Advanced Interconnection technology with Laser Assisted Bonding Process for PET Substrate

As a state-of-the-art interconnection technology, laser assisted bonding process has been applied to the LED bonding process with PET substrates. In conventional reflow processes, when PET substrate is exposed to the 150° C environment, the PET substrate is easily deformed due to the low glass transition temperature of 70° C. Therefore, it is necessary to carry out the semiconductor bonding process without changing the dimension of PET substrate during the bonding process. In this study, laser assisted bonding process was carried out using solvent free epoxy based solder paste which was newly developed. LED device (2mm × 2mm × 1mm) was bonded to a 0. 2mm thickness PET substrate with a laser of 980nm wavelength. The absorption, transmission and reflection of the laser were examined on the PET substrate. The power and time of the laser were precisely tuned to optimize device and substrate temperatures during the laser reflow process and prevent deformation of the PET substrate. Temperature of LED device and the PET substrate were measured by IR camera and thermo-couple during laser bonding process. The laser bonding process using the newly developed solvent free epoxy based solder paste was successfully performed on LED device and PET substrate without any damage. Laser reflow bonding process are expected to be extensively used in semiconductor packaging in the near future.