Recent years have witnessed an explosion of interest in the application of polymers as the substrates for various electronic and display devices. The advantages of polymers are their mechanical flexibility, light weight, enhanced durability, roll-to-roll fabrication and low cost compared with rigid materials (such as silicon and glass). Hybrid polymers have drawn great attention because they offer the opportunity to prepare high-performance multifunctional advanced materials through the combination of properties of organic and inorganic segments. Recently, a new approach to construction of nanohybrid materials based on polyhedral oligomeric silsesquioxne (POSS) as an inorganic moiety has attracted a lot of interest. Double-decker-shaped silsesquioxane (DDSQ) is a new family of silsesquioxane consisting of nanometer-sized Si-O-Si cage structure functionalized with a wide variety of organic groups. DDSQ-based hybrid polymer (Double-decker-shaped polysilsesquioxane, DDPSQ) possesses many fascinating properties such as high thermal stability, good mechanical properties, low dielectric constant, excellent transparency, excellent flexibility and so on. Due to these fascinating properties, DDPSQ can be used as a potential candidate substrate for various flexible electronic devices. For such applications drawing of conductive metal (Au, Cu, Ag) patterns on a DDPSQ substrate is required. Herein, we have described fabrication of Ag microwiring with submicron resolution on a DDPSQ film by laser direct writing. The line width of the Ag-wiring fabricated by this laser direct-write maskless technique can be controlled flexibly by changing the objective lens magnification and the focusing point. With an objective lens magnification 100x, Ag microwiring with a line width of about 5 μm has been achieved. The Ag-wiring shows an excellent adhesion to DDPSQ surface as evaluated by Schotch tape test. The resistivity of the Ag-wiring is determined to be 4.3 × 10-6 Ω cm ,which is comparable that of bulk Ag (1.6 × 10-6 Ω cm).

This work investigates the effects of mechanical strain on electrical characteristics of polycrystalline thin film transistors (poly-Si TFTs). Poly-Si TFTs were fabricated on steel foil substrate and characterized under the strain ranging from -1.2% to 1.1% induced by bending. The electron mobility increased under tensile and decreased under compressive strain while that of the hole exhibited an opposite trend. For p-channel TFTs the normalized threshold voltage and subthreshold slope were a function of strain. In both n- and p-channel TFTs the off current decreased under tensile while it increased under compressive strain. The observed mobility trends in poly-Si TFTs are similar to those reported in single crystalline silicon devices.

It is important to quantitatively measure the adhesion strength at the interface in a small area of electronics devices to ensure their reliability. In this study, a simple technique for measuring the adhesion using the nanoindentation method by considering the energy balance during the indentation process was proposed and applied to measure the adhesion of three kinds of UV-cured SiOC films with a thickness of 500 nm on a Si substrate. The discontinuous points of approximately 300 nm in depth appeared in all the indentation curves with a high reproducibility, and it was confirmed that these points reflect the occurrence of an interfacial delamination. The total dissipated energies calculated from the load vs. indentation depth curves indicate a good correlation with the indentation load. The delamination energies can be estimated using this relationship. The energy release rates at the interface of the UV-cured SiOC films calculated from the energy balance increases with the increasing UV curing time. From these result, we can confirm the technique proposed in this study is quite useful to simply and quantitatively measure the adhesion, especially against a thin film or the small area, even if the film is ductile.

A flexible electrode array consisting of a thin metal film on a polymer substrate has been developed for neural implantation in rats. The biocompatible arrays record cortical brain signals from awake and mobile rats in order to gather significant neurological data. Four point bend testing of the metal-Kapton system has been used to characterize the interfacial toughness, and therefore the mechanical durability, of the array. Several different adhesion layers on were evaluated using this method. Use of a titanium-tungsten interlayer increases the mixed-mode fracture toughness from approximately 1 J/m2 to approximately 2 J/m2, while a titanium interlayer provides a toughness of more than 4 J/m2. Gold-Kapton arrays were implanted in rats for periods exceeding 200 days, and neural recordings were taken frequently. The arrays exhibit excellent long-term reliability, with no decrease in signal recording capability over the course of the implantation.

Flexible audible display (FAD) based on PVDF(Poly-vinylidene fluoride) film is researched to combine piezoelectric property with light emitting diode. Indium-Tin-Oxide (ITO) is deposited on PVDF film at low temperature condition with the vacuum web coating. Under the optimized working pressure and the oxygen/argon pressure ratio, ITO on PVDF shows good electrical property of sheet resistance about 120 ohm/sq at 160 nm thickness, good transmittance of 76%, and sound pressure level more than 70 dB. OLED device with Al/LIF/Alq3/ NPB/ 2T-NATA structure is fabricated on ITO/PVDF and shows the turn-on voltage of 3.5 V and the maximum luminescence of 1011.2 cd/cm2 at the driving voltage of 13 V. C-F chemical bondings are measured to decrease in the XPS spectrum of ITO/PVDF interface. This is originated from the bonding scission caused by incident energetic particles, such as sputtered atoms, backscattered Ar ions, and negative O ions during the sputtering and deposition process. These particles have energy, which is simulated by TRIM and is more than 5 eV, enough to cause the scission of C-F bondings with binding energy of 4 eV/atom.

The rotation of Sn grains in Pb-free flip chip solder joints hasn't been reported in literature so far although it has been observed in Sn strips. In this letter, we report the detailed study of the grain orientation evolution induced by electromigration by synchrotron based white beam X-ray microdiffraction. It is found that the grains in solder joint rotate more slowly than in Sn strip even under higher current density. On the other hand, based on our estimation, the reorientation of the grains in solder joints also results in the reduction of electric resistivity, similar to the case of Sn strip. We will also discuss the reason why the electric resistance decreases much more in strips than in the Sn-based solders, and the different driving force for the grain growth in solder joint and in thin film interconnect lines.