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In this study, indium-zinc oxide (IZO)/silver (Ag)/IZO (ZAZ) flexible transparent electrodes were prepared on polyethylene terephthalate substrate using radio frequency sputtering technique. Experimental results showed that when the Ag film transited from semi-continuous state to continuous state, the ZAZ electrode exhibited high optoelectronic performance. The best ZAZ sample had a quite wide range of high transmittance and an average transmittance of 78.9% in visible light region, and sheet resistance of $6.54\mathrm{\Omega }$/sq and a Haacke Index of ${\mathrm{\Phi }}_{\mathrm{\text{vis}}}=14.41\times 10^{-3}{\mathrm{\Omega }}^{-1}$. The bending test revealed that the $R_c$ (change in sheet resistance) of ZAZ electrodes after 1000 bends was still less than 25% while the electrical properties of IZO films deteriorated after only 100 bending tests.

In the present study, we demonstrate the performance of Zinc oxide thin film transistors (ZnO TFTs) array subjected to the strain under high bending test and the reliability of TFTs was confirmed for the bending fatigue test of 2000 cycles. Initially, ZnO TFTs were fabricated on Si substrate and subsequently transferred on flexible PET substrate using transfer printing process. It was observed that when the bending radius reached ≥ 11 mm then cracks start to initiate first at SiO₂ bridges, acting as interconnecting layers among individual TFT. Whatever the strain is applied to the devices, it is almost equivalently adopted by the SiO₂ bridges, as they are relatively weak compared to rest of the part. The initial cracking of destructed SiO₂ bridge leads to the secondary cracks to the ITO electrodes upon further increment of bending radius. Numerical simulation suggested that the strain of SiO₂ layer reached to fracture level of 0.55% which was concentrated at the edge of SiO₂ bridge layer. It also suggests that the round shape of SiO₂ bridge can be more fruitful to compensate the stress concentration and to prevent failure of device.

The fracture strength of LOC (lead-on-chip) packages was measured through three-point bending tests. Metallurgical examination shows that failure in an LOC package begins at a pre-existing flaw in the form of a scratch on the bottom surface of the plastic-encapsulated silicon chip. The flexural strength of LOC packages was estimated as a function of the geometry of the grinding-induced scratches on the back surface of the chips. The major conclusion is that the fracture strength of the plastic package, including the silicon chip, can be enhanced up to 80% by changing its scratch marks from 0°, running parallel to its lateral direction, to 90°, running parallel to its longitudinal direction.