Investigation of Laser Pulse Energy and Grinding Tool Characteristic on Marking Legibility of FOPLP

Recently, more players in the semiconductor industry have embarked on Fan Out Panel Level Packaging (FOPLP) due to key advantages in terms of lower packaging cost, higher performance and better components integration. As part of the manufacturing process of FOPLP, laser marking is done on Encapsulation Mold Compound (EMC) after grinding process. Therefore, marking legibility requires innovative characterization to achieve desired result. This study was conducted to investigate the marking legibility challenges in FOPLP and to find a creative solution that meets quality and cost expectation. Automated Optical Inspection (AOI) was used as a tool to recognize marking information and marking legibility beyond the coverage of JEDEC [1] requirement. According to this fundamental study, higher pulse energy with higher pulse frequency can have higher laser ablation rate for resin and filler (SiO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>), resulted in similar marking depth but good contrast and legibility. The mesh size of grinding wheel also played a role. A full matrix of Design of Experiment (DOE) was performed to fully characterize marking legibility performance and overcome limitation even on high warpage panel. Based on the comprehensive DOE results, laser marking energy density optimization, grinding wheel mesh size and laser marking with tape are the potential creative solutions to achieve good marking legibility on FOPLP.