|dc.description.abstract||Micro-LED (µLED) is a very promising technology for creating highly efficient and great looking flexible displays. It, however, includes numerous sophisticated apparatuses that involve complex processes. One of the critical challenges for the commercialization of LED display technology is to develop a cost-effective method for transferring massively LEDs. Among the competitive mass transfer techs of µLED, this study aims at facilitating the laser-induced forward transfer (LIFT) technology. Transferring an array of µLEDs from a blue tape to the final destination substrate includes two steps: adhesive transfer and laser transfer. The former is to move µLEDs from the blue tape to the the sacrificial layer on a transition substrate; the latter, then transfer them to the destination substrate.
Firstly, instead of the UV laser, a commonly used light source in LIFT, we use a infrared fiber laser, with nano-second pulse duration, that is cost effective and popular in the industry. Secondly, the adhesive transfer process is tested based on the composition and thickness of the sacrificial layer. Its materials are developed by a domestic manufacturer, hereby named as the light absorbing polymer glue (LAPG). The recipes for LAPG and various thicknesses for the sacrificial layer that are achievable for effective adhesive transfer are obtained for the subsequent LIFT process. Thirdly, the LIFT transfer results based various parameters of the LAPG film thickness, laser power and repetition rate are examined. Finally, the random forest method is used to analyze the three parameters in the LIFT process and the priority of their importance is determined.
Results show that the proposed LIFT scheme can successfully transfer massively LEDs to the destination substrate. In addition, this method has the advantage of local transfer, moving an individual LED to a specified location. The lighting test is executed by connecting the transferred LEDs in series on a test pad that consists of two copper lines linking the LEDs’ anode and cathode, respectively. It proves that the LEDs function is well preserved throughout the transfer process. Finally, the random forest analysis shows that, under the current experimental configuration, the film thickness of LAPG is the most relevant to the success of LIFT transfer.