Mold process development of C90 LowK and ultra-finepitch BGA for robust reliability performance

The use of porous material as dielectric for C90 has imposed significant challenge for package encapsulation due to its porous nature which requires extremely low stress condition under thermal excursion. This paper discussed the challenges in defining the critical characteristics in packaging with special emphasis on molding process in order to achieve robust and reliable package. Key challenges in this particular development was imposed by the increase in package body size, the tightening in wirebond pitch, increased in wire count and tiers, and the inclusion of metal heat spreaders. These factors have significant impact on the mold compound flow and the distribution of filler in the molded package which was found to be responsible for delamination and electrical failure. The resolution to the problem focused on the reduction in average filler size and distribution to improve filler and matrix composition across the molded region. The improvement in these areas has enabled the package to surpass 1000 cycles of temperature cycling and met qualification reliability stress requirement.