Fabrication of bottom-emitting organic light-emitting diode panels interconnected with encapsulation substrate by Au-Au flip-chip bonding and capillary-driven filling process

We present fabrication and testing of bottom-emitting organic light-emitting diode (OLED) panels based on flip-chip assembly and non-destructive scanning. In this method, the OLED and electric circuits are fabricated on separate substrates and interconnected by low temperature assembly to create a high-performance bottom-emitting OLED including other functions such as thin-film transistor (TFT) circuits. The low temperature assembly process consists of two steps. First, an OLED substrate and encapsulation glass with circuits are bonded at 100 °C via Au-Au bond. Encapsulation glass is utilized for the functional substrate with circuits. Next, the bonded panel is sealed by capillary underfill within and by applying and curing seal materials to the panel edge. The fabricated OLED was non-destructively evaluated by scanning acoustic microscopy (SAM). The SAM image shows all φ500 μm Au bumps were bonded to Au pads, indicating that OLED and encapsulation substrates were assembled. Electroluminescence of the OLED was demonstrated by applying voltage. Stable current-luminance characteristics were obtained for the fabricated OLED with an operating voltage of 3.25 V. The results indicate that the proposed fabrication is available for bottom-emitting OLED controlled by TFT circuits. In future, the assembly process can be widely applied to other flexible organic electronic devices with roll assembly by altering OLED or circuits with other devices because this is a simple pressure method with low temperature, achieving encapsulation at same time.