High Resolution Dry-film Photo Imageable Dielectric (PID) Material for Fowlp, Foplp, and High Density Package Substrates

This paper reports a new dry-film type photo imageable dielectric (PID) material with fine patterning capability, which is suitable for FOWLP, FOPLP, and high density package substrates. Features of this material are; 1) Dry-film type for high surface planarity, 2) Low curing temperature (180 deg. C), 3) Low coefficient of thermal expansion (CTE), 4) High resolution for 6–10 μm via formation, 5) Resistance to organic solvents, and 6) High dielectric reliability. Flatness of the surface is advantageous for multi -layering, as well as fine pitch circuit patterning by semi-additive process (SAP). Low curing temperature is beneficial for reduction in internal stress. This PID has both low CTE of 35–45 ppm/deg. C and high resolution below $10 \mu \mathrm{m}$ which is excellent for multilayer RDL structures. This study focuses on how to improve solvent resistance and dielectric resistance of PID materials by material design. This study also performed reliability demonstration of the biased highly accelerated stress test (BHAST) with the PID material. Cu comb structures with line & space (L/S) = 2/2 μm were formed on the PID material by SAP and electrical voltage was applied under high temperature & moisture condition. It was confirmed that the PID material has high insulation reliability and kept more than 300 hours without electrical failure.