Effect of laser on passivation photo-dielectric during laser de-bonding process for Fan-Out Wafer Level Package

• Published in: 2019 IEEE 21st Electronics Packaging Technology Conference (EPTC) pp. 671 - 675
• Main Authors: Hsiang-Yao, Hsiao, Wee, David Ho Soon
• Format: Conference Proceeding
• Language: English
• Published: IEEE 01.12.2019
• Subjects: Chemical lasers; Laser beams; Passivation; Polyimides; Power lasers
• DOI: 10.1109/EPTC47984.2019.9026673

Four different types of Photo-dielectric passivation including polybenzoxazoles (PBO), epoxy phenolic, low and high temperature cured polyimide (PI) were evaluated for laser de-bonding process used in FO-WLP fabrication. The laser de-bonding spot size in the laser release layer scaled up with the increase in laser power. The laser release layer spot size is dependent on the polymer passivation materials, such as in the case of high temperature cured polyimide, the spot size was much larger than the other passivation materials. Micro-cracks were observed on the epoxy phenolic passivation during laser de-bonding. Fourier transform infrared spectrometry (FTIR) was used to characterize the effect of laser de-bonding on the chemical bonds of the passivation materials. FTIR results show that the peak intensity of the chemical bonds for all passivation decreased, showing some degree of degradation in the chemical bonds during the laser scanning process. The reduction in peak intensity for epoxy phenolic passivation was the most significant and this coincide with the micro-cracks observed in epoxy phenolic passivation in the laser de-bonding process. PBO and high temperature polyimide passivation shows the least amount of degradation and may be more suited for the laser de-bonding process.