BS IEC 62951-2:2019 pdf free.Semiconductor devices – Flexible and stretchable semiconductor devices.
The stability test of a flexible TFT is carried out using four kinds of biased evaluation. The negative-bias-stress (NBS) test is carried out with a VGs of -20 V at a fixed Vps of 10 V under dark and the substrate temperature is maintained at 20 °C and 60 °C. The negative-bias-illumination-stress (NBIS) test is carried out with a VGs of -20 V at a fixed Vps of 10 V under illumination with a white light-emitting diode of 300 cd/m2 brightness and the substrate temperature is maintained at 20 °C and 60 °C. The positive-bias-stress (PBS) test is carried out with a Vgs of +20 V at a fixed Vos of 0,1 V under dark and the substrate temperature is maintained at 20 °C and 60 °C. The positive-bias-illumination-stress (PBIS) test is carried out with a VGs of +20 V at a fixed Vps of 0,1 V under illumination with a white light-emitting diode of 300 cd/m2 brightness and the substrate temperature is maintained at 20°Cand 60 °C.To characterize the effects of mechanical stress on flexible TFTs, strain is applied on the TFTs by bending the device convexly (i.e., inducing a tensile strain on the active devices) or concavely (i.e., inducing a compressive strain on the active devices) with varied radius of curvature R as shown in Figure 3. The bending direction is parallel or perpendicular to the drain-to-source current path. The TFTs are first bent to the maximum R for 1 min and then released to the flat state and are measured. This test cycle is repeated at decreasing R down to the minimum R. After each mechanical bending, the TFT on-current, the off-current and the gate leakage current are monitored.Where, 1T and ds are the corresponding thicknesses of the TFT stack and the flexible substrate. Simple mechanical fatigue testing is performed by putting the flexible TFTs through repeated bending (i.e., at constant R) and flattening up to 50 000 times. The substrate temperature is maintained at 20°C and 60°C. The TFTs are periodically measured while flat without removal from the bending apparatus.BS IEC 62951-2 pdf download.