Process window of simultaneous transfer and bonding materials using laserassisted bonding for mini- and micro-LED display panel packaging

A simultaneous transfer and bonding (SITRAB) process using areal laser irradiation is introduced for high-yield and cost-effective production of mini- or micro-light-emitting diode (LED) display panels. SITRAB materials are special epoxy-based solvent-free pastes. Three types of pot life are studied to obtain a convenient SITRAB process: Room temperature pot life (RPL), stage pot life (SPL), and laser pot life (LPL). In this study, the RPL was found to be 1.2 times the starting viscosity at 25 degrees, and the SPL was defined as the time the solder can be wetted by the SITRAB paste at given stage temperatures of 80 degrees, 90 degrees, and 100 degrees. The LPL, on the other hand, was referred to as the number of areal laser irradiations for the tiling process for red, green, and blue LEDs at the given stage temperatures. The process windows of SPL and LPL were identified based on their critical time and conversion requirements for good solder wetting. The measured RPL and SPL at the stage temperature of 80 degrees were 6 days and 8 h, respectively, and the LPL was more than six at these stage temperatures.