can be measured for wide ranges of spatial pulsation. Suggested improvements of the existing experimental set can give rise to an industrial measurement set intended for thermal characterization of power module packages.